Stimuli-Responsive Micelles of Amphiphilic AMPS-b-AAL Copolymers in Layer-by-Layer Films

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Polymers and High Performance Materials


Aqueous reversible addition-fragmentation chain transfer polymerization was used to synthesize poly(N-[3-(dimethylamino)propyl]acrylamide) (PDMAPA) cationic homopolymers and micelle-forming, pH-responsive, amphiphilic diblock copolymers of poly(sodium 2-acrylamido-2-methyl-1-propanesulfonate-block-N-acryloyl-L-alanine) (P(AMPS-b-AAL)). At low pH, the AAL blocks are protonated rendering them hydrophobic, whereas the AMPS blocks remain anionically charged because of the pendant sulfonate groups. Self-assembly results in core shell micelles consisting of hydrophobic cores of AAL and negatively charged shells of AMPS. Using solutions of these micelles with anionic coronas and of the cationic homopolymer PDMAPA, layer-by-layer (LbL) films were assembled at low pH, maintaining the micelle structures. Several block copolymers with varying AMPS and AAL block lengths were synthesized and used in the formation of LbL films. The thickness and morphology of the films were examined using ellipsometry and atomic force microscopy. The stimuli-responsive behavior can be triggered by submersion of the film in water at neutral pH to disrupt the micelles. This behavior was monitored by observing the decrease in film thickness and alteration of the film morphology. The micelles were also loaded with a model hydrophobic compound, pyrene, and incorporated into LbL films. The release of pyrene from the films was monitored by fluorescence spectroscopy at varying pH values (1, 3, 5, and 7). As the pH of the solution increases, the rate of release increases. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1104-1111, 2011

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Journal of Polymer Science Part A-Polymer Chemistry





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