Preparation of poly(ethylene glycol)–polystyrene block copolymers using photochemistry of dithiocarbamate as a reduced cell-adhesive coating material

This article reports a novel preparation method of poly(ethylene glycol) (PEG)–polystyrene (PST) amphiphilic block copolymers with well-defined block lengths by using photopolymerization of an iniferter, benzyl N,N-diethyldithiocarbamate. PEG macroiniferters, which were prepared by end-capping of PEG monomethyl ethers with benzyl N,N-diethyldithiocarbamate group at one end, were irradiated with UV light in the presence of styrene (ST). NMR analyses showed that the PST block was chain-extended from the PEG block, resulting in the preparation of PEG–PST block copolymers. The number-average molecular weights of the copolymers increased almost linearly with irradiation time, light intensity, and concentration of ST. The polydispersities of the copolymers remained relatively small throughout the reaction (Mw/Mn≈1.3). The composition of two PEG-PST block copolymers thus obtained was as follows: PEG (Mn; 1.9×103 g mol-1)–PST (3.0×103 g mol-1) and PEG (4.9×103 g mol-1)–PST (2.6×103 g mol-1). These copolymers were coated onto a poly(ethylene terephthalate) film surface. X-ray photoelectron spectroscopy analyses and water wettability measurements showed that the PST block was enriched at the outermost layer as cast in air, whereas upon immersion into water, the PEG block was oriented toward water. Enhanced wettability was observed for the diblock copolymer with a higher PEG content. Significantly reduced cell adhesion was observed on both the coated surfaces. Thus, the PEG–PST block copolymer may function as a cell adhesion-resistant coating which reduced cell–substrate interaction.