Precise Synthesis of Dendron-Like Hyperbranched Polymers and Block Copolymers by an Iterative Approach Involving Living Anionic Polymerization,Coupling Reaction,and Transformation Reaction

摘要

Dendritic hyperbranched poly(methyl methacrylate)s (PMMA)s,whose branched architectures resemble the "dendron"part(s)of dendrimer,were synthesized by an iterative methodology consisting of two reactions in each iteration process:(a)a coupling reaction of a-functionalized,living,anionic PMMA having two tert-butyldimethylsilyloxymethylphenyl (SMP)groups with benzyl bromide (BnBr)-chain-end-functionalized PMMA,and (b)a transformation reaction of the introduced SMP groups into BnBr functionalities.These two reactions,(a)and (b),were repeated three times to afford a series of dendron-like,hyperbranched (PMMA)s up to third generation.Three dendron-like,hyperbranched (PMMA)s different in branched architecture were also synthesized by the same iterative methodology using a low molecular weight,functionalized 1,1 -diphenylalkyl anion prepared from sec-BuLi and l,l-bis(3-tert-butyldime-thylsilyloxymethylphenyl)ethylene in the reaction step (b)in each iterative process.Furthermore,structurally similar,dendron-like,hyperbranched block copolymers could be successfully synthesized by the iterative methodology using a-functionalized,living,anionic poly(2-(perfluorobutyl)ethyl methacrylate)(PRfMA)in addition to a-functionalized,living PMMA.Accordingly,the resulting block copolymers were comprised of both PMMA and PRfMA segments with different sequential orders.After the block copolymers were cast into films and annealed,their surface structures were characterized by angle-dependent XPS and contact angle measurements.All three samples showed significant segregation and enrichment of PRfMA segments at the surfaces.