Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, USA.
J Phys Chem B. 2013 Jun 13;117(23):7106-12. doi: 10.1021/jp4008398. Epub 2013 Jun 4.
The variation in dielectric constant is measured for thin films of poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF) using confocal fluorescence microscopy. Spatial variation in the local dielectric constant of the polymer films on the ~250 nm length scale is measured using the solvochromatic emission from incorporated nile red (NR) at "quasi-single molecule" (10(-7) M) and true single molecule (SM) concentrations (10(-9) M). Correlation of the NR fluorescence wavelength maximum with dielectric constant is used to transform images of NR's emission maxima to spatial variation in local dielectric constant. We demonstrate that the distributions of dielectric environments measured in the quasi- and true SM approaches are equivalent; however, the enhanced signal rates present in the quasi-SM approach result in this technique being more efficient. In addition, the quasi-SM technique reports directly on the continuous spatial variation in dielectric constant, information that is difficult to obtain in true SM studies. With regards to the polymers of interest, the results presented here demonstrate that a limited distribution of dielectric environments is present in PMMA; however, a broad distribution of environments exists in PVDF consistent with this polymer existing as a distribution of structural phases.
利用共焦荧光显微镜测量了聚甲基丙烯酸甲酯（PMMA）和聚偏二氟乙烯（PVDF）薄膜的介电常数变化。通过在“准单分子”（10^(-7) M）和真正单分子（SM）浓度（10^(-9) M）下掺入尼罗红（NR）的溶剂致变色发射，测量了聚合物薄膜在约 250nm 长度尺度上的局部介电常数的空间变化。将 NR 荧光波长最大值与介电常数相关联，用于将 NR 发射最大值的图像转换为局部介电常数的空间变化。我们证明，在准 SM 和真正 SM 方法中测量的介电环境分布是等效的；然而，准 SM 方法中存在的增强信号速率使得该技术更有效率。此外，准 SM 技术直接报告介电常数的连续空间变化，这是真正 SM 研究中难以获得的信息。关于感兴趣的聚合物，这里呈现的结果表明 PMMA 中存在有限的介电环境分布；然而，在 PVDF 中存在广泛的环境分布，这与该聚合物作为结构相分布的存在一致。
