Guzik Aleksander, de Maere d'Aertrycke Fabrice, Stuart Marc C A, Raffa Patrizio
Smart and Sustainable Polymeric Products, Engineering and Technology Institute Groningen, University of Groningen, Nijenborgh 4 9747 AG, The Netherlands.
DPI, P.O. Box 902, 5600 AX Eindhoven, The Netherlands.
Soft Matter. 2024 Nov 13;20(44):8727-8741. doi: 10.1039/d4sm00763h.
The objective of this work was to synthesize high molecular weight polyelectrolyte complex (PEC) micelles that are effective in controlling the rheology of aqueous solutions at low concentrations, paving the way for industrial applications of thickeners based on the principle of electrostatic self-assembly. Redox-initiated RAFT (reversible addition-fragmentation chain-transfer) polymerization was used to obtain anionic block polyelectrolytes based on poly(sodium 2-acrylamido-2-methylpropane sulfonate) and poly(acrylamide)-poly(AMPS)--poly(AM) (di-block) and poly(AMPS)--poly(AM)--poly(AMPS) (tri-block), with molecular weights of 237 kDa and 289 kDa and polydispersities of 1.29 and 1.34, respectively. A random poly(AMPS)--poly(AM) copolymer was also synthesized for comparison. PEC micelles were obtained upon mixing with cationic poly(-[3-(dimethylamino)propyl]methacrylamide hydrochloride) - poly(DMAPMA), forming viscoelastic gels at unprecedented low concentrations of <3 wt% for the di-block and <1 wt% for the tri-block, which to date is the lowest demonstrated gelation concentration for a synthetic PEC micelle system. Differences between tri-block and di-block architectures are discussed, with the former being more affected by the addition of salt, which is attributed to percolated network breakdown. The random co-polymer was shown not to be an effective thickener but displayed a surprising lack of phase separation upon coacervation. The assemblies were characterized using dynamic light scattering (DLS) and cryo transmission electron microscopy (cryoTEM), revealing spherical micelles with a diameter of approximately 200 nm for the diblock and a mixture of spherical micelles and network particles for the tri-block PEC micelles. The micelles were not affected by dilution down to a polymer concentration of 7.8 × 10% (approx. 0.03 μM). Responsiveness to salinity, pH, and temperature was studied using DLS, revealing a critical NaCl concentration of 1.1 M for the block copolymer micelles.
这项工作的目标是合成高分子量聚电解质复合物（PEC）胶束，该胶束能在低浓度下有效控制水溶液的流变学，为基于静电自组装原理的增稠剂的工业应用铺平道路。采用氧化还原引发的可逆加成-断裂链转移（RAFT）聚合反应来制备基于聚（2-丙烯酰胺基-2-甲基丙烷磺酸钠）和聚（丙烯酰胺）-聚（AMPS）-聚（AM）（二嵌段）以及聚（AMPS）-聚（AM）-聚（AMPS）（三嵌段）的阴离子嵌段聚电解质，其分子量分别为237 kDa和289 kDa，多分散指数分别为1.29和1.34。还合成了无规聚（AMPS）-聚（AM）共聚物用于比较。将其与阳离子聚（-[3-（二甲氨基）丙基]甲基丙烯酰胺盐酸盐）-聚（DMAPMA）混合后得到PEC胶束，对于二嵌段胶束，在低至<3 wt%的前所未有的低浓度下形成粘弹性凝胶，对于三嵌段胶束，在<1 wt%的浓度下形成粘弹性凝胶，这是迄今为止合成的PEC胶束体系中所展示的最低凝胶化浓度。讨论了三嵌段和二嵌段结构之间的差异，前者受盐添加的影响更大，这归因于渗流网络的破坏。结果表明，无规共聚物不是一种有效的增稠剂，但在凝聚时显示出令人惊讶的无相分离现象。使用动态光散射（DLS）和冷冻透射电子显微镜（cryoTEM）对组装体进行了表征，结果显示二嵌段胶束为直径约200 nm的球形胶束，三嵌段PEC胶束为球形胶束和网络颗粒的混合物。将胶束稀释至聚合物浓度为7.8×10%（约0.03 μM）时，其不受影响。使用DLS研究了胶束对盐度、pH值和温度的响应，结果表明嵌段共聚物胶束的临界NaCl浓度为1.1 M。
