title: Kinetics of pH-Induced formation and dissociation of polymeric vesicles assembled from a water-soluble zwitterionic diblock copolymer.
abstract: The kinetics of pH-induced formation and dissociation of vesicles self-assembled from a biocompatible zwitterionic diblock copolymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine)-b-poly(2-(diisopropylamino)ethyl methacrylate) (PMPC- b-PDPA), was investigated in detail via a combination of stopped-flow light scattering and laser light scattering (LLS). Upon jumping from pH 2 to 10, stopped-flow light scattering reveals three distinct relaxation processes for the early stages of vesicle self-assembly (0-40 s). Kinetic sequences associated with the obtained three characteristic relaxation times have been tentatively proposed. Moreover, the kinetics of vesicle formation in the later stage (from 3 min onward) was investigated by dynamic LLS. It was found that both the intensity-averaged hydrodynamic radius, R h, and the polydispersity, mu2/Gamma (2), decrease exponentially, yielding a characteristic relaxation time of approximately 350 s. To our knowledge, this is the first report on the kinetics of the unimer-to-vesicle transition of a stimulus-responsive diblock copolymer. The kinetics of vesicle dissociation for a pH jump from 12 to 2 was also investigated. The breakdown of polymeric vesicles is extremely fast and is independent of polymer concentration; it is complete within approximately 5 ms and is in marked contrast to the much slower rate of vesicle formation.
authors.affiliation: Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Shen
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Du
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: Shiyong
authors.initials: S
authors.lastname: Liu
mesh_terms: D002627:Chemistry, Physical / Q000379:methods*; D004563:Electrochemistry / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D008027:Light; D008956:Models, Chemical; D015233:Models, Statistical; D011108:Polymers / Q000737:chemistry*; D011199:Potentiometry / Q000379:methods; D012542:Scattering, Radiation; D013499:Surface Properties; D013997:Time Factors
chemical_list: D007477:Ions; D011108:Polymers