title: Formation of cage-like particles by poly(amino acid)-based block copolymers in aqueous solution.
abstract: When dissolved in N,N-dimethylformamide and then dialyzed against phosphate-buffered saline, A-B-A block copolymers composed of poly [N5-(2-hydroxyethyl)-L-glutamine]-block-poly(gamma-benzyl-L-glutamate)- block-poly [N5-(2-hydroxyethyl)-L-glutamine] form particles. The particles are cage-like structures with average diameters of 300 nm (average polydispersity, 0.3-0.5). They are stable in aqueous solution at 4 degrees C for up to 3 weeks, at which time flocculation becomes apparent. Negative staining and freeze-fracture electron microscopy suggest that cage-like particles are formed by selective association of segregated micelle populations. A model of particle formation is presented in which B blocks form micelles in dimethylformamide. On dialysis against an aqueous solution, the extended A blocks then associate intermolecularly to form rod-shaped micelles, which connect the B block micelles. The result is a meshed cage-like particle. The implications of these observations on the aggregation behavior of polymeric surfactants in dilute solution are discussed.
authors.affiliation: Ciba-Geigy Pharmaceuticals, Horsham, West Sussex, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Cudd
authors.forename: M
authors.initials: M
authors.lastname: Bhogal
authors.forename: J
authors.initials: J
authors.lastname: O'Mullane
authors.forename: P
authors.initials: P
authors.lastname: Goddard