Computational Study of Segregation Phenomena in Polymer Systems in and out of Equilibrium
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Abstract
Segregation phenomena play a key role in the pattern evolution of immiscible multicomponent
mixture ranging from simple to complex fluids such as polymers, surfactants,
colloids, emulsions etc., and have applications in various fields. In this thesis,
we investigate the flow and phase separation of different polymer architectures using
computer simulation techniques. We report the effect of macromolecular architecture
on the flow properties of polymers and show that the polymer distribution
is uniform throughout the channel for both star and chain polymers under steady
conditions. While in the presence of flow, the star-shaped polymers migrate more
strongly towards the channel center, leading to a flow-based separation of linear and
star polymers, with chains accumulating near the channel walls and star polymers
at the center. This can help in designing the microfluidic devices for separating polymers
based on their architecture. Furthermore, we study the phase separation of
triblock copolymers in the melt and solution. We show that the blending of B homopolymer
into lamella morphologies of ABC triblock terpolymer allows the continuous
tuning of the B microphase in the melt and solution. We vary the volume
fraction of homopolymer in the system and find that for polymer melts, the morphological
transition of B microphase goes from cylinder to perforated lamellae and
further to continuous lamellae. Moreover, for the polymer solution, the transition is
from concentric rings to perforated lamellae and finally to continuous lamellae in a
microemulsion droplet. Along with the morphological evolution, we rationalize the
stability of such microemulsion droplets with our simulations and theoretical considerations.
The results from our study suggest that we can generate more complex
Janus nanostructures from triblock copolymers. Lastly, we show that the amphiphilic
triblock copolymer phase separates into polymerosomes; the architecture and the
arrangement of blocks within the triblock copolymer impact the morphology. Additionally,
we display that the volume fraction of the hydrophilic blocks influences the self-assembled morphology of the polymerosome by changing its cavity size, shape,
and patches. In general, we show a way to design the polymerosomes with distinct
patches on the surface, which can aid in enhancing the on-target effects in drug delivery
applications.