Co-reporter:Hyungwoo Kim;Jung Ho Ryu;Hwan Kyu Kim
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 21) pp:12366-12370
Publication Date(Web):2017/10/24
DOI:10.1039/C7NJ02221B
A versatile coordination structure for lanthanide(III) ions has been demonstrated. Complexes with various ions formed an entangled fibrous network in aliphatic solvents via organogelation. In particular, an Er(III)-containing polymer nanocomposite was fabricated from an organogel template via post-gelation polymerisation, showing an enhanced NIR emission.
Co-reporter:Jong Gil Kim;Jeongmin Lee;Jieun Lee;Seong In Jo
Macromolecular Research 2017 Volume 25( Issue 6) pp:629-634
Publication Date(Web):18 July 2017
DOI:10.1007/s13233-017-5122-9
A compressible polyimide composite having metal binding sites was prepared by in situ polymerization inside a melamine sponge. 1,3,5-Tris(4-aminophenyl)benzene and pyromellitic dianhydride were used as a triamine and a dianhydride monomer, respectively, to construct the microporous framework, and 5-amino-1,10-phenanthroline was used as a functional monomer. The microporous polyimide containing phenanthroline groups (MPI-Phen) was obtained as insoluble powders. However, when the polymerization was carried out in the melamine sponge, MPI-Phen formed a coating layer on the sponge skeletons. The melamine sponge/microporous polyimide composite (MS/MPI-Phen) had an open cellular structure with a hierarchical porosity composed of macropores between the sponge skeletons and meso- and micropores of the MPI-Phen coating. It showed the higher compressive strength than the melamine sponge, indicating the reinforcement by the microporous polymer. The BET surface areas of MPI-Phen and MS/MPI-Phen were 723 m2g-1 and 524 m2g-1, respectively. Pd(II) ions were coordinated with the phenanthroline groups of MS/MPI-Phen for heterogeneous catalysis. The catalytic activity of MS/MPI-Phen-Pd was evaluated for the Suzuki coupling reaction between bromobenzene and phenylboronic acid.
Co-reporter:Jeongmin Lee and Ji Young Chang
Chemical Communications 2016 vol. 52(Issue 68) pp:10419-10422
Publication Date(Web):27 Jul 2016
DOI:10.1039/C6CC04817J
A compressible and monolithic microporous polyimide sponge was prepared from an aliphatic tetracarboxylic dianhydride and an aromatic triamine. The sponge had a hierarchical pore structure, in which spherical microporous polyimide particles were interconnected to form a macroscopic network. It showed an amphiphilic character, because of the balanced presence of hydrophobic and hydrophilic groups.
Co-reporter:Youngdo Kim, Jae Bum Jeon, Ji Young Chang
Materials Letters 2016 Volume 182() pp:235-239
Publication Date(Web):1 November 2016
DOI:10.1016/j.matlet.2016.06.099
•A molecularly imprinted sensor is fabricated using C60 as a signal transducer.•Delicate binding sites are formed in the silica network by the sol–gel chemistry.•C60 fullerenes form a nanoparticulate cluster that shows quantum confinement effects.•The sensor shows concentration dependent fluorescence quenching for the analyte.A highly sensitive, molecularly imprinted fluorescent sensor was fabricated using a C60 fullerene as the signal transducer and silica as the imprinting matrix. The incorporation of C60 and the formation of diethylstilbestrol (DES) imprinted sites in the silica network were achieved by the sol–gel method. C60 has a narrow band gap between the ground and excited states, resulting in a weak photoluminescence. However, C60 showed a strong emission when it was incorporated into a molecularly imprinted silica matrix. DES imprinted fullerene-silica nanocomposite particles (MIFSNCs) showed an intense fluorescence emission with the peak maximum at ∼600 nm. The fluorescence intensity of MIFSNCs significantly decreased with increasing DES concentration. MIFSNCs exhibited a linear Stern–Volmer relationship for DES and its structural analogs. The quenching constant of MIFSNCs for DES was about five times higher than those for DES analogs, indicating the highly selective recognition property.A highly sensitive, molecularly imprinted fluorescent sensor is fabricated using a C60 fullerene as a signal transducer and silica as an imprinting matrix.
Co-reporter:Tae Jin Choi
Macromolecular Research 2016 Volume 24( Issue 12) pp:1055-1061
Publication Date(Web):2016 December
DOI:10.1007/s13233-016-4148-8
Thermochromic polymer nanocomposite films were prepared from polymerizable organogels. Organogelator 1 had a structure which 3,4,5-tris(ω-decenyl)benzamide groups were attached to a quarterthiophene core through amide bonds. Organogelator 2 had the same structure except that tris(ω-decenyl) groups were replaced by tris(n-decanyl) groups. The PMMA nanocomposite films were prepared by the photopolymerization of the organogels formed in methyl methacrylate (MMA). The film containing 1 (0.5 wt%) showed reversible thermochromism. The emission under 365 nm irradiation was changed to bright green from orange by heating up to 120 °C and returned to its initial orange by cooling. To the contrary, the PMMA composite film prepared from the organogel of 2 (0.5 wt%) did not show a reversible thermochromic property. Organogelator 1 with polymerizable terminal vinyl groups was covalently embedded in the PMMA matrix, but 2 was not. The reversible thermochromism was likely caused by the thermally reversible conformational change of quarterthiophene units in the polymer fibers.
Co-reporter:Youngdo Kim, Ji Young Chang
Sensors and Actuators B: Chemical 2016 Volume 234() pp:122-129
Publication Date(Web):29 October 2016
DOI:10.1016/j.snb.2016.04.161
•A MIP-based histamine fluorescent sensor was fabricated through an organogelation process.•The sensor was made up of a molecularly imprinted nanofiber as a receptor and a CdSe/ZnS quantum dot as a signal transducer.•The in-situ gel-state polymerization of a polymerizable organogelator produced the QD-incorporated, histamine imprinted organogel nanofibers (QD-HIOGNF).•QD-HIOGNF showed highly sensitive and selective molecular recognition properties toward histamine.We describe a molecularly imprinted polymer (MIP)-based fluorescent sensor fabricated through an organogelation process. The sensor was comprised of a molecularly imprinted nanofiber as a receptor and a CdSe/ZnS quantum dot (QD) as a signal transducer. The sensor fabrication was carried out in three steps: (1) organogelation of a polymerizable gelator (PG) in the presence of the QD and a template, (2) gel-state polymerization and (3) extraction of the template. We chose histamine as a model template. PG had two different polymerizable groups: an acrylate and a diacetylene. As a functional monomer for complexation with the template, an acrylate having a carboxyl group was used. The QD and template-containing organogel formed in n-decane were polymerized in the presence of a photoinitiator and a cross-linker by UV irradiation to produce highly cross-linked organogel nanofibers. The template molecules were removed by extraction with methanol/acetic acid (9:1 v/v) to give the QD-incorporated, histamine imprinted organogel nanofibers (QD-HIOGNF). QD-HIOGNF showed high molecular recognition properties toward histamine in respects to both sensitivity and selectivity. The fluorescence intensity of QD-HIOGNF was quenched sensitively as the concentration of histamine increased. QD-HIOGNF could be reused for sensing after removing the bound analytes.
Co-reporter:Hyunpyo Lee, Hyungwoo Kim, Tae Jin Choi, Hyun Woo Park and Ji Young Chang
Chemical Communications 2015 vol. 51(Issue 48) pp:9805-9808
Publication Date(Web):07 May 2015
DOI:10.1039/C5CC02269J
A microporous polymer with sulfide and thiol groups was synthesized using the thiol–yne reaction. Au nanoparticles were prepared by in situ reduction reaction inside the polymer and were found to be well dispersed. The Au-containing polymer showed catalytic activity in the reduction of 4-nitrophenol.
