MICELLIZATION OF AMPHIPHILIC STAR POLYMERS WITH POLY(ETHYLENE OXIDE) ARMS IN AQUEOUS-SOLUTIONS

Well-defined three- and four-armed amphiphilic star polymers with a la rge hydrophobic core were made by the reaction of methoxypoly(ethylene glycol)s (MPEG) and tri- or tetrafunctional isocyanates abbreviated a s T3TMI and D4TMI. The latter are the hydrosilylation products of m-is opropenyl-alpha,alpha-dimethylbenzyl isocyanate (m-TMI) with methyltri s(dimethylsiloxy)silane and 2,4,6,8-tetramethylcyclotetrasiloxane, res pectively. In aqueous media the stars aggregate, the critical micelle concentrations (cmc) being in the order of 10(-4) M, with In cmc being proportional to the hydrophile-lipophile balance (HLB) of the stars. Cloud points (T(p)) were measured in the absence and presence of salts . For the salting-out electrolytes NaF and NaH2PO4, T(p) is proportion al to the molal salt concentration. The proportionality constant, K(s) , is found to be inversely proportional to the length of the MPEG arm of the star.