Thin films from pH and thermoresponsive triblock copolymers: from network dynamics to defect-free films

提出的研究项目调查的自组织和动力学的三嵌段共聚物，具有温度响应的端块和pH响应的中间块。末端嵌段是疏水性和温敏性单体的统计共聚物，具有较低的临界溶液行为。中间嵌段是弱阳离子聚电解质，其具有强烈的pH依赖性链构象。末端嵌段的温敏特性使得能够控制网络动力学：在低于相变温度下，交联是动态的，而在相变温度以上，交联是冻结的。端块和中间块的响应性应被利用来制备完全有序的纳米结构薄膜。它们在水或水蒸气中强烈膨胀，因此是传感器的模型系统。溶胀程度取决于制备条件。首先，网络结构将被研究在依赖于聚合物浓度，H值，离子强度和温度。网络动力学将与动态光散射研究，无论是在传统的方式和旋转的样品。其次，在此基础上，研究了厚膜在不同pH值、离子强度和温度条件下的溶胀行为和溶胀过程中的结构变化。这些调查进行了同步辐射小角X射线散射。第三，将在选定的pH值和离子强度下制备薄膜。它们在水蒸气中溶胀和干燥过程中的溶胀行为和结构变化。在这一点上，网络动态将通过温度的变化而变化，以实现无缺陷的结构并保存它们。这些薄膜可以被认为是传感器的模型系统。

The research project proposed investigates the self-organisation and dynamics of triblock copolymers which have thermoresponsive end blocks and a pH responsive middle block. The end blocks are statistical copolymers from hydrophobic and thermoresponsive monomers and feature lower critical solution behavior. The middle blocks are weak cationic polyelectrolytes which have strongly pH dependent chain conformations. The thermoresponsive properties of the end blocks enable the control of the network dynamics: At temperatures below the phase transition, the crosslinks are dynamic, whereas they are frozen above. The responsivity of the end and middle blocks shall be exploited to prepare perfectly ordered, nanostructured thin films. These swell strongly in water or water vapor and are therefore a model system for sensors. The degree of swelling depends on the preparation conditions. Firstly, the network structures will be studied in dependence on polymer concentration, H value, ionic strength and temperature. The network dynamics will be investigated with dynamic light scattering, both in the conventional way and with a rotating sample. Secondly, on the basis of these results, the swelling behavior of thick films and the structural changes shall be studied during swelling in water at different relevant pH values, ionic strength and temperatures. These investigations are carried out using synchrotron small-angle X-ray scattering. Thirdly, thin films will be prepared at selected pH values and ionic strengths. Their swelling behavior and structural changes during swelling in water vapor and during drying. At this, the network dynamics will be varied by change of temperature to achieve defect-free structures and to conserve them. These films may be considered as model systems for sensors.