Real‐Time Raman Tracking of Composition Evolution During Crosslinking Methacrylate/Styrenic Photopolymerization

ABSTRACT Composition drift during copolymerization can alter residual functionality and network composition, yet overall conversion measurements may conceal this evolution. Real‐time Raman spectroscopy with programmable irradiation separately quantifies methacrylate (MA) and styrenic (ST) vinyl conversion and tracks the residual MA/ST ratio during crosslinking photopolymerization. Raman‐derived compositions of uncured UDMA/TEG‐DVBE mixtures agree closely with prepared compositions and proton nuclear magnetic resonance measurements. Five equimolar MA/ST formulations are examined at irradiation intensities of 10–1000 mW cm −2 . TEGDMA/TEG‐DVBE and EBPADMA/TEG‐DVBE exhibit preferential early MA consumption, followed by persistent or largely compensated composition bias, respectively. UDMA/TEG‐DVBE maintains near‐feed composition across intensities, whereas Bis‐GMA/TEG‐DVBE exhibits similar behavior during rapid, high‐intensity curing. Substantial drift in Bis‐GMA/styrene indicates that intraspecies hydrogen bonding alone is insufficient for composition control. Irradiation intensity changes polymerization kinetics, but its effect on composition drift depends on formulation. Fourier transform infrared spectra indicate redistribution of hydrogen‐bonding environments upon mixing Bis‐GMA with TEG‐DVBE, without directly establishing specific interspecies associations or their persistence during curing. These findings identify hydrogen bonding as a possible contributor rather than an established controlling mechanism. Real‐time Raman spectroscopy reveals distinct residual‐composition trajectories that overall conversion alone cannot resolve and provides a framework for evaluating composition control in photocured networks.