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Effect of cyclic chain architecture on properties of dilute solutions of polyethylene from molecular dynamics simulations

Jang, Seung Soon and Çağin, Tahir and Goddard, William A., III (2003) Effect of cyclic chain architecture on properties of dilute solutions of polyethylene from molecular dynamics simulations. Journal of Chemical Physics, 119 (3). pp. 1843-1854. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:JANjcp03

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Abstract

We have used molecular dynamics methods to investigate the effects of cyclic chain architecture on the properties of dilute solutions. In order to include solvent effects in estimating these properties, we use a van der Waals scaling factor determined for each solvent by matching to the theta condition. We predict that the theta temperature (theta) of cyclic PE (c-PE) is ~10% lower than for the linear case (l-PE). This can be compared to the experimental results for polystyrene (PS), where theta for cyclic PS is 2% lower. For conditions corresponding to n-pentane solvent, we predict that <R<sub>g</sub><sup>2</sup>>cyclic/<R<sub>g</sub><sup>2</sup>>linear is 0.59 for all temperatures above 350 K. The deviation from the ratio of 0.50–0.53 expected from analytic theory is due to the competition between chain stiffness and excluded volume effects. To calculate the intrinsic viscosity of c-PE and l-PE we extended the Bloomfield–Zimm type theory to include chain stiffness corrections. We find that for the theta temperature, the ratio of viscosities for c-PE and l-PE is 0.71, which is 7% higher than the value of 0.66 from the freely jointed chain model. This difference is caused by the larger value of <R<sub>g</sub><sup>2</sup>>cyclic/<R<sub>g</sub><sup>2</sup>>linear from the simulations.


Item Type:Article
Additional Information:©2003 American Institute of Physics. (Received 6 February 2003; accepted 16 April 2003) We particularly thank Professor Robert Grubbs for alerting us to his results prior to publication and to Diego Benitez and Professor Grubbs for spirited discussions. This research was partially supported by NSF (CHE 99-85574) and ARO (DAAG55-97-1-0126). The computational facilities were provided by DURIP grants from ARO and ONR, and MRI grant from NSF, and a SUR grant from IBM. The facilities of the Materials and Process Simulation Center are also supported by DOE (ASCI ASAP), NSF (CHE), MURI-ARO, MURI-ONR, General Motors, Chevron Texaco, Seiko-Epson, Beckman Institute, and Asahi Kasei.
Subject Keywords:polymer solutions; molecular dynamics method; viscosity
Record Number:CaltechAUTHORS:JANjcp03
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:JANjcp03
Alternative URL:http://dx.doi.org/10.1063/1.1580802
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2092
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:07 Mar 2006
Last Modified:26 Dec 2012 08:47

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