Synthesis of polystyrene-b-poly(ethylene glycol) block copolymers by radical exchange reactions of terminal RAFT agents

Abstract

In this study, a mechanistic transformation was achieved by taking advantage of coupling reaction of reversible addition-fragmentation chain transfer (RAFT) agents. Polymers prepared by different polymerization modes were coupled to form polystyrene-b-poly(ethylene glycol) (PS-b-PEG) block copolymer. For this purpose, two prepolymers, namely azo and RAFT functional polymers were prepared independently. In the first step, a new macroazoinitiator (MI)-containing PEG units was synthesized by direct esterification of 4,4-azobis(4-cyanopentanoic acid) (ACPA) with poly(ethylene glycol) (PEG) at ambient conditions. The other component, polystyrene (PS) was synthesized by atom transfer radical polymerization and modified with a reversible addition-fragmentation chain transfer(RAFT) agent (xanthate moiety) and used as a polymeric RAFT agent for the block copolymer formation. In the block copolymerization process, polymeric radicals stemming from the thermolysis of PEG-MI were coupled with the RAFT moiety of PS. The PEG-MI, PS, PS-XANTH, and PS-PEG block copolymers were characterized by spectral analysis using FT-IR, 1 H NMR, GPC, and DSC.

Dibenzoyldiethylgermane as a visible light photo-reducing agent for CuAAC click reactions

“…ω-Bromo functional polystyrene (PS-Br) was synthesized by ATRP according to the previously reported procedure 76 (M n,NMR : 4250 g/mol, M n,GPC : 4190 g/mol, M w /M n : 1.08). In a flask equipped with a stirrer, PS-Br (1 eq), sodium azide (5 eq) and 15 mL DMF was added.…”

Synthesis and characterization of polyphenylenes with polypeptide and poly(ethylene glycol) side chains

“…Although polymers bearing bound polypeptides provide unique properties and advantage as regards biofunctionalization, the use of soluble support is a more essential requirement in biological application . Water solubility can be achieved by the incorporation of polyethers, such as poly(ethylene glycol) (PEG).…”