In situ synthesis of polyisoprene/grafted single-walled carbon nanotube composites

Designing multimodal carbon nanotubes by covalent multi-functionalization

Carbon nanotubes (CNTs) are a unique tool in nanotechnology owing to their exceptional properties that offer a variety of opportunities for applications in different fields. Nevertheless, their low dispersibility in organic solvents and in aqueous media hampers their development. The functionalization of their surface allows overcoming this issue, while exploiting and tuning their properties. Thanks to their high specific surface area, multi-functionalization strategies give the possibility to conjugate several copies of different molecules to endow the nanotubes with multiple functionalities. In this context, this review wishes to focus on the preparation of multimodal CNTs designed by covalent multi-functionalization. More specifically, we describe the different approaches that have been developed to prepare multi-functionalized CNTs through double and triple covalent functionalization of the nanotube framework. We also emphasize the strategies used to control the derivatization of multi-functionalized CNTs with molecules of interest mainly via sequential or simultaneous methodologies.

Morphological transformations in polymer brushes in binary mixtures: DPD study

Morphological transformations in polymer brushes in a binary mixture of good and bad solvents are studied using dissipative particle dynamics simulations drawing on a characteristic example of polyisoprene natural rubber in an acetone-benzene mixture. A coarse-grained DPD model of this system is built based on the experimental data in the literature. We focus on the transformation of dense, collapsed brush in bad solvent (acetone) to expanded brush solvated in good solvent (benzene) as the concentration of benzene increases. Compared to a sharp globule-to-coil transition observed in individual tethered chains, the collapsed-to-expanded transformation in brushes is found to be gradual without a prominent transition point. The transformation becomes more leveled as the brush density increases. At low densities, the collapsed brush is highly inhomogeneous and patterned into bunches composed of neighboring chains due to favorable polymer-polymer interaction. At high densities, the brush is expanded even in bad solvent due to steric restrictions. In addition, we considered a model system similar to the PINR-acetone-benzene system, but with the interactions between the solvent components worsened to the limit of miscibility. Enhanced contrast between good and bad solvents facilitates absorption of the good solvent by the brush, shifting the collapsed-to-expanded transformation to lower concentrations of good solvent. This effect is especially pronounced for higher brush densities.