We 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)/ZnEt 2 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.

In this study, the thermal hydrolysis of the poly(L-lactic acid) (PLLA) films was investigated for its potential use as a food-packaging ecomaterial. The surface morphology, mass loss, molecular weight, thermal properties, and medium pH were routinely investigated; meanwhile, in particular, the composition and cytotoxicity of the water-soluble degradation products were studied. The changes in the mass loss and molecular weight revealed a random chain-scission mechanism. Differential scanning calorimetry analysis implied that the hydrolysis preferentially took place in the amorphous region. The medium pH decreased with time because of the accumulation of acid water-soluble products in the medium. Liquid chromatography/mass spectrometry analysis proved that these products were composed of 1-13 lactic acid units, in which the content of L-lactic acid increased with time and reached 9.71 mmol/L after hydrolysis for 84 days. The in vitro cell culture indicated that the water-soluble degradation products from the PLLA films had no cytotoxicity to human umbilical vein endothelial cells.