title: Temperature-responsive phase transition of polymer vesicles: real-time morphology observation and molecular mechanism.
abstract: Novel thermosensitive polymer vesicles with controlled temperature-responsive phase transition at the lower critical solution temperature (LCST) varying from 8 to 81 degrees C were prepared via self-assembly of amphiphilic hyperbranched star copolymers having a hydrophobic hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many hydrophilic polyethylene oxide (PEO) arms. Real-time optical microscopic observation revealed that the polymer vesicles have undergone sequential morphology changes including enrichment, aggregation, fusion, and vesicle-to-membrane transformation near the LCST. Molecular-level investigation indicates that the LCST transition results from the decreasing water solubility of the polymer vesicles with increasing temperature based on the partial dehydration of the PEO vesicle corona. On the basis of these results, a LCST transition mechanism, in view of the molecular configuration, balance of hydrophilic and hydrophobic moieties, and the vesicle morphology transformations, was proposed. As far as we know, the work presented here is the first demonstration of thermosensitive vesicles based on PEO, and the finding may be useful to design the thermosensitive core-shell structures by introducing the PEO segments.
authors.affiliation: College of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China.
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Zhou
authors.forename: Deyue
authors.initials: D
authors.lastname: Yan
authors.forename: Wenyong
authors.initials: W
authors.lastname: Dong
authors.forename: Ye
authors.initials: Y
authors.lastname: Tian
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D004337:Drug Carriers; D004988:Ethers, Cyclic / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012995:Solubility; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D004337:Drug Carriers; D004988:Ethers, Cyclic; D008823:Micelles; D011108:Polymers; D011092:Polyethylene Glycols; C005287:oxetane