Co-reporter:Min Chul Cha;Yoonbin Lim
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 20) pp:2336-2342
Publication Date(Web):
DOI:10.1002/pola.27670
ABSTRACT
The use of a hyperbranched polymer as a building block for the synthesis of a microporous organic polymer was demonstrated. Hyperbranched polyphenylenes (HBPs) were prepared from (3,5-dibromophenyl)boronic acid, which contained numerous unreacted bromophenyl end groups. Utilizing metal-catalyzed coupling reactions between these functional groups, cross-linked porous polymers were obtained. Although the HBPs did not show porosity, their cross-linked polymers had highly porous structures with Brunauer–Emmett–Teller surface areas of up to 2030 m2/g. An insoluble porous thin film was fabricated by spin casting of a solution containing a HBP followed by Sonogashira cross-coupling reaction. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2336–2342
Co-reporter:Geo San Lim, Hyungwoo Kim and Ji Young Chang
Journal of Materials Chemistry A 2014 vol. 2(Issue 47) pp:10184-10188
Publication Date(Web):08 Oct 2014
DOI:10.1039/C4TC01493F
We report a photosensitive, double-layered anti-reflection film, which is composed of a UV cured acrylate film containing a photoluminescent europium(III) complex as a high refractive index layer and a film of a colloidal nano-silica as a low refractive index layer. The refractive index of the high refractive index layer can be tuned from 1. 53 to 1.69 as the composition of the europium(III) complex increases. The reflectance of the anti-reflection film on the glass substrate is as low as 0.48% when the refractive indices and thicknesses of the two layers are controlled. The anti-reflection film is applied as the top layer of a liquid crystal display (LCD). Since the absorption and excitation spectra of the europium(III) complex barely overlap with the backlight spectrum of the LCD, the europium(III) complex in the anti-reflection film does not disturb the display images. The images are visible even under irradiation using an indoor fluorescent lamp. It is also possible to highlight a specific point on the display screen using laser light. When a 405 nm laser pointer is aimed at a specific area, the area appeared as a bright red spot.
Co-reporter:Yoonbin Lim, Insil Choi, Hyunpyo Lee, Il Won Kim and Ji Young Chang
Journal of Materials Chemistry A 2014 vol. 2(Issue 29) pp:5963-5968
Publication Date(Web):21 May 2014
DOI:10.1039/C4TC00822G
The piezochromic behaviours of C3-symmetric molecules with p-bromophenyl side groups connected to a phenyl ring core through cyano-vinylene bridges were studied. Upon grinding, α-BPAN-Br having cyano groups at the α-position to the phenyl ring core exhibited substantial quenching of a bluish green emission (on–off switching) and its constitutional isomer, β-BPAN-Br, showed an emission colour change from bluish green to deep blue (colour tuning). When the molecules were exposed to an organic vapour, the initial emission of each molecule was restored. The powder X-ray diffraction and DSC studies revealed that the as-synthesized and vapour-annealed samples had the same crystalline structures, while the ground samples had amorphous structures. Their structural analogues, α-BPAN-H and β-BPAN-H which had no bromo groups, did not show any piezochromic or vapochromic behaviour. Poly(β-BPAN) consisting of covalently linked β-BPAN units were prepared by Ullmann reaction of β-BPAN-Br. The polymer showed similar luminescence to that of crystalline β-BPAN-Br, but its initial emission was not changed by grinding.
Co-reporter:Hyungwoo Kim and Ji Young Chang
RSC Advances 2014 vol. 4(Issue 82) pp:43549-43549
Publication Date(Web):15 Sep 2014
DOI:10.1039/C4RA90013H
Correction for ‘White light emission from a mixed organogel of lanthanide(III)-containing organogelators’ by Hyungwoo Kim et al., RSC Adv., 2013, 3, 1774–1780.
Co-reporter:Hyungwoo Kim;Youngdo Kim
Macromolecular Chemistry and Physics 2014 Volume 215( Issue 13) pp:1274-1285
Publication Date(Web):
DOI:10.1002/macp.201400128
Co-reporter:Hyungwoo Kim and Ji Young Chang
Langmuir 2014 Volume 30(Issue 45) pp:13673-13679
Publication Date(Web):October 23, 2014
DOI:10.1021/la502932x
We report a reversible thermochromic nanocomposite polymer film composed of fluorescent organogel fibers and a highly cross-linked polymer matrix. A series of cyano-substituted oligo(p-phenylenevinylene) (CN-OPV) derivatives were synthesized by the reaction of dialdehydes with phenyl or naphthyl acetonitrile under basic conditions. Among the CN-OPV derivatives, NA-DBA having naphtyl moieties and dodecyloxy chains formed a stable organogel in a cross-linkable monomeric solvent (ethylene glycol dimethacrylate). The organogel showed a thermoreversible sol–gel transition, accompanying the emission color change. A nanocomposite polymer film obtained by photopolymerization of the organogel between two quartz plates also exhibited reversible thermochromism. Under 365 nm irradiation, the orange color of the film at 25 °C became yellowish green at 120 °C. The fluorescence spectroscopy, DSC, and microscopy results determined that the thermally reversible self-assembly of NA-DBA occurred in the polymer matrix, resulting in reversible thermochromism. The melted gelator molecules at 120 °C did not diffuse into the polymer matrix probably because of poor interactions of the gelator molecules with the polymer matrix. The NA-DBA molecules dispersed in poly(methyl methacrylate), without forming a supramolecular structure, did not show thermochromism.
Co-reporter:Min Soo Kim, Jae Bum Jeon, Ji Young Chang
Microporous and Mesoporous Materials 2013 Volume 172() pp:118-124
Publication Date(Web):15 May 2013
DOI:10.1016/j.micromeso.2013.01.028
We prepared selectively functionalized, spherical mesoporous silica particles (SMSPs) with a polyethylene glycol (PEG)-grafted outer surface and a doxorubicin-grafted inner surface for drug delivery. The SMSPs were fabricated by co-condensation of an amphiphilic organotriethoxysilane with a thermally cleavable urethane bond and tetraethoxysilane (TEOS) in the presence of cetyltrimethylammonium bromide (CTAB) under basic conditions. The outer surface of the as-precipitated silica particles was functionalized by grafting with 3-(triethoxysilyl)propyloxy–PEG. The PEG-grafted SMSPs were refluxed in methanol in the presence of HCl, resulting in the removal of surfactant molecules and the formation of a methoxy urethane group tethered to the pore wall. After the reaction of the methoxy urethane group with hydrazine, doxorubicin was chemically introduced into the pores through a pH-sensitive hydrazone linkage. A high loading content was achieved through chemical loading followed by physical loading. The doxorubicin-loaded SMSPs showed a pH-sensitive and sustained release behavior.Graphical abstractHighlights► Selective functionalization of mesoporous silica particles for drug delivery. ► PEG and doxorubicin were grafted onto the outer and inner surfaces, respectively. ► Doxorubicin was grafted the pore wall through a pH-sensitive hydrazone linkage. ► High loading efficiency achieved via chemical loading followed by physical loading.
