QiXin Zhuang

Novel Fully Biobased Benzoxazines from Rosin: Synthesis and Properties

Co-reporter:Xiaoyun Liu, Ruhong Zhang, Tianquan Li, Pengfei Zhu, and Qixin Zhuang

ACS Sustainable Chemistry & Engineering November 6, 2017 Volume 5(Issue 11) pp:10682-10682

Publication Date(Web):October 12, 2017

DOI:10.1021/acssuschemeng.7b02650

In the present study, two novel fully biobased benzoxazines were synthesized using modified products of rosin, dehydroabietylamine, guaiacol, 4-methylumbelliferone, and paraformaldehyde. The chemical structures of DM (dehydroabietylamine, 4-methylumbelliferone) and DG (dehydroabietylamine, guaiacol) were characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (NMR) and 13C NMR spectra, dimensional nuclear magnetic and high-resolution mass spectrometry. The curing process of DM and DG was monitored by differential scanning calorimetry and in situ FTIR. The results demonstrated that the corresponding polymers PDM and PDG had high thermal stability. In addition, they had low dielectric constants below 3.30 at 25 °C and 1 kHz condition. Water contact angle measurements, OPC-time curves, and Tafel plots of PDG and PDM were also studied. The results showed that anticorrosion performances of PDG and PDM were stable during the immersion process and had strong abilities as shield corrosive media. Therefore, these two benzoxazine resins based on dehydrobietylamine may have potential applications in many fields.Keywords: Anticorrosion; Benzoxazine; Biobased resin; Dielectric properties; Rosin;

Graphene/MWNT/Poly(p-phenylenebenzobisoxazole) Multiphase Nanocomposite via Solution Prepolymerization with Superior Microwave Absorption Properties and Thermal Stability

Co-reporter:Jiasong HuaYanxiao Li, Xiaoyun Liu, Xinxin Li, Shaoliang Lin, Jinlou Gu, Zhong-Kai Cui, Qixin Zhuang

The Journal of Physical Chemistry C 2017 Volume 121(Issue 2) pp:

Publication Date(Web):December 27, 2016

DOI:10.1021/acs.jpcc.6b11925

This paper demonstrates both the high-performance microwave absorption properties and the superior thermal stability of graphene/multiwalled carbon nanotubes (MWNTs)/poly(p-phenylenebenzobisoxazole) (PBO) composites synthesized via in situ polymerization of functionalized PBO precursor with graphene oxide/MWNTs nanocomposites, followed by high-temperature calcination. The incorporation of three-dimensional graphene/MWNTs network significantly improved the reflection loss of PBO composites (−50.17 dB at 12.58 GHz) by over 20 times than that of pure PBO (−2.33 dB at 12.58 GHz) with a sample thickness of only 2.6 mm. The effect of graphene/MWNTs content on the microwave absorption performance was also investigated. The graphene/MWNTs/PBO composite shows great promise as a microwave absorber in high-temperature environments.

Core/shell-structured hyperbranched aromatic polyamide functionalized graphene nanosheets-poly(p-phenylene benzobisoxazole) nanocomposite films with improved dielectric properties and thermostability

