Synthesis and characterization of novel amphiphilic block copolymers di-, tri-, multi-, and star blocks of PEG and PIB

Abstract

A simple but efficient strategy has been developed for the synthesis of novel di-, tri-, multi-, and star-block copolymers comprising poly(ethylene glycol) (PEG) and polyisobutylene (PIB) blocks. The synthesis principle involves the coupling of appropriately terminally functionalized PEG and PIB sequences, specifically the hydrosilation of mono-, di-, and tetra-allyl-telechelic PEGs (PEG-allyl, allyl-PEG-allyl, and C(-PEG-allyl)4 by mono- and di-Si(CH3)2H telechelic PIBs (PIB-SiH and HiS-PIB-SiH). Representative block copolymers, for example, PEG-PIB, PIB-PEG-PIB, (-PIB-PEG-)n, and C(-PEG-PIB)4 have been assembled and their structures determined by 1H and 13C NMR spectroscopy. The bulk and surface morphology of select triblocks have been investigated by DSC end AFM and the findings interpreted in terms of phase-separated PEG and PIB microdomains. The swelling behavior in water of various block copolymers also has been studied. Block copolymers containing 50-70 wt % PIB produce hydrogels, the integrity of which is maintained by physical crosslinks by PIB segments.