Co-reporter:Hyungwoo Kim and Ji Young Chang
RSC Advances 2013 vol. 3(Issue 6) pp:1774-1780
Publication Date(Web):23 Nov 2012
DOI:10.1039/C2RA22908K
We prepared Eu(III) and Tb(III) complexes (Eu2 and Tb2) with phenanthroline derivatives which formed organogels in n-decane. The organogels of Eu2 and Tb2 showed red and green emissions, respectively, when excited at 330 nm. TEM images of dry gels of Eu2 and Tb2 showed entangled fiber network structures with fiber diameters ranging from 20 to 60 nm. Eu2 and Tb2 formed stable mixed gels of different compositions in n-decane. The emission spectrum of a mixed gel showed emission peaks from Eu(III) at 595 and 618 nm and from Tb(III) at 496 and 551 nm when excited at 330 nm. A broad emission was observed around 470 nm that was attributed primarily to the ligands of Tb2. At a ratio of Eu2/Tb2 of 1:19 by weight, the mixed gel exhibited white luminescence. The CIE color coordinates of the mixed gel were x = 0.36 and y = 0.30 in the white region. The TEM image of the dry gel revealed entangled fibers with diameters ranged from 20 nm to 80 nm without evidence of self-sorting. Trimetallic organogelators, Eu4 and Tb4, were prepared by coordination of Eu2 and Tb2 with two 1,3-diketone groups. Eu4 showed three transitions of Eu(III) ion in the red region and a ligand-centered emission but Tb4 showed only a broad emission in the greenish blue region from the ligands. Eu4 and Tb4 also formed a homogeneous mixed gel in n-decane, showing a whitish luminescence at the ratio of 3:1 by weight.
Co-reporter:Hyunpyo Lee;Hyun Woo Park
Macromolecular Research 2013 Volume 21( Issue 11) pp:1274-1280
Publication Date(Web):2013 November
DOI:10.1007/s13233-013-1175-6
Co-reporter:Hyungwoo Kim;Min Chul Cha;Hyun Woo Park
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 24) pp:5291-5297
Publication Date(Web):
DOI:10.1002/pola.26962
ABSTRACT
We synthesized a Yb(III)-incorporated microporous polymer (Yb-ADA) and studied its gas adsorption property and catalytic activity. The adamantane-based porous polymer (ADA) was obtained from an ethynyl-functionalized adamantane derivative and 2,5-dibromoterephthalic acid through Sonogashira–Hagihara cross-coupling. ADA had two carboxyl groups which were used for Yb(III) coordination under basic conditions. The Brunauer-Emmett-Teller (BET) surface area of ADA was 970 m2 g−1. As Yb(III) ions were incorporated into ADA, the surface area of the polymer (Yb-ADA) was reduced to 885 m2 g−1. However, Yb-ADA exhibited a significantly enhanced CO2 adsorption capacity despite the reduction of surface area. The CO2 uptakes of ADA and Yb-ADA were 1.56 and 2.36 mmol g−1 at 298 K, respectively. The H2 uptake of ADA also increased after coordination with Yb(III) from 1.15 to 1.40 wt % at 77 K. Yb-ADA showed high catalytic activity in the acetalization of 4-bromobenzaldehyde and furfural with trimethyl orthoformate and could be reused after recovery without severe loss of activity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5291–5297
Co-reporter:Hyungwoo Kim;Taejin Choi;Min Chul Cha
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 17) pp:3646-3653
Publication Date(Web):
DOI:10.1002/pola.26763
ABSTRACT
A microporous polymer is prepared by a catalyst-free Diels–Alder reaction. A cyclopentadiene with both a diene and a dienophile functionality and a dienophilic maleimide are used for the Diels–Alder reaction. 1,3,5-Tris(bromomethyl)-2,4,6-trimethylbenzene is reacted with sodium cyclopentadienide to produce the multicyclopentadiene-functionalized monomer. A crosslinked polymer (CDAP) is obtained by the reaction of the cyclopentadiene monomer with N,N′-1,4-phenylenedimaleimide. The thermal dissociation of the cyclopentadiene dimeric unit and the subsequent Diels–Alder reaction with the maleimide group are investigated by the model reaction. We are able to restructure the crosslinked polymer network by taking advantage of the thermal reversibility of the Diels–Alder linkage. After the post thermal treatment, the BET surface area of the polymer (CDAP-T) is greatly increased from 317 to 1038 m2 g−1. CDAP-T is functionalized with pyrene by bromination with N-bromosuccinimide and the subsequent substitution reaction with aminopyrene. The adsorption property of the pyrene-functionalized polymer for an aromatic dye is investigated using malachite green. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3646–3653
Co-reporter:Youngdo Kim, Jae Bum Jeon and Ji Young Chang
Journal of Materials Chemistry A 2012 vol. 22(Issue 45) pp:24075-24080
Publication Date(Web):26 Sep 2012
DOI:10.1039/C2JM34798A
We prepared a highly sensitive molecularly imprinted fluorescent sensor by using a CdSe quantum dot (QD) as a signal transducer and a mesoporous silica nanoparticle as an imprinting material. Bisphenol-A (BPA) was chosen as a model template, which is known as an endocrine disruptor. Binding sites were selectively formed between the pores and CdSe QDs were encapsulated in the pores of the mesoporous silica. QD-encapsulated, molecularly imprinted mesoporous silica (QD-MIMS) particles exhibited excellent molecular recognition properties in terms of both sensitivity and selectivity. Owing to the proximity of the binding sites to the QDs, a significant, concentration-sensitive fluorescence quenching was observed in the presence of BPA. QD-MIMS showed a linear Stern–Volmer relationship for BPA and its analogs. QD-MIMS had a much larger quenching constant for BPA (by more than ten times) than for BPA analogs, demonstrating the high selectivity of QD-MIMS.
Co-reporter:Min Soo Kim, Jae Bum Jeon and Ji Young Chang
Journal of Materials Chemistry A 2012 vol. 22(Issue 38) pp:20713-20718
Publication Date(Web):10 Aug 2012
DOI:10.1039/C2JM34188C
We prepared mesoporous silica particles with inner surfaces coated with carbonaceous materials. A functional mesoporous silica particle (FSP) having methoxy urethane moieties tethered to the pore wall was synthesized by the template method from tetraethoxysilane (TEOS) and an amphiphilic organotriethoxysilane bearing a thermally reversible urethane bond. The surfactant template molecules in the pores were extracted in methanol in the presence of HCl. An atom transfer radical polymerization (ATRP) initiator was selectively introduced onto the inner surface by the reaction of 2-hydroxyethyl-2-bromo-2-methylpropanoate with the methoxy urethane group. The ATRP of acrylonitrile was carried out inside the pores to yield polyacrylonitrile (PAN) grafted to the pore wall. Subsequent pyrolysis of PAN resulted in the formation of mesoporous silica particles with carbon-coated pore walls. The property changes in the inner surface were investigated by analyzing the hydrogen adsorption. Carbonized silica particles showed an improved hydrogen adsorption capacity of 1.26 wt% at 1 bar and 77 K compared to 0.46 wt% for FSP.
Co-reporter:Ho Lim, Min Chul Cha and Ji Young Chang
Polymer Chemistry 2012 vol. 3(Issue 4) pp:868-870
Publication Date(Web):16 Feb 2012
DOI:10.1039/C2PY00511E
Adamantane-based microporous polymers were prepared by Friedel–Crafts reaction of 1-bromoadamantane with benzene, biphenyl and terphenyl and then post-functionalized with 4-nitrobenzoyl chloride. At 298 K, the CO2 uptake capacity of the functionalized polymers was increased by 18–25%, owing to the interaction between the nitro group and CO2.