Co-reporter:Hao Feng;Wenjun Ma;Zhong-Kai Cui;Xiaoyun Liu;Jinlou Gu;Shaoliang Lin

Journal of Materials Chemistry A 2017 vol. 5(Issue 18) pp:8705-8713

Publication Date(Web):2017/05/10

DOI:10.1039/C7TA00587C

This study reports the synthesis of core/shell-structured hyperbranched aromatic polyamide functionalized graphene nanosheets-poly(p-phenylene benzobisoxazole) (GNs-HAP-PBO) nanocomposite films with improved dielectric properties and thermostability. PBO precursor polymer chains were grafted onto the ample amino-terminated GNs-HAP via in situ polymerization, and then the reduction of GNs-HAP and the intramolecular cyclization of PBO precursors were achieved through thermal treatment. The unique core/shell-structure is effective to prevent the aggregation of GNs and improves the dispersion of GNs in the GNs-HAP-PBO nanocomposites, forming microcapacitor networks in the matrix. The GNs-HAP-PBO nanocomposite films exhibit lower dielectric loss in comparison with solvothermally reduced graphene oxide/PBO nanocomposite films. At 1 kHz and 200 °C, a dielectric constant of 66.27 and a dielectric loss of 0.045 are observed in the GNs-HAP-PBO nanocomposite films with 2 wt% GNs-HAP. Moreover, the maximum energy density of the GNs-HAP-PBO nanocomposite films is up to 6 J cm−3 owing to the high breakdown strength (132.5 ± 9.3 kV mm−1). The GNs-HAP-PBO nanocomposite films with 2 wt% GNs-HAP also exhibit excellent tensile strength (125 MPa), Young's modulus (6.4 GPa), and high thermal stability (temperature of 5 wt% loss = 643 °C). This work demonstrates a promising strategic approach to fabricating high dielectric materials under extreme environments.

Synthesis, structure, and properties of high-impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

Co-reporter:Kun Hu;Zhong-Kai Cui;Yongliang Yuan;Tongxin Wang;Xiaoyun Liu;Zhewen Han

Polymer Composites 2016 Volume 37( Issue 4) pp:1049-1055

Publication Date(Web):

DOI:10.1002/pc.23265

The organic–inorganic hybrid nanocomposites from high-impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H-NMR, thermal gravity analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS-POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers

In situ synthesis of ternary BaTiO3/MWNT/PBO electromagnetic microwave absorption composites with excellent mechanical properties and thermostabilities

Co-reporter:Jia Wei, Shuo Zhang, Xiaoyun Liu, Jun Qian, Jiasong Hua, Xinxin Li and Qixin Zhuang

Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:8205-8214

Publication Date(Web):12 Mar 2015

DOI:10.1039/C5TA01410G

Different from traditional microwave absorbing nanoparticles as fillers in non-mechanical coatings, the BaTiO3/MWNT/PBO ternary composites can be potentially used as a structural microwave absorption device in broader applications, especially in the aerospace industry. BaTiO3 particles with a diameter of 5–15 nm were immobilized onto the surface of MWNTs via a solvothermal synthesis method. BaTiO3/MWNT/PBO ternary composites with varied compositions were then prepared via the in situ polymerization of p-phenylenebenzobisoxazole (PBO) with a uniform dispersion of BaTiO3/MWNT nanocomposites in the polymer-poly p-phenylenebenzobisoxazole (PBO)-matrix (a conjugated polymer with splendid mechanical properties and thermal stability). The BaTiO3/MWNT/PBO composites possessed outstanding microwave absorbing performances in addition to desirable mechanical properties and thermal stability.

Preparation and properties of thermostable well-functionalized graphene oxide/polyimide composite films with high dielectric constant, low dielectric loss and high strength via in situ polymerization

Co-reporter:Xinliang Fang, Xiaoyun Liu, Zhong-Kai Cui, Jun Qian, Jijia Pan, Xinxin Li and Qixin Zhuang

Journal of Materials Chemistry A 2015 vol. 3(Issue 18) pp:10005-10012

Publication Date(Web):30 Mar 2015

DOI:10.1039/C5TA00943J

This study proposes a novel and facile method to synthesize high-quality NH2-functionalized and carboxyl-functionalized graphene oxide (PPD–CFGO)/polyimide (PI) composite films with high dielectric constant (ε), low dielectric loss, high-temperature resistance and outstanding mechanical properties by in situ polymerization. In addition to the partial carboxyl groups located at the edges, the ample hydroxyl and epoxy groups bonded on the basal plane of graphene sheets were exploited to covalently bond to the amines. GO was modified by oxalic acid to obtain carboxyl-functionalized GO (CFGO) before amidation. NH2-functionalized CFGO (PPD–CFGO), dispersing well in dimethylacetamide (DMAc), was the initial platform for polymer grafting to improve the CFGO dispersion in the polymer matrix. Partially reduced graphene nanosheets are formed during the imidization process. The PPD–CFGO/PI composite films exhibit high tensile strength (up to 848 MPa) and Young's modulus (18.5 GPa). The thermogravimetric analysis results indicate that the PPD–CFGO/PI composites have good thermal stability below 500 °C. The dielectric constant increases up to 36.9 with an increasing amount of PPD–CFGO, higher than that of the pure PI polymer by a factor of 12.5, while the dielectric loss is only 0.0075 and the breakdown strength still remains at a high level (132.5 ± 9.3 MV m−1).

