6533b827fe1ef96bd1286493

RESEARCH PRODUCT

Multi-Arm Star Polyglycerol-block-poly(tert-butyl acrylate) and the Respective Multi-Arm Poly(acrylic acid) Stars

subject

description

Well-defined multi-arm star block copolymers, polyglycerol-block-poly(tert-butyl acrylate) (PG-b-PtBA), with average arm-numbers of 17, 27, 36, 66 and 90 arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of tBA in acetone, using a core-first strategy. After hydrolysis with excess concentrated HCl in refluxing dioxane, full hydrolysis of the tert-butyl ester groups was achieved, resulting in multi-arm star polyelectrolytes, polyglycerol-block-poly(acrylic acid) (PG-b-PAA). The hyperbranched macroinitiators employed were prepared on the basis of hyperbranched polyglycerols via esterification with 2-bromoisobutyryl bromide. Both CuBr/PMDETA and CuBr/Me 6 TREN catalyst systems have been employed for ATRP of tBA. CuBr/PMDETA was found to permit good control. Polydispersity indices for the new multi-arm stars were mainly in the range of 1.22 to 1.4, and the absolute M n data were in agreement with the calculated values. Moreover, kinetic curves show a linear dependence of ln([M] 0 /[M] t ) on time, confirming that the polymerizations are controlled. Relationship between arm numbers of the multi-arm stars and maximum conversion achieved.