S. Cramail et al., Controlled synthesis and solution behavior of macrocyclic poly[(styrene)-b-(ethylene oxide)] copolymers, MACRO CH P, 201(17), 2000, pp. 2328-2335
A series of cyclic poly[(styrene)-b-(ethylene oxide)] diblock copolymers 4
(1.5 kg/mol < <(M)over bar>(n) < 1.1 kg/mol) with narrow molecular weight d
istributions (I <less than or equal to> 1.12) have been synthesized. They w
ere obtained by intramolecular cyclization of linear a-diethyl acetal-omega
-styrenyl poly(styrene ethylene oxide) 3, under high dilution conditions.
The use of well-defined linear precursors in association with a cyclization
process based on an unimolecular end-to-end coupling reaction allows the f
ormation of macrocyclic diblocks in high yield (more than 90%). The structu
ral characterization and the solution behavior of both the linear and cycli
c amphipathic diblock copolymers have been investigated by means of NMR, si
ze exclusion chromatography, and viscosimetry.