Photochemical Modification Of Hydrogels To Control The Site-release Of Substances

This study selected the hydrogel prepared from 2-(dimethylamino)ethyl methacrylate(DMAEMA)and crosslinker N,N'-methylene diacrylamide(MBA)hydroxyethyl acrylate(HEA)through photopolymerization as an example.The monomer glycidyl methacrylate(GMA),which possesses two different functional groups,namely,double-bond acrylate,which can be radically photopolymerized,and an epoxy group,which can be cationic-photopolymerized,was photo-grafted on the hydrogel surface through hydrogen abstraction photopolymerization.Cationic photopolymerization of epoxy on each building block of polyglycidyl methacrylate(PGMA)was then used to crosslink the PGMA polymer chain.The two photopolymerizations can be sequentially carried out due to different photoinitiators matching with various mechanisms and wavelengths.The reaction can be controlled by selecting different photoinitiators with various absorption wavelengths.Hydrogen abstraction photopolymerization is a radical-chain polymerization,and coating thickness can be controlled by irradiation time during photo grafting.Crosslinking density can be controlled by photo-crosslinking.The crosslinking polymer layer changes the hydrogel surface texture.The diffusion rate of a substance(Rhodamine B(RhB)was selected as release substance in this study)through this modified hydrogel can be regulated by the thickness of the crosslinked surface.Photopolymerization was spatiotemporally controlled.Thus,photo-grafting can be site-conducted,that is,the grafted layer can be patterned,thereby resulting in site-controllable diffusion.