Scholarly Works, Center for Intelligent Material Systems and Structures (CIMSS)

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Browsing Scholarly Works, Center for Intelligent Material Systems and Structures (CIMSS) by Subject "Charged clusters"

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    Computational analysis of ionic polymer cluster energetics
    Weiland, Lisa M.; Leo, Donald J. (American Institute of Physics, 2005-06-01)
    In recent years there has been considerable study of the potential mechanisms underlying the electromechanical response of ionic-polymer-metal composites. The most recent models have been based on the response of the ion-containing clusters that are formed when the material is synthesized. Most of these efforts have employed assumptions of uniform ion distribution within spherical cluster shapes. This work investigates the impact of dispensing with these assumptions in order to better understand the parameters that impact cluster shape, size, and ion transport potential. A computational micromechanics model has been developed to predict the equilibrium state of a single cluster of an ionomeric polymer with cluster morphology. No assumptions are made regarding the distribution of charge or the shape of the cluster. For a constant solvated state, the model tracks the position of individual ions within a given cluster in response to ion-ion interaction, mechanical stiffness of the pendant chain, cluster surface energy, and external electric-field loading. Expressions are developed to directly account for forces imposed on ions due to ion-cluster surface interaction. Results suggest that ion pairing is rarely complete; this in turn suggests that the classic assumptions will tend to underpredict electromechanical actuation response. (C) 2005 American Institute of Physics.
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    Ionic polymer cluster energetics: Computational analysis of pendant chain stiffness and charge imbalance
    Weiland, Lisa M.; Leo, Donald J. (American Institute of Physics, 2005-06-15)
    In recent years there has been considerable study of the potential mechanisms underlying the electromechanical response of ionic-polymer-metal composites. The most recent models have been based on the response of the ion-containing clusters that are formed when the material is synthesized. Most of these efforts have employed assumptions of uniform ion distribution within spherical cluster shapes. This work investigates the impact of dispensing with these assumptions in order to better understand the parameters that impact cluster shape, size, and ion transport potential. A computational micromechanics model applying Monte Carlo methodology is employed to predict the equilibrium state of a single cluster of a solvated ionomeric polymer. For a constant solvated state, the model tracks the position of individual ions within a given cluster in response to ion-ion interaction, mechanical stiffness of the pendant chain, cluster surface energy, and external electric-field loading. Results suggest that cluster surface effects play a significant role in the equilibrium cluster state, including ion distribution; pendant chain stiffness also plays a role in ion distribution but to a lesser extent. Moreover, ion pairing is rarely complete even in cation-rich clusters; this in turn supports the supposition of the formation of anode and cathode boundary layers. (c) 2005 American Institute of Physics.