Synthesis and characterization of epsilon-caprolactam-L-phenylalanine copolymers

A series of copolyamides has been prepared by hydrolytic polymerization of epsilon-caprolactam (CL) in the presence of various amounts of L-phenylalan ine (Phe). The solution viscosity of the obtained copolymers decreases by i ncreasing comonomer content, [eta] values ranging from 1.27 dl/g for neat p oly(epsilon-CL) (PCL) to 0.33 dl/g for the copolymer obtained, when 16.2 mo l % of Phe is present in the reaction medium. A similar, less pronounced tr end is shown by copolymer thermal transitions (both T-g and T-m are lowered by ca. 8 and 19 degrees C, respectively, in the copolyamide originated fro m 12.6 mol % of Phe present in the monomer pair). The environmental degrada bility has been ascertained by testing the resistance of CL-Phe copolymers to both alkaline hydrolysis and composting conditions. The degradation rate and the extent of hydrolysis of the above copolyamides have been evaluated by using the mass loss and thermogravimetric analysis for the former, and solution viscosity measurements for the latter. The CL-Phe copolymers could be envisaged as suitable film-forming materials for environmentally degrad able applications in various fields, such as agricultural coverage and food packaging, when time-limited performances are requested. (C) 1999 Elsevier Science Ltd. All rights reserved.