State Key Laboratory Cultivating Base for New Fiber Materials and Modern Textile, Department of Polymer Science and Engineering, Qingdao University, Qingdao, 266071, China.
Langmuir. 2012 Jan 10;28(1):153-60. doi: 10.1021/la2031472. Epub 2011 Dec 15.
Double hydrophilic brush copolymer poly(ethylene oxide)-graft-poly(N,N-dimethylaminoethyl methacrylate) (PEO-g-PDMAEMA) was successfully prepared via atom transfer radical polymerization (ATRP). We investigated the pH/thermoresponsive behaviors of PEO-g-PDMAEMA brush-shaped copolymer concentrated aqueous solutions by rheology. The observed LCST strongly decreased with increasing pH of the solutions, which was lower than that of linear block copolymer for different pH, indicating rapid thermoresponsiveness of the brush PDMAEMA chains. An unexpected shear thickening behavior was observed and could be tuned by the pH, resulting from the mobile nature and tractive force of the densely grafted hydrophobic chains of PDMAEMA at high pH. Self-assembly of the brush copolymer in a different pH and ionic strength environment was studied by transmission electron microscopy. A wormlike cylinder structure was formed at low pH. Fractals were observed for the brush copolymer aqueous solution in the presence of NaCl. The results showed that by adjusting the pH and NaCl concentration of the dispersions fractal aggregates with different topology were obtained. The observations reported here can supply a better understanding of the molecular self-assembling nature and be used to develop responsive materials with better performance.
通过原子转移自由基聚合（ATRP）成功制备了双亲水刷状共聚物聚（氧化乙烯）-接枝-聚（N，N-二甲基氨基乙基甲基丙烯酸酯）（PEO-g-PDMAEMA）。我们通过流变学研究了 PEO-g-PDMAEMA 刷状共聚物浓水溶液的 pH/温敏行为。观察到的 LCST 随溶液 pH 的升高而显著降低，低于不同 pH 值的线性嵌段共聚物，表明 PDMAEMA 刷状链具有快速温敏性。观察到一种意外的剪切增稠行为，并且可以通过 pH 进行调节，这是由于在高 pH 下 PDMAEMA 的疏水性支链具有较大的流动性和牵引力。通过透射电子显微镜研究了在不同 pH 值和离子强度环境下刷状共聚物的自组装。在低 pH 值下形成了蠕虫状圆柱结构。在存在 NaCl 的情况下，观察到了刷状共聚物水溶液的分形。结果表明，通过调节分散体的 pH 值和 NaCl 浓度，可以得到具有不同拓扑结构的分形聚集体。这里的观察结果可以提供对分子自组装性质的更好理解，并用于开发具有更好性能的响应性材料。
