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应用同步辐射X射线小角散射(SAXS)方法研究了PS/甲苯/CO_2体系压缩流体抗溶剂过程中PS链的尺寸和构象。结果发现随着抗溶剂压力的增加,第二Virial系数A_2和均方旋转半径〈R_g~2〉~(1/2)都将减小。在不同抗溶剂压力(0,0.6,1.5,2.4,3.3和4.2 MPa)下,PS链的散射强度符合I(h)∝h~(-α),说明PS链在压缩流体抗溶剂过程中具有自相似行为或分形结构。所有这些现象都表明,溶液中抗溶剂压力或CO_2的溶解性都对PS链的结构有很大影响。体系的分形维数随着抗溶剂压力的增加而增加,说明高分子链在这一过程中由近似于无规线团的构象发展成一种近似于球形的形状。
The size and conformation of PS chains in PS / toluene / CO 2 system anti-solvent were studied by using synchrotron radiation X-ray small angle scattering (SAXS) method. The results show that the second Virial coefficient A_2 and the mean square radius of gyration ~ (1/2) decrease with the increase of anti-solvent pressure. The scattering intensities of PS chains conform to I (h) αh ~ (-α) at different antisolvent pressures (0, 0.6, 1.5, 2.4, 3.3 and 4.2 MPa) Self-similar behavior or fractal structure. All of these phenomena show that the anti-solvent pressure in solution or the solubility of CO 2 have a great influence on the structure of PS chains. The fractal dimension of the system increases with the increase of the pressure of anti-solvent, which indicates that the polymer chain develops into a nearly spherical shape in this process from a conformation similar to a random coil.