Phase separation of a polymer mixture driven by a gradient of light intensity
Phase separation of a polymer mixture driven by a gradient of light intensity
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DOI：
10.1021/ma992088a
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发表时间：
2000-05
期刊：
影响因子：
5.5
通讯作者：
H. Nishioka;Kaname Kida;O. Yano;Q. Tran-Cong
中科院分区：
文献类型：
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作者：
H. Nishioka;Kaname Kida;O. Yano;Q. Tran-Cong
热力学平衡下物理化学系统的稳定性由吉布斯自由能最小值决定。1到目前为止，大多数关于聚合物混合物相分离的实验和理论都是在热力学平衡下进行的，其中变量如压力，组成和温度（P，V，T）保持恒定。2、3在实践中，相分离常常发生在热力学非平衡条件下。例如，材料加工是在大尺度下进行的，其中热力学变量不再是常数4，5，并且可以随时间变化或作为空间分布存在。因此，系统远离平衡，相分离成为时空现象。6对这些时间演化过程的基本认识将有助于最终产品的质量控制。我们研究了温度梯度诱导的聚（2-氯苯乙烯）/聚（乙烯基甲基醚）（P2CS/PVME）共混物的相分离。7然而，实验观察受到PVME在梯度高温侧的热分解的限制，特别是受到在这些高温区域发生的非常快的相分离动力学的限制。在此通信中，我们报告的形态和相分离动力学的trans-stilbene标记的聚苯乙烯/聚（乙烯基甲基醚）（PSS/PVME）共混物的紫外线（UV）光强度梯度照射产生的初步结果。以前的研究表明，这种特殊的共混物的相容性，使用小角中子散射（SANS）表明，反式f顺式光异构化的苯乙烯标记的聚苯乙烯链可以诱导相分离，通过改变两个链段体积的PSS链和顺式异构体标记的聚苯乙烯和PVME之间的相互作用。8
The stability of a physicochemical system under thermodynamic equilibrium is dictated by the Gibbs free-energy minimum. 1 So far, most of the experiments as well as theories on phase separation of polymer mixtures have been performed under thermodynamic equilibrium where the variables such as pressure, composition, and temperature (P, V, T) are kept constant. 2, 3 In practice, phase separation often occurs under thermodynamic nonequilibrium conditions. For example, materials processing is performed under large scales where thermodynamic variables are no longer constant4, 5 and can either vary with time or exist as a spatial distribution. The system is thus far from equilibrium, and phase separation becomes a spatiotemporal phenomenon. 6 Basic knowledge of these time-evolution processes would be helpful for quality control of the final products.We have studied phase separation of poly (2-chlorostyrene)/poly (vinyl methyl ether)(P2CS/PVME) blends induced by a temperature gradient. 7 However, the experimental observation was limited by the thermal decomposition of PVME on the high temperature side of the gradient and particularly by the very fast phase separation kinetics taking place in these high-temperature regions. In this communication, we report a preliminary result on the morphology and phase separation kinetics of trans-stilbene-labeled polystyrene/poly (vinyl methyl ether)(PSS/PVME) blends resulting from irradiation with a gradient of ultraviolet (UV) light intensity. Previous studies on the miscibility of this particular blend using small-angle neutron scattering (SANS) indicated that trans f cis photoisomerization of stilbene labeled on polystyrene chains can induce phase separation by changing both the segmental volumes of the PSS chains and the enthalpic interactions between the cis-isomer-labeled polystyrene and PVME. 8