Synthesis and Self‐Assembly of New Double‐Crystalline Amphiphilic Polyethylene‐block‐Poly[oligo(ethylene glycol) Methyl Ether Methacrylate] Coil‐Brush Diblock Copolymer

Abstract

AbstractWe report on the synthesis and self‐assembly of a novel well‐defined coil‐brush diblock copolymer with linear crystalline polyethylene (PE) as the coil block and hydrophilic poly [oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) as rod brush via a combination of chain shuttling ethylene polymerization (CSEP) and atom transfer radical polymerization (ATRP). Initially, bromine end‐terminated PE macroinitiator (PE–Br) was synthesized through the esterification of 2‐bromo‐2‐methylpropionyl bromide with monohydroxyl‐terminated PE (PE–OH) which was prepared by means of CSEP with 2,6‐bis[1‐(2,6‐dimethylphenyl)imino ethyl] pyridine iron (II) dichloride/methylaluminoxane (MAO)/ZnEt2 and subsequent in situ oxidation with oxygen. The resultant PE‐b‐POEGMA coil‐brush diblock copolymer was synthesized by ATRP of monomethoxy‐capped oligo(ethylene glycol)methacrylate (OEGMA) using PE–Br as macroinitiator. The self‐assembly of the double‐crystalline PE‐b‐POEGMA in aqueous solution was investigated by dynamic light scattering, transmission electron microscopy and cryofield emission scanning electron microscopy. It was found that, in water, a solvent selectively good for the POEGMA brush, PE‐b‐POEGMA chains could self‐assemble to form sandwich‐like micelles with the insoluble and crystallized PE blocks as the interlayer cores and the soluble and swollen POEGMA brush as the outer‐layer shell. The crystallization of both PE and POEGMA blocks in self‐assembled structure formed from aqueous solution was investigated by differential scanning calorimetry.magnified image