Responsive Azobenzene-Containing Polymers and Gels

The photoviscosity effect in aqueous solutions of novel poly(4-methacryloyloxyazobenzene-co-N,N-dimethyl acrylamide) (MOAB-DMA) was demonstrated. The observed significant reduction in the zero-shear viscosity upon UVirradiation of MOAB-DMA aqueous solutions was due to the dissociation of the interchain azobenzene aggregates. Such phenomena can be advantageously used in photoswitchable fluidic devices and in protein separation. Introduction of enzymatically degradable azo cross-links into Pluronic-PAA microgels allowed for control of swelling due to degradation of the cross-links by azoreductases from the rat intestinal cecum. Dynamic changes in the cross-link density of stimuliresponsive microgels enable novel opportunities for the control of gel swelling, of importance for drug delivery and microgel sensoric applications. such microgels by using the azoaromatic cross-links. To this end, we synthesized an azoreductase-cleavable crosslinker, 4,4’-di(methacryloylamino)azobenzene, which could be cleaved by the enzyme, thus allowing the microgels to swell. Kinetics of swelling of such microgels responsive to the biological stimulus is reported herein. II. EXPERIMENTAL SECTION