Institute of Particle Science and Engineering, School of Processing, Environment and Materials Engineering, University of Leeds, Leeds LS2 9JT, UK.
Langmuir. 2010 Dec 7;26(23):18408-14. doi: 10.1021/la1033564. Epub 2010 Oct 28.
Responsive core-shell latex particles are used to prepare colloidosome microcapsules using thermal annealing and internal cross linking of the shell, allowing the production of the microcapsules at high concentrations. The core-shell particles are composed of a polystyrene core and a shell of poly[2-(dimethylamino)ethyl methacrylate]-b-poly[methyl methacrylate] (PDMA-b-PMMA) chains adsorbed onto the core surface, providing steric stabilization. The PDMA component of the adsorbed polymer shell confers thermally responsive and pH-responsive characteristics to the latex particle, and it also provides glass transitions at temperatures lower than those of the core and reactive amine groups. These features facilitate the formation of stable Pickering emulsion droplets and the immobilization of the latex particle monolayer on these droplets to form colloidosome microcapsules. The immobilization is achieved through thermal annealing or cross linking of the shell under mild conditions feasible for large-scale economic production. We demonstrate here that it is possible to anneal the particle monolayer on the emulsion drop surface at 75-86 °C by using the lower glass-transition temperature of the shell compared to that of the polystyrene cores (∼108 °C). The colloidosome microcapsules that are formed have a rigid membrane basically composed of a densely packed monolayer of particles. Chemical cross linking has also been successfully achieved by confining a cross linker within the disperse droplet. This approach leads to the formation of single-layered stimulus-responsive soft colloidosome membranes and provides the advantage of working at very high emulsion concentrations because interdroplet cross linking is thus avoided. The porosity and mechanical strength of the microcapsules are also discussed here in terms of the observed structure of the latex particle monolayers forming the capsule membrane.
响应性核壳乳胶粒子可用于通过热退火和壳的内部交联来制备胶体囊微胶囊，从而可以在高浓度下生产微胶囊。核壳粒子由聚苯乙烯核和吸附在核表面的聚[2-(二甲氨基)乙基甲基丙烯酸酯]-b-聚甲基甲基丙烯酸酯链组成的壳组成，提供空间稳定化。吸附聚合物壳的 PDMA 组分赋予乳胶粒子热响应性和 pH 响应性特征，并且还在低于核和反应性胺基的温度下提供玻璃化转变温度。这些特征有利于形成稳定的Pickering 乳液液滴，并将乳胶粒子单层固定在这些液滴上以形成胶体囊微胶囊。通过在温和条件下对壳进行热退火或交联来实现固定，这些温和条件对于大规模经济生产是可行的。我们在这里证明，通过使用比聚苯乙烯核(约 108°C)更低的玻璃化转变温度的壳，可以在 75-86°C 下对乳液滴表面上的粒子单层进行退火。形成的胶体囊微胶囊具有刚性膜，基本上由紧密堆积的单层粒子组成。通过将交联剂限制在分散液滴内，也成功地实现了化学交联。这种方法导致形成单层刺激响应性软胶体囊膜，并且由于避免了液滴间交联，因此具有在非常高的乳液浓度下工作的优势。还讨论了微胶囊的孔隙率和机械强度，这是根据形成胶囊膜的乳胶粒子单层的观察结构得出的。
