Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE A series of crosslinked PMMA films was fabricated. Crosslinked films show enhanced ethanol resistance compared to pure PMMA film. The ethanol resistance is positively correlated with the crosslinking degree. The optical properties remain comparable to those of pure PMMA after crosslinking. The crosslinked films show enhanced toughness at lower crosslinking degrees.

ABSTRACT
The inherent poor solvent resistance and brittleness of poly(methyl methacrylate) (PMMA) limit its applications requiring frequent ethanol disinfection, where the material is susceptible to cracking and failure. A crosslinked system is designed to improve the ethanol resistance of PMMA. To preserve the optical properties of crosslinked PMMA, varying molar ratios of the comonomer butyl methacrylate, which imparts additional free volume to compensate for transmittance loss of the final crosslinked material, are pre-copolymerized with MMA to obtain copolymer syrups. Crosslinked films are then fabricated via one-pot in situ polymerization and crosslinking by casting copolymer syrups containing the crosslinker 1,4-butanediol dimethacrylate. The crosslinked film with the highest crosslinking density (5 mol% crosslinker) possesses the maximum strength retention rates of 101.5% and 68.7% after immersion in ethanol for 5 min and 24 h, respectively. It represents a significant improvement over the pure PMMA, which retained only 93.8% and 53.8% under same conditions. Although crosslinked structures generally sacrifice the transmittance of optical resins, the 5 mol% crosslinked film exhibited the lowest transmittance (92.0% ± 0.6%), only slightly lower than that of pure PMMA (92.3% ± 0.2%). The toughness crosslinked films varied from 2.7 to 1.2 MJ/m3, which exceeded that of pure PMMA (1.0 MJ/m3).