Chemoenzymatic Synthesis of New Brush Copolymers Comprising Poly(ω-pentadecalactone) with Unusual Thermal and Crystalline Properties

Abstract

Lipases from different sources were screened to determine their relative performance to catalyze ω-pentadecalactone (PDL) ring-opening polymerization from the hydroxyl group of 2-hydroxyethyl methacrylate (2-HEMA) and ω-hydroxyl-ω‘-methacrylate−poly(ethylene glycol) [PEGMA ( M n 360)]. Novozym 435 was found to be the most active biocatalyst for 2-HEMA/PEGMA-initiated PDL ring-opening polymerizations at 70 °C for 48 h in toluene (1:2 w/v of monomers). Thus, 2-HEMA-terminated PPDL was synthesized in yields of ∼80% and with <2 mol % carboxyl-terminated PPDL from initiation by water. Similarly, PEGMA-terminated PPDL was prepared. The free radical polymerizations of the corresponding macromers were carried out with AIBN at 70 °C in toluene. Thermal analysis of 2-HEMA- co - b -PPDL and PEGMA- co - b -PPDL macromers showed them to be stable and highly crystalline ( T m from 80 to 90 °C). In PEGMA- co - b -PPDL macromers, X-ray diffraction measurements show that the ethylene oxide units of the PEG block crystallize in the PPDL lattice. The main change observed upon polymerization of the macromers is a decrease of crystallinity (by both DSC and X-ray measurements).