Morphological Transition Behavior of ABC Star Copolymers in asymmetric interaction parameter
Date Issued
2008
Date
2008
Author(s)
Lin, Chih-Hao
Abstract
We employ dissipative particle dynamics (DPD) to examine the effects of asymmetric interaction parameter on the resulting structures of ABC star copolymers, and further, compare our results with PI-PS-P2VP star copolymers. Here, we assume two of the interaction parameters: aAB and aBC, are equal, and increasing the amount of aAC. It can be found that lots of morphology which formed in symmetric interaction parameter system can still be observed in our results. But due to the repulsive of A and C component, regions of morphology are vary toward the direction of increasing B composition (fB). When the composition of three components are fA / fB / fC = 0.25 / 0.25 / 0.5, a kind of polygonal cylinder which called [6.4.10; 8.4.10] (3.3.4.3.4) + [6.4.12] is observed. The [6.4.12] polygonal cylinder are always be observed in experimental system, but cannot be predicted in DPD when interaction parameters are symmetry. Additionally, a structure called hexagonally packed core-shell cylinders, which be found in PS-PI-PMMA star copolymers by Thomas et al., can also be observed in our system when fA / fB / fC = 0.3 / 0. 6 / 0.1 and 0.1 / 0.6 / 0.3, prove that we can use DPD to simulate some morphology which easily be found in experimental system while interaction parameters are asymmetry, even make a prediction for PI-PS-P2VP experimental system. Compare our results with PI-PS-P2VP star copolymers, although the resulting phase behaviors are similar, the morphologies result from two systems still cannot to match absolutely. According to adjust the relationship of interaction parameters and increasing all of them, we successfully find single [6.4.12] polygonal cylinder, but the structure called cylinders-in-lamellae which found by Matsushita et al. still cannot simulated by DPD. We suggest that the value of aAC must maintain a difference in aAB and aBC, and each interaction parameter also has to large enough to separate each component completely.
Subjects
dissipative particle dynamics
ABC star copolymer
phase transition
morphology
interaction parameter
Type
thesis
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