(697c) Structural and Mechanical Properties of ABA/AB Gels: Dissipative Particle Dynamics Study
AIChE Annual Meeting
Friday, November 13, 2009 - 1:10pm to 1:30pm
Amphiphilic triblock ABA copolymers undergo microphase separation in a midblock-selective solvent that results in a formation of three-dimensional physical network that typically exhibits thermal and environmental stability. The rheology of these gels depends on their morphological properties, such as number of bridging chains and trapped entanglements One way to control the mechanical properties of ABA triblock gels is to add AB diblock copolymer. To ascertain which features govern the mechanical properties of entangled ABA/AB copolymer gels in midblock-selective solvent, we have systematically evaluated the mechanical and structural properties of these gels by employing the dissipative particle dynamics (DPD) method and a non-equilibrium oscillatory shear technique. We have observed that addition of the diblock increases number density of micelles, which is inversely related to the average distance between micellar cores. The decrease in the micellar distance leads to increase in number of bridging chains and consequently an increase in the value of plateau of storage modulus in the low frequency regime. While not explicitly calculated in the DPD model, the impact of trapped entanglements can be qualitatively assessed by comparing experimental and theoretical results. We have demonstrated that our simulation results are in good qualitative agreement with experimental data. In this talk we will also review emerging developments of DPD to investigate increasingly complicated systems with physical entanglements, complex chain architecture and incorporation of nano-fillers.