STAR-SHAPED POLYMERS BY LIVING CATIONIC POLYMERIZATION .2. SYNTHESIS OF AMPHIPHILIC STAR-SHAPED BLOCK POLYMERS OF VINYL ETHERS WITH HYDROXYL-GROUPS

Amphiphilic star-shaped polymers (5) of vinyl ethers (VEs) where the arms consist of a polyalcohol/poly(alkyl vinyl ether) AB block copolymer were prepared on the basis of living cationic polymerization. For example, a sequential polymerization of an ester-containing VE (CH2 = CHOCH2CH2OCOCH3) and isobutyl VE with HI/ZnI2 at -15-degrees-C in toluene led to a living block polymer (3a), which was subsequently allowed to react with a small amount of a bifunctional vinyl ether [1; CH2 = CHOCH2CH2OC6H4C(CH3)2C6H4OCH2CH2OCH = CH2] to give a star-shaped block copolymer (4a). Alkaline hydrolysis of the ester functions of 4a gave the amphiphilic star polymer 5a, [H[-CH2CH(OCH2CH2OH)]m-[CH2CH(OiBu)]n-]f-(core), with hydrophilic polyalcohol segments in the outer region. Amphiphilic star polymers 5b, [H[-CH2CH(OiBu)]m-[CH2CH(OCH2CH2OH)]n-]f-(core), with an opposite segment sequence (inner polyalcohol chains) were also prepared. The star polymer 5a (m = 10, n = 29, 8 arms/molecule) is soluble in methanol, whereas the corresponding linear block copolymer (identical with the arm chains) and the inner-alcohol counterpart 5b are insoluble.