New approaches to stimuli-responsive polymeric micelles and hollow spheres |
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Authors: | Youwei Zhang Ming Jiang |
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Institution: | (1) Department of Macromolecular Science and the Key Laboratory of Molecular Engineering of Polymers, Minister of Education of China, Fudan University, Shanghai, 200433, China;(2) College of Materials Science and Engineering, Donghua University, Shanghai, 200051, China |
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Abstract: | This article briefly describes some new approaches to stimuli-sensitive polymeric micelles and hollow spheres, which were
developed in the authors’ laboratory in recent years. (1) Self-assembly of component polymers to non-covalently connected
micelles (NCCM) driven by specific interactions. For example, in water, PCL and PAA formed core-shell nanospheres due to interpolymer
hydrogen bonding. After crosslinking the PAA shell and removing the PCL core, “nanocages” made of PAA network were obtained.
This hollow structure shows perfect reversible size-pH dependence. (2) Simultaneous in-situ polymerization of monomers and
self-assembly of the polymers. In this approach, PNIPAM network was formed by radical polymerization covering PCL particles.
Hollow spheres of PNIPAM network were then obtained by biodegradation of the PCL core. Both the core-shell spheres and hollow
spheres show reversible size dependence on temperature change because of the phase transition of PNIPAM around 32°C. (3) Complexation-induced
micellization and transition between the micelles and hollow spheres. Graft copolymers of hydroxylethyl cellulose (HEC) and
PAA were prepared by free radical polymerization. The copolymers showed pH dependent micellization, i.e., micelles formed
when pH of the graft copolymer solution decreased to around 3. The micellar structure could be locked by crosslinking the
PAA grafts. The resultant cross-linked micelles undergo pH-dependent transition between the micelles and hollow spheres, which
accompanies a remarkable particle size change. Both the micellization and the structure transition were found to be reversible
and associated with H-bonding complexation between the main chain and grafts.
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Translated from Acta Polymerica Sinica, 2005, 650(5) (in Chinese) |
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Keywords: | micelle hollow sphere hydrogen bonding self-assembly stimuli-sensitivity |
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