Environment-induced self-assembly in phase separated block copolymer systems
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Date
2005-11-27
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The Bragg Institute, Australian Nuclear Science and Technology Organisation
Abstract
Polymer chain sequence with different repeating unit and thermodynamic incompatibility between the segments can be chemically linked together through covalent bonds to form block copolymers of unique ordered microstructure and characteristics. Such block copolymers are characterized by fluid-like disorder ion the molecular scale and a high degree of morphological order at longer length scales, resulting in complex equilibrium phase behaviors, giving rise to a large variety of microdomain structures. A specific block copolymer may be optimum nanomaterial, either for their intrinsic properties as self-organized assemblies; or could be used as a strategy to template the organization of the desired inorganic. semi-conducting, metallic or biologically relevant materials into particles, nano planes, wires, or spheres within the polymer matrix. The amphiphilic block copolymers that self-assemble in selective solvents are also of significant scientific interest and of extensive importance in the field of controlled drug delivery systems, detergents, paints, cosmetics, oil recovery.. The situation is versatile and complicated since for a block copolymer system a solvent that is good for one block may be neutral, slightly selective, or strongly selective, or a non-solvent for the other block/ls. in multiblock copolymer with selective solvents the dramatic expansion of parameter space poses both experimental and theoretical challenges; and there has been very limited systematic research on the environment-induced self-organization of the phase behavior of triblock copolymer. ln this research work the effect of selective solvent and temperature on the phase behavior of a polystyrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (SEBS) are presented. We examine the adaptive nature of the ordering in asymmetric block copolymers, using a small angle neutron scattering techniques (SANS). The effect of solvent selectivity and temperature on the evolution of the scattering pattern and trends of the interference maximum in the lovv q (structure factor related to interdomain interference and indicates relatively higher level of ordering of the micelle cores) and high q regimes (form factor related to the contribution of the smaller intradomain distances) has been monitored. The organizational behavior has also been confirmed using Atomic force microscopy (AFM), transmission electron microscopy (TEM) and rheolgical investigation. Morphological evolution of the self-assembled phase behavior of such polymer with the thermodynamic selectivity of solvent, temperature, heat treatment, and time will been discussed in detail. © The Authors
Description
Physical copy held by ANSTO Library at DDC 539.7217/2
Keywords
Asymmetry, Butenes, Copolymers, Ethylene, Gels, Morphology, Nanostructures, Neutron diffraction, Small angle scattering, Solvents, Structural chemical analysis, Styrene
Citation
Dutta, N. K., Thompson, S., Roy Choudhury, N., & Knott, R. (2006). Environment-induced self-assembly in phase separated block copolymer systems. Paper presented at the Eighth International Conference on Neutron Scattering ICNS 2005: "Neutrons for structure and dynamics - a new era", Sydney Convention & Exhibition Centre, Sydney, Australia, 27 November-2 December 2005. In Final Programme and Abstract Book, (pp. 270-271).