Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
J Chem Phys. 2011 Jan 14;134(2):024901. doi: 10.1063/1.3507255.
A temperature-ramping anisotropy measurement is introduced as an efficient way to study molecular motion in polymer glasses. For these experiments, fluorescent molecules were dispersed in the polymer glass and the reorientation of these dyes was used as a probe of segmental dynamics. For thick samples of polystyrene, poly (4-tert-butyl styrene), and poly(2-vinyl pyridine), temperature-ramping anisotropy measurements have a shape similar to differential scanning calorimetry measurements and nearly the same transition temperature. We present results using different fluorescent molecules and different temperature-ramping rates; such experiments show potential for accessing slow molecular motions considerably below T(g). Temperature-ramping anisotropy measurements were performed on freestanding poly (4-tert-butyl styrene) films of varying thicknesses. The anisotropy decay of a 22 nm film was shifted about 12 K lower in temperature as compared to a bulk sample.
升温各向异性测量被引入作为一种研究聚合物玻璃中分子运动的有效方法。对于这些实验，荧光分子被分散在聚合物玻璃中，这些染料的重取向被用作段动态的探针。对于聚苯乙烯、聚（4-叔丁基苯乙烯）和聚（2-乙烯基吡啶）的厚样品，升温各向异性测量的形状类似于差示扫描量热法测量，并且具有几乎相同的转变温度。我们使用不同的荧光分子和不同的升温速率呈现了结果；这些实验显示了在 Tg 以下相当慢的分子运动的潜力。升温各向异性测量在不同厚度的自由站立聚（4-叔丁基苯乙烯）薄膜上进行。与块状样品相比，22nm 薄膜的各向异性衰减温度降低了约 12K。
