Lipase-catalyzed formation of end-functionalized poly(ε-caprolactone) by initiation and termination reactions

Macromonomers based on end-functionalized poly(epsilon-caprolactone) (EF-PCL) were prepared by different synthetic strategies using Candida antarctica lipase B as the catalyst. The first strategy: an alcohol containing the target end-functionality initiated the ring-opening polymerization of epsilon-caprolactone (epsilon-CL) (initiation reaction). The second strategy: acids and esters containing the target end-functionality were added to prepolymerized epsilon-CL. Consequently acid-terminated PCL was formed (termination reaction). Using the first strategy, 9-decenol-initiated PCL was formed (24 h, 99% conversion of epsilon-CL) with an average M-w of 1980 D. From the second strategy, linoleic acid-terminated PCL was formed with an average M-w of 2400 D (51 h, 99% conversion). The last strategies: initiation and termination was combined either by using a di-functionalized ester or by addition, in sequence, of initiator and terminator. By these di-functionalization strategies, 2-(4-hydroxyphenyl)-ethyl-poly(epsilon-caprolactone)-acrylate, di-EF-PCL was synthesized with an average M-w of 1960 D (52 h, 60 degrees C) and 1720 D (30 h, 60 degrees C), respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.