Inhaltszusammenfassung

Extensive Monte Carlo simulations are presented for bottle-brush polymers under good solvent conditions, using the bond fluctuation model on the simple cubic lattice. Varying the backbone length (from N(b)=67 to N(b) = 259 effective monomers) as well as the side chain length (from N = 6 to N = 48), for a physically reasonable grafting density of one chain per backbone monomer, we find that the structure factor describing the total scattering from the bottle-brush provides an almost perf...Extensive Monte Carlo simulations are presented for bottle-brush polymers under good solvent conditions, using the bond fluctuation model on the simple cubic lattice. Varying the backbone length (from N(b)=67 to N(b) = 259 effective monomers) as well as the side chain length (from N = 6 to N = 48), for a physically reasonable grafting density of one chain per backbone monomer, we find that the structure factor describing the total scattering from the bottle-brush provides an almost perfect match for some combinations of (N(b), N) to experimental data of Rathgeber et al. [J. Chem. Phys. 2005, 122, 124904], when we adjust the length scale of the simulation to reproduce the experimental gyration radius of the bottle-brush. While in the experiment other length scales (gyration radius of side chains, backbone persistence length, scale characterizing the radial monomer density profile in the plane normal to the backbone) can be extracted only via fitting to a complicated and approximate theoretical expression derived by Pedersen and Schurtenberger, all these properties can he extracted from the simulation directly. In this way, quantitatively more reliable estimates for the persistence length and side chain gyration radius of the experimental systems can be extracted. In particular, we show that the popular assumption of a Gaussian radial monomer density profile is inaccurate. in the very good solvent regime studied by the simulation. and show that alternative forms based on scaling, theory work better. We also show that the persistence length of the bottle brush in the simulation depends systematically on the backbone length and not only on the side chain length. For the cases where an explicit comparison with the experimental results (based on their evaluation within the Pedersen-Schurtenberger model) is possible, simulation and experiment are consistent with each other and some of the (rather minor) differences between simulation and experiment can be attributed to the weaker strength of excluded volume in the latter. Thus, we show that by suitable mapping between simulation and experiment on length scales of the local concentration fluctuations (here < 2 nm) the analysis of experimental data can be systematically refined » weiterlesen» einklappen

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DDC Sachgruppe:
Allgemeines, Wissenschaft