Co-reporter:Ho Lim;Min Chul Cha
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 13) pp:1385-1390
Publication Date(Web):
DOI:10.1002/macp.201200195
Abstract
Microporous polymers based on 1,3,5-triazine units are prepared by Friedel-Crafts reaction of 2,4,6-trichloro-1,3,5-triazine with aromatic compounds. 2,4,6-Trichloro-1,3,5-triazine is polymerized with benzene, biphenyl, and terphenyl in dichloromethane in the presence of aluminum chloride. The surface areas of the polymers are in the range of 558 to 1266 m2 g−1, depending on the aromatic linker length. At ambient pressure and temperature, the polymers exhibit high CO2 uptakes of 38–51 cm3 g−1. The CO2 uptake is significantly enhanced by 70–90% for the polymers carbonized at 400 °C for 1 h and at 800 °C for an additional 1 h under nitrogen. This result suggests that rigid microporous polymers can be used as precursor polymers for the synthesis of advanced porous carbon materials without the activation process.
Co-reporter:Hyungwoo Kim;Youngdo Kim
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 23) pp:4990-4994
Publication Date(Web):
DOI:10.1002/pola.26314
Co-reporter:Min Soo Kim and Ji Young Chang
Journal of Materials Chemistry A 2011 vol. 21(Issue 24) pp:8766-8771
Publication Date(Web):12 May 2011
DOI:10.1039/C1JM10440C
The mesoporous silica particle has three different areas as a functionalization site, including an outer surface, a silica framework and an inner surface. We functionalized the inner surface selectively using an amphiphilic silica precursor with latent amine functionality and prepared a multifunctional mesoporous silica particle showing fluorescence resonance energy transfer (FRET). An organotriethoxysilane consisting of a perylene diimide unit and two triethoxysilyl groups was co-condensed with tetraethoxysilane and the amphiphilic organotriethoxysilane [(4-octylphenyl-3-(triethoxysilyl)propylcarbamate)] in the presence of cetyltrimethylammonium bromide under basic conditions. The resulting periodic mesoporous silica particle contained perylene diimide units in a silica framework as a FRET donor. The hydrophobic part of the amphiphile was tethered to the pore wall through a thermally reversible urethane bond. The surfactant molecules were extracted by reflux in a mixture of 1,4-dioxane, HCl and water. In this process, hydrophobic groups in the pore were also removed to produce amino groups on the inner surface. The rhodamine units were introduced into the pore as a FRET acceptor by the reaction of the isothiocyanate group of Rhodamine B isothiocyanate with the amino group on the inner surface, forming a thiourea linkage. The outer surface of the silica particle could be also functionalized by grafting with 3-(trimethoxysilyl)propyl acrylate before extraction of the surfactant molecules. A silica–polymer thin film was prepared where the silica particles were embedded in a poly(2-hydroxyethyl methacrylate) matrix. Both the suspension of the silica particles in ethanol and their polymer composite film showed the efficient FRET effect.
Co-reporter:Woo Jin Kim, Byung Mun Jung, Suk Hoon Kang and Ji Young Chang
Soft Matter 2011 vol. 7(Issue 9) pp:4160-4162
Publication Date(Web):24 Mar 2011
DOI:10.1039/C1SM05166K
Molecularly imprinted organogel nanofibers were prepared using a polymerizable organogelator. A functional monomer having a similar structure to the organogelator was used for complexation with the template. The imprinted nanofibers showed a specific binding property for the template and a fast kinetic binding profile.
Co-reporter:Hyungwoo Kim and Ji Young Chang
Soft Matter 2011 vol. 7(Issue 18) pp:7952-7955
Publication Date(Web):21 Jul 2011
DOI:10.1039/C1SM05669G
A trimetallic disc-like europium(III) complex having an organogelation and film-forming property was prepared. The complex showed a much higher PL intensity of the 5D0 → 7F2 transition in the gel state than in the solution state at the same concentration (1 wt%).
Co-reporter:Woo Jin Kim, Ji Young Chang
Materials Letters 2011 Volume 65(Issue 9) pp:1388-1391
Publication Date(Web):15 May 2011
DOI:10.1016/j.matlet.2011.02.010
An estrone imprinted polyimide nanofiber mat was prepared by using an electrospinning method. The diamine monomer–template complex was synthesized by the reaction of the diamine monomer having an isocyanate group and estrone (template) having a phenol moiety, in which the template was attached to the monomer via a thermally reversible urethane bond. A poly(amic acid) was synthesized by polymerization of the diamines (1:19 mole ratio of the diamine monomer–template complex to 4,4′-oxydianiline) and pyromellitic dianhydride in N,N-dimethylformamide and the reaction solution was used for electrospinning. The poly(amic acid) fibers were thermally imidized and then heated in 1,4-dioxane in the presence of water to remove the template molecules. The imprinted polyimide nanofibers showed the specific recognition ability and fast kinetic adsorption for estrone.
Co-reporter:Hyunpyo Lee;Jun Beum Park
Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/pola.24720
Abstract
Core-shell structured nanoparticles of poly(ethylene glycol) (PEG)/polypeptide/poly(D,L-lactide) (PLA) copolymers were prepared and their properties were investigated. The copolymers had a poly(L-serine) or poly(L-phenylalanine) block as a linker between a hydrophilic PEG and a hydrophobic PLA unit. They formed core-shell structured nanoparticles, where the polypeptide block resided at the interface between a hydrophilic PEG shell and a hydrophobic PLA core. In the synthesis, poly(ethylene glycol)-b-poly(L-serine) (PEG-PSER) was prepared by ring opening polymerization of N-carboxyanhydride of O-(tert-butyl)-L-serine and subsequent removal of tert-butyl groups. Poly(ethylene glycol)-b-poly(L-phenylalanine) (PEG-PPA) was obtained by ring opening polymerization of N-carboxyanhydride of L-phenylalanine. Methoxy-poly(ethylene glycol)-amine with a MW of 5000 was used as an initiator for both polymerizations. The polymerization of D,L-lactide by initiation with PEG-PSER and PEG-PPA produced a comb-like copolymer, poly(ethylene glycol)-b-[poly(L-serine)-g-poly(D,L-lactide)] (PEG-PSER-PLA) and a linear copolymer, poly(ethylene glycol)-b-poly(L-phenylalanine)-b-poly(D,L-lactide) (PEG-PPA-PLA), respectively. The nanoparticles obtained from PEG-PPA-PLA showed a negative zeta potential value of −16.6 mV, while those of PEG-PSER-PLA exhibited a positive value of about 19.3 mV. In pH 7.0 phosphate buffer solution at 36 °C, the nanoparticles of PEG/polypeptide/PLA copolymers showed much better stability than those of a linear PEG-PLA copolymer having a comparable molecular weight. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Co-reporter:Ho Lim and Ji Young Chang
Journal of Materials Chemistry A 2010 vol. 20(Issue 4) pp:749-754
Publication Date(Web):23 Nov 2009
DOI:10.1039/B920203J
We prepared thermally stable, low dielectric polymers by thermal polymerization of cyclotriphosphazenes bearing acetylene or styrene groups. Homosubstituted cyclotriphosphazene 1, containing acetylene groups, was synthesized by reaction of hexachlorocyclotriphosphazene with sodium salts of 4′-trimethylsilylethynyl-1,1′-biphenyl-4-ol and subsequent removal of trimethylsilyl groups under basic conditions. Heterosubstituted cyclotriphosphazene 2 was prepared using 4-phenylphenol as a cosubstituent. Cyclotriphosphazene 3 with styrene groups was prepared by reaction of hexachlorocyclotriphosphazene with sodium salts of 4-hydroxystyrene. Highly cross-linked polymers were obtained by thermal polymerization of the cyclotriphosphazenes at 200 °C for 1 and 2 and at 150 °C for 3. The 5% weight loss temperatures of the cross-linked polymers of compounds 1–3, measured by TGA, were above 470 °C. The flame-retardant property of the polymers was evaluated by measuring LOI (limiting oxygen index) values. The polymers of cyclotriphosphazenes 1–3 showed very high LOI values of 52, 50 and 49, respectively. We also prepared copolymers of cyclotriphosphazene 3 with styrene by UV irradiation in the presence of a photoinitiator (2,2-dimethoxy-2-phenylacetophenone). In the TGA thermograms, the copolymers showed good thermal stability, nearly comparable to the homopolymer of 3 when the composition of 3 was higher than 60%. The dielectric properties of the polymers were measured by a metal–insulator–metal method. The polymer obtained from acetylene-containing cyclotriphosphazene 1 showed dielectric constant and dielectric loss values of about 3.12 and 0.0016, respectively, at 1 GHz. The polymer of cyclotriphosphazene 3 showed a dielectric constant of 2.4 and a dielectric loss of 0.0014 at 1 GHz.
