Pollak T, Köhler W
Physikalisches Institut, Universitat Bayreuth, D-95440 Bayreuth, Germany.
J Chem Phys. 2009 Mar 28;130(12):124905. doi: 10.1063/1.3098403.
We have measured collective diffusion coefficients of dilute, semidilute, and concentrated solutions of polystyrene in toluene up to a polymer concentration of 0.832 mass fractions at T=25 degrees C. The three employed experimental techniques of photon correlation spectroscopy, thermal diffusion forced Rayleigh scattering, and optical beam deflection cover four orders of magnitude with respect to their characteristic diffusion lengths (200 nm-2.9 mm), corresponding to more than 8 decades of the diffusion time constants. Contrary to existing literature data, which suggest a length scale dependent anomalous diffusion at high concentrations, all our techniques yield identical diffusion coefficients and purely Fickian diffusion, irrespective of their characteristic length scale.
我们在T = 25摄氏度下测量了聚苯乙烯在甲苯中的稀溶液、半稀溶液和浓溶液的集体扩散系数，聚合物浓度高达0.832质量分数。所采用的三种实验技术，即光子相关光谱法、热扩散强迫瑞利散射法和光束偏转法，就其特征扩散长度（200纳米 - 2.9毫米）而言覆盖了四个数量级，对应于超过8个数量级的扩散时间常数。与现有文献数据相反，现有文献数据表明在高浓度下存在长度尺度依赖性的反常扩散，而我们所有的技术都给出了相同的扩散系数和纯菲克扩散，与它们的特征长度尺度无关。
