Student Poster Presentation #14 (Session 2)
Photo-responsive Bio-inspired Adhesives: Facile Control of Adhesion
Strength via Photocleavable Crosslinker
Minkyu Kim 1 and Hoyong Chung 1
1
Department of Chemical and Biomedical Engineering, Florida State University, Tallahassee, Florida
32310, United States
Abstract
A new bioinspired adhesive that includes zwitterionic polymer, poly(sulfobetaine methacrylate) (pSBMA),
catechol group, and photocleavable nitrobenzyloxycarbonyl containing crosslinker was synthesized by
convenient thermally-initiated free radical polymerization. The main component pSBMA is highly hydrophilic
and biocompatible polymer which has high potential as the biocompatible materials. The mussel’s adhesive
protein inspired catechol group is recently studied bioinspired functionality that enhances adhesion property on
universal surfaces even in the presence of water. The third component, nitrobenzyloxycarbonyl containing
diacryl crosslinker cleaves upon UV irradiation. UV/vis spectra analysis revealed that chemical bonding
cleavage rapidly occurs within 30 min and then slowly continued until 3hr, resulting in continuous decrease of
crosslinking density. The loss of crosslinking results weakened adhesion property according to lap shear strength
measurement. The decrease tendency in adhesion strength was similar with loss tendency of crosslinking in the
polymer. By conducting 1 H NMR experiment, we could confirm pure crosslinker shows fast chemical bonding
cleavage within 30 min and then slowly proceeds until 3hr in the same way as was discovered in adhesion
property tests. The photo-cleavage of nitrobenzyloxycarbonyl group occurs through a sequential 3 steps of
reaction with rate constants k1, k2, and k3, yielding carboxylic acid and aldehyde. The carboxylic acid and
aldehyde follows third-exponential rate law with three rate constants. The third-exponential rate law can be
simplified to a single exponential because a rate determining step k3 is order of magnitude smaller than other
rate constants. By using the obtained kinetic equation, the reduction of adhesion strength (kPa) could be
conveniently predicted at designated UV irradiation time.
Reference
1. Johnson JA, Finn MG, Koberstein JT, Turro NJ. 2007 Synthesis of Photocleavable Linear Macromonomers by ATRP
and Star Macromonomers by a Tandem ATRP-Click Reaction: Precursors to Photodegradable Model Networks.
Macromolecules 40 3589.
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