Co-reporter:Byung Mun Jung, Min Soo Kim, Woo Jin Kim and Ji Young Chang
Chemical Communications 2010 vol. 46(Issue 21) pp:3699-3701
Publication Date(Web):14 Apr 2010
DOI:10.1039/C003173A
We used periodic mesoporous silica particles for molecular imprinting. The imprinted silica particles showed fast kinetic binding for the template due to their nanosized wall thickness and high surface area.
Co-reporter:Hyukkeun Oh, Byung Mun Jung, Hyun Pyo Lee, Ji Young Chang
Journal of Colloid and Interface Science 2010 Volume 352(Issue 1) pp:121-127
Publication Date(Web):1 December 2010
DOI:10.1016/j.jcis.2010.08.025
We prepared hybrid organogels, where single walled carbon nanotubes (SWNTs) were incorporated into organogel fibers. The SWNTs were covalently functionalized with organic branches that had a similar structure to the organogelator. The effect of relative interactions between the carbon nanotubes (CNTs), organogelator, and solvent molecules on the hybrid organogel structure was investigated. Compounds 1 and 2 were synthesized from 3,4,5-tris(decyloxy)benzoic acid and 1,8-diaminooctane, as an organogelator and a functional group for SWNTs, respectively. Organogelator 1 showed excellent ability to gelate alkanes and alcohols. The pristine SWNTs were oxidized by acids to create carboxylic acid groups and functionalized covalently with compound 2 using thionyl chloride. Hybrid organogels of compound 1 with functionalized SWNTs (f-SWNTs) were prepared in decane and N,N-dimethylformamide (DMF). Transmission electron microscopy (TEM) images showed that the f-SWNTs in the hybrid organogel formed in decane were mainly located inside or on the surface of the organogel fibers, while the f-SWNTs in the hybrid organogel formed in DMF were distributed evenly over the sample. When an organogelator had a different chemical structure to that of an organic functional group on the SWNT surface, SWNTs existed as large aggregates, or long bundles, which were not incorporated inside of the organogel fibers.Graphical abstractHybrid organogels were prepared, where single walled carbon nanotubes (SWNTs) were incorporated into organogel fibers.Research highlights► Hybrid organogels bearing SWNTs mainly in gel fibers are prepared. ► Dispersion of SWNTs in organogels changes the gel properties. ► A gel-to-sol transition temperature is influenced by a dispersion structure of SWNTs.
Co-reporter:Yoon Sung Kwon, Byung Mun Jung, Hyunpyo Lee and Ji Young Chang
Macromolecules 2010 Volume 43(Issue 12) pp:5376-5381
Publication Date(Web):May 26, 2010
DOI:10.1021/ma1003198
Polymeric carbon nanotube (CNT)−liquid crystal composites were prepared using single-walled CNTs (SWNTs) and a polymerizable surfactant (dodecyldimethylammonium ethyl methacrylate, DDAM). The pristine SWNTs were dispersed in a lyotropic liquid crystal (LC) of DDAM (70 wt % in water). The bare lyotropic LC of DDAM and the dispersions showed columnar hexagonal phases. In X-ray diffraction analysis, the d-spacings were increased as the pristine SWNT concentration was increased up to 0.15 wt %, indicating that the pristine nanotubes were well incorporated in the hexagonal LC phase where they induced a swelling of the structure. The dispersions were photopolymerized to give polymeric composites. With increasing pristine SWNT concentration, the electrical resistivities of the composites continuously decreased, while their dielectric constants increased. The method reported herein provides a facile way to prepare a polymeric CNT−LC composite that combines the properties of both LCs and SWNTs.
Co-reporter:Ho Lim and Ji Young Chang
Macromolecules 2010 Volume 43(Issue 17) pp:6943-6945
Publication Date(Web):August 9, 2010
DOI:10.1021/ma101361b
Co-reporter:Seung Cheol Lee and Ji Young Chang
Macromolecules 2009 Volume 42(Issue 14) pp:5402-5405
Publication Date(Web):June 24, 2009
DOI:10.1021/ma900405t
Co-reporter:SangHyuk Seo, JunHa Park and JiYoung Chang
Langmuir 2009 Volume 25(Issue 15) pp:8439-8441
Publication Date(Web):March 13, 2009
DOI:10.1021/la804319e
We prepared 1H-imidazolecarboxamide amphiphiles as potential organogelators. Compounds A1−A3, in which an imidazole head was connected to a hydrophobic trialkyloxyphenyl group, showed an ability to gelate nonpolar solvents, including alkanes. The dry gels obtained from compounds A1−A3 had columnar hexagonal structures. Polycatenar 1H-imidazolecarboxamide amphiphile B2, consisting of a 1H-imidazole head connected through a benzene ring to a tridecyloxyphenyl tail, formed an organogel in DMSO. In a concentrated THF solution (30 wt %), compound B2 exhibited a lyotropic liquid-crystalline phase with a columnar hexagonal structure. X-ray diffraction (XRD) results suggested a molecular arrangement consisting of a disk, via hydrogen bonding between successive imidazole moieties, and an assembly of columnar structures.
Co-reporter:Young Taek Oh;Woo Jin Kim;Sang Hyuk Seo
Macromolecular Research 2009 Volume 17( Issue 2) pp:84-90
Publication Date(Web):2009 February
DOI:10.1007/BF03218659
We prepared side-chain liquid crystalline polymers comprising two monomeric units, one having a mesogenic side group that could form a smectic mesophase and the other having a phenolic group attached to the polymer backbone via a thermally reversible urethane bond. The urethane linkage between the isocyanate and phenol groups was stable at room temperature, but it cleaved to generate an isocyanate group when the temperature was increased. When annealed, the copolymers in their smectic mesophases became insoluble in common organic solvents, suggesting the formation of network structures. XRD analysis showed that the annealed polymers maintained their smectic LC structures. The crosslinking process probably proceeded via the reaction of the dissociated isocyanate groups. Some of the isocyanate groups would have first reacted with moisture in the atmosphere to yield amino groups, which underwent further reaction with other isocyanate groups, resulting in the formation of urea bonds. We presume that only polymer chains in the same layer were crosslinked by the reaction of the isocyanate groups, resulting in the formation of a layered polymer network structure. Reactions between the layers did not occur because of the wide layer spacing.
