Interfacial growth as a model of tube-width heterogeneities in concentrated solutions of stiff polymers

Abstract

Recent experimental measurements of the distribution P(w) of transverse chain fluctuations w in concentrated solutions of F-actin filaments [B. Wang, J Guan, S. M. Anthony, S. C. Bae, K. S. Schweizer, and S. Granick, Phys. Rev. Lett. 104, 118301 (2010); J. Glaser, D. Chakraborty, K. Kroy, I. Lauter, M. Degawa, N. Kirchgessner, B. Hoffmann, R. Merkel, and M. Giesen, Phys. Rev. Lett. 105, 037801 (2010)] are shown to be well-fit to an expression derived from a model of the conformations of a single harmonically confined weakly bendable rod. The calculation of P(w) is carried out essentially exactly within a path integral approach that was originally applied to the study of one-dimensional randomly growing interfaces. Our results are generally as successful in reproducing experimental trends as earlier approximate results obtained from more elaborate many-chain treatments of the confining tube potential.

Confining Potential as a Function of Polymer Stiffness and Concentration in Entangled Polymer Solutions

“…This change continues until the Rouse time is reached (here τ R = 2.5 s) and for larger time intervals, it seems that the concept of the tube is vanishing while approaching the disentanglement time and a completely new tube is formed. A similar anharmonic tube softening for large strains on DNA has been observed by Robertson et al using optical tweezers, which is in agreement with simulations. − In another study, the tube heterogeneities were explored theoretically on confined, weakly bendable rods and the shape predicted for the confining potential shows both the harmonic and anharmonic parts that fit to our observations for polyisocyanides. In Figure a, we plot the dynamical confining potential V for three concentrations of matrix 2 (5 (black squares), 6.5 (red circles) and 8 mg mL –1 (green triangles)).…”

Single-Molecule Study of Peptide Gel Dynamics Reveals States of Prestress

“…The tube width fluctuations of entangled semiflexible polymer solutions have been found to demonstrate inhomogeneity in the reptation tubes in previous studies of ungelled samples. ,, This is again seen in the present study, which is studying entangled semiflexible polymer gels, and the autocorrelation of the tube widths calculated along the I 3 K fibrils shows a decorrelation, which is characteristic of the mesh size of the network of 3.5 μm. Furthermore, certain fibrils, such as those shown in Figure A, show significant curvature in an apparent equilibrium state and the dynamic thermal motion with tight cross-links occurs, creating minima on the tube width, as shown in Figure B.…”

“…Using singlemolecule fluorescence techniques, we show how the immediate region around each fibril in a gelled network is inhomogeneous and has significant spatial variation, which builds upon the recent work on actin filaments in ungelled networks. 16,42 Furthermore, we investigated the internal dynamics of peptide fibrils, which revealed significant differences between the apparent persistence length of the fibrils in their networks and that measured from their dynamic motion. This has important implications for the network as a whole (the dominant mechanical response is due to the exchange of bending energy between different regions of the network 2 ) and suggests that SSS are present within the network and detailed structural engineering approaches are needed to understand their mechanical properties.…”