Computational modeling of fluctuations and phase behavior in polymeric systems
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This research focuses on the computational modeling of fluctuations, interactions, phase behavior and structural characteristics of multicomponent polymeric systems. The role of fluctuations is studied in the context of block copolymer melts and polymer blends stabilized using copolymers exhibiting different sequence architectures. The relationship between interparticle interactions and structural characteristics of the aggregates formed in particle-polymer solutions is examined for charged nanoparticle-polymer and charged dendrimer-polyelectrolyte system. A hybrid Monte Carlo and self consistent field theory approach employed in single chain in mean field simulations (SCMF) is utilized in order to achieve the equilibrium morphologies/aggregates in such polymeric systems. We examine the effect of composition fluctuations on the phase behavior of polydisperse block copolymer melts quantified in terms of fluctuation-induced shift in the order-disorder transition temperature from the corresponding mean-field predictions. Fluctuation effects can also play an important role in stabilizing bicontinuous microemulsions phases. To study this effect, we examine polymer blend systems compatibilized by a copolymer having different sequence architectures such as monodisperse and polydisperse block copolymer, and gradient copolymer. We systematically assess the efficiency of such system in forming bicontinuous microemulsions phases. We also study the effect of sequence architecture on the phase behavior of gradient copolymer solutions. We extend above framework to account for electrostatic effects arising from charged polymers and dendrimers. Using such a framework, we characterize the clusters formed due to electrostatic binding between oppositely charged dendrimers and polyelectrolytes. Our results indicate that, the binding is maximum when the charge on dendrimers is balanced by the charge on the polyelectrolytes. We extend the above study to probe the phase behavior of charged nanoparticles suspended in polymer solutions. We examine the influence of polymer concentration, particle volume fraction, and particle charge on the structure and size of clusters. We also examine the influence of multibody effects on the resulting structure of nanoparticle clusters. The charged nanoparticle-polymer solution is seen to exhibit significant multibody effects and the effective two-body interparticle potentials are seen to be a function of nanoparticle density.