Co-reporter:Seung Cheol Lee
Macromolecular Research 2009 Volume 17( Issue 7) pp:522-527
Publication Date(Web):2009 July
DOI:10.1007/BF03218901
A photocrosslinkable polyphosphazene was used for molecular imprinting. We synthesized polyphosphazene (3) having urea groups for complexation withN-carbobenzyloxyglycin (Z-Gly-OH, template) and chalcone groups for cross-linking reaction. As substituents, 4-hydroxychalcone (1) andN-(4-hydroxyphenyl)-N’-ethylurea (2) were prepared. Choloro groups of poly(dichlorophosphazene) were replaced by the sequential treatment with sodium salts of compounds 1 and 2, and trifluoroethanol. The template molecule was complexed with the urea groups on the polymer chains via hydrogen bonding. A thin polymer film was prepared by casting a solution of the complex of polymer 3 and the template in dimethylformamide on a quartz cell and irradiated with 365 nm UV light to yield a cross-linked film with a thickness of about 16 ώm. The template molecules in the film were removed by Soxhlet extraction with methanol/acetic acid. The control polymer film was prepared in the same manner for the preparation of the imprinted polymer film, except that the template and triethylamine were omitted. In the rebinding test, the imprinted film exhibited much higher recognition ability for the template than the control polymer. We also investigated the specific recognition ability of the imprinted polymer for the template and its structural analogues. The rebinding tests were conducted using Z-Glu-OH, Z-Asp(OtBu)-OH, and Z-Glu-OMe. The imprinted film showed higher specific recognition ability for the template and the lowest response for Z-Asp(OtBu)-OH.
Co-reporter:Suk Hoon Kang, Byung Mun Jung, Woo Jin Kim and Ji Young Chang
Chemistry of Materials 2008 Volume 20(Issue 17) pp:5532
Publication Date(Web):August 9, 2008
DOI:10.1021/cm800867b
We demonstrate the embedding of nanofibers in a polymer matrix through the polymerization of an organogel. A series of organogelators based on a biphenyl ester having two different polymerizable groups, namely, acryl and diacetylene groups, are prepared. The resulting heterobifunctional gelators show the ability to gelate various monomeric solvents. The photopolymerization of an organogel of a heterobifunctional gelator (1.5 or 10 wt %), formed in hexyl methacrylate (HMA), is carried out by UV irradiation in the presence of 2,2-dimethoxy-2-phenylacetophenone (photoinitiator, 4 wt %). The polymerization of HMA forms a polymer matrix, while the polymerization of the acryl and diacetylene groups of the gelator forms the nanofibers with a cross-linked structure. The copolymerization of a gelator and HMA at the interface will improve the adhesion between the nanofiber and the polymer matrix. The polymerized gels appear yellowish and exhibit strong fluorescence when irradiated with 365 nm UV light. This is due to the presence of polydiacetylene chains. The fluorescent polydiacetylene nanofibers embedded in the polymer matrix are visualized by using confocal laser scanning microscopy. The thermal and mechanical properties of the nanofibers embedded in polyHMA are investigated using differential scanning calorimetry, dynamic mechanical analysis, and a universal testing machine. The polymerized gels show improved thermal and physical properties in comparison to the matrix polymer (polyHMA).
Co-reporter:Beom Jin Kim;Dong Kung Oh
Macromolecular Research 2008 Volume 16( Issue 2) pp:103-107
Publication Date(Web):2008 February
DOI:10.1007/BF03218837
Carbon nanodots were prepared by the pyrolysis of a triblock copolymer. The triblock copolymer, poly(methyl methacrylate)-b-polystyrene-b-poly(methyl methacrylate) was synthesized by atom transfer radical polymerization using an initiator containing a diacetylene group. A polymer thin film on a mica substrate was prepared by spin-casting at 2,000 rpm from a 0.5 wt% toluene solution of the triblock copolymer. After drying, the cast film was vacuum-annealed for 48 h at 160 °C. The annealed film formed a spherical morphology of polystyrene domains with a diameter of approximately 30 nm. The film was exposed to UV irradiation to induce a cross-linking reaction between diacetylene groups. In the subsequent pyrolysis at 800 °C, the cross-linked polystyrene spheres were carbonized and the poly(methyl methacrylate) matrix was eliminated, resulting in carbon nanodots deposited on a substrate with a diameter of approximately 5 nm.
Co-reporter:Hyeoncheol Song;Seung Cheol Lee;Hye Young Heo;Dong Il Kim;Dong-Hwal Lee;Ju Ho Lee
Journal of Polymer Science Part A: Polymer Chemistry 2008 Volume 46( Issue 17) pp:5850-5858
Publication Date(Web):
DOI:10.1002/pola.22900
Abstract
We prepared sulfonated polyphosphazenes having various aryloxy substituents, and studied their thermal stabilities and membrane properties. Sulfonated polyphosphazenes were synthesized by the reaction of polydichlorophosphazene with sodium aryloxides and subsequent sulfonation with fuming sulfuric acid. With increasing the degree of sulfonation, the polymers showed higher proton conductivity, but suffered more from swelling in an aqueous solution. We introduced a hydroxymethylphenoxy group onto the phosphazene backbone as a self-crosslinkable group by reaction of poly(dichlorophosphazene) and a sodium salt of 4-hydroxymethylphenol. When a film of a sulfonated polymer having a methylol group was heated at 80 °C under vacuum for 1 h, it became insoluble in NMP, indicating the formation of a network structure. We investigated the crosslinking reaction of the polymers by DSC and FTIR. The crosslinking reaction proceeded only in the sulfonated polymers. Because the sulfonated polymers provide acidic protons, the methylol groups became more electrophilic and reacted with neighboring aromatic rings. A condensation reaction between themselves could also occur. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5850–5858, 2008
Co-reporter:Hye Jin Park, Junkyung Kim, Ji Young Chang and Patrick Theato
Langmuir 2008 Volume 24(Issue 18) pp:10467-10473
Publication Date(Web):August 21, 2008
DOI:10.1021/la801341t
A mutilayered film was prepared by layer-by-layer (LBL) assembly of active ester modified multiwalled carbon nanotubes (MWCNTs) and poly(allylamine hydrochloride) (PAH). For this purpose, carboxylic groups on the surface of the oxidized MWCNTs were converted to the acyl chlorides by their reaction with thionyl chloride. Subsequent reaction of the acyl chlorides with pentafluorophenol formed the active esters. These active ester modified MWCNTs (MWCNTs-COOC6F5) were air-stable and moisture resistant, but showed a high reactivity toward primary or secondary amines resulting in amide bonds. For the preparation of a multilayered film, the surface of a quartz slide was first activated and sacrificial double layers of PAH and poly(sodium 4-styrene sulfonate) (PSS) were deposited. Subsequently, LBL assembly of MWCNTs-COOC6F5 and PAH was then conducted on these double layers [(PAH/PSS)2]. In the process of the assembly, a reaction occurred between the active ester on the surface of MWCNTs and the amine groups of polyallylamine yielding amide bonds, which resulted in a mechanically stable thin film. A free-standing film was obtained after dissolving the sacrificial layer [(PAH/PSS)2] in a concentrated aqueous NaOH solution. The surface resistance of the multilayered film with 20 bilayers decreased to around 10 kΩ while remaining a reasonable transparency (70% at 500 nm).
Co-reporter:J. Y. Chang;B. M. Jung;S. H. Kang
Advanced Materials 2007 Volume 19(Issue 19) pp:2780-2784
Publication Date(Web):21 AUG 2007
DOI:10.1002/adma.200700117
A hetero-bifunctional gelator composed of two different polymerizable groups, acryl and diacetylene, and used to gelate an acrylic monomer has been prepared. The photopolymerization of the organogel formed in hexyl methacrylate produces a free-standing film, in which fluorescent polydiacetylene nanofibers are embedded in a poly(hexyl methacrylate) matrix (see figure).
