ORDER-DISORDER TRANSITION OF LOW-MOLECULAR-WEIGHT POLYSTYRENE-BLOCK-POLYISOPRENE .1. SAXS ANALYSIS OF 2 CHARACTERISTIC TEMPERATURES
ORDER-DISORDER TRANSITION OF LOW-MOLECULAR-WEIGHT POLYSTYRENE-BLOCK-POLYISOPRENE .1. SAXS ANALYSIS OF 2 CHARACTERISTIC TEMPERATURES
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DOI：
10.1021/ma00124a018
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发表时间：
1995-09-25
期刊：
影响因子：
5.5
通讯作者：
HASHIMOTO, T
中科院分区：
文献类型：
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作者：
SAKAMOTO, N;HASHIMOTO, T
进行了高温分辨率小角X射线散射（SAXS）实验，以阐明低分子量聚苯乙烯-嵌段-聚异戊二烯在温度T（T-ODT）下的有序-无序转变以及从Brazovskii型非平均场理论表征的无序态到T（T-MF）下Leibler平均场理论表征的无序态的交叉 具有大约相同嵌段分子量的共聚物。在T-ODT上，反峰散射强度I-m(-1)和峰宽sigma(q)明显表现出非常尖锐的不连续性，但浓度波动的特征长度D几乎没有变化。 T-ODT 以下存在的二阶散射最大值在 T-ODT 以上肯定消失，表明通过 T-ODT 增加 T 时，空间浓度波动轮廓从方波型变为正弦波型轮廓。从 I-m(-1)、sigma(q)(2) 和 D 与 T 的温度相关性的变化可以清楚地识别交叉温度 T-MF：偏导数 I-m(-1)/偏导数(1/T)、偏导数 sigma(q)(2)/偏导数(1/T) 和偏导数 D/偏导数(1/T) 均在 相同温度T-MF。 T > T-MF 时的温度依赖性 D 通过未受扰动的嵌段共聚物链的回转半径 R(g0) 来解释，而 T < T-MF 时的温度依赖性则远大于 R(g0)。
High-temperature-resolution small-angle X-ray scattering (SAXS) experiments were performed to elucidate the order-disorder transition at temperature T (T-ODT) and the crossover from the disordered state characterized by the Brazovskii-type non-mean-field theory to the disordered state characterized by the Leibler mean-field theory at T (T-MF) for low molecular weight polystyrene-block-polyisoprene copolymers having about equal block molecular weights. Across T-ODT, the inverse peak scattered intensity I-m(-1) and the peak width sigma(q) clearly show a very sharp discontinuity, but the characteristic length D of the concentration fluctuations shows almost no change. The second-order scattering maximum existing below T-ODT definitely disappears above T-ODT, indicating that the spatial concentration fluctuation profile changes from a square-wave-type to a sinusoidal-wave-type profile upon increasing T through T-ODT. The crossover temperature T-MF is clearly identified from the changes in the temperature dependencies of I-m(-1), sigma(q)(2), and D with T: partial derivative I-m(-1)/partial derivative(1/T), partial derivative sigma(q)(2)/partial derivative(1/T), and partial derivative D/partial derivative(1/T) all show a discontinuity at the same temperature T-MF. The temperature dependence D at T > T-MF is explained by that of the radius of gyration R(g0) of the unperturbed block copolymer chains, while that at T < T-MF is much greater than that of R(g0).