Thermoresponsive unimolecular micelles with a hydrophobic dendritic core and a double hydrophilic block copolymer shell

Biocompatible stimuli-responsive unimolecular polymeric micelles have attracted much interest due to their unique structures and potential applications in biomedical fields such as drug delivery and tissue engineering. Here, we report the preparation of dendritic unimolecular polymeric micelles with temperature sensitive shells via reversible addition–fragmentation transfer (RAFT) technique. A multi-arm star amphiphilic copolymer (H40-PDEA) with a hydrophobic hyperbranched polyester (Boltorn H40) as the core and the grafted poly(N,N-diethylacrylamide) (PDEA) as the shell was prepared using H40 based macroRAFT agent. And a dendritic unimolecular polymer (H40-PDEA–PDMA) with a double hydrophilic block copolymer (DHBC) [PDEA-b-poly(2-(dimethylamino)ethyl methacrylate) (PDEA-b-PDMA)] as the dual thermoresponsive shells was synthesized by H40-PDEA based macroRAFT agent. Both H40-PDEA and H40-PDEA–PDMA have a reversible phase transition behavior in aqueous solution. In particular, the unimolecular polymeric micelles H40-PDEA–PDMA with double thermoresponsive shells exhibit a two-stage phase transition behavior. Laser light scattering (LLS), UV–vis transmittance, excimer fluorescence measurements, and micro-differential scanning calorimetry (micro-DSC) were used in combination to probe the conformational changes of chains located at the inner layer and outer corona during the phase transition process.

Graphical abstractThe dual stimuli-responsive umimolecular polymeric micelles (H40-PDEA–PDMA) with biocompatible coronas have two-stage reversible phase transition behavior during a heating-and-cooling cycle.Figure optionsDownload full-size imageDownload high-quality image (88 K)Download as PowerPoint slideResearch highlights► The dual stimuli-responsive umimolecular polymeric micelles with biocompatible coronas. ► The unimolecular micelles present a reversible two-stage process in thermosensityive particle size change during a heating-and-cooling cycle. ► The architecture of core–shell–corona for polymeric micelles has a great potential for a variety of applications ranging from drug delivery, separation, to gene delivery.