Stavila_2014_Biomacromolecules_15_234

The enzymatic ring-opening copolymerization of sigma-caprolactone (sigma-CL) and beta-lactam by using Candida antarctica lipase B (CAL-B) as catalyst was studied. Variation of the feed ratios of 25:75, 50:50, and 75:25 of sigma-CL/beta-lactam was performed. The products contain poly(sigma-CL-co-beta-lactam) and the homopolymers of poly(sigma-CL) and poly(beta-lactam). The structure of the copolymers was determined by MALDI-ToF MS. Poly(sigma-CL-co-beta-lactam) has an alternating and random structure consisting of alternating repeating units with oligo(sigma-CL) or oligo(beta-lactam). The highest fraction of the alternating copolymers resulted from the reaction with a feed ratio 50:50. The copolymer is a semicrystalline polymer with a Tm at 124 degreesC and Tgs at -15 and 50 degreesC. Interestingly, the copolymer also demonstrated cold crystallization at 29 and 74 degreesC, after quenching the sample from the melt in liquid nitrogen.