Miscibility in Binary Polymer Blends: Correlation and Prediction

Spinodal Decomposition of Filled Polymer Blends: The Role of the Osmotic Effect of Fillers

The reported work addresses the effect of fillers on the thermodynamic stability and miscibility of compressible polymer blends. We calculate the spinodal transition temperature of a filled polymer blend as a function of the interaction energies between the blend species, as well as the blend composition, filler size, and filler volume fraction. The calculation method relies on the developed thermodynamic theory of filled compressible polymer blends. This theory makes it possible to obtain the excess pressure and chemical potential caused by the presence of fillers. As a main result of the reported work, we demonstrate that the presence of neutral (non-adsorbing) fillers can be used to enhance the stability of a polymer blend that shows low critical solution temperature (LCST) behavior. The obtained results highlight the importance of the osmotic effect of fillers on the miscibility of polymer blends. The demonstrated good agreement with the experiment proves that this effect alone can explain the observed filler-induced change in the LCST.

Mikto-Arm Stars as Soft-Patchy Particles: From Building Blocks to Mesoscopic Structures

We present an atomistic molecular dynamics study of self-assembled mikto-arm stars, which resemble patchy-like particles. By increasing the number of stars in the system, we propose a systematic way of examining the mutual orientation of these fully penetrable patchy-like objects. The individual stars maintain their patchy-like morphology when creating a mesoscopic (macromolecular) self-assembled object of more than three stars. The self-assembly of mikto-arm stars does not lead to a deformation of the stars, and their shape remains spherical. We identified characteristic sub-units in the self-assembled structure, differing by the mutual orientation of the nearest neighbor stars. The current work aims to elucidate the possible arrangements of the realistic, fully penetrable patchy particles in polymer matrix and to serve as a model system for further studies of nanostructured materials or all-polymer nanocomposites using the mikto-arm stars as building blocks.

Nanostructuring Single-Molecule Polymeric Nanoparticles via Macromolecular Architecture

Heterogeneous polymer-based nanoparticles comprise a very promising family of materials for a broad range of applications. Here, we present a detailed study of structural heterogeneities in nanostructured single-molecule nanoparticles in various environments by means of atomistic molecular dynamics simulations. The nanoparticles consist of mikto-arm star copolymers with two types of chemically incompatible arms, namely poly(ethylene oxide) (PEO) and polystyrene (PS), (PS) _n,(PEO) _n, where n is the number of arms. The immiscibility between the two components gives rise to intramolecularly nanostructured particles. The nanostructured objects resemble either "Janus-like" or "patchy-like" particles, depending on the number or the length of the arms (or both) as well as the interaction with the surrounding medium. The degree of intramolecular heterogeneity increases with increasing number of arms and with decreasing affinity of star components to the polymer host. We provide a detailed analysis of the internal structure of the star-shaped particles, focusing on the intramolecular packing and the spatial arrangement of the arms. The results of our study can be used to design heterogeneous, internally nanostructured particles with two phases of distinct static properties for challenging specific applications of next-generation materials.