title: Lipase catalyzed HEMA initiated ring-opening polymerization: in situ formation of mixed polyester methacrylates by transesterification.
abstract: 2-Hydroxyethyl methacrylate (HEMA) was used as initiator for the enzymatic ring-opening polymerization (ROP) of omega-pentadecalactone (PDL) and epsilon-caprolactone (CL). The lipase B from Candida antarctica was found to catalyze the cleavage of the ester bond in the HEMA end group of the formed polyesters, resulting in two major transesterification processes, methacrylate transfer and polyester transfer. This resulted in a number of different polyester methacrylate structures, such as polymers without, with one, and with two methacrylate end groups. Furthermore, the 1,2-ethanediol moiety (from HEMA) was found in the polyester products as an integral part of HEMA, as an end group (with one hydroxyl group) and incorporated within the polyester (polyester chains acylated on both hydroxyl groups). After 72 h, as a result of the methacrylate transfer, 79% (48%) of the initial amount of the methacrylate moiety (from HEMA) was situated (acylated) on the end hydroxyl group of the PPDL (PCL) polyester. In order to prepare materials for polymer networks, fully dimethacrylated polymers were synthesized in a one-pot procedure by combining HEMA-initiated ROP with end-capping using vinyl methacrylate. The novel PPDL dimethacrylate (>95% incorporated methacrylate end groups) is currently in use for polymer network formation. Our results show that initiators with cleavable ester groups are of limited use to obtain well-defined monomethacrylated macromonomers due to the enzyme-based transesterification processes. On the other hand, when combined with end-capping, well-defined dimethacrylated polymers (PPDL, PCL) were prepared.
authors.affiliation: School of Biotechnology, Department of Biochemistry, AlbaNova University Center, Royal Institute of Technology, SE-106 91 Stockholm, Sweden
authors.forename: Mohamad
authors.initials: M
authors.lastname: Takwa
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiao
authors.forename: Neil
authors.initials: N
authors.lastname: Simpson
authors.forename: Eva
authors.initials: E
authors.lastname: Malmström
authors.forename: Karl
authors.initials: K
authors.lastname: Hult
authors.forename: Cor E
authors.initials: CE
authors.lastname: Koning
authors.forename: Andreas
authors.initials: A
authors.lastname: Heise
authors.forename: Mats
authors.initials: M
authors.lastname: Martinelle
mesh_terms: D002384:Catalysis / Q000187:drug effects; D004951:Esterification; D008049:Lipase / Q000737:chemistry* / Q000494:pharmacology; D008689:Methacrylates / Q000138:chemical synthesis*; D011091:Polyesters / Q000138:chemical synthesis*; D011108:Polymers / Q000138:chemical synthesis*
chemical_list: D008689:Methacrylates; D011091:Polyesters; D011108:Polymers; C005044:hydroxyethyl methacrylate; D008049:Lipase