Synthesis and characterization of new multiblock copolymers based on poly(dimethylsiloxane) and aromatic polyamides

A new class of high-temperature-resistant block copolymer materials based on poly(dimethylsiloxane) (PDMS) and aromatic polyamides (aramids) was developed. PDMS--aramid multiblock copolymers of wide ranging compositions were successfully synthesized by low-temperature solution polycondensation through two different procedures. In the two-step method, alpha , omega -diacid chloride terminated aramid oligomers, which were preformed by the reaction of 3-(4-aminophenoxy)aniline (3,4'-ODA) with isophthaloyl chloride (IPC) in chloroform, were subjected to polycondensation with alpha , omega -bis(3-aminopropyl)poly(dimethylsiloxane) (PDMS-diamine) in the same flask, leading to the formation of the 3,4'-ODA series multiblock copolymers. In the one-step method, three reaction components, 3,4'-ODA, IPC, and PDMS-diamine, were reacted all together in chloroform. The other multiblock copolymers of the 4,4'-ODA series were synthesized in a similar manner starting from bis(4-((trimethylsilyl)amino)phenyl) ether (N-silylated 4,4'-ODA), IPC, and PDMS-diamine through the one-step and two-step procedures. The multiblock copolymers of both series having inherent viscosities of 0.2-0.8 dl g exp --1 were obtained by these polymerizations. They are soluble in N, N-dimethylacetamide (DMAc) and could be cast into transparent, ductile, and elastomeric films from the DMAc solutions. Calorimetric measurements showed that the multiblock copolymer films obtained by the two-step method had better defined, microphase-separated morphology than those obtained by the one-step method, and the 4,4'-ODA series multiblock copolymers had better defined structures than the 3,4'-ODA series copolymers. The mechanical properties of films of the PDMS--aramid multiblock copolymers depended markedly on the PDMS content; at low PDMS levels the materials behave as rubber-toughened aramid plastics, and at higher PDMS contents the materials are analogous to thermoplastic elastomers. . 16 ref.--AA