Effect of Molecular-Scale Features on the Polymer Coil Size of Model Viscosity Index Improvers
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Temperature-induced changes in coil size have been proposed as a mechanism underlying the functionality of viscosity index improving polymers. Here, molecular dynamics simulations are used to characterize the effect of temperature on the coil size of model additive polymers. The simulations reproduce experimental observations, where only some polymers increase in size with increasing temperature. The results also reveal that the presence of oxygen atoms in the polymer structure is a key factor in determining whether the polymer expands or contracts. This new simulation approach provides a general methodology for investigating temperature-induced coil size changes in polymeric lubricant additives.
KeywordsVI improvers Polymers Coil size Temperature effects
The authors thank Lelia Cosimbescu, Michael Covitch, and Kieran Trickett for helpful discussions. USR and AM were supported by the US Department of Energy’s (DOE) Office of Vehicle Technology (under Contract No. 27029) of the PNNL AOP project. PNNL is a multiprogram national laboratory operated by Battelle for DOE under Contract DEAC05-76RL01830. USR and AM also acknowledge the American Chemical Society Petroleum Research Fund (# 55026-ND6) for partial support of this research. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by National Science Foundation Grant No. ACI-1053575.
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