Determination of diffusion coefficient and partition coefficient of photoinitiator 2-hydroxy-2-methylpropiophenone in nanoporous polydimethylsiloxane network and aqueous poly(ethylene glycol) diacrylate solution

Abstract We determine diffusion and partition coefficients of 2-hydroxy-2-methylpropiophenone, a widely used photo-initiator, in nanoporous polydimethylsiloxane network and poly(ethylene glycol) diacrylate solution as model precursor solution. We spectroscopically measure average concentration of 2-hydroxy-2-methylpropiophenone in each media, which is compared to the one estimated from one-dimensional diffusion models to obtain diffusion coefficient. Partition coefficient is obtained by measuring saturated concentration of 2-hydroxy-2-methylpropiophenone in each media. Our results enables predicting concentration of 2-hydroxy-2-methylpropiophenone as it diffuses from precursor solution to crosslinked PDMS, which typically occurs when hydrogel is formed inside microfluidic device via photo-polymerization to create nano-structured or micro-structured hydrogel including microfluidic valves.