An investigation into the hydrogen bond of poly (p-phenylene benzobisoxazole)/carboxylic carbon nanotube composites, insight from quantum mechanics/molecular mechanics simulation

Co-reporter:Kun Hu;Xiaoyun Liu ;Zhewen Han

Polymer Composites 2015 Volume 36( Issue 8) pp:1454-1461

Publication Date(Web):

DOI:10.1002/pc.23051

Poly (p-phenylene benzobisoxazole)/carbon nanotube (PBO/CNTs) composites have already been experimentally synthesized with the outstanding mechanical and electrical properties. Carboxylic carbon nanotubes (CNT-COOH), obtained by acid treatment, can better disperse than pristine nanotubes in PBO matrix, which is estimated due to hydrogen bonds between them and investigated by Quantum Mechanics/Molecular mechanics (QM/MM) calculation. In the dynamic simulation, the N atoms in PBO and H atoms in carboxyl can be close enough to form hydrogen bond and the angle of oxygen–hydrogen–nitrogen (OHN) is obtuse, suitable for hydrogen bond. Further more, the electrostatic potential (ESP) and ESP fit charge of N and O atoms in PBO has been measured by Density Functional Theory (DFT) calculation to prove that hydrogen bonds can be formed only by N atoms in the heterocycle of PBO and H atoms in carboxyl of the CNT-COOH. POLYM. COMPOS., 36:1454–1461, 2015. © 2014 Society of Plastics Engineers

Preparation and characterization of STRG/PI composite films with optimized dielectric and mechanical properties

Co-reporter:Pengtu Zhang, Jianjie He, Zhong-Kai Cui, Xinxin Li, Xiaoyun Liu, Shuo Zhang, Qixin Zhuang, Zhewen Han

Polymer 2015 Volume 65() pp:262-269

Publication Date(Web):18 May 2015

DOI:10.1016/j.polymer.2015.04.015

•Solvothermally reduced graphene oxide/PI composite films were fabricated.•Dielectric constant of the composite containing 1 wt% STRG was measured to be 71.•Structure and morphology of the composite films was investigated.•Mechanical and thermal properties of the composites were optimized.Polymer-based high dielectric composites have attracted considerable research attention due to their unique advantages in electronic applications. Polyimide (PI) is a class of high-performance polymers with improved heat-resistance and mechanical properties owing to its aromatic and heteroatomic functionalities, yielding an ideal material for high-temperature applications. In this paper, STRG (solvothermally reduced graphene oxide) was prepared and introduced into PI matrix by solution blending, and the dielectric, mechanical and thermal properties of these STRG/PI composites were studied. The STRG/PI composite (1 wt%) witnessed a significant increase by a factor of 23 in dielectric constant (71 at 103 Hz), compared to neat PI. In addition, the tensile strength of STRG/PI composites was improved by 105%. This study demonstrated a promising strategic approach to fabricate STRG/PI composites with enhanced dielectric and mechanical properties, serving potential candidates for high-temperature and high-dielectric applications.

