Dependence of reinforcement degree of nanocomposites polymer/carbon nanotubes on nanofi ller structure and molecular characteristics of polymer matrix

The possibility for simulation of carbon nanotubes structure in polymer matrix as complex reinforcing element, consisting of nanofiller and covered it interfacial layer is shown. It is concluded that size (radius) of annular formations of such complex element is determined by normalized content of interfacial regions or ability of nanofiller to generate interfacial regions. The change of phase state of polymer matrix from glassy to rubber-like one leads to change of its molecular characteristics, namely, the length of statistical segment of polymer chain. The qualitative jump in reinforcement degree of nanocomposites is realized at transition from closed annular formations of carbon nanotubes to open (circular arc) one.

The Statistical Segment Length of DNA: Opportunities for Biomechanical Modeling in Polymer Physics and Next-Generation Genomics

The development of bright bisintercalating dyes for deoxyribonucleic acid (DNA) in the 1990s, most notably YOYO-1, revolutionized the field of polymer physics in the ensuing years. These dyes, in conjunction with modern molecular biology techniques, permit the facile observation of polymer dynamics via fluorescence microscopy and thus direct tests of different theories of polymer dynamics. At the same time, they have played a key role in advancing an emerging next-generation method known as genome mapping in nanochannels. The effect of intercalation on the bending energy of DNA as embodied by a change in its statistical segment length (or, alternatively, its persistence length) has been the subject of significant controversy. The precise value of the statistical segment length is critical for the proper interpretation of polymer physics experiments and controls the phenomena underlying the aforementioned genomics technology. In this perspective, we briefly review the model of DNA as a wormlike chain and a trio of methods (light scattering, optical or magnetic tweezers, and atomic force microscopy (AFM)) that have been used to determine the statistical segment length of DNA. We then outline the disagreement in the literature over the role of bisintercalation on the bending energy of DNA, and how a multiscale biomechanical approach could provide an important model for this scientifically and technologically relevant problem.

Unperturbed dimensions of polymers revisited through the blob theory: the viscometric expansion factor

Plotting log([η]/M1/2) versus log(N/Nc) where [η] is the intrinsic viscosity of the macromolecular chain of molecular mass equal to M and N/Nc is the number of blobs of which this chain consists (N: the number of statistical segment of the chain and Nc : the number of statistical segment of one blob), we obtain the unperturbed dimensions parameter of the blob, Kθb. This graphical representation in this article is based on a modified, original equation of Han [6] based on the blob theory. The obtained value of Kθb for a given polymer, dissolved in a good solvent, is lower than the unperturbed dimensions parameter, Kθ, obtained for the same polymer in the Flory’s theta conditions. Having Kθb < Kθ we obtain for the viscometric expansion factors of a polymer, based on Kθb or Kθ, αηb > αη. With the obtained values of αηb we find αηb3/αs2αH ≈ 1, as predicted by Weill and des Cloizeauz [1], where using αη we obtain αη3/αs2αH ≈ 0.85 (αs and αH are the static and dynamical expansions factors).