Synthesis and characterization of copolymers with the same proportions of polystyrene and poly(ethylene oxide) compositions but different connection sequence by the efficient Williamson reaction

Abstract

The AB type diblock PS-b-PEO and ABA type triblock PS-b-PEO-b-PS copolymers containing the same proportions of polystyrene (PS) and poly(ethylene oxide) (PEO) but different connection sequence were synthesized and investigated. Using the sequential living anionic polymerization and ring-opening polymerization mechanisms, diblock PS-b-PEO copolymers with one hydroxyl group at the PEO end were obtained. Then, using the classic and efficient Williamson reaction (realized in a ‘click’ style), triblock PS-b-PEO-b-PS copolymers were achieved by a coupling reaction between hydroxyl groups at the PEO end of PS-b-PEO. The PS-b-PEO and PS-b-PEO-b-PS copolymers were well characterized by 1H NMR spectra and SEC measurements. The critical micelle concentration (CMC) and thermal behaviors were also investigated by steady-state fluorescence spectra and DSC, respectively. The results showed that, because the PEO segment in triblock PS-b-PEO-b-PS was more restricted than that in diblock PS-b-PEO copolymer, the former PS-b-PEO-b-PS copolymer always gave higher CMC values and lower crystallization temperature (Tc), melting temperature (Tm) and degree of crystallinity (Xc) parameters. © 2015 Society of Chemical Industry