Co-reporter:Xiaofeng Zhou, Zhipeng He, He Huang
Vibrational Spectroscopy 2017 Volume 92(Volume 92) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.vibspec.2017.08.001
Secondary structure transitions of Bovine Serum Albumin (BSA) in H2O and D2O under temperature variation were investigated by in-situ IR spectral analysis and they were found to exhibit the same tendency with the only difference that the significant transition temperature of BSA's secondary structure moved towards a lower temperature in D2O. Before this significant transition temperature, the native secondary structures of BSA were essentially changing in a cooperative fashion with temperature variation, except for the intermolecular β-sheet (high-wavenumber) which increased as a result of thermal denaturation at a later stage. After the transition temperature, the relative contents of α-helix and extended chain continued to drop sharply and they were transformed into random coil, β-turn and β-sheet.
Co-reporter:Yangzhi Xie
Journal of Applied Polymer Science 2016 Volume 133( Issue 36) pp:
Publication Date(Web):
DOI:10.1002/app.43910
ABSTRACT
On the basis of 2-hydroxyl-2-methyl-1-phenylpropanone (HMPP) and poly(ethylene glycol) (PEG), we prepared amphiphilic macrophotoinitiators (HMPP–PEG–HMPP) by first reacting HMPP with isophorone diisocyanate and subsequently reacting it with PEGs with different chain lengths. Fourier transform infrared spectroscopy, high-performance liquid chromatography, and 1H-NMR were used to confirm the structure of the amphiphilic macrophotoinitiators. Ultraviolet (UV) absorption spectra showed that the amphiphilic macrophotoinitiators had maximum absorption wavelengths that were similar to those of the low-molecular-weight photoinitiator HMPP. The photolysis rate of the amphiphilic macrophotoinitiators was slightly lower than that of HMPP, but the migration rate of the amphiphilic macrophotoinitiators from a UV-cured matrix was much lower compared to that of HMPP. Because of their amphiphilic nature, these macrophotoinitiators may play roles as both photoinitiators and emulsifiers, and they have been applied to the solution polymerization of water-soluble monomer acrylamide in water and the emulsion polymerization of methyl methacrylate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43910.
Co-reporter:Yue Wang;Zhipeng He;Qiong Liu
Journal of Applied Polymer Science 2015 Volume 132( Issue 39) pp:
Publication Date(Web):
DOI:10.1002/app.42598
ABSTRACT
Polymerizable epoxy resin (PER) surfactants have been prepared from the reaction of bisphenol A epoxy resin with acrylic acid, followed by the reaction with polyethylene glycol (PEG) with different molecular weights. The reaction procedures were monitored by chemical titrations, infrared spectroscopy, and NMR. The products show typical surface-active properties as but much higher water solubility than nonpolymerizable nonionic surfactant OP-10. With the increase of PEG's molecular weight, the HLB value, the water solubility, and the critical micellar concentration (CMC) of the PER surfactants, the cloud point of the PER surfactant solutions, as well as the solubilization capability of the PER surfactants to organic compounds increase under the experimental conditions. The copolymerization under UV radiation indicated that about 75–80 wt % of PER surfactants participated in the copolymerization with epoxy diacrylate (EdA), except for the PER surfactant with the lowest PEG molecular weight of 1 k. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42598.
Co-reporter:Tingting Zhao, Mei Tan, Yulin Cui, Chao Deng, He Huang and Mingyu Guo
Polymer Chemistry 2014 vol. 5(Issue 17) pp:4965-4973
Publication Date(Web):07 May 2014
DOI:10.1039/C4PY00554F
Highly stretchable hydrogels based on the micellar copolymerization technique often dissolve in water; they may also become fragile or not exhibit their initially good mechanical performance when submerged in large amounts of water. In addition, the shape-deformation and shape-recovery processes of most reported shape-memory hydrogels need to be carried out at high temperatures. As yet, there have been no published reports on hydrogels which are both highly resilient and have water-responsive shape-memory properties. In this work, a novel, highly elastic polyacrylamide-based hydrogel was developed based on the micellar copolymerization technique using a polymerizable macromolecular micelle with hydrophobic cores locked by hydrogen bonds as a multifunctional crosslinker. The equilibrium water-swelling micelle crosslinked hydrogels still showed highly stretchable behaviour (elongation at break >700%) and even better resilience (almost no hysteresis and residual strains) than the as-prepared hydrogels. Together with the advantages of the highly elastic properties of the hydrogels and the dehydration-induced glass transition of the polyacrylamide network, the hydrogels also have a water-responsive shape-memory behaviour, which can be realized under mild and “green” conditions, i.e., in air and water at room temperature.
