Spatially resolved studies on the photopolymerization of dimethacrylate monomers

摘要: AbstractThe photopolymerization of four dimethacrylate monomers under different irradiating conditions was followed in situ by 1 H stray-fieldmagnetic resonance imaging ( STRAFI-MRI). This technique is capable discriminating local changes at a spatial resolution tens ofmicron and suitable for studying larger samples than infrared spectroscopy photocalorimetry. The evolution proton magnetizationwith irradiation time intensity recorded correlated with volumetric polymerization shrinkage, extent reaction spatiallyresolved rates.q 2005 Elsevier Ltd. All rights reserved. Keywords: Dimethacrylates; Photopolymerization; Kinetics 1. IntroductionPhotopolymerization multifunctional oroligomers, often referred to as radiation curing, aubiquitous technology specialty polymer processing[1,2]. Key competitive advantages arise from thepossibility spatially controlling the byselectively desired regions ultra-fastreaction rates achievable intense [3].Additionally, it solvent-free (or solvent-poor) andenergy efficient polymerizations can beconducted room temperature, thus consideredeconomical minimum environmental impact.Common applications this include widevariety coatings, paints, printing inks, adhesives,composite materials dental restorations. Most theseapplications are two-dimensional their essence, i.e. onlythin layers (typically 100 mm or less) polymerized atime. There cases, however, where isdesirable occur thicker bulk specimens. Aparadigmatic example resinsand composites commonly used Infact, several established photopolymerizationprocesses adopt thin-layer approaches given difficultiesassociated light attenuation through ‘optically thick’films. In these situations, absorbing species inthe formulations lead gradients theirradiated surface interior specimen hencetonon-uniformratesofpolymerization.Asaresult,polymernetwork formation occurs an inhomogeneous fashionwith almost inevitable deleterious consequences theproduct final properties. Therefore, understanding bulkpolymerization photocurable seems worthundertaking.Spatially resolved studies werealready reported on resin based materials, whichwere performed using