Length controlled kinetics of self-assembly of bidisperse nanotubes/nanorods in polymers

DPD Modelling of the Self- and Co-Assembly of Polymers and Polyelectrolytes in Aqueous Media: Impact on Polymer Science

This review article is addressed to a broad community of polymer scientists. We outline and analyse the fundamentals of the dissipative particle dynamics (DPD) simulation method from the point of view of polymer physics and review the articles on polymer systems published in approximately the last two decades, focusing on their impact on macromolecular science. Special attention is devoted to polymer and polyelectrolyte self- and co-assembly and self-organisation and to the problems connected with the implementation of explicit electrostatics in DPD numerical machinery. Critical analysis of the results of a number of successful DPD studies of complex polymer systems published recently documents the importance and suitability of this coarse-grained method for studying polymer systems.

Local Structural Fingerprints of Nanoparticle-Bound Polymer Layers

The molecular structure of bound layers at attractive polymer-nanoparticle interfaces strongly influences the properties of nanocomposites. Thus, a unifying theoretical framework that can provide insights into the correlations between the molecular structure of the bound layers, their thermodynamics, and macroscopic properties is highly desirable. In this work, molecular dynamics simulations were used in combination with local fingerprint analysis of configurational entropy and interaction energy at the segmental scale, with the goal to establish such physical grounds. The thickness of bound polymer layers is found to be independent of the polymer chain length, as deduced from density oscillations at the surface of a nanotube. The local configurational entropy of layers is estimated from pair correlations in equilibrium structures. By plotting mean layer entropy vs internal energy on a phase diagram, a one-to-one equivalence is established between the local structures of layers and their thermodynamic properties. Moreover, a gradient in local dynamics of segments in bound layers under equilibrium is observed normal to the nanoparticle surface. The relaxation times of individual layers show correspondence to their phase diagram fingerprints, thus suggesting that a unified perspective can be envisioned for such materials built on the grounds of locally heterogeneous interfaces.

Antistatic Fibers for High-Visibility Workwear: Challenges of Melt-Spinning Industrial Fibers

Safety workwear often requires antistatic protection to prevent the build-up of static electricity and sparks, which can be extremely dangerous in a working environment. In order to make synthetic antistatic fibers, electrically conducting materials such as carbon black are added to the fiber-forming polymer. This leads to unwanted dark colors in the respective melt-spun fibers. To attenuate the undesired dark color, we looked into various possibilities including the embedding of the conductive element inside a dull side-by-side bicomponent fiber. The bicomponent approach, with an antistatic compound as a minor element, also helped in preventing the severe loss of tenacity often caused by a high additive loading. We could melt-spin a bicomponent fiber with a specific resistance as low as 0.1 Ωm and apply it in a fabric that fulfills the requirements regarding the antistatic properties, luminance and flame retardancy of safety workwear.

Entropic Effects in Polymer Nanocomposites

Polymer nanocomposite materials, consisting of a polymer matrix embedded with nanoscale fillers or additives that reinforce the inherent properties of the matrix polymer, play a key role in many industrial applications. Understanding of the relation between thermodynamic interactions and macroscopic morphologies of the composites allow for the optimization of design and mechanical processing. This review article summarizes the recent advancement in various aspects of entropic effects in polymer nanocomposites, and highlights molecular methods used to perform numerical simulations, morphologies and phase behaviors of polymer matrices and fillers, and characteristic parameters that significantly correlate with entropic interactions in polymer nanocomposites. Experimental findings and insight obtained from theories and simulations are combined to understand how the entropic effects are turned into effective interparticle interactions that can be harnessed for tailoring nanostructures of polymer nanocomposites.