Jungju Ryu

Preparation of an imogolite/poly(acrylic acid) hybrid gel

Many efforts in the field of hydrogels have been focused toward increasing the mechanical strength of the gel using inorganic materials. In this study, we synthesized a hydrogel that has excellent mechanical properties using surface-modified inorganic nanofibers composed of imogolite (Al2SiO3(OH)4), which is a hydrated aluminum silicate that has a hollow tube structure. Gamma ray radiation generates peroxide radicals on the nanofibers (imogolite), resulting in an additive free hybrid hydrogel. Structural optimization was carried out by changing the composition of imogolite and poly(acrylic acid). Chemical bonding between the nanofiber and the polymer was simulated by a cluster model and characterized by wide area Raman spectroscopy. The results indicate that imogolite embedded in a polymer matrix can align along the direction of an elongational force, as confirmed by small angle X-ray scattering (SAXS).

Time-dependent increase in aqueous solubility caused by the gradual disruption of hydrophobic aggregation

We report the preparation of a thermoresponsive polymer whose solubility in water can be controlled simply by time elapse. Most importantly, we showed that the gradual disruption of hydrophobic aggregation originated from strong π–π stacking between side chain triazole rings resulting in an increase in the cloud point. As time progressed, hydrogen bonds between one of the triazole ring nitrogen atoms and water molecules became dominant. This caused disruption of the hydrophobic domains by breaking π–π stacking between the triazole rings, leading to a thermodynamically stable hydration state. The gradual disruption of hydrophobic aggregation induced a time-dependent increase in the apparent cloud point. This time-dependent increase in aqueous solubility was not driven by hydrolytic degradation of ester linkages. This behavior was carefully characterized using a number of techniques, including percent transmission analysis, UV-Vis spectroscopy and 1H-NMR spectroscopy, and dynamic light scattering (DLS) measurements, all supporting our hypothesis. This macromolecule, which offers tailored control over aqueous solubility, may be a unique potential platform for drug delivery scaffolds where the release of encapsulated molecules is controlled simply by time.