Self-Assembly and Chemo-Ligation Strategies for Polymeric Multi-Responsive Microgels
Poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-AAc) copolymeric multi-responsive microgels demonstrate responsivity to temperature, pH, and ionic strength. A temperature-programmed polymerization protocol is proposed for the synthesis of large pNIPAm-AAc microgel particles with a hydrodynamic diameter of 2~5 ?m. Immediately after preparation of concentrated pNIPAm-AAc dispersions in closed system, the average hydrodynamic diameter is smaller than the unperturbed diameter probably due to osmotic de-swelling effect. During the aging process, pNIPAm-AAc microgel particles start to swell while their dynamics slow down. The snapshots of phase behavior of pNIPAm-AAc microgel dispersions at different pH values are illustrated. The formation of crystalline phase should follow a nonergodic path in which microgel particles swell to the extent that they build up weak attractive interaction to allow them to associate while maintaining the opportunity of rearrangement to minimize local Gibbs free energy. The age-dependent thermostability of pNIPAm-AAc microgel dispersions suggests strong attractive interactions evolve between particles during aging-convoluted crystallization. Finally, to introduce multiple biological handles on the microgel particles for biomedical applications, the Cu(I)-catalyzed azide-terminal alkyne 1,3-dipolar cycloaddition, also called Sharpless-Meldal click reaction, is used to functionalize pNIPAm-AAc microgel particles.
Advisor:Lyon, Louis; Breedveld, Victor; Srinivasarao, Mohan; Collard, David; Bunz, Uwe
School:Georgia Institute of Technology
School Location:USA - Georgia
Source Type:Master's Thesis
Keywords:chemistry and biochemistry
Date of Publication:06/18/2009