Phase behavior and structure of an ABC triblock copolymer dissolved in selective solventN.P. Shusharina1, P. Alexandridis1, P. Linse2, S. Balijepalli3 and H.J.M. Gruenbauer4
1 Department of Chemical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260-4200, USA
2 Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
3 New Product & Mathematical Modeling Group, Corporate R&D, The Dow Chemical Co., Midland, MI 48674, USA
4 New Business Development, Dow Benelux N.V., 4530 AA Terneuzen, The Netherlands
(Received 17 April 2002 Published online: 21 January 2003)
A mean-field lattice theory is applied to predict the self-assembly into ordered structures of an ABC triblock copolymer in selective solvent. More specifically, the composition-temperature phase diagram has been constructed for the system (C) 14(PO) 12(EO) 17/water, where C stands for methylene, PO for propylene oxide and EO for ethylene oxide. The model predicts thermotropic phase transitions between the ordered hexagonal, lamellar, reverse hexagonal, and reverse cubic phases, as well as the disordered phase. The thermotropic behavior is a result of the temperature dependence of water interaction with EO- and PO-segments. The lyotropic effect (caused by changing the solvent concentration) on the formation of different structures has been found weak. The structure in the ordered phases is described by analyzing the species volume fraction profiles and the end segment and junction distributions. A "triple-layer" structure has been found for each of the ordered phases, with each layer rich in C-, PO-, and EO-segments, respectively. The blocks forming the layers are not stretched. The dependence of the domain spacing on polymer volume fraction and temperature is also considered.
36.20.-r - Macromolecules and polymer molecules.
64.75.+g - Solubility, segregation, and mixing; phase separation.
61.20.Gy - Theory and models of liquid structure.
07.05.Tp - Computer modeling and simulation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003