Preparation of Solution-Processable Reduced Graphene Oxide/Polybenzoxazole Nanocomposites with Improved Dielectric Properties

Co-reporter:Yi Chen, Shuo Zhang, Xiaoyun Liu, Qibing Pei, Jun Qian, Qixin Zhuang, and Zhewen Han

Macromolecules 2015 Volume 48(Issue 2) pp:365-372

Publication Date(Web):January 13, 2015

DOI:10.1021/ma502326v

The abilities to enhance the degree of orientational freedom of dipole in polymer dielectrics and strengthen the homogeneous dispersion of conductive fillers in matrix are of crucial importance for fabricating composite materials with high dielectric constant, low dielectric loss, low density, and good processability. Compared with conventional main-chain polybenzoxazoles, whose processability and dielectric performance are strictly limited by the conjugated benzoxazole groups on the backbone, improved solubility in dimethylformamide and dielectric constant (4.92) were observed for poly(2-isopropenylbenzoxazole) (P(2-IBO)), due to the high mobility of the dipole (benzoxazole ring) on the side chains. In addition, improved dispersion of conductive graphene nanosheets was achieved by a surface-initiated atom transfer radical polymerization (ATRP) of the N-(2-hydroxyphenyl)methacrylamide (o-HPMAA), the precursor of 2-isopropenylbenzoxazole from reduced graphene oxide (RGO). The nanocomposites of functionalized graphene and P(2-IBO) possess a dielectric constant of 8.35 (approximately 70% higher than that of pure P(2-IBO) at 1 kHz) when the weight fraction of functionalized graphene reaches 0.015, the lowest so far among the reports on dielectric property of the graphene/polybenzoxazole system.

γ-Fe2O3–MWNT/poly(p-phenylenebenzobisoxazole) composites with excellent microwave absorption performance and thermal stability

Co-reporter:Yi Chen, Xiaoyun Liu, Xiaoyang Mao, Qixin Zhuang, Zhong Xie and Zhewen Han

Nanoscale 2014 vol. 6(Issue 12) pp:6440-6447

Publication Date(Web):12 Mar 2014

DOI:10.1039/C4NR00353E

Ferromagnetic γ-Fe2O3 nanoparticles were successfully loaded into multi-walled carbon nanotubes (MWNTs) as probed by transmission electron microscopy. Upon incorporation of the γ-Fe2O3–MWNTs into poly(p-phenylenebenzobisoxazole) (PBO), a conjugated polymer with high mechanical strength and outstanding thermal and oxidative stability, microwave absorbing materials were obtained. Attributed to the special structure of the γ-Fe2O3–MWNTs, synergistic effects on dielectric loss and magnetic loss, and a better matched characteristic impedance of the composites were achieved. The optimal minimum reflection loss reached −32.7 dB at 12.09 GHz on a composite containing 12 wt% γ-Fe2O3–MWNTs with a thickness of 2.7 mm, and the corresponding bandwidth below −5 dB was 6.2 GHz. This demonstrated its potential applications as a low-density microwave absorbing material operating under extreme environments.

Charge distribution of poly (p-phenylene benzobisoxazole) investigated by quantum chemical simulation

Co-reporter:Kun Hu, Liquan Wang, Xiaoyun Liu, Qixin Zhuang, Zhaojun Xue, Zhewen Han

Computational and Theoretical Chemistry 2014 Volume 1042() pp:1-7

Publication Date(Web):15 August 2014

DOI:10.1016/j.comptc.2014.04.034

•The N atoms of PBO owned about twice negative ESP charge as that of O atoms.•The ESP charges of PBO are well consistent with the electrostatic potential.•The ESP charges are also well consistent with the deformation electron density.•The ESP charges fit well with the chemical trend exhibited by the protonation.•The ESP scheme has better performance on PBO than the other three schemes.The electrostatic potential fit (ESP) charges of the atoms of PBO model compound were evaluated by quantum chemical simulation. The geometry optimization with B3LYP functional and STO-3G, 6-31G(d), 6-311++G(2d,p), cc-pVTZ basis sets were applied, respectively. The charge distributions at these basis sets all indicate the N atoms to own the highest electronegativity, which are much stronger than that of O atoms. The result possesses successful representation of the electrostatic potential and deformation electron density. Moreover, the ESP charges fit well with the chemical trend exhibited by the protonation of PBO. Compared to the those derived from Mulliken, Hirshfeld and Natural Population Analysis (NPA) schemes, the charge distribution derived from electrostatic potential has the best performance both theoretically and experimentally.Graphical abstract

