Komarova Galina A, Kozhunova Elena Yu, Gumerov Rustam A, Potemkin Igor I, Nasimova Irina R
Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, 119991 Moscow, Russia.
Gels. 2025 Jan 11;11(1):58. doi: 10.3390/gels11010058.
Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water-tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM.
了解具有不同化学组成和结构的聚合物微凝胶的吸附特性对于研究各自乳液稳定化机制至关重要。具体而言,使用刺激响应性颗粒可以引入新特性并拓宽此类复杂体系的应用范围。最近,我们证明,与聚N-异丙基丙烯酰胺(PNIPAM)均聚物及其他相关的基于PNIPAM的共聚物对应物相比,由聚N-异丙基丙烯酰胺(PNIPAM)和聚丙烯酸(PAA)的互穿网络(IPN)组成的微凝胶稳定的乳液在加热时表现出更高的胶体稳定性。在本工作中,我们使用悬滴张力测定法研究了PNIPAM-PAA IPN颗粒吸附过程中水-十四烷界面张力的变化,并将其与单网络P-(NIPAM-co-AA)和PNIPAM微凝胶进行比较。结果表明,尽管具有相同的化学组成,但与其他微凝胶结构相比,共聚物颗粒表现出完全不同的吸附行为。观察到的差异可归因于通过沉淀聚合获得的P-(NIPAM-co-AA)网络中带电丙烯酸基团的分布不均匀。相反,IPN结构的存在使不同单体在各自微凝胶内部均匀分布。此外,PNIPAM和PAA子链之间的氢键似乎降低了静电能垒,增强了IPN颗粒成功覆盖液体界面的能力。总体而言,我们的研究结果证实了使用PNIPAM-PAA IPN微凝胶制备水包油乳液及其稳定性的有效性,即使温度升高到PNIPAM的低临界溶液温度以上。