Polyamide 6-polycaprolactone multiblock copolymers : synthesis, characterization, and degradation

This work describes the synthesis and characterization of polyamide 6 (PA 6)-polycaprolactone (PCL) multiblock copolymers. Low molar mass, fully amine end-capped PA 6 was prepared by the addition of a diamine monomer during e-caprolactam polymerization. A low molar mass PCL was selected to be incorporated as the biodegradable block and was fully end-capped with toluene 2,4-diisocyanate. End group analysis and molecular weight characterizations were performed for both end-functionalized polymers by SEC, NMR and titration analysis. Incorporation of PCL into PA 6 was mainly achieved by solution mixing of the two end-functional blocks and, was continued after the removal of the solvent with solid state polymerization (SSP) by gradual heating until about 40 ??C below the melting temperature of the PA 6. Molecular weights started to grow immediately during solution mixing and only increased marginally during the SSP treatment. FTIR and SEC studies confirmed the reaction between the two components. DSC data, in combination with the enhanced molar mass during solution mixing pointed to a blocky microstructure, for which distinct melting and crystallization temperatures were observed for the PCL and the PA 6 blocks. Hydrolytic and enzymatic degradation studies were performed at 25 ??C where the degree of degradation was followed by weight loss analysis, SEM and SEC.