Study on the photoinduced electron-transfer activity of poly(p-phenylene benzobisoxazole)/carboxylic multiwalled carbon nanotubes composites prepared by in situ polymerization

Co-reporter:Zhong Xie;Xiaoyun Liu;Yi Chen;Xiaoyang Mao ;Zhewen Han

Polymer Composites 2012 Volume 33( Issue 8) pp:1295-1301

Publication Date(Web):

DOI:10.1002/pc.22255

Abstract

This article focused on the synthesis of poly(p-phenylene benzobisoxazole)/carboxylic multiwalled carbon nanotubes (PBO/MWNT-COOH) composites through in situ polymerization. The effect of MWNT-COOH on thermal stability and photophysical properties was investigated thoroughly. Especially an in-depth study was carried out on the detailed process of energy transfer. Ultraviolet-visible-near infrared and fluorescence spectroscopy of composites revealed that MWNT interacted with PBO through strong covalent bonds, which was a significant photoinduced charge-transfer interaction between the two components. Therefore, compared with PBO, both the thermal stability and PL quantum efficiency of PBO/MWNT-COOH composites were improved. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Molecular simulation of the effect of graft structure on the miscibility of high-impact polystyrene blends

Co-reporter:Zhaojun Xue;Xiaoyun Liu;Kun Hu ;Zhewen Han

Polymer Composites 2012 Volume 33( Issue 3) pp:430-435

Publication Date(Web):

DOI:10.1002/pc.22166

Abstract

High-impact polystyrene (HIPS) is a kind of thermoplastic with good impact, which is considered to derive from the biphase of microstructure studied with SEM, etc. In this article, the influence of polystyrene (PS)/polybutadiene (PB) graft structure to the behavior of HIPS was studied through molecular simulation. The analysis of Flory-Huggis parameter χ and radial distribution function (RDF) shows that the blend system of PS/PB has the best miscibility when the mass ratio of PS/PB is 60/40. In the toughening process, however, the graft copolymer PB-g-S is formed. For the PS/PB-g-S system with the same repeat unit of PS, PB-g-S chains with two grafts [PB-g-S(G = 2)] are better than PB-g-S chains with one graft [PB-g-S(G = 1)] in miscibility, which is in accord with the study of Fischer and Hellmann. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

Co-reporter:Zhong Xie, Qixin Zhuang, Qing Wang, Xiaoyun Liu, Yi Chen, Zhewen Han

Polymer 2011 Volume 52(Issue 23) pp:5271-5276

Publication Date(Web):27 October 2011

DOI:10.1016/j.polymer.2011.09.013

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV–vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.

Enhanced conductivity in polybenzoxazoles doped with carboxylated multi-walled carbon nanotubes

Co-reporter:Chengjun Zhou, Shanfeng Wang, Qixin Zhuang, Zhewen Han

Carbon 2008 Volume 46(Issue 9) pp:1232-1240

Publication Date(Web):August 2008

DOI:10.1016/j.carbon.2008.05.005

Two representative polybenzazoles, poly(p-phenylene benzobisoxazole) (PBO) and poly(2,5-benzoxazole) (ABPBO), have been used as matrix materials for fabricating electrically conducting nanocomposite films. In this strategy, pristine multi-walled carbon nanotubes (MWCNTs) were first treated with nitric acid to form carboxylated multi-walled carbon nanotubes (MWCNTs–COOH). Subsequently, MWCNTs–COOH were dispersed efficiently in the methanesulfonic acid (MSA) solution of polybenzazole, sonicated, and then processed into thin films. MWCNTs–COOH in MSA formed an isotropic regime at the concentration of ∼0.1 wt.%. Nanotubes could form net like structures and conductive channels in the polymer matrix to improve electrical conductivity, mechanical properties, and thermal stability. At the MWCNT–COOH composition of 5 wt.%, polybenzazole/MWCNT–COOH composite films exhibited a dramatic enhancement in electrical conductivity by 8 orders of magnitude from ∼10−12 to 1.6 × 10−4 S cm−1 without significantly sacrificing optical transparency.

