Notwithstanding
the progress of dental material adhesion on tooth
surfaces in the past several decades, debonding strongly adhered restorative
materials from tooth surfaces remains a challenging issue. Herein,
we propose the use of photodegradable polyrotaxanes (PRXs), which
are supramolecular-interlocked polymers comprising α-cyclodextrin
threaded along a poly(ethylene glycol) (PEG) axle, as a component
of adhesive resin cements to attenuate debonding strength via light irradiation. We synthesized photodegradable PRXs
(iNB-PRXs) using internally o-nitrobenzyl ester-introduced
PEG as an axle polymer. Notably, approximately 60% of iNB-PRX degraded
into its constituent molecules after 5 min of irradiation with ultraviolet
(UV) light. Thereafter, iNB-PRX was combined with the clinically utilized
adhesive resin cement, and a poly(methyl methacrylate) (PMMA) block
was adhered on the surface of bovine dentin using an adhesive resin
cement cross-linked with iNB-PRX. Although the PMMA block was successfully
adhered onto the dentin with a clinically acceptable adhesive force,
the tensile strength of the PMMA–dentin specimens decreased
significantly upon UV irradiation for 2 min owing to the UV-induced
degradation of the iNB-PRX cross-linker. According to these results,
the adhesive resin cement containing photodegradable iNB-PRX cross-linkers
is a promising candidate for facilitating the debonding of dental
materials from tooth surfaces via UV light irradiation.
A thermal-swing adsorption system for Eu(III) was developed using the thermosensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), combined with the acidic extractants, acid phosphoxy ethyl methacrylate (Phosmer-M) or acrylic acid. The phase transition of the PNIPAM/acidic extractant copolymers was successfully achieved by changing the temperature around the lower critical solution temperature (LCST). The thermal-swing adsorption of Eu(III) was correspondingly achieved by changing the temperature of the aqueous solution. The adsorption ability of Eu(III) was increased when the temperature became higher than the LCST, due to the change in the hydrophobicity as well as in the volume of the copolymer. The difference in the adsorption at lower and higher temperatures against the LCST was increased with decreasing crosslinking agent during the preparation of the copolymer. The copolymer possessed sufficient loading and release capacity for Eu(III) even in repeated processes of the thermal-swing adsorption.
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