Micro!uidic fabrication of smart microgels from macromolecular precursors
Page Currently Being Edited by Joseph Muth
Title of Original Work: Mirofluidic Fabrication of Smart Microgels from Macromolecular Precursors
Journal of Original Work: Polymer, Volume 51, Pages 5883-5889, October 16, 2010
Authors: Sebastian Seiffert, David A. Weitz
Author of Review: Joseph Muth - AP 225 - Fall 2012 - 11/27/2012
Stimuli-responsive (smart) microgels are micron sized polymer particles that change shape in response to enviornmental stimuli. This responsiveness makes them useful in the fields of drug delivery, catalysis, sensing, and photonics. The most commonly used smart microgel material is poly(N-isopropylacrylamide) (pNIPAAm) because it has a lower critical solution temperature (LCST) around 32°C. Both the LCST and Tg of (pNIPAAm) are readily tunable by changing its composition or its particle geometry. As such controlling each of these aspects independently is critical to optimizing the characteristics of the microgel.
One way to achieve independent optimization is by using microfluidic techniques to template pre-fabricated precursor polymers. In this way simultaneous solidifcation and polymerization are avoided because gelation occurs via a polymeric analogous route instead of by monomeric chain growth. Using prefabricated precursor polymers, allows the molecular structure to be tuned through polymer synthesis, while microfluidics allows the shape to be accurately and precisely controlled. In this work, the author explores various ways to exploit this smart microgel fabrication technique.
The formation of microgels from precursor polymers is illustrated by the sequence of reactions in Figure 1, where pNIPAAm is prepared from N-isopropylacrylamide and dimethylmaleimide. The resulting pNIPAAm is then photocrosslinked. Molecular weight is controlled by running the pNIPAAm precursor is controlled by running the copolymerization step in the prescence of sodium formate. This synthesis route allows the weight average molecular weight to be controlled between 100,000-2,000,000 g/mol.