Co-reporter:Sang Woon Nam;Suk Hoon Kang
Macromolecular Research 2007 Volume 15( Issue 1) pp:74-81
Publication Date(Web):2007 February
DOI:10.1007/BF03218755
A series of photoreactive mesogens based on chalcone were prepared and their morphological behavior and reactivity were studied according to a variable number of alkyloxy tail carbons. The linear ester compounds3a-h comprised two chalcone units connected to a benzene ring through ester linkages. All linear ester compounds showed enantiotropic liquid crystalline phases. The X-ray diffractograms for the mesophases of compounds3a-h showed a set of reflections in the small-angle region which consisted of more than three sharp diffraction peaks with d spacings in the ratio of 1∶1/2∶1/3, confirming the well defined smectic A structures of the compounds. Compounds3a-h were considered to be bifunctional monomers due to the presence of two photoreactive chalcone groups. Upon UV irradiation, its polymerization proceeded through the [2+2] addition reaction between chalcone units in a stepwise manner. An image pattern was obtained by the photopolymerization of the liquid crystal of the compound (3h) with decyloxy tails through a photomask. The irradiated part became dark while the masked part remained birefringent under polarized optical microscopy, which was ascribed to the production via the UV irradiation of a polymer or a dimer having cyclobutane rings by [2+2] addition, which thereby disrupted the alignment of the molecules.
Co-reporter:Sang Hyuk Seo, Gregory N. Tew and Ji Young Chang
Soft Matter 2006 vol. 2(Issue 10) pp:886-891
Publication Date(Web):22 Aug 2006
DOI:10.1039/B606870G
Polycatenar 1H-imidazole amphiphiles, consisting of a 1H-imidazole head connected through a benzene ring to a trialkyloxyphenyl tail, were synthesized and their self-assembling properties investigated. The 1H NMR and fluorescence spectroscopy studies showed that in nonpolar solvents, the amphiphiles formed reverse micelles in which the hydrophilic imidazole heads aggregated inside the micelles through intermolecular hydrogen bonding and the nonpolar alkyl chains were located at the periphery of the micelles. In concentrated solutions, they formed lyotropic liquid crystals having columnar hexagonal structures. The molecules were arranged in a disk via hydrogen bonding between successive imidazole moieties. When dilute solutions of the amphiphiles in n-hexane (0.1 wt%) were spin-coated on to a plasma-cleaned Si wafer, a band-like structure with a width of 60–100 nm was imaged by AFM. Microscopic fiber bundles with a diameter as large as 13 µm were observed by SEM when the lyotropic liquid crystals in 30 wt% hexane solution were dried on the glass.
Co-reporter:C. D. Ki;T. Emrick;J. Y. Chang
Advanced Materials 2005 Volume 17(Issue 2) pp:
Publication Date(Web):25 JAN 2005
DOI:10.1002/adma.200400184
Nanoporous silica–quantum dot composites are produced using an amphiphilic organotrialkoxysilane containing a thermally reversible urethane moiety. Nanoporous silica is formed by co-condensation of the amphiphile and a silicate precursor (see Figure). After heating, the urethane dissociates to form an isocyanate group tethered to the silica. This can be used to make thiol-functionalized nanoporous silica that can encapsulate cadmium selenide nanoparticles.
Co-reporter:Tae Jin Choi, Do Yeon Kim, Ji Young Chang
Microporous and Mesoporous Materials (April 2017) Volume 242() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.micromeso.2017.01.007
•A microporous polymer composite showed water wettability and compressibility.•The polymer composite had a hierarchical pore structure.•The polymer composite was used for fast removal of a pollutant in an aqueous solution.Compressible and hierarchically porous polymer composite (PUS-MOP-A) was prepared by carrying out Sonogashira-Hagihara coupling reaction of 1,3,5-triethynyl benzene, 1.4-diiodobenzene and 2,5-diiodobenzoic acid in a polyurethane sponge (PUS). 2,5-Diiodobenzoic acid was used as a co-monomer to provide acidic functionality to the pore surface. The microporous organic polymer (MOP-A) formed inside the PUS network showed fibrous morphology when 1,4-diiodobenzene was used as a major aryl halide. For the synthesis of PUS-MOP-A, the molar ratio between 1,4-diiodobenzene and 2,5-diiodobenzoic acid was chosen as 4:1. The Brunauer-Emmett-Teller (BET) surface area of PUS-MOP-A was 306 m2 g-1. PUS-MOP-A was treated with KOH, which converted the carboxyl groups on the MOP-A backbone to the carboxylate anions. The resulting polymer composite (PUS-MOP-Aa) absorbed water quickly, showing a water contact angle of 0°. Adsorption ability of PUS and PUS-MOP-Aa to remove chemical pollutants in an aqueous solution was studied using a cationic dye, Methylene Blue (MB) and an anionic dye, Methylene Orange (MO) as a model chemical. PUS-MOP-Aa could be manually compressed and released in an aqueous solution of MB, resulting in the fast dye removal. When an aqueous solution contained both the anionic and the cationic dye, PUS-MOP-Aa preferentially removed the cationic dye. PUS-MOP-Aa was recyclable after removing the adsorbed dyes by treating with an acid and washing.
Co-reporter:Hyunpyo Lee, Hyungwoo Kim, Tae Jin Choi, Hyun Woo Park and Ji Young Chang
Chemical Communications 2015 - vol. 51(Issue 48) pp:NaN9808-9808
Publication Date(Web):2015/05/07
DOI:10.1039/C5CC02269J
A microporous polymer with sulfide and thiol groups was synthesized using the thiol–yne reaction. Au nanoparticles were prepared by in situ reduction reaction inside the polymer and were found to be well dispersed. The Au-containing polymer showed catalytic activity in the reduction of 4-nitrophenol.
Co-reporter:Min Soo Kim and Ji Young Chang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 24) pp:NaN8771-8771
Publication Date(Web):2011/05/12
DOI:10.1039/C1JM10440C
The mesoporous silica particle has three different areas as a functionalization site, including an outer surface, a silica framework and an inner surface. We functionalized the inner surface selectively using an amphiphilic silica precursor with latent amine functionality and prepared a multifunctional mesoporous silica particle showing fluorescence resonance energy transfer (FRET). An organotriethoxysilane consisting of a perylene diimide unit and two triethoxysilyl groups was co-condensed with tetraethoxysilane and the amphiphilic organotriethoxysilane [(4-octylphenyl-3-(triethoxysilyl)propylcarbamate)] in the presence of cetyltrimethylammonium bromide under basic conditions. The resulting periodic mesoporous silica particle contained perylene diimide units in a silica framework as a FRET donor. The hydrophobic part of the amphiphile was tethered to the pore wall through a thermally reversible urethane bond. The surfactant molecules were extracted by reflux in a mixture of 1,4-dioxane, HCl and water. In this process, hydrophobic groups in the pore were also removed to produce amino groups on the inner surface. The rhodamine units were introduced into the pore as a FRET acceptor by the reaction of the isothiocyanate group of Rhodamine B isothiocyanate with the amino group on the inner surface, forming a thiourea linkage. The outer surface of the silica particle could be also functionalized by grafting with 3-(trimethoxysilyl)propyl acrylate before extraction of the surfactant molecules. A silica–polymer thin film was prepared where the silica particles were embedded in a poly(2-hydroxyethyl methacrylate) matrix. Both the suspension of the silica particles in ethanol and their polymer composite film showed the efficient FRET effect.
Co-reporter:Byung Mun Jung, Min Soo Kim, Woo Jin Kim and Ji Young Chang
Chemical Communications 2010 - vol. 46(Issue 21) pp:NaN3701-3701
Publication Date(Web):2010/04/14
DOI:10.1039/C003173A
We used periodic mesoporous silica particles for molecular imprinting. The imprinted silica particles showed fast kinetic binding for the template due to their nanosized wall thickness and high surface area.
