| 초록 |
In this study, we seek to understand the phenomenon that we call “swelling hysteresis” of polymer hydrogels. When radical-polymerized hydrogels were dried and reswollen, we found that the equilibrium swelling ratios of reswollen hydrogels were substantially (0~50%) lower than those of initial hydrogels, depending on both polymerization and drying conditions (pregel composition, polymerization kinetics, dehydration level, time spent in dry condition). We used various methods (SS-NMR, FT-IR, MALDI-TOF, XPS, etc.) and confirmed that “swelling hysteresis” did not involve any chemical reaction during the drying process. Instead, we are currently finding various evidences using SAXS, TD-NMR, XPCS, and other measurements that “swelling hysteresis” originated from defect sites, specifically hyperbranched dangling chains created during the hydrogel formation, and their reptation into adjacent network during the drying process, which resulted in irreversible and permanent entanglements. |
