title: Thermosensitive behavior of poly(ethylene glycol)-based block copolymer (PEG-b-PADMO) controlled via self-assembled microstructure.
abstract: Stimuli-responsive, well-defined diblock copolymers (PEG-b-PADMO) comprising poly(ethylene glycol) (PEG, DP (degree of polymerization)=45) as the hydrophilic and temperature-sensitive part and poly(N-acryloyl-2,2-dimethyl-1,3-oxazolidine) (PADMO, DP=18-47) as the hydrophobic and acid-labile part self-assembled in water into spherical micelles with high aggregation number. The micellar structures and thermally induced phase transitions of the copolymers were investigated with (1)H NMR spectroscopy, light scattering, microscopy, turbidimetry, and fluorescence techniques. Thermoresponsive phase transitions of the copolymers in water were controlled via formation of core-shell-type micelles with densely compact PEG corona. Their lower critical solution temperatures (LCSTs) were modulated within the range 40-72 °C by varying PADMO block length. This unusually low LCST was attributed to the densely packed PEG structure in the polymer micelles, which resulted in strong n-clustering attractive interactions and insufficient hydration of PEG chains in the shell and greatly enhanced the thermosensitivity. The LCST behavior can also be modulated by partial acid hydrolysis of PADMO segments through the resulting change of hydrophobicity.
authors.affiliation: Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China.
authors.forename: Qianling
authors.initials: Q
authors.lastname: Cui
authors.forename: Feipeng
authors.initials: F
authors.lastname: Wu
authors.forename: Erjian
authors.initials: E
authors.lastname: Wang
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry*; D012542:Scattering, Radiation; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D008823:Micelles; C560997:poly(ethylene glycol)-poly(N-acryloyl-2,2-dimethyl-1,3-oxazolidine) block copolymer; D014867:Water; D011092:Polyethylene Glycols