We report on three-dimensional Monte Carlo simulations of dilute solutions of multiblock copolymers made of regularly spaced hydrophobic and hydrophilic blocks in the limit of long chains with a large number of blocks. Using a lattice model we investigate the effects of the ratio of hydrophobic to hydrophilic block lengths and impact of the quality of the solvent on the intramolecular structure of the copolymers. In poor solvent and for given block lengths the simulations show evidence for the existence of different kinds of intramolecular self-assemblies depending on solvent quality: Micelles, chains of micelles, tubes, and layered structures are revealed by both statistical properties and visualization. The form factor signature of the different structures has been identified and is discussed in connection with its experimental observability. The existence region of the different conformations in terms of energy and entropy is summarized in a phase diagram.

We use molecular dynamics simulations to study a semidilute, unentangled polymer solution containing well dispersed, weakly attractive nanoparticles (NP) of size (σN ) smaller than the polymer radius of gyration Rg. We find that if σN is larger than the monomer size the polymers swell, while smaller NPs cause chain contraction. The diffusion coefficient of polymer chains (Dp) and NPs (DN ) decreases if the volume fraction φN is increased. The decrease of Dp can be well described in terms of a dynamic confinement parameter, while DN shows a more complex dependence on σN , which results from an interplay between energetic and entropic effects. When φN exceeds a σN -dependent value, the NPs are no longer well dispersed and DN and Dp increase if φN is increased. arXiv:1804.06993v2 [cond-mat.soft]

The phase behaviour of amphiphilic multiblock copolymers with a large number of blocks in semidilute solutions is studied by lattice Monte Carlo simulations. The influence on the resulting structures of the concentration, the solvent quality and the ratio of hydrophobic to hydrophilic monomers in the chains has been assessed explicitely. Several distinct regimes are put in evidence. For poorly substituted (mainly hydrophilic) copolymers formation of micelles is observed, either isolated or connected by the hydrophilic moieties, depending on concentration and chain length. For more highly substituted chains larger tubular hydrophobic structures appear which, at higher concentration, join to form extended hydrophobic cores. For both substitution ratios gelation is observed, but with a very different gel network structure. For the poorly substituted chains the gel consists of micelles cross-linked by hydrophilic blocks whereas for the highly substituted copolymers the extended hydrophobic cores form the gelling network. The interplay between gelation and phase separation clearly appears in the phase diagram. In particular, for poorly substituted copolymers and in a narrow concentration range, we observe a sol-gel transition followed by an inverse gel-sol transition when increasing the interaction energy. The simulation results are discussed in the context of the experimentally observed phase properties of methylcellulose, a hydrophobically substituted polysaccharide.