Co-reporter:Chao Deng, Yulin Cui, Tingting Zhao, Mei Tan, He Huang and Mingyu Guo
RSC Advances 2014 vol. 4(Issue 46) pp:24095-24102
Publication Date(Web):12 May 2014
DOI:10.1039/C4RA02597K
Mechanically strong hydrogels have attracted much interest as a result of their potential applications as biomaterials. However, it is still a challenge to produce mechanically strong supramolecular hydrogels because of the inherently weak characteristics of non-covalent interactions. A novel polyurethane–urea supramolecular hydrogel with excellent mechanical properties was developed in our laboratory by chance during the preparation of a water-borne dispersion of polyurethane with an excess amount of –NCO groups. Subsequent studies showed that this mechanical strength was because of the slow formation of multi-urea linkages and further chain extension because of the reaction of water with the excess –NCO groups in the isocyanate prepolymer chains or the free diisocyanate, or both. The mechanical properties of the polyurethane–urea supramolecular hydrogels obtained can be adjusted by simply altering the diisocyanate content. The following ranges of properties were obtained: shear modulus, 0.2–0.8 MPa; elongation at breakage, 970–2420%; tensile strength, 3.3–34 MPa; and compression stress, up to 38 MPa. Further analysis showed that the elongation ratio and tensile stress at breakage linearly decreased and increased, respectively, with an increase in the ratio of the hard segment.
Co-reporter:Zhipeng He, Yue Wang, Tingting Zhao, Zichuan Ye and He Huang
Analytical Methods 2014 vol. 6(Issue 12) pp:4257-4261
Publication Date(Web):13 Mar 2014
DOI:10.1039/C4AY00439F
A relatively long time is required to determine the epoxide value of an epoxy resin or epoxy compound by chemical analysis (titration) methods, including the commonly used hydrochloric acid–acetone method, which may be referred to as the hydrochloric acid–acetone-standing method, because the mixture of epoxy resins or epoxy compounds, hydrochloric acid and acetone must be left standing in the dark for at least 30 min. In this study, ultrasonication was first introduced to this method, aiming to rapidly determine the epoxide value of an epoxy resin by accelerating the dissolution of epoxy resin in acetone solvent as well as the reaction between epoxide groups and hydrogen chloride. Further study of this approach was then carried out to determine the epoxide values of a series of epoxy resin–polyethylene glycol mixtures. This new approach which may be referred to as the hydrochloric acid–acetone-ultrasonication method provides a much faster and more accurate measurement of the epoxide value of an epoxy resin (within 2 min) or its mixture with polyethylene glycol (PEG-4000, within 5 min), compared to the hydrochloric acid–acetone-standing method. This ultrasonication method may be readily extended to other chemical analysis (titration) methods.
Co-reporter:Mei Tan, Tingting Zhao, He Huang and Mingyu Guo
Polymer Chemistry 2013 vol. 4(Issue 22) pp:5570-5576
Publication Date(Web):11 Jul 2013
DOI:10.1039/C3PY00745F
In order to overcome the poor mechanical property of classic hydrogels, many methods have been explored to prepare hydrogels with excellent performance during the last few decades. In this paper, we developed a novel micellar cross-linking copolymerization method without small molecular surfactants to prepare highly stretchable and resilient hydrogels. The polymerization is based on free-radical copolymerization of water soluble acrylamide and a polymerizable macromolecular surfactant (i.e., amphiphilic polyurethane (PU) macromonomer) which can self-assemble into micelles acting as multifunctional cross-linkers. The mechanical properties, such as breaking elongation ratio, modulus and fracture toughness can be easily adjusted by varying the concentration of the polymerizable macromolecular surfactants. In addition, the mechanical energy storage efficiency (also known as resilience) is more than 96% at a strain up to 400%. The high resilience of the obtained hydrogels is due to the reversible assembly of the hydrogen-bonded hydrophobe, which contributes to the dissipation of the crack energy along the hydrogel sample, inside the micelles within the gel network.
Co-reporter:He Huang, Xiaomin Ding, Chunlei Zhu, Zhipeng He, and Yibiao Yu
Analytical Chemistry 2013 Volume 85(Issue 4) pp:2161
Publication Date(Web):January 28, 2013
DOI:10.1021/ac3027355
Using a two-dimensional (2D) correlation analysis technique to determine the sequential order of physical or chemical events has received keen interests in the past ten years. However, our continuous work demonstrates that the sequential order of events determined by the “sequential order” rules of this technique may lead to ambiguous or even wrong conclusions, because the physical significance of the sequential order in generalized 2D correlation analysis is neither well-defined nor meaningful in general situations, and the word “occur” used in the “sequential order” rules may easily give rise to ambiguity. In contrast to the integrated sequential order derived from periodic changes as in mechanical perturbation based 2D correlation infrared spectroscopy, there is a local/chronological sequential order for nonperiodic changes in general situations. The current work shows that the integrated sequential order in 2D correlation analysis is a reflection of the sequential order of the phases, i.e., phase sequence/difference. The integrated sequential order may indicate the relative state of two events (one event occurs/exists before or after the other one) according to a specific reference, only if both are obtained under the same frequency for periodic changes or even speeds for nonperiodic changes in general situations. The integrated sequential order may not always be able to reveal whether one event occurs/happens before or after another one for nonperiodic changes in terms of timings of happenings. For nonperiodic changes, the integrated sequential order is not so meaningful and must be replaced by the local/chronological sequential order. To judge whether one event occurs/happens before or after another one for two nonperiodic changes in general situations, the original spectral intensity changes must be verified to determine if a chronological/local sequential order exists between two events.
