离子强度
共聚物
共单体
动态光散射
差示扫描量热法
高分子化学
分散性
丙烯酸
胶体
水溶液
化学工程
材料科学
离子键合
聚合物
化学
纳米颗粒
复合材料
物理化学
纳米技术
热力学
有机化学
离子
工程类
物理
作者
Martin J. Snowden,Babur Z. Chowdhry,Brian Vincent,Gayle E. Morris
摘要
Aqueous colloidal microgels have been prepared, based on poly(N-isopropylacrylamide)[poly(NIPAM)], cross-linked with bisacrylamide, containing 5% w/w acrylic acid (AAc) as a comonomer. Transmission electron micrographs of the microgels show that the copolymer microgels are monodisperse spheres. The size of the microgel particles containing 5% AAc has been studied, using dynamic light scattering, as a function of pH (3–10), ionic strength (10–4–10–1M NaCl) and temperature (20–75 °C). The hydrodynamic diameter of the copolymer microgels decrease both with increasing ionic strength (at pH 6 and 25 °C) and reversibly with increasing temperature at pH values of 2.6, 3.4 and 6.5. However, under isothermal conditions in 10–3M NaCl at 25 °C, the hydrodynamic diameter increases in going from pH 3.3–9.4. In addition, the temperature-induced conformational changes in the polymer chains have been followed using high-sensitivity differential scanning calorimetry (HSDSC). A comparison is made with the behaviour of poly(NIPAM) microgel particles, not containing AAc. Explanations are offered to account for the pronounced difference in the physico-chemical properties observed.
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