聚合物水凝胶体积相变过程中自发生成的新图案

聚合物水凝胶在 p H、温度等外界条件变化之下可发生连续或不连续的体积相变1～ 6] .近年来 ,国际学术界认识到 ,凝胶的体积变化并不总是均匀地发生 ,伴随着剧烈的体积相变过程 ,凝胶中往往会呈现丰富多彩的图案7～ 10 ] .这些图案已引起国际高分子学术界、包括研究材料力学行为和水母等“透明状动物”的科学家的极大兴趣 11] .已发现了凝胶膨胀过程中的准六方凸起 7]、凝胶急剧收缩过程中的竹节状条纹等图案 8] .本文首次报道了凝胶的螺旋状图案 .Fig.1　 Typical Bamboo-like patterns formed in hydrogelshrinking after immersed…

A Novel Macroscopic Pattern Formation During Volume Phase Transition of Polymeric Hydrogel

Pattern formation in polymeric hydrogel associated with volume phase transition was observed in strong gel shrinking. Chemically cross linked poly(sodium acrylate/acrylamide) gel was prepared and shaped by capillary. The gel cylinder was suddenly dipped into acetone or into an acid aqueous solution. The former exhibited bamboo like pattern, similar to the report in the literature. But a novel pattern, gel helix or gel spring, was found in the latter case. Macroscopic patterns only occurred in a strong gel collapse, and nothing was found in a step by step volume shrinking. The helix is with period between 0 1 to 1 mm and formed within 100 second. Both right hand sense and left hand sense could be obtained. Once formed, the gel helix cannot be recovered by re swelling in basic solution. Surface crack and its helical growth were observed and could account for the formation of gel helix preliminarily.