Park Min Soo, Joo Wonchul, Kim Jin Kon
National Creative Research Center for Block Copolymer Self-Assembly, Department of Chemical Engineering and Polymer Research Institute, Pohang University of Science and Technology, Kyungbuk 790-784, Korea.
Langmuir. 2006 May 9;22(10):4594-8. doi: 10.1021/la053009t.
We investigate the effects of interfacial energy between water and solvent as well as polymer concentration on the formation of porous structures of polymer films prepared by spin coating of cellulose acetate butyrate (CAB) in mixed solvent of tetrahydrofuran (THF) and chloroform under humid condition. The interfacial energy between water and the solvent was gradually changed by the addition of chloroform to the solvent. At a high polymer concentration (0.15 g/cm3 in THF), porous structures were limited only at the top surfaces of CAB films, regardless of interfacial energies, due to the high viscosity of the solution. At a medium concentration (approximately 0.08 g/cm3 in THF), CAB film had relatively uniform pores at the top surface and very small pores inside the film because of the mixing of the water droplets with THF solution. When chloroform was added to THF, pores at the inner CAB film had a comparable size with those at the top surface because of the reduced degree of the mixing between the water droplets and the mixed solvent. A further decrease in polymer concentration (0.05 g/cm3 in THF) caused the final films to have a two-layer porous structure, and the size of pores at each layer was almost the same.
我们研究了在潮湿条件下，水与溶剂之间的界面能以及聚合物浓度对通过旋涂醋酸丁酸纤维素（CAB）于四氢呋喃（THF）和氯仿的混合溶剂中制备的聚合物膜多孔结构形成的影响。通过向溶剂中添加氯仿，水与溶剂之间的界面能逐渐改变。在高聚合物浓度（在THF中为0.15 g/cm³）下，由于溶液的高粘度，无论界面能如何，多孔结构仅局限于CAB膜的顶面。在中等浓度（在THF中约为0.08 g/cm³）下，由于水滴与THF溶液的混合，CAB膜顶面具有相对均匀的孔，且膜内部有非常小的孔。当向THF中添加氯仿时，由于水滴与混合溶剂之间混合程度的降低，CAB膜内部的孔与顶面的孔尺寸相当。聚合物浓度进一步降低（在THF中为0.05 g/cm³）导致最终的膜具有两层多孔结构，且每层孔的尺寸几乎相同。