Co-reporter:Yanli Su;Jian Song;Rui Liu
Journal of Electroceramics 2013 Volume 30( Issue 3) pp:166-171
Publication Date(Web):2013 May
DOI:10.1007/s10832-013-9779-y
High dielectric Na0.5Bi0.5Cu3Ti4O12 (NBCTO) ceramics were firstly prepared by co-precipitation method at low temperature. X-ray diffraction results revealed that pure phase of NBCTO was achieved by calcination at 950 °C for 2 h. Thermo-gravimetric analysis on a dried NBCTO precursor was carried out to study the thermal decomposition process. The microstructure and dielectric properties of NBCTO ceramics sintered at different temperatures were investigated. The results indicate that the sintering temperature has a sensitive influence on the microstructure and dielectric properties. Higher sintering temperature gave rise to increased dielectric constant and dielectric loss of NBCTO samples, and the sample sintered at 975 °C for 8 h exhibits high dielectric constant of 8.3 × 103 and low dielectric loss of 0.069 at 10 kHz. The dielectric properties were further discussed by the impedance spectroscopy.
Co-reporter:Yan-li Su;Cheng Sun;Wen-qin Zhang
Journal of Materials Science 2013 Volume 48( Issue 23) pp:8147-8152
Publication Date(Web):2013 December
DOI:10.1007/s10853-013-7627-8
Na0.5Bi0.5Cu3Ti4O12 (NBCTO)/poly(vinylidene fluoride) (PVDF) composites with various NBCTO volume fractions were prepared via solution mixing and hot pressing process. The structure, morphology, and dielectric properties of the composites were characterized with X-ray diffraction (XRD), thermal-gravimetric analysis (TGA), scanning electron microscope (SEM), and broadband dielectric spectrometer. The dielectric constant (ε) and dielectric loss (tan δ) of the composites were both found to increase with increasing NBCTO volume fraction within the frequency range of 1–106 Hz at room temperature. Relatively high dielectric constant of 79.8 and low loss of 0.21 at 1 kHz were obtained for the NBCTO/PVDF composite with 50 vol% NBCTO. Additionally, theoretical models like Logarithmic mixture rule, Maxwell–Garnet, Effective medium theory, and Yamada model were also employed to predict the dielectric constant of these composites. The values obtained by the EMT model are in close agreement with the experimental values.
Co-reporter:He Huang, Jing Xie and Hong Chen
Analyst 2011 vol. 136(Issue 8) pp:1747-1752
Publication Date(Web):25 Feb 2011
DOI:10.1039/C0AN00890G
The time-dependent adsorption behavior of human serum albumin (HSA) onto an ATR (ZnSe) crystal was investigated by two-dimensional (2D) correlation analysis and in situATR-FTIR spectroscopy following the secondary structural changes in the amide I region. The two major advantages of the generalized 2D correlation spectroscopy were first tested. New extra bands have been resolved by 2D correlation analysis, but they are either artifacts or a result of uncertainty on band position in generalized 2D correlation spectroscopy. The sequence of the intensity variations of the three sub-bands under the amide I band profile deduced from the ‘sequential order’ rules is contradictory to the experimental observation, which supports our argument on the ‘sequential order’ rules in generalized 2D correlation spectroscopy (H. Huang, Anal. Chem., 2007, 79, 8281–8292). Subsequent detailed analysis on the in situATR-IR spectra shows that the adsorption process of HSA on the ATR (ZnSe) crystal in aqueous solutions can be divided into three stages: no obvious conformational transitions in the first 25 min of adsorption of HSA molecules; large structural rearrangement from α-helix to random coil and short extended chain structures in a fully cooperative way from 25 to 50 min of adsorption; and further slight conformational transformation of short extended chain and turn structures into random coil with no sequential order after 50 min of adsorption.
