Synthesis of amphiphilic star block copolymer with photosensitive core by ATRP

Well-defined photo and pH-sensitive amphiphilic star block copolymers were synthesized by copper based atom transfer radical polymerization, which consisted of a hydrophilic pH sensitive shell and photosensitive hydrophobic core structure. For this, photosensitive n-butyl acrylate (nBA) star polymer was synthesized with a multi-functionalized initiator including Pd-coordinated porphyrin in combination with CuBr and 4,4′-dinonyl-2,2′-bipyridyl (dNbpy) (PDI < 1.09). This hydrophobic photosensitive nBA star polymer was then used as a macroinitiator and polymerized with N,N′-dimethylamino ethyl methacrylate (DMAEMA) in the CuCl/CuCl₂/dNbpy catalytic system to synthesize PnBA-PDMAEMA star block copolymer, where the PDMAEMA block segment worked as a base exterior. For the arm chain consisted of an acid exterior block segment, the nBA star polymer macroinitiator was polymerized with tert-butyl acrylate (tBA) in the CuBr/dNbpy catalytic system to synthesize the PnBA-PtBA star block copolymer followed by a treatment with strong acid for deprotecting the tert-butyl groups in the PtBA block segment to give PnBA-poly(acrylic acid) (PAA) star block copolymer. Both amphiphilic photosensitive star block copolymers showed well defined molecular weights with narrow polydispersities (PDI < 1.23). [Figure not available: see fulltext.]