Analytical data belonging to the publication "Harnessing the polymer-particle duality of ultra-soft nanogels to stabilise smart emulsions"

Micro- and nanogels are widely used to stabilise emulsions and simultaneously implement their responsiveness to the external stimuli. One of the factors that improves the emulsion stability is the nanogel softness. Here, we study how the softest nanogels that can be synthesised with precipitation polymerisation of N-isopropylacrylamide (NIPAM), the ultra-low crosslinked (ULC) nanogels, stabilise oil-in-water emulsions. We show that ULC nanogels can efficiently stabilise emulsions already at low mass concentrations. These emulsions are resistant to droplet flocculation, stable against coalescence, and can be easily broken upon an increase in temperature. The resistance to flocculation of the ULC-stabilised emulsion droplets is similar to the one of emulsions stabilised by linear pNIPAM. In contrast, the stability against coalescence and the temperature-responsiveness closely resemble the one of emulsions stabilised by regularly crosslinked pNIPAM nanogels. The reason for this combination of properties is that ULC nanogels can be thought of as colloids in between flexible macromolecules and particles. As a polymer, ULC nanogels can efficiently stretch at the interface and cover it uniformly. As a regularly crosslinked nanogel particle, ULC nanogels protect emulsion droplets against coalescence by providing a steric barrier and rapidly respond to changes in external stimuli thus breaking the emulsion. This polymer-particle duality of ULC nanogels can be exploited to improve the properties of emulsions for various applications, for example in heterogeneous catalysis or in food science.

微米及纳米凝胶（micro- and nanogels）被广泛用于稳定乳液，并同时赋予其对外界刺激的响应性。提升乳液稳定性的关键因素之一，便是纳米凝胶的柔软性。本研究聚焦于通过N-异丙基丙烯酰胺（N-isopropylacrylamide, NIPAM）沉淀聚合法合成的最柔软纳米凝胶——超低交联（ultra-low crosslinked, ULC）纳米凝胶，探究其稳定水包油乳液的效果。研究表明，ULC纳米凝胶仅需较低的质量浓度即可高效稳定乳液。此类乳液可抗液滴絮凝、耐聚结，且在温度升高时可轻易破乳。经ULC纳米凝胶稳定的乳液液滴，其抗絮凝性能与线性聚N-异丙基丙烯酰胺（linear pNIPAM）稳定的乳液相当；而其抗聚结稳定性与温度响应性，则与常规交联聚N-异丙基丙烯酰胺（regularly crosslinked pNIPAM）纳米凝胶稳定的乳液高度相似。这种性能组合的成因在于，ULC纳米凝胶可被视为介于柔性大分子与颗粒之间的胶体体系：作为聚合物，ULC纳米凝胶可在界面处高效舒展并均匀覆盖界面；而作为常规交联纳米凝胶颗粒，其可通过构建空间位阻屏障保护乳液液滴免受聚结，并快速响应外界刺激变化以实现破乳。ULC纳米凝胶的这种聚合物-颗粒双重特性，可用于优化各类应用场景下的乳液性能，例如多相催化或食品科学领域。