THE COUPLING BEHAVIOR OF DEWETTING AND CRYSTALLIZATION IN CRYSTALLINE DIBLOCK COPOLYMER THIN FILMS
We have studied the coupling behavior of dewetting and crystallization in double crystalline diblock copolymer thin films where the velocities of these two growth are controlled by varying the temperature from a low temperature regime, where crystallization occurs quickly and dominates, an intermediate temperature regime, where the dewetting and crystallization are weakly or strongly coupled and determine the final morphology together, and then to a high temperature regime, where dewetting occurs first and completely and dominates the film structure. Specifically, thin films of poly(ecaprolactone)-block-poly(L-lactide) (PCL-b-PLLA) double crystalline diblock copolymer on carbon-coated mica substrates are investigated as a model system exhibiting this phenomenon mentioned above. Structure formation at low temperatures is dominated by PLLA dendritic structures that show very high fractal dimension; at high temperatures, where crystallization of PLLA block is sufficiently suppressed, dewetting causes holes to spontaneously develop and finally form small droplets throughout the whole film. At intermediate temperatures, the situation is a little more complicated due to the interaction between dewetting and crystallization. When the two are weakly coupled, the film dewetting begins first, but soon the formed patterns are replaced by the crystallization of PLLA block. The dewetting process is strangled at its sprout stage. The formed PLLA dendrites are quite dense and characteristic of high fractal dimension. When the two are strongly coupled, PLLA block initiates the crystallization after the film dewetting is progressive mostly. At certain distance away from the crystallization front of PLLA dendrites the dewetting patterns abruptly form small holes from inside and again dewetted so that the patterns become spreading and pseudo-wetting which results in relatively low fractal dimension crystalline structures.
Derong Yan Tianbai He
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
国际会议
PP’2010，Jinan International Symposium on Polymer Physics(2010济南国际高分子物理学术研讨会)
济南
英文
236-237
2010-06-06（万方平台首次上网日期，不代表论文的发表时间）