Preparation And Study On Phenolphthalein And Bisphenol AF Based Poly(arylene Ether Nitrile) Copolymers

Poly(arylene ether nitrile)(PEN)is a new type of special engineering plastic.Its main chain contains flexible aryl ether bonds and side chains have polar cyano groups.PEN has high glass transition temperature(T_g>170?)and excellent dielectric properties(?=3.3?4.3).It has huge application prospects in high-performance structural parts or functional materials.In this thesis,the twisted non-coplanar phenolphthalein structural unit(Cardo)and trifluoromethyl group(-CF₃)were introduced into the main chain of the PEN to increase the rigidity of the polymer molecular chain,improve the heat resistance of the polymer,and reduce the material dielectric constant.By controlling the ratio of the Cardo and-CF₃,a series of phenolphthalein-bisphenol AF copolymer polyaryl ether nitrile(PP/BPAF-PEN)with different structures were synthesized.And the comprehensive properties of PP/BPAF-PEN were systematically discussed.In addition,the PP/BPAF-PEN film was prepared by solid-phase cross-linking,and the thermal cross-linking reaction mechanism and the comprehensive properties of the film were characterized.On this basis,a cross-linking agent was introduced to prepare film.It was desirable to improve the processing characteristics of the resin system while further improving its thermal properties.To sum up,the specific research contents of this thesis are as follows:1.PP/BPAF-PEN was synthesized by nucleophilic substitution condensation polymerization by changing the molar ratio of phenolphthalein and bisphenol AF.The effect of molar ratio of diphenols on PP/BPAF-PEN was studied.The structure of the prepared PP/BPAF-PEN was verified by ATR-FTIR,¹H-NMR and EDS,and molecular weight was measured by GPC.At the same time,the thermal properties of PP/BPAF-PEN powder and the film were tested and characterized,the mechanical and electrical properties of the film were systematically characterized,and the correspondence relationship between PP/BPAF-PEN molecular structures were discussed in detail.The influence of the introduction of-CF₃ group on the microstructure and dielectric properties of polymer materials were analyzed.2.The molecular backbone of PP/BPAF-PEN contains cyano groups,which can undergo trimerization and cyclization to generate triazine ring structures at high temperatures.In the experiment,different cross-linked films were successfully prepared by solid-phase cross-linking,and the structures and properties were tested and characterized.The degree of thermal crosslinking reaction was explored by the gel content and T_g.With the increase of heat treatment temperature,the gel content of the film increased.The more stable triazine rings were formed in the system,the heat resistance of the film increased.At the same time,the properties of the cross-linked film were characterized by TGA and mechanical property tests.The decomposition temperature of PP/BPAF-PEN cross-linked film increased with the increase of cross-linking degree,but the mechanical properties decreased to a certain extent.And the dielectric constant showed a tendency of first decreasing and then increasing.Through the characterization of various properties,the thermal crosslinking behavior was verified.3.Due to the larger length of PP/BPAF-PEN molecular chain and the lower content of side cyano groups,the polymerization degree of direct solid-phase crosslinking reaction is lower.Therefore,by introducing cross-linking agent,the cross-linking reaction sites of the system were increased,and its degree of cross-linking was further improved.Through DSC and TGA testing,4-aminobenzonitrile(4-ABN)was selected as the effective crosslinking agent of the system.Then PP/BPAF-PEN composite films with different proportions were prepared,and the comprehensive properties of the films were characterized.Adding 4-ABN to the copolymer was easier to form a network structure with the increase of heat treatment temperature,which could improve the thermal properties and mechanical properties of the cross-linked PP/BPAF-PEN films.The dielectric constant of PP/BPAF-PEN film also decreased.In summary,adding a crosslinking agent can improve the processing performance and overall performance of PP/BPAF-PEN film.