Synthesis and properties of polybenzazoles containing flexible methylene in backbone

Co-reporter:Xiaohui Xu;Xiaoyun Liu;Chengjun Zhou

Frontiers of Chemical Science and Engineering 2008 Volume 2( Issue 4) pp:412-416

Publication Date(Web):2008 December

DOI:10.1007/s11705-008-0073-5

A novel series of polybenzazoles with rigid-rod benzoxazole cycle and soft methylene segment was designed and synthesized via solution condensation polymerizations from 4,6-diamino-1,3-benzenediol diphosphate, terephthalic acid and aliphatic dicarboxylic acid. The structures of polybenzazoles were characterized by means of FT-IR, 1H NMR and Wide-angle X-ray diffraction (WAXRD). All the polymers show excellent thermal stability and the Tds was above 471°C. The intrinsic viscosities [η] of the polymers ranged from 0.8 to 0.9. The UV-Vis absorption peaks of the polymers in MSA were blue-shifted from 429 nm for PBO to 291 nm for PBOC7, and the Stokes shifts in PL spectra enlarged.

Synthesis and Optical Properties of Novel Conjugated Rigid-Rod Polymer Derived from Fluorene and Benzobisoxazole

Co-reporter:Xiaoyun Liu;Xiaohui Xu;Zhewen Han

Polymer Bulletin 2008 Volume 60( Issue 6) pp:765-774

Publication Date(Web):2008 June

DOI:10.1007/s00289-008-0917-7

A kind of new conjugated rigid-rod polymer poly(9,9-dioctyl fluorenol benzobisoxazole) (PBOF) containing an fluorene and benzobisoxazole structure was prepared by the 4,6-diamino-1,3-benzenediol dihydrochloride (DAR) and 9,9-dioctyl fluorene. The polymer was characterized by the elemental analysis, 1HNMR, FTIR, thermogravimetric analysis (TGA) and photoluminescence (PL) spectra. The results indicated that the thermal stability of polymer was much lower than that of well-known poly(p-phenyl benzobisoxazole) (PBO). Unlike PBO, PBOF was readily soluble at room temperature in DMSO and NMP and even partly dissolved in m-cresol and CHCl3 due to the introduction of alkyl groups. The absorption and photoluminescence spectra of the polymer were also studied. The protonated PBOF in dilute methanesulfonic acid solutions exhibits a blue emission with a peak at 468 nm. In contrast with that of PBO, the maximal emissions spectra and absorption spectra of PBOF red-shifted due to the introduction of the fluorene group which enhanced effective conjugation of polymer structure unit.

Preparation and properties of thermostable well-functionalized graphene oxide/polyimide composite films with high dielectric constant, low dielectric loss and high strength via in situ polymerization

Co-reporter:Xinliang Fang, Xiaoyun Liu, Zhong-Kai Cui, Jun Qian, Jijia Pan, Xinxin Li and Qixin Zhuang

Journal of Materials Chemistry A 2015 - vol. 3(Issue 18) pp:NaN10012-10012

Publication Date(Web):2015/03/30

DOI:10.1039/C5TA00943J

This study proposes a novel and facile method to synthesize high-quality NH2-functionalized and carboxyl-functionalized graphene oxide (PPD–CFGO)/polyimide (PI) composite films with high dielectric constant (ε), low dielectric loss, high-temperature resistance and outstanding mechanical properties by in situ polymerization. In addition to the partial carboxyl groups located at the edges, the ample hydroxyl and epoxy groups bonded on the basal plane of graphene sheets were exploited to covalently bond to the amines. GO was modified by oxalic acid to obtain carboxyl-functionalized GO (CFGO) before amidation. NH2-functionalized CFGO (PPD–CFGO), dispersing well in dimethylacetamide (DMAc), was the initial platform for polymer grafting to improve the CFGO dispersion in the polymer matrix. Partially reduced graphene nanosheets are formed during the imidization process. The PPD–CFGO/PI composite films exhibit high tensile strength (up to 848 MPa) and Young's modulus (18.5 GPa). The thermogravimetric analysis results indicate that the PPD–CFGO/PI composites have good thermal stability below 500 °C. The dielectric constant increases up to 36.9 with an increasing amount of PPD–CFGO, higher than that of the pure PI polymer by a factor of 12.5, while the dielectric loss is only 0.0075 and the breakdown strength still remains at a high level (132.5 ± 9.3 MV m−1).

