Reversible restructuring of aqueous block copolymer assemblies through stimulus-induced changes in amphiphilicity.
ABC triblock copolymers with a hydrophilic-thermomorphic-hydrophobic block sequence can assemble into distinct structures in water above and below the lower critical solution temperature for the thermomorphic block. Characterization of aqueous solutions of a representative poly(ethylene oxide)-block-poly(N-isopropylacrylamide)-block-polyisoprene copolymer by light scattering and transmission electron microscopy shows that small spherical micelles are formed at low temperatures and that large vesicles are favored at higher temperatures. The transformation from micelles to vesicles is reversible but slow, occurring over several weeks.
Sundararaman
Anand
A
Department of Chemistry and Center for Nanomaterials Research, Dartmouth College, Hanover, New Hampshire 03755, USA.
Stephan
Tim
T
Grubbs
Robert B
RB
D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins; D002070:Butadienes / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry*; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D046529:Microscopy, Electron, Transmission; D010420:Pentanes / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D012542:Scattering, Radiation; D012996:Solutions; D014867:Water / Q000737:chemistry
D000178:Acrylamides; D000180:Acrylic Resins; D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D011108:Polymers; D012996:Solutions; D014867:Water; C005059:isoprene; C052970:poly-N-isopropylacrylamide; D011092:Polyethylene Glycols