Macromolecular Theory and Simulations

Cover: Polymerizations in confined geometries result in deviations from predicted properties, including molecular weight distribution, topology, and composition. Similar effects are encountered in surface-initiated polymerizations, where confinement arises from grafting of chain ends. Recent developments in computer simulations of bulk, confined, and surface-initiated polymerizations are reviewed, and the cover image compares systems with varying degrees of confinement and analogous surface-initiated examples. Further details can be found in the article by E. D. Bain, S. Turgman-Cohen, J. Genzer* on page 8.

A brief summary of computational techniques applied to investigate polymerization reactions in general, with a focus on systems under confinement and initiated from surfaces. We review a variety of studies from the literature employing stochastic methods and molecular modeling and offer an outlook for application to “grafting from” polymerizations.

We show via Monte-Carlo simulation that under microphase separation the free volume concentrates on the interfaces between the domains comprising the incompatible units. The magnitude of the effect is unexpectedly significant and depends on the macromolecule architecture. A special crystalline-like ordering is observed for the amphiphilic diblock copolymers.

The coexistence model of spherulite and shish-kebab is proposed to investigate the thermally and flow induced crystallization behavior of polymer melts in practical processing. Both the distribution of crystallites and evolution of crystalline size within the extrusion die are obtained. The effects of processing conditions on the crystallization kinetics process are discussed.

A hybrid PSO-SVR approach is proposed to model/predict the glass transition temperature of polymethacrylates via six quantum chemical descriptors, and reveals that the obtained SVR model is more accurate than MLR or ANN model. A clue is provided that the method proposed in this study may be useful in computer-aided design of new polymethacrylates with desired T_g.

Dynamic Monte Carlo simulation of the association behavior of gradient block copolymers in selective solvents. A comparison of distribution functions of insoluble (×) and soluble (□) segments using the original (green) and improved (red) classification criterion shows that the correct interpretation of the self-assembling behavior requires detailed analysis based on a combination of both criteria.

Cyclic-shear deformation of simulated 5 nm-thick atactic-polystyrene film is shown. Upon cyclic yield the stress–strain behavior of the film slowly evolves towards a steady state, which is characterized by a decrease of the maximum stress and by an enhanced dissipative process. Such changes reflect the mechanical rejuvenation of a polymer glass, which is connected to the increase in the simulated segmental mobility.