|Name||Mr. Christopher Kabb|
|Organization||University Of Florida|
Reversible-covalent hydrogels linked by photosensitive coumarin dimers
Christopher P. Kabb1, Christopher S. O'Bryan2, W. Gregory Sawyer2, Thomas E. Angelini2, Brent S. Sumerlin1
1. George & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida
Coumarin derivatives undergo a [2+2] cyclization upon exposure to long-wave UV irradiation (365 nm). This process can be reversed using short-wave UV light (254 nm) to revert the dimers to their monomeric form. Therefore, networks crosslinked by coumarin groups are an ideal candidate as reversible-covalent gels. In this work, copolymerization of coumarin-containing monomers with a hydrophilic comonomer resulted in water soluble, linear polymers. These “prepolymers” were irradiated with long-wave UV in the absence of a photoinitiator to yield free-standing hydrogels. Importantly, the gels were reverted back to soluble copolymers upon short-wave UV irradiation. This material provides an opportunity for preparing patterned hydrogels through a post-gelation photoetching method. Traditional limitations of this technique, such as the requirement for uniform etching in one direction, have been overcome by combining these materials with a 3D soft matter printing methodology. We have printed cylinders in which the interior coumarin gel is surrounded by a nondegradable gel, and upon exposure of these cylinders to short-wave UV irradiation, the coumarin gel is reverted to soluble prepolymers and washed away to yield a thin, hollow hydrogel tube.