Zhu Peng Wei
Department of Materials Science and Engineering, Monash University, Clayton, VIC 3800, Australia.
Soft Matter. 2021 Jul 21;17(28):6817-6832. doi: 10.1039/d1sm00523e.
In this work, based on the framework of preferential adsorption concept and analytical self-consistent field (SCF) theory, a model is proposed to investigate the reentrant transition experimentally observed from the thermoresponsive spherical brush in a series of aqueous alcohol solutions. The interaction between monomers is incorporated into the model. Conformational transitions of the spherical brush are quantitatively correlated to the physical parameters, including the number of adsorbed cosolvents which facilitates the solvent quality, the number of cosolvent bridges which drives the brush collapse, as well as their partition coefficients between the brush and the bulk solution. An analytical formula for the number of Kuhn segments per tethered chain is obtained based on the analytical SCF theory, which elucidates the flexibility of tethered chains in the intricate system of multicomponents involving the conformational transitions. Under the experimental conditions associated with the cosolvent-brush interaction, the variation of the monomer chemical potential with the monomer concentration indicates that the monomer distribution of the spherical brush remains continuous. The analysis based on the SFC theory also reveals that the distribution of adsorbed cosolvents is a positive parabola while the distribution of cosolvent bridges appears to be an exponential decay function, implying that the intervening space between tethered chains, rather than the number of adsorbed cosolvents, plays a crucial role in forming the cosolvent bridge. We demonstrate that the model formulated for the reentrant transition under weaker cosolvent-brush interactions provides guidelines for the one under stronger nanoparticle-brush interactions.
在这项工作中，基于优先吸附概念和解析自洽场（SCF）理论的框架，提出了一个模型，以研究在一系列醇水溶液中从热响应球形刷实验观察到的折返转变。单体之间的相互作用被纳入该模型。球形刷的构象转变与物理参数定量相关，这些参数包括促进溶剂质量的吸附助溶剂数量、驱动刷塌缩的助溶剂桥数量，以及它们在刷与本体溶液之间的分配系数。基于解析SCF理论得到了每个接枝链的库恩链段数的解析公式，该公式阐明了在涉及构象转变的复杂多组分体系中接枝链的柔性。在与助溶剂 - 刷相互作用相关的实验条件下，单体化学势随单体浓度的变化表明球形刷的单体分布保持连续。基于SFC理论的分析还表明，吸附助溶剂的分布是正抛物线，而助溶剂桥的分布似乎是指数衰减函数，这意味着接枝链之间的间隔空间而非吸附助溶剂的数量在形成助溶剂桥中起关键作用。我们证明，为较弱助溶剂 - 刷相互作用下的折返转变制定的模型为较强纳米颗粒 - 刷相互作用下的折返转变提供了指导。