Co-reporter: Dr. He Huang;Jing Xie ;Xiaoli Liu ; Dr. Lin Yuan ;Shasha Wang;Songxi Guo ;Haoran Yu; Dr. Hong Chen;Dr. Yanliang Zhang;Dr. Xiaohu Wu
ChemPhysChem 2011 Volume 12( Issue 18) pp:3642-3646
Publication Date(Web):
DOI:10.1002/cphc.201100398
Abstract
Changes in the bioactivity of a protein after being adsorbed on a material surface may result from conformational changes of the protein. Unfortunately, however, direct evidence of such conformational changes of proteins adsorbed on a flat material surface is sparse so far. This is because probing the conformation of an adsorbed protein on material surfaces, especially flat ones, remains a challenge due to considerable experimental difficulties. In this study, the surface-enhanced Raman scattering (SERS) technique is used to characterize the conformational changes of a protein (lysozyme) adsorbed on tailored flat gold substrates with different chemistries. Two such substrates are formed by self-assembly of octadecanethiol and thiolated PEG on gold chips (Au-C18 and Au-PEG). Preliminary results reveal that, compared to the hydrophobic Au-C18 surface, the hydrophilic Au-PEG surface has much smaller effect on the conformation of lysozyme in aqueous solution, which thereby keeps its high bioactivity. The conformational changes of lysozyme adsorbed on material surfaces with different chemistries are well correlated with changes in its bioactivity.
Co-reporter:Jing Xie, He Huang
Colloids and Surfaces B: Biointerfaces 2011 Volume 85(Issue 1) pp:97-102
Publication Date(Web):15 June 2011
DOI:10.1016/j.colsurfb.2010.09.026
The time-dependent adsorption behavior of β-Lactoglobulin (β-Lg) on ATR crystal (ZnSe) surface was studied by two-dimensional (2D) correlation ATR/FTIR spectroscopy. More bands were resolved by 2D correlation spectroscopy compared to the results from second derivative (SD) and Fourier self-deconvolution (FSD) analyses, but some of the new bands resolved may originate from bandwidth changes, wavenumber shifts, etc. The integrated/overall sequential order of the intensity changes of the four sub-bands in amide I region obtained from 2D correlation spectroscopy was not consistent with the experimental observation. Adsorption-induced conformational changes did not occur until 10 min of adsorption of β-Lg molecules on the ZnSe crystal surface. The relative contents of the low-wavenumber component of the antiparallel β-strands (1627 cm−1) and random segments with α-helix (1651 cm−1) changed prior to β-turns (1666 cm−1) and the high-wavenumber component of the antiparallel β-strands (1684 cm−1). More specifically, from about 10 to 15 min of adsorption, the loss content of the low-wavenumber component of the antiparallel β-strands (1627 cm−1) was simultaneously transformed into random segments (1651 cm−1). After 20 min of adsorption, the content of β-turns (1666 cm−1) started to decrease, and the loss of β-turns (1666 cm−1) was also transformed into antiparallel β-strands (high-wavenumber component at 1684 cm−1) in a cooperative way as the β-Lg molecules become more extended.
Co-reporter:Yanxia Zhang, Qian Yu, He Huang, Feng Zhou, Zhaoqiang Wu, Lin Yuan, Dan Li and Hong Chen
Soft Matter 2010 vol. 6(Issue 12) pp:2616-2618
Publication Date(Web):12 May 2010
DOI:10.1039/C0SM00138D
A simple and attractive method was introduced to construct bioactive surfaces that exhibit non-specific protein resistant properties and high loading capacities for immobilizing various specific biomolecules. These bioactive surfaces may find wide potential biomedical applications.
Co-reporter:
Analytical Methods (2009-Present) 2014 - vol. 6(Issue 12) pp:
Publication Date(Web):
DOI:10.1039/C4AY00439F
A relatively long time is required to determine the epoxide value of an epoxy resin or epoxy compound by chemical analysis (titration) methods, including the commonly used hydrochloric acid–acetone method, which may be referred to as the hydrochloric acid–acetone-standing method, because the mixture of epoxy resins or epoxy compounds, hydrochloric acid and acetone must be left standing in the dark for at least 30 min. In this study, ultrasonication was first introduced to this method, aiming to rapidly determine the epoxide value of an epoxy resin by accelerating the dissolution of epoxy resin in acetone solvent as well as the reaction between epoxide groups and hydrogen chloride. Further study of this approach was then carried out to determine the epoxide values of a series of epoxy resin–polyethylene glycol mixtures. This new approach which may be referred to as the hydrochloric acid–acetone-ultrasonication method provides a much faster and more accurate measurement of the epoxide value of an epoxy resin (within 2 min) or its mixture with polyethylene glycol (PEG-4000, within 5 min), compared to the hydrochloric acid–acetone-standing method. This ultrasonication method may be readily extended to other chemical analysis (titration) methods.
![Poly[oxy(1-methyl-3-oxo-1,3-propanediyl)]](http://img.cochemist.com/ccimg/26800/26744-04-7.png)
![Poly[oxy(1-methyl-3-oxo-1,3-propanediyl)]](http://img.cochemist.com/ccimg/26800/26744-04-7_b.png)
