Bulletin of the American Physical Society
2005 Ohio Sections of the APS and AAPT Joint Fall Meeting
Friday–Saturday, October 14–15, 2005; Cleveland, OH
Session D5: Polymers - Theory and Simulation |
Hide Abstracts |
Chair: Mark Taylor Room: Cleveland State University 3 |
Saturday, October 15, 2005 11:00AM - 11:12AM |
D5.00001: Solvation potentials for polymer chains in solution Mark Taylor The conformation of a polymer chain in solution is intrinsically coupled to properties of the solvent. In much of the theoretical work on polymers in dilute solution the effects of solvent are treated in an implicit fashion: thus one studies an isolated chain interacting via an effective site-site potential. Although a formally exact mapping is possible between the chain-in-solvent and corresponding effective- potential-chain, this mapping involves a many-site solvation potential which is not practical to compute. Thus, one generally resorts to a two-site potential approximation. Here we examine the validity of this two-site approximation for short hard-sphere and square-well chain-in-solvent systems. We demonstrate that at least for some systems, the two site approach is rigorously valid, however a set of two-site potentials (rather than a single effective potential) is required. [Preview Abstract] |
Saturday, October 15, 2005 11:12AM - 11:24AM |
D5.00002: Monte Carlo Study of Reversible Polymer Brushes Chun-Chung Chen, Elena E. Dormidontova We study end-adsorption of reversibly associated polymers formed through head-to-tail reversible self-assembly. The surface contains uniformly distributed adsorption sites attractive only for head-groups of associating polymers, so there is no possibility of forming loops at the surface. At low density of adsorption sites, the density profile of adsorbed layer corresponds to a polydisperse mushroom regime. In this regime the adsorption constant was found to decay as inverse square root of the chain length based on loss of conformational entropy near the surface. With an increase of adsorption site density and polymer bulk concentration the average height of associated polymer layer increases as chains stretch out away from the surface. Such stretching, however, is rather limited as the chains are getting shorter and the occupancy of adsorption sites on the surface is lower. Despite the high adsorption density regime considerably differs from traditional monodisperse brush, a transition from non-stretched to stretched chain conformations with the increase of anchoring density is quite evident. [Preview Abstract] |
Saturday, October 15, 2005 11:24AM - 11:36AM |
D5.00003: Monte Carlo Simulation of Reversibly Associated Network Shihu Wang, Chun-Chung Chen, Elena E. Dormidontova Using the Monte Carlo simulation (MC) of bond fluctuation model (BFM) we have studied the reversible association between linear end-functionalized oligomers and crosslinkers (analogous to metal-ligand complexation) leading to network formation. The crosslinkers were capable of binding up to three oligomer end groups with different energies of association with the first, second and third end-groups respectively. By varying oligomer concentration and crosslinker/oligomer ratio in our simulations, a three dimensional structure spanning the whole system was obtained, signifying gel formation. We further studied the gel properties in terms of the average molecular weight and gel fraction. An analytical model based on the equilibrium among different associating species and classical gelation theory, was developed. This model allows prediction of fractions (concentrations) of different crosslinkers, bonded to three, two, one or none oligomer end groups as well as the sol-gel transition, which favorably compares to the simulation results. [Preview Abstract] |
Saturday, October 15, 2005 11:36AM - 11:48AM |
D5.00004: On the range of interlayer interactions in smectic-C liquid crystals Mehdi Bagheri-Hamaneh, Philip Taylor The origin of the long-range interlayer interactions responsible for the variety of phases exhibited by ferroelectric liquid crystals is discussed. It is shown that the anisotropy of the elastic constants that govern layer bending in smectic-$C$ liquid crystals results in an effective long-range interaction between the smectic layers. The nature of this interaction is such as to favor a mutual alignment of the $c$-directors of the layers in either a parallel or antiparallel orientation. The effects of size of the sample, boundary conditions, and parameters such as layer compression modulus, and elastic constants, on the strength and distance-dependence of the interactions will be discussed. [Preview Abstract] |
Saturday, October 15, 2005 11:48AM - 12:00PM |
D5.00005: Phylogenetic methods for computationally correlating genotypes and phenotypes Farhat Habib, Daniel Janies, Ralf Bundschuh Single nucleotide polymorphisms or SNPs are DNA sequence variations among genomes of a population or other closely related group. While many SNPs have no effect on cell functions other SNPs predispose an organism to disease and or influence its response to a drug. Thus, SNPs are important for biomedical, biophysical, and pharmaceutical research. Given that SNP databases now have millions of SNPS it is imperative to develop automated methods of finding SNPs that are correlated with a phenotype of interest. We demonstrate a method of correlating phenotypes with genotypes with the aid of phylogenetic trees. Phylogenetic trees serve as hierarchical summaries of evolutionary change between ancestors and descendants. Our method maps phenotype data on the phylogenetic tree based on SNPs to look for associations with a chosen phenotype. The patterns in variation in SNPs and phenotypes are assessed using the Maddison's concentrated changes test (CCT). Some exemplary results from large SNP datasets from many strains of inbred mice will be presented. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700