Combining Ring-Opening Multibranching and RAFT Polymerization: Multifunctional Linear-Hyperbranched Block Copolymers via Hyperbranched Macro-Chain-Transfer Agents

The synthesis of a hyperbranched macro-chaintransfer agent for RAFT polymerization of functional methacrylate or methacrylamide monomers was achieved by selectively attaching one single CTA onto hyperbranchecl polyglycerol dendron analogues. The combination of ring-opening rnultibranching polymerization of glycidol and subsequent RAFT polymerization of the hyperbranched macro-chain-transfer agents created a new route to a variety of multifunctional linear-hyperbranched block topologies. All linear-hyperbranched block copolymers could be synthesized with controlled molecular weight (M-n = 3.2-43.7 kg/mol) and low polydispersity (PDI = 1.15-1.34). As first examples for this universal approach, we present block copolymer syntheses with thermoresponsive methacrylate (tri(ethylene glycol) methyl ether methacrylate) and biocompatible methacrylarnide (2-hydroxypropylniethacrylamide). Because of the presence of dithioberizoate esters at the end of each linear polymer chain end, selective end-group modification with functional methanethiosulfonates for bioconjugation to proteins (via the biotin-avidin interaction) or drugs (and dyes as model compounds, respectively) could be achieved. This expands the scope of this class of polymer architectures and renders the obtained multifunctional linear-hyperbranched block copolymers applicable as topologically advanced polymeric drug delivery systems.