Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and polyamides from dicarboxylic acid and diisocyanate terminated functionalities

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Abstract
Polydimethylsiloxane (PDMS)–polyamide multiblock copolymers were successfully synthesized via diisocyanate route by two different procedures, i.e., the one‐step and two‐step methods, In the two‐step method, α, ω‐diisocyanate‐terminated polyamide oligomers, which were prepared in situ from a mixture of isophthalic acid (IPA) and azelaic acid (AZA) with 4,4′‐methylenedi (phenyl isocyanate) (MDI) in 1,3‐dimethyl‐2‐imidazolidone (DMI) in the presence of 3‐methyl‐1‐phenyl‐2‐phosopholene 1‐oxide catalyst, were reacted with α, ω‐bis (10‐carboxydecyl) polydimethylsiloxane (PDMS‐diacid) leading to the formation of multiblock copolymers. In the one‐step method, the reaction components, MDI, IPA, AZA, and PDMS‐diacid were reacted all together in DMI in the presence of the catalyst. These polymerizations gave multiblock copolymers having inherent viscosities in the range of 0.36–1.12 dL/g in N,N‐dimethylacetamide (DMAc). These multiblock copolymers were soluble in amide‐type solvents, and transparent (or translucent) and ductile films could be cast from the solutions in a mixture of DMAc and bis(2‐ethoxyethyl) ether. The multiblock copolymers prepared by the two‐step method had better‐defined, microphase‐separated morphology than those obtained by the one‐step method. The mechanical properties of PDMS–polyamide multiblock copolymer films were found to be highly dependent on the PDMS content; the tensile strength and modulus of the films decreased with increasing the PDMS content.