Target molecule-responsive hydrogels with β-cyclodextrin (β-CD) were prepared via molecular imprinting using bisphenol A (BPA) as a template. BPA-imprinted hydrogels showed greater shrinkage than non-imprinted hydrogels because CD ligands arranged at suitable positions formed CD-BPA-CD complexes that acted as crosslinks.
At the start of our research program concerned with the elucidation of the crosslinking polymerization mechanism leading to interpenetrating polymer network (IPN) formation, in which IPNs consist of both polymethacrylates and polyurethane (PU) networks, this article deals with the polyaddition crosslinking reaction leading to PU network formation. Therefore, 2-methacryloyloxyethyl isocyanate (MOI) was radically copolymerized with methyl methacrylate (MMA) in the presence of CBr 4 as a chain-transfer agent. The resulting poly(MMA-co-MOI)s, having pendant isocyanate (NCO) groups as novel multifunctional polyisocyanates, were used for polyaddition crosslinking reactions with ethylene glycol as a typical diol. The second-order rate constants depended on both the functionality of poly(MMA-co-MOI) and the NCO group concentration. The actual gel points were compared with the theoretical ones calculated according to Macosko's equation; the deviation of the actual gel point from the theoretical value became more remarkable for a greater functionality of poly(MMA-co-MOI) and at a lower NCO group concentration or at a lower poly(MMA-co-MOI) concentration. These are discussed mechanistically, with consideration given to the significance of intramolecular cyclization and intramolecular crosslinking reactions leading to the shrinkage of the molecular size of the prepolymer, along with the data of the intrinsic viscosities of resulting prepolymers and the swelling ratios of resulting gels.
The equimolar polyaddition cross-linking reaction of poly(methyl methacrylate-co-2-methacryloyloxyethyl isocyanate) with tri(oxytetramethylene) glycol leading to polyurethane (PU) networks
was carried out in methyl benzoate at a 0.1 mol/L concentration of functional groups at 80 °C.
Simultaneously, the free-radical cross-linking copolymerization of methyl methacrylate with tri(oxytetramethylene) dimethacrylate leading to polymethacrylate (PM) networks was progressed at a
dilution of 1/10 in the presence of CBr4 as a chain transfer agent. The simultaneous interpenetrating
networks (SINs) were formed via the topological cross-links between PU and PM network structures
introduced by the respective intramolecular cross-linking reactions. Under the same polymerization
conditions, no gelation was observed for respective cross-linking homopolymerizations leading to PU and
PM homo-networks because respective intramolecular cross-linking reactions would be enhanced at a
diluted solution. The topological cross-link formation between PU and PM network polymer precursors
was pursued by SEC monitored with a multichannel UV−vis spectrometer device. The enhanced
occurrence of intermolecular cross-linking via the topological cross-link formation was reflected on the
variations of both the UV−vis monitored SEC curves and the molecular weights of the resulting PU and
PM network polymer precursors with conversion. In addition, the respective actual gel points were
compared with the corresponding theories for PU and PM networks formation or gelation. The swelling
ratio of the resulting gel was quite high, suggesting a rather low cross-link density of PU/PM SIN produced
through the topological cross-link formation between PU and PM network polymer precursors.
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