University of Utah, Department of Chemistry, 315 South 1400 East Salt Lake City, UT 84112 USA.
Appl Spectrosc. 2014;68(6):633-41. doi: 10.1366/13-07337.
Small polymeric particles are increasingly employed as adsorbent materials, as molecular carriers, as delivery vehicles, and in preconcentration applications. The rational development of these materials requires in situ methods of analysis to characterize their synthesis, structure, and applications. Optical-trapping confocal Raman microscopy is a spectroscopic method capable of acquiring information at several stages of the development of such dispersed particulate materials. In the present study, an example material is developed and tested using confocal Raman microscopy for characterization at each stage of the process. Specifically, the method is used to investigate the synthesis, structure, and applications of individual polymeric surfactant particles produced by the vinyl polymerization of sodium 11-acrylamidoundecanoate (SAAU). The kinetics of polymerization can be monitored over time by measuring the loss of the acrylamide C=C functional groups using confocal Raman microscopy of particles optically trapped by the excitation laser, where, within the limits of detecting the vinyl functional group, the complete polymerization of the SAAU monomer was achieved. The polymerized SAAU particles are spherical, and they exhibit uniform access to water throughout their structure, as tested by the penetration of heavy water (D2O) and collection of spatially resolved Raman spectra from the interior of the particle. These porous particles contain hydrophobic domains that can be used to accumulate molecules for adsorption or carrier applications. This property was tested by using confocal Raman microscopy to measure the accumulation equilibria and kinetics of a model compound, dioxybenzone. The partitioning of this compound into the polymer surfactant could be determined on a quantitative basis using relative scattering cross sections of the SAAU monomer and the adsorbate. The study points out the utility of optical-trapping confocal Raman microscopy for investigating the synthesis, structure, and potential carrier applications of polymeric particle materials.
小的聚合粒子越来越多地被用作吸附材料、分子载体、输送工具以及在预浓缩应用中。这些材料的合理开发需要原位分析方法来表征它们的合成、结构和应用。光学捕获共焦拉曼显微镜是一种能够在这些分散颗粒材料的几个发展阶段获取信息的光谱分析方法。在本研究中，使用共焦拉曼显微镜对示例材料进行了开发和测试，以在每个过程阶段进行表征。具体来说，该方法用于研究通过 11-丙烯酰胺基十一烷酸钠（SAAU）的乙烯基聚合制备的单个聚合表面活性剂颗粒的合成、结构和应用。通过使用光学捕获颗粒的共焦拉曼显微镜测量丙烯酰胺 C=C 官能团的损失，可以监测聚合反应随时间的动力学，其中在检测到乙烯基官能团的限制内，实现了 SAAU 单体的完全聚合。聚合的 SAAU 颗粒是球形的，并且它们表现出在整个结构中均匀地进入水，这通过重水（D2O）的渗透和从颗粒内部收集空间分辨拉曼光谱来测试。这些多孔颗粒包含疏水区，可以用于积累分子进行吸附或载体应用。通过使用共焦拉曼显微镜测量模型化合物二氧芐酮的积累平衡和动力学，测试了这种性质。可以使用 SAAU 单体和吸附剂的相对散射截面来定量确定该化合物在聚合物表面活性剂中的分配。该研究指出了光学捕获共焦拉曼显微镜在研究聚合粒子材料的合成、结构和潜在载体应用方面的效用。