Co-reporter:Jeongmin Lee and Ji Young Chang
Chemical Communications 2016 - vol. 52(Issue 68) pp:NaN10422-10422
Publication Date(Web):2016/07/27
DOI:10.1039/C6CC04817J
A compressible and monolithic microporous polyimide sponge was prepared from an aliphatic tetracarboxylic dianhydride and an aromatic triamine. The sponge had a hierarchical pore structure, in which spherical microporous polyimide particles were interconnected to form a macroscopic network. It showed an amphiphilic character, because of the balanced presence of hydrophobic and hydrophilic groups.
Co-reporter:Yoonbin Lim, Insil Choi, Hyunpyo Lee, Il Won Kim and Ji Young Chang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 29) pp:NaN5968-5968
Publication Date(Web):2014/05/21
DOI:10.1039/C4TC00822G
The piezochromic behaviours of C3-symmetric molecules with p-bromophenyl side groups connected to a phenyl ring core through cyano-vinylene bridges were studied. Upon grinding, α-BPAN-Br having cyano groups at the α-position to the phenyl ring core exhibited substantial quenching of a bluish green emission (on–off switching) and its constitutional isomer, β-BPAN-Br, showed an emission colour change from bluish green to deep blue (colour tuning). When the molecules were exposed to an organic vapour, the initial emission of each molecule was restored. The powder X-ray diffraction and DSC studies revealed that the as-synthesized and vapour-annealed samples had the same crystalline structures, while the ground samples had amorphous structures. Their structural analogues, α-BPAN-H and β-BPAN-H which had no bromo groups, did not show any piezochromic or vapochromic behaviour. Poly(β-BPAN) consisting of covalently linked β-BPAN units were prepared by Ullmann reaction of β-BPAN-Br. The polymer showed similar luminescence to that of crystalline β-BPAN-Br, but its initial emission was not changed by grinding.
Co-reporter:Min Soo Kim, Jae Bum Jeon and Ji Young Chang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 38) pp:NaN20718-20718
Publication Date(Web):2012/08/10
DOI:10.1039/C2JM34188C
We prepared mesoporous silica particles with inner surfaces coated with carbonaceous materials. A functional mesoporous silica particle (FSP) having methoxy urethane moieties tethered to the pore wall was synthesized by the template method from tetraethoxysilane (TEOS) and an amphiphilic organotriethoxysilane bearing a thermally reversible urethane bond. The surfactant template molecules in the pores were extracted in methanol in the presence of HCl. An atom transfer radical polymerization (ATRP) initiator was selectively introduced onto the inner surface by the reaction of 2-hydroxyethyl-2-bromo-2-methylpropanoate with the methoxy urethane group. The ATRP of acrylonitrile was carried out inside the pores to yield polyacrylonitrile (PAN) grafted to the pore wall. Subsequent pyrolysis of PAN resulted in the formation of mesoporous silica particles with carbon-coated pore walls. The property changes in the inner surface were investigated by analyzing the hydrogen adsorption. Carbonized silica particles showed an improved hydrogen adsorption capacity of 1.26 wt% at 1 bar and 77 K compared to 0.46 wt% for FSP.
Co-reporter:Geo San Lim, Hyungwoo Kim and Ji Young Chang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 47) pp:NaN10188-10188
Publication Date(Web):2014/10/08
DOI:10.1039/C4TC01493F
We report a photosensitive, double-layered anti-reflection film, which is composed of a UV cured acrylate film containing a photoluminescent europium(III) complex as a high refractive index layer and a film of a colloidal nano-silica as a low refractive index layer. The refractive index of the high refractive index layer can be tuned from 1. 53 to 1.69 as the composition of the europium(III) complex increases. The reflectance of the anti-reflection film on the glass substrate is as low as 0.48% when the refractive indices and thicknesses of the two layers are controlled. The anti-reflection film is applied as the top layer of a liquid crystal display (LCD). Since the absorption and excitation spectra of the europium(III) complex barely overlap with the backlight spectrum of the LCD, the europium(III) complex in the anti-reflection film does not disturb the display images. The images are visible even under irradiation using an indoor fluorescent lamp. It is also possible to highlight a specific point on the display screen using laser light. When a 405 nm laser pointer is aimed at a specific area, the area appeared as a bright red spot.
Co-reporter:Ho Lim and Ji Young Chang
Journal of Materials Chemistry A 2010 - vol. 20(Issue 4) pp:NaN754-754
Publication Date(Web):2009/11/23
DOI:10.1039/B920203J
We prepared thermally stable, low dielectric polymers by thermal polymerization of cyclotriphosphazenes bearing acetylene or styrene groups. Homosubstituted cyclotriphosphazene 1, containing acetylene groups, was synthesized by reaction of hexachlorocyclotriphosphazene with sodium salts of 4′-trimethylsilylethynyl-1,1′-biphenyl-4-ol and subsequent removal of trimethylsilyl groups under basic conditions. Heterosubstituted cyclotriphosphazene 2 was prepared using 4-phenylphenol as a cosubstituent. Cyclotriphosphazene 3 with styrene groups was prepared by reaction of hexachlorocyclotriphosphazene with sodium salts of 4-hydroxystyrene. Highly cross-linked polymers were obtained by thermal polymerization of the cyclotriphosphazenes at 200 °C for 1 and 2 and at 150 °C for 3. The 5% weight loss temperatures of the cross-linked polymers of compounds 1–3, measured by TGA, were above 470 °C. The flame-retardant property of the polymers was evaluated by measuring LOI (limiting oxygen index) values. The polymers of cyclotriphosphazenes 1–3 showed very high LOI values of 52, 50 and 49, respectively. We also prepared copolymers of cyclotriphosphazene 3 with styrene by UV irradiation in the presence of a photoinitiator (2,2-dimethoxy-2-phenylacetophenone). In the TGA thermograms, the copolymers showed good thermal stability, nearly comparable to the homopolymer of 3 when the composition of 3 was higher than 60%. The dielectric properties of the polymers were measured by a metal–insulator–metal method. The polymer obtained from acetylene-containing cyclotriphosphazene 1 showed dielectric constant and dielectric loss values of about 3.12 and 0.0016, respectively, at 1 GHz. The polymer of cyclotriphosphazene 3 showed a dielectric constant of 2.4 and a dielectric loss of 0.0014 at 1 GHz.
Co-reporter:Youngdo Kim, Jae Bum Jeon and Ji Young Chang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 45) pp:NaN24080-24080
Publication Date(Web):2012/09/26
DOI:10.1039/C2JM34798A
We prepared a highly sensitive molecularly imprinted fluorescent sensor by using a CdSe quantum dot (QD) as a signal transducer and a mesoporous silica nanoparticle as an imprinting material. Bisphenol-A (BPA) was chosen as a model template, which is known as an endocrine disruptor. Binding sites were selectively formed between the pores and CdSe QDs were encapsulated in the pores of the mesoporous silica. QD-encapsulated, molecularly imprinted mesoporous silica (QD-MIMS) particles exhibited excellent molecular recognition properties in terms of both sensitivity and selectivity. Owing to the proximity of the binding sites to the QDs, a significant, concentration-sensitive fluorescence quenching was observed in the presence of BPA. QD-MIMS showed a linear Stern–Volmer relationship for BPA and its analogs. QD-MIMS had a much larger quenching constant for BPA (by more than ten times) than for BPA analogs, demonstrating the high selectivity of QD-MIMS.
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