Thermoresponsive and Reducible Hyperbranched Polymers Synthesized by RAFT Polymerisation
School of Chemistry, Bangor University, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
Charles Institute of Dermatology, University College Dublin, Dublin 4, Ireland
Author to whom correspondence should be addressed.
Polymers 2017, 9(9), 443; https://doi.org/10.3390/polym9090443
Received: 20 July 2017 / Revised: 24 August 2017 / Accepted: 6 September 2017 / Published: 13 September 2017
(This article belongs to the Special Issue Living Polymerization)
Here, we report the synthesis of new thermoresponsive hyperbranched polymers (HBPs) via one-pot reversible addition-fragmentation chain transfer (RAFT) copolymerisation of poly(ethylene glycol)methyl ether methacrylate (PEGMEMA, Mn = 475 g/mol), poly(propylene glycol)methacrylate (PPGMA, Mn = 375 g/mol), and disulfide diacrylate (DSDA) using 2-cyanoprop-2-yl dithiobenzoate as a RAFT agent. DSDA was used as the branching agent and to afford the HBPs with reducible disulfide groups. The resulting HBPs were characterised by Nuclear Magnetic Resonance Spectroscopy (NMR) and Gel Permeation Chromatography (GPC). Differential Scanning Calorimetry (DSC) was used to determine lower critical solution temperatures (LCSTs) of these copolymers, which are in the range of 17–57 °C. Moreover, the studies on the reducibility of HBPs and swelling behaviours of hydrogels synthesized from these HBPs were conducted. The results demonstrated that we have successfully synthesized hyperbranched polymers with desired dual responsive (thermal and reducible) and crosslinkable (via thiol-ene click chemistry) properties. In addition, these new HBPs carry the multiplicity of reactive functionalities, such as RAFT agent moieties and multivinyl functional groups, which can afford them with the capacity for further bioconjugation and structure modifications.