Preparation Of PIPD-POSS Copolymer Membrane Materials And Study Of Their Structure And Properties

Poly[2,5-dihydroxy-1,4-phenylene-pyridinediimidazole](PIPD)is a liquid crystal polymer obtained by molecular design based on poly(p-phenylene-p-benzodioxole)(PBO).PIPD also has some shortcomings,such as unsatisfactory UV resistance and poor dielectric properties due to polar groups.However,the unique hydrogen bonding structure of PIPD makes it potential to be prepared for film applications,so it is necessary to modify PIPD or change its application form,etc.In this paper,a caged sesquisiloxane(POSS)with reactive groups was used as the third monomer,and octaaminopropyl POSS was incorporated into the main chain of PIPD to prepare a cross-linked polymer with POSS content of 1wt%,2 wt%,3wt%,4 wt%,and 5 wt%,and then the PIPD-POSS copolymer film was prepared by dissolving the PIPD-POSS polymer solution with methane sulfonic acid and scraping the film.The PIPD-POSS copolymer was characterized by Fourier infrared spectroscopy and laser Raman spectroscopy,and its chemical structure was determined.The molecular weight of the copolymer was characterized by viscosity method,and it was found that the molecular weight of PIPD-POSS copolymer gradually increased with increasing POSS content,and at 5 wt%POSS addition the molecular weight increased by 45.9%compared with that of pure PIPD.The crystallization properties of PIPD-POSS copolymers were investigated by X-ray diffraction(XRD),and it was found that the introduction of POSS improved the crystallinity of PIPD.The PIPD before and after POSS copolymerization was characterized by ¹³C-HMR,and the results indicated that the introduction of POSS did not affect the formation of the PIPD backbone,and POSS was grafted into the PIPD backbone in a cage structure.The mechanical properties of the PIPD-POSS copolymer films were characterized using a universal tensile tester,and the results showed that the mechanical properties of the PIPD-POSS copolymer films improved with the introduction of POSS,and the tensile strength of the copolymer films increased by80%compared to the pure PIPD films at 5 wt%.Thermal loss experiments were used to characterize the heat resistance of PIPD-POSS copolymer films,and the results showed that the introduction of POSS increased the thermal decomposition temperature of the copolymer and led to a 15%increase in the thermal residual rate of the PIPD-POSS copolymer.The characterization of the dielectric properties of the PIPD-POSS copolymer films showed that the introduction of POSS improved the dielectric properties of PIPD and reduced the dielectric loss.After characterization of the UV resistance of the copolymer films,it was found that the introduction of POSS greatly enhanced the UV resistance of PIPD.