Biomaterials Research Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Manchester, United Kingdom.
Langmuir. 2012 Mar 20;28(11):5227-36. doi: 10.1021/la204606v. Epub 2012 Jan 24.
In this study we report the preparation of a new family of core-shell microgels that are water-swellable and have a morphology that is controllable by particle composition. Here, nearly monodisperse core-shell PNVF-xGMA [poly(N-vinylformamide-co-glycidyl methacrylate)] particles (where x is the weight fraction of GMA used) were prepared via nonaqueous dispersion (NAD) polymerization in one step. The shells were PGMA-rich and were cross-linked by reaction of epoxide groups (from GMA) with amide groups (from NVF). The core of the particles was PNVF-rich. A bifunctional cross-linking monomer was not required to prepare these new microgels. The particles had a remarkable "cane-ball"-like morphology with interconnected ridges, and this could be controlled by the value for x. The particle size was tunable over the range 0.8-1.8 μm. Alkaline hydrolysis was used to hydrolyze the PNVF segments to poly(vinylamine), PVAM. The high swelling pressure of the cationic cores caused shell fragmentation and release of some of the core polymer when the hydrolyzed particles were dispersed in pure water. The extent to which this occurred was controllable by x. Remarkably, the PGMA-rich shells could be detached from the hydrolyzed particles by dispersion in water followed by drying. The hydrolyzed PNVF-0.4GMA particles contained both positively and negatively charged regions and the dispersions appeared to exhibit charge-patch aggregation at low ionic strengths. The new cross-linking strategy used here to prepare the PNVF-xGMA particles should be generally applicable for amide-containing monomers and may enable the preparation of a range of new water-swellable microgels.
在这项研究中，我们报告了一种新型核壳微凝胶的制备，这种微凝胶具有可溶胀的水凝胶特性，且其形态可通过颗粒组成来控制。在这里，通过一步非水相分散（NAD）聚合制备了近乎单分散的核壳 PNVF-xGMA[聚（N-乙烯基甲酰胺-co-甲基丙烯酸缩水甘油酯）]颗粒（其中 x 为 GMA 的重量分数）。壳层富含 PGMA，通过环氧基团（来自 GMA）与酰胺基团（来自 NVF）的反应交联。颗粒的核富含 PNVF。制备这些新型微凝胶不需要使用双官能团交联单体。这些颗粒具有独特的“棍棒球”状形貌，具有相互连接的脊，并且可以通过 x 值来控制其形貌。颗粒尺寸可在 0.8-1.8μm 的范围内调节。采用碱性水解将 PNVF 段水解为聚（乙烯胺），PVAM。当水解后的颗粒分散在纯水中时，带正电荷的核会产生高的溶胀压力，导致壳层破裂并释放出部分核聚合物。这种情况的发生程度可以通过 x 值来控制。值得注意的是，富含 PGMA 的壳层可以通过在水中分散并干燥来从水解后的颗粒上分离。水解的 PNVF-0.4GMA 颗粒含有正电荷和负电荷区域，并且在低离子强度下，分散体似乎表现出电荷斑块聚集。这里用于制备 PNVF-xGMA 颗粒的新交联策略应该普遍适用于含酰胺单体，并且可能能够制备一系列新型的可溶胀微凝胶。
