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

A simple but efficient strategy has been developed for the synthesis of nov el di-, tri-, multi-, and star-block copolymers comprising poly(ethylene gl ycol) (PEG) and polyisobutylene (PIB) blocks. The synthesis principle invol ves the coupling of appropriately terminally functionalized PEG and PIE seq uences, specifically the hydrosilation of mono-, di-, and tetra-allyl-telec helic PEGs (PEG-allyl, allyl-PEG-allyl, and Ct-PEG-allyl)(4) by mono- and d i-Si(CH3)(2)H telechelic PIBs (PIB-SiH and HiS-PIB-SiH). Representative blo ck copolymers, for example, PEG-PIB, PIB-PEG-PIB, (-PIB-PEG-)(n), and Ct-PE G-PIE), have been assembled and their structures determined by H-1 and C-13 NMR spectroscopy. The bulk and surface morphology of select triblocks have been investigated by DSC and AFM and the findings interpreted in terms of phase-separated PEG and PIE microdomains. The swelling behavior in water of various block copolymers also has been studied. Block copolymers containin g 50-70 wt % PIE produce hydrogels, the integrity of which is maintained by physical crosslinks by PIE segments. (C) 2000 John Wiley & Sons, Inc.