We report results of a molecular dynamics simulation of an “isotope” mixture of polymer chains, which are represented by a standard bead–spring model, and whose two species differ only by their monomer masses. Detailed analysis of the Rouse modes shows that for sufficiently short (non-entangled) chains this system can be well described by the Rouse model. Each species is described by its individual monomeric friction coefficient, whose dependence on both mass ratio as well as mixing ratio is studied. The main effect of mixing is an acceleration of the slower chains and a slowdown of the faster ones, while both species remain dynamically different. Some microscopic insight into the mechanism is obtained by studying the short-time behavior of the monomeric velocity autocorrelation function. Studies in the slightly entangled regime (chain length up to N=150, where the typical entanglement chain length is Ne≈35) seem to further corroborate the hypothesis that the “tube diameter” of the reptation model is a quantity which results mainly from the static configurations, i.e., is an equilibrium thermal average. The usefulness of recently suggested analysis methods in this regime is briefly discussed.

The adsorption process of the single polymer chain in a polymer brush of varying surface coverages is studied by means of Monte Carlo simulations of the bond-fluctuation lattice model. Only the end monomers can adsorb at the grafting surface, whereas inner monomers interact repulsively with it. The brush builds up a steric hindrance which forces the penetrating polymer to stretch strongly and which is responsible for small adsorption probabilities at surface coverages close to the overlap density. The final step of the adsorption process is determined by a fluctuation of the end monomer around its average position, which is comparable to the initial step of the desorption process.

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The use of poly(styrene-co-maleic acid) (SMA) for the solubilization of lipid membranes and membrane proteins is becoming more widespread, and with this, the need increases to better understand the chemical properties of the copolymer and how these translate into membrane solubilization properties. SMA comes in many different flavors that include the ratio of styrene to maleic acid, comonomer sequence distribution, average chain length, dispersity, and potential chemical modifications. In this work, the synthesis and membrane active properties are described for 2:1 (periodic) SMA copolymers with M w varying from ∼1.4 to 6 kDa. The copolymers were obtained via an iterative RAFTmediated radical polymerization. Characterization of these polymers showed that they represent a well-defined series in terms of chain length and overall composition (F MAnh ∼ 0.33), but that there is heterogeneity in comonomer sequence distribution (F MSS ∼ 0.50) and some dispersity in chain length (1.1 < Đ < 1.6), particularly for the larger copolymers. Investigation of the interaction of these polymers with phosphatidylcholine lipid self-assemblies showed that all copolymers inserted equally effectively into lipid monolayers, independent of the copolymer length. Nonetheless, smaller polymers were more effective at solubilizing lipid bilayers into nanodiscs, possibly because longer polymers are more prone to become intertwined with each other, thereby hampering their solubilization efficiency. Nanodisc sizes were independent of the copolymer length. However, nanodiscs formed with larger copolymers were found to undergo slower lipid exchange, indicating a higher stability. The results highlight the usefulness of having well-defined copolymers for systematic studies.