In situ synthesis of ternary BaTiO3/MWNT/PBO electromagnetic microwave absorption composites with excellent mechanical properties and thermostabilities

Co-reporter:Jia Wei, Shuo Zhang, Xiaoyun Liu, Jun Qian, Jiasong Hua, Xinxin Li and Qixin Zhuang

Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN8214-8214

Publication Date(Web):2015/03/12

DOI:10.1039/C5TA01410G

Different from traditional microwave absorbing nanoparticles as fillers in non-mechanical coatings, the BaTiO3/MWNT/PBO ternary composites can be potentially used as a structural microwave absorption device in broader applications, especially in the aerospace industry. BaTiO3 particles with a diameter of 5–15 nm were immobilized onto the surface of MWNTs via a solvothermal synthesis method. BaTiO3/MWNT/PBO ternary composites with varied compositions were then prepared via the in situ polymerization of p-phenylenebenzobisoxazole (PBO) with a uniform dispersion of BaTiO3/MWNT nanocomposites in the polymer-poly p-phenylenebenzobisoxazole (PBO)-matrix (a conjugated polymer with splendid mechanical properties and thermal stability). The BaTiO3/MWNT/PBO composites possessed outstanding microwave absorbing performances in addition to desirable mechanical properties and thermal stability.

Core/shell-structured hyperbranched aromatic polyamide functionalized graphene nanosheets-poly(p-phenylene benzobisoxazole) nanocomposite films with improved dielectric properties and thermostability

Co-reporter:Hao Feng, Wenjun Ma, Zhong-Kai Cui, Xiaoyun Liu, Jinlou Gu, Shaoliang Lin and Qixin Zhuang

Journal of Materials Chemistry A 2017 - vol. 5(Issue 18) pp:NaN8713-8713

Publication Date(Web):2017/04/03

DOI:10.1039/C7TA00587C

This study reports the synthesis of core/shell-structured hyperbranched aromatic polyamide functionalized graphene nanosheets-poly(p-phenylene benzobisoxazole) (GNs-HAP-PBO) nanocomposite films with improved dielectric properties and thermostability. PBO precursor polymer chains were grafted onto the ample amino-terminated GNs-HAP via in situ polymerization, and then the reduction of GNs-HAP and the intramolecular cyclization of PBO precursors were achieved through thermal treatment. The unique core/shell-structure is effective to prevent the aggregation of GNs and improves the dispersion of GNs in the GNs-HAP-PBO nanocomposites, forming microcapacitor networks in the matrix. The GNs-HAP-PBO nanocomposite films exhibit lower dielectric loss in comparison with solvothermally reduced graphene oxide/PBO nanocomposite films. At 1 kHz and 200 °C, a dielectric constant of 66.27 and a dielectric loss of 0.045 are observed in the GNs-HAP-PBO nanocomposite films with 2 wt% GNs-HAP. Moreover, the maximum energy density of the GNs-HAP-PBO nanocomposite films is up to 6 J cm−3 owing to the high breakdown strength (132.5 ± 9.3 kV mm−1). The GNs-HAP-PBO nanocomposite films with 2 wt% GNs-HAP also exhibit excellent tensile strength (125 MPa), Young's modulus (6.4 GPa), and high thermal stability (temperature of 5 wt% loss = 643 °C). This work demonstrates a promising strategic approach to fabricating high dielectric materials under extreme environments.

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