SYNTHESIS OF POLY(DIMETHYLSILOXANE)-NYLON-6 DIBLOCK COPOLYMERS

Poly(dimethylsiloxane)-polyamide-6 (PDMS-PA6) diblock copolymers have been synthesized anionically from omega-N-acyllactam-PDMS macroinitiators using newly developed di(tert-butoxy)-lithium aluminium hydride catalysts and bulk ultrasonic mixing of the reactants. These copolymers possess high PA6 block molecular weights and good thermal stability in the melt (ca. 250-degrees-C) because they do not contain carbamates. Size exclusion chromatography has revealed that traditional catalysts for the ring-opening polymerization of epsilon-caprolactam (CPL) such as alkali metal caprolactamates or LiA1H4, significantly depolymerize the PDMS to cyclics (D3, D4) in CPL at moderate temperatures of 100 - 170-degrees-C. New coordinating catalysts, produced by derivatizing LiA1H4, reduced the nucleophilicity of the CPL anion but did not interfere with the activated monomer mechanism. These new catalysts eliminated the depolymerization of PDMS to cyclics during growth of the polyamide-6 block to make the macroinitiator technique viable.