Effect of substituted positions of acetylene groups in benzene rings on the properties of poly(silane arylether arylacetylene)s

Performing investigations on the structure-property relationship of poly(silane arylether arylacetylene)s (PSEAs) is very important and instructive for designing novel high-performance polymers. In this work, three bifunctional acetylene-terminated triphenyl-ether monomers with either para-acetylene, meta-acetylene or ortho-acetylene, i.e., 1,3-bis(4'-ethynylphenoxy)benzene (pmp-BEPB), 1,3-bis(3'-ethynylphenoxy)benzene (mmm-BEPB) and 1,3-bis(2'-ethynylphenoxy)benzene (omo-BEPB) were synthesized and used to prepare three PSEA resins, namely, pmp-PSEA, mmm-PSEA and omo-PSEA. The PSEA resins were characterized by 1H-nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction analysis, and the properties were explored. The resins possess a wide processing window in the following order: pmp-PSEA < mmm-PSEA < omo-PSEA. The DSC results revealed that pmp-PSEA shows the highest reactivity, followed by omo-PSEA and mmm-PSEA. In the cured networks of the resins, the densities increase in the following order: pmp-PSEA-C < mmm-PSEA-C < omo-PSEA-C. Compared with pmp-PSEA-C, mmm-PSEA-C possesses better mechanical properties with a flexural strength of 66.5 MPa and a flexural modulus of 3.71 GPa. The decomposition temperatures of 5% weight loss (Td5) of pmp-PSEA-C and mmm-PSEA-C are over 530 °C.