Amphiphilic Unimolecular Nanoparticles Based on a Hyperbranched Polyacrylate Core and a PNIPAm Shell: Synthesis via ATRP and Properties

A novel amphiphilic unimolecular nanoparticle, multi-HPBPEA-g-PNIPAm, for encapsulation and release of hydrophobic guest molecules, is developed. The polymer shows coreshell architecture and is synthesized from inimer 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) by atom transfer radical polymerization (ATRP) in three steps. The hydrophobic core (multi-HPBPEA) is composed of hyperbranched poly(2-((2-bromopropionyl)oxy)ethyl acrylate) (HPBPEA), which is synthesized by self-condensing vinyl polymerization (SCVP) of BPEA. Multi-HPBPEA-g-PNIPAm is obtained by multi-HPBPEA core initiating ATRP of N-isopropylacrylamide (NIPAm). The encapsulation behavior of the core of multi-HPBPEA-g-PNIPAm in an aqueous solution is investigated by fluorescent spectra. It is found that multi-HPBPEA-g-PNIPAm can efficiently encapsulate and release a hydrophobic drug like nifedipine.