Structural and Dynamical Insights into Self-Assembly Kinetics in Miktoarm Star Polymer Solutions: Role of Arm Size and Topology

DK Verma and AK Singh and A Singh, LANGMUIR, 41, 31860-31874 (2025).

DOI: 10.1021/acs.langmuir.5c03895

We employ dissipative particle dynamics (DPD) simulations to study phase separation (PS) kinetics of miktoarm star polymer (MSP) solutions composed of chemically incompatible arms. We explore two distinct scenarios: (i) symmetric variation in arm lengths at fixed arm numbers and (ii) symmetric variation in arm numbers at fixed arm lengths. A thermal quench from a homogeneous state induces thermodynamic instability, which drives PS through a competition between enthalpic and entropic effects. Our analysis reveals that architectural parameters, such as arm length and arm number, play a critical role in determining the morphology of the system, leading to variations from disordered phases to well-ordered lamellae, as well as influencing growth kinetics, the thermodynamic description of PS, and dynamic scaling behavior. In case 1, PS is significantly suppressed for shorter arms, whereas distinct domain formation and lamellar ordering emerge with larger arm lengths. Increasing arm length enhances domain size at late times and slows down the growth rate at early times. In case 2, increasing the number of arms leads to enhanced intramolecular interactions and structural anisotropy, while preserving the lamellar morphology across all arm numbers. Thermodynamic analyses reveal that configurational entropy increases with arm length but decreases with arm number due to topological crowding, whereas enthalpy systematically decreases with increasing intrachain interactions. Domain coarsening follows a diffusive scaling regime, R(t) similar to t 1/3, at early times, with saturation in domain size R(t) at later times for a larger number of arms and their size. These insights have important implications for designing architecturally complex polymeric materials with tunable self- assembly behavior.

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