Department of Applied Chemistry, Kyushu University, Fukuoka 819-0395, Japan.
Phys Chem Chem Phys. 2013 Oct 21;15(39):16574-8. doi: 10.1039/c3cp52673a. Epub 2013 Aug 16.
Polymer nanoparticles have been used in a wide variety of applications. In most of these applications, they are generally dispersed in a non-solvent. However, the effect of the non-solvent on the structure, physical properties and function of the nanoparticles has not yet ever taken into account. In this study, monodispersed poly(methyl methacrylate) (PMMA) nanoparticles were prepared by a surfactant-free emulsion polymerization. The PMMA nanoparticles were dispersed in water and in methanol, both typical non-solvents for PMMA, so that we could discuss the effect of the non-solvent on the nanoparticles. Dynamic light scattering measurements revealed that the hydrodynamic radius of the PMMA nanoparticles in methanol was larger than the same PMMA dispersed in water. Their DLS values were also larger than the radius of the nanoparticles measured by atomic force microscopy. When pyrene was dispersed in methanol with the PMMA nanoparticles, it was incorporated into the nanoparticles. These results clearly indicate that non-solvent molecules can be sorbed into polymer nanoparticles because the area of the interface, where polymer segments might be dissolved into liquid phases, as the total volume is quite larger for such nanoparticles. Therefore, based on our findings, it can be arguably established that the present assumption for a polymer not to be swollen in its non-solvent is not necessarily true.
聚合物纳米粒子在各种应用中得到了广泛的应用。在这些应用中，它们通常分散在非溶剂中。然而，非溶剂对纳米粒子的结构、物理性质和功能的影响尚未得到考虑。在这项研究中，通过无表面活性剂乳液聚合制备了单分散聚甲基丙烯酸甲酯（PMMA）纳米粒子。PMMA 纳米粒子分散在水中和甲醇中，甲醇是 PMMA 的典型非溶剂，因此我们可以讨论非溶剂对纳米粒子的影响。动态光散射测量表明，甲醇中 PMMA 纳米粒子的水动力半径大于在水中分散的相同 PMMA。它们的 DLS 值也大于原子力显微镜测量的纳米粒子的半径。当芘与 PMMA 纳米粒子一起分散在甲醇中时，它被掺入到纳米粒子中。这些结果清楚地表明，非溶剂分子可以被吸附到聚合物纳米粒子中，因为聚合物链段可能溶解到液相中的界面面积对于这些纳米粒子来说要大得多。因此，根据我们的发现，可以说目前关于聚合物在其非溶剂中不溶胀的假设不一定是正确的。
