%0 Book Section %1 statphys23_0287 %A Moreno, A.J. %A Colmenero, J. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K binary blends coupling glass mixtures mode model polymer rouse statphys23 theory topic-9 transition %T Anomalous Glassy Dynamics in Polymeric and Non-Polymeric Mixtures %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=287 %X We present simulations on mixtures of large and small particles with and without chain connectivity. By varying the size disparity different relaxation scenarios are observed for the small particles. For small disparity only small quantitative differences are observed between dynamic features for large and small particles. On the contrary, large disparity induces a clear time scale separation between the large (slow) and the small (fast) particles. Hence, the small particles move in the slowly relaxing confining matrix formed by the large ones. Density-density correlators for the small particles display unusual logarithmic relaxation. Self-correlators exhibit a much faster relaxation than density-density correlators. These anomalous features are also observed for the small particles in mixtures with chain connectivity, which are used as simple models for polymer blends. In contrast to the usual observation in homopolymers, the intrachain collective correlations show a much slower relaxation than self-correlations. The existence of a structure of preferential paths for the diffusion of the small particles is suggested as the origin of this dynamic decoupling between self- and collective dynamics. We discuss analogies and differences with similar features found for the diffusion of alkaline ions in silica matrices. For very large disparity, full decoupling between self- and collective dynamics is observed for the small particles. Self-correlators decay to zero at temperatures where density-density correlations are frozen. The mentioned anomalous features for structural relaxation are discussed within the framework of the Mode Coupling Theory (MCT) for the glass transition. The dynamic picture obtained by varying the size disparity resembles features associated to MCT transition lines of the types B and A at, respectively, small and very large disparity. Both lines might merge, at some intermediate disparity, at a MCT (``quasi-'') higher order point, to which logarithmic relaxation would be associated. Relaxation of the chain normal modes in the mixtures with connectivity (polymer blends) is analyzed within the framework of the Rouse model. In particular we test its two basic predictions: orthogonality and exponentiality of the chain normal modes. While simulation results show a reasonable agreement with orthogonality, a full breakdown of exponentiality is observed for the fast component, with stretching exponents of about 0.5. These results implicitly demonstrate that the spatial decorrelation of the external random forces on the monomers assumed by the Rouse model is a reasonable approach, but there is a strong time correlation of such forces for the fast component in the blend.

@incollection{statphys23_0287, abstract = {We present simulations on mixtures of large and small particles with and without chain connectivity. By varying the size disparity different relaxation scenarios are observed for the small particles. For small disparity only small quantitative differences are observed between dynamic features for large and small particles. On the contrary, large disparity induces a clear time scale separation between the large (slow) and the small (fast) particles. Hence, the small particles move in the slowly relaxing confining matrix formed by the large ones. Density-density correlators for the small particles display unusual logarithmic relaxation. Self-correlators exhibit a much faster relaxation than density-density correlators. These anomalous features are also observed for the small particles in mixtures with chain connectivity, which are used as simple models for polymer blends. In contrast to the usual observation in homopolymers, the intrachain collective correlations show a much slower relaxation than self-correlations. The existence of a structure of preferential paths for the diffusion of the small particles is suggested as the origin of this dynamic decoupling between self- and collective dynamics. We discuss analogies and differences with similar features found for the diffusion of alkaline ions in silica matrices. For very large disparity, full decoupling between self- and collective dynamics is observed for the small particles. Self-correlators decay to zero at temperatures where density-density correlations are frozen. The mentioned anomalous features for structural relaxation are discussed within the framework of the Mode Coupling Theory (MCT) for the glass transition. The dynamic picture obtained by varying the size disparity resembles features associated to MCT transition lines of the types B and A at, respectively, small and very large disparity. Both lines might merge, at some intermediate disparity, at a MCT (``quasi-'') higher order point, to which logarithmic relaxation would be associated. Relaxation of the chain normal modes in the mixtures with connectivity (polymer blends) is analyzed within the framework of the Rouse model. In particular we test its two basic predictions: orthogonality and exponentiality of the chain normal modes. While simulation results show a reasonable agreement with orthogonality, a full breakdown of exponentiality is observed for the fast component, with stretching exponents of about 0.5. These results implicitly demonstrate that the spatial decorrelation of the external random forces on the monomers assumed by the Rouse model is a reasonable approach, but there is a strong time correlation of such forces for the fast component in the blend.}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Moreno, A.J. and Colmenero, J.}, biburl = {https://www.bibsonomy.org/bibtex/25d831c8e9c194c77ea14dd61355b28aa/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {46f169501422b0df7961b52e732bc865}, intrahash = {5d831c8e9c194c77ea14dd61355b28aa}, keywords = {binary blends coupling glass mixtures mode model polymer rouse statphys23 theory topic-9 transition}, month = {9-13 July}, timestamp = {2007-06-20T10:16:16.000+0200}, title = {Anomalous Glassy Dynamics in Polymeric and Non-Polymeric Mixtures}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=287}, year = 2007 }