Faraudo Jordi, Moncho-Jordá Arturo, Bastos-González Delfi, Drummond Carlos
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, E-08193 Bellaterra, Spain.
Biocolloid and Fluid Physics Group, Department of Applied Physics, University of Granada, Avenida Fuentenueva 2, E-18071 Granada, Spain.
Macromolecules. 2023 Mar 17;56(6):2246-2257. doi: 10.1021/acs.macromol.3c00132. eCollection 2023 Mar 28.
We have investigated the formation of stable clusters of poly(-isopropylacrylamide) (pNIPAM) chains in water at temperatures above the lower critical solution temperature (LCST), induced by the presence of sodium tetraphenylborate, NaPhB. The hydrophobic PhB ions interact strongly with the pNIPAM chains, providing them with a net effective negative charge, which leads to the stabilization of pNIPAM clusters for temperatures above the LCST, with a mean cluster size that depends non-monotonically on salt concentration. Combining experiments with physical modeling at the mesoscopic level and atomistic molecular dynamic simulations, we show that this effect is caused by the interplay between the hydrophobic attraction between pNIPAM chains and the electrostatic repulsion induced by the associated PhB ions. These results provide insight on the significance of weak associative anion-polymer interaction driven by hydrophobic interaction and how this anionic binding can prevent macroscopic phase separation. Harvesting the competition between attractive hydrophobic and repulsive electrostatic interaction opens avenues for the dynamic control of the formation of well-calibrated polymer microparticles.
我们研究了在高于低临界溶液温度（LCST）的温度下，在水中由四苯硼酸钠（NaPhB）的存在诱导形成的聚（N-异丙基丙烯酰胺）（pNIPAM）链的稳定簇。疏水性的PhB离子与pNIPAM链强烈相互作用，赋予它们净有效负电荷，这导致在高于LCST的温度下pNIPAM簇的稳定，其平均簇尺寸非单调地依赖于盐浓度。通过将实验与介观水平的物理建模以及原子分子动力学模拟相结合，我们表明这种效应是由pNIPAM链之间的疏水吸引力与相关PhB离子诱导的静电排斥之间的相互作用引起的。这些结果深入了解了由疏水相互作用驱动的弱缔合阴离子-聚合物相互作用的重要性，以及这种阴离子结合如何防止宏观相分离。利用有吸引力的疏水相互作用和排斥性静电相互作用之间的竞争为动态控制校准良好的聚合物微粒的形成开辟了道路。
