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Chemical Research in Chinese Universities ›› 2012, Vol. 28 ›› Issue (5): 926-930 .

• Articles • Previous Articles    

Influence of Steric Hindrance Between Hydrogen Atoms of Linkage Groups and Adjacent Phenyls on Properties of Polyimide

PANG Yu-wei1, LUO Long-bo1, CHEN Yi1, ZHANG Peng1, WANG Xu1, PENG Chao-rong2, LIU Xiang-yang1   

  1. 1. State key Laboratory of Polymer Material and Engineering, College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, P. R. China;
    2. Sichuan Institute of Atomic Energy, Chengdu 610066, P. R. China
  • Received:2011-09-13 Revised:2012-03-15 Online:2012-09-25 Published:2012-09-07
  • Supported by:
    Supported by the National Natural Science Foundation of China(No.50973073) and the Science and Technology Projects of Chengdu City, China(No.10GGYB114GX-182).

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Abstract: A diamine monomer 4,4′-methylenedianiline(MDA) was introduced to modify the polyimide of pyromellitic dianhydride(PMDA) and 4,4′-oxydianiline(ODA) by polycondensation. A series of polyamic acids was synthesized from MDA and ODA of different molar ratios with PMDA of sum mole of moles of MDA and ODA, and polyimide films were obtained by thermal imidization. Polyimide(PI) films were characterized by tensile testing, dynamic mechanical analysis(DMA), thermal gravimetry analysis(TGA), Fourier transform infrared spectroscopy (FTIR), wide X-ray diffraction(WAXD) and molecular simulation. With the increase of MDA content, the tensile strength and thermal decomposition temperature remained generally stable compared with those of PMDA/ODA polyimide. Unexpectedly, the glass transition temperature(Tg) and Young’s modulus increased from 388.7 ℃ and 2.37 GPa to 408.3 ℃ and 5.74 GPa, respectively. The results of WAXD and molecular simulation indicate the steric hindrance among hydrogen atoms of the linkage groups and adjacent phenyls enhanced the properties of the polyimide modified with MDA.

Key words: Polyimide, Modification, Glass transition temperature, Steric hindrance