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Interfacial characteristics of polymer nanocomposites represent a crucial aspect to understand their global properties and to evaluate the interaction between nanofillers and matrix. In this work we used a molecular dynamics (MD) approach to characterize the interfacial region at the atomistic scale of graphene-based polymer nanocomposites. Three different polymer matrixes were considered, polylactic acid (PLA), polypropylene (PP) and epoxy resin (EPO), which were reinforced with three types of graphene fillers: pristine graphene (G), graphene oxide (GO) and reduced graphene oxide (rGO). In particular, the compatibility of the nanofillers in polymer matrixes were evaluated in terms of the interaction energy, while the interfacial thermal resistance (Kapitza resistance) between matrices and fillers was calculated with a nonequilibrium molecular dynamics (NEMD) method. Results showed that the oxidation degree plays an important role on the studied properties of the interfacial region. In particular, it was observed that the Kapitza resistance is decreased in the oxidized graphene (GO and rGO), while interaction energy depended on the polarity of the polymer matrix molecules and the contribution of the Coulombic component.
Francesco Bellussi; Carlos Sáenz Ezquerro; Manuel Laspalas; Agustín Chiminelli. Effects of Graphene Oxidation on Interaction Energy and Interfacial Thermal Conductivity of Polymer Nanocomposite: A Molecular Dynamics Approach. Nanomaterials 2021, 11, 1709 .
AMA StyleFrancesco Bellussi, Carlos Sáenz Ezquerro, Manuel Laspalas, Agustín Chiminelli. Effects of Graphene Oxidation on Interaction Energy and Interfacial Thermal Conductivity of Polymer Nanocomposite: A Molecular Dynamics Approach. Nanomaterials. 2021; 11 (7):1709.
Chicago/Turabian StyleFrancesco Bellussi; Carlos Sáenz Ezquerro; Manuel Laspalas; Agustín Chiminelli. 2021. "Effects of Graphene Oxidation on Interaction Energy and Interfacial Thermal Conductivity of Polymer Nanocomposite: A Molecular Dynamics Approach." Nanomaterials 11, no. 7: 1709.
This study describes the development of representative models of cellulose fibril surface (CFS) as a first approximation to the study of the molecular interactions that are developed between cellulose fibres. In order to assess its sensitivity and representativeness towards the main factors affecting the bonding properties at the fibre scale, these models were non-covalently surface modified with two types of polyelectrolytes, sodium carboxymethyl cellulose (CMC–ONa) and a cationic polyacrylamide (CPAM). From the analysis of pair correlation functions (g(r)) it was possible to assess the main interactions of adsorption of polyelectrolytes towards the (1–10) hydrophilic cellulose, which were due to electrostatic interactions coupled with hydrogen bonding. Besides, the bond strength between fibril surfaces through the (100) hydrophobic surface was calculated from pull out simulations (using steered molecular dynamics). Using a rate of change of force of 0.159 nN ps−1, the calculated bond strength for the neat CFS model (nanometer scale) was two to three orders of magnitude higher than the experimental values observed at the fibre scale (micrometer scale). The results for the polyelectrolyte modified setups supported the validity of the CFS models to reproduce the expected behavior of inter-fibre joints in terms of the specific bond strength and the relative bonded area at the fibre scale in cellulose materials, and thereby the CFS models are a suitable complement, in conjunction with other techniques, for the systematic study of the effect (in qualitative terms) of chemical or physical factors on the bond strength properties of cellulosic materials.
Carlos Sáenz Ezquerro; Cristina Crespo Miñana; Salvador Izquierdo; Manuel Laspalas. A molecular dynamics model to measure forces between cellulose fibril surfaces: on the effect of non-covalent polyelectrolyte adsorption. Cellulose 2018, 26, 1449 -1466.
AMA StyleCarlos Sáenz Ezquerro, Cristina Crespo Miñana, Salvador Izquierdo, Manuel Laspalas. A molecular dynamics model to measure forces between cellulose fibril surfaces: on the effect of non-covalent polyelectrolyte adsorption. Cellulose. 2018; 26 (3):1449-1466.
Chicago/Turabian StyleCarlos Sáenz Ezquerro; Cristina Crespo Miñana; Salvador Izquierdo; Manuel Laspalas. 2018. "A molecular dynamics model to measure forces between cellulose fibril surfaces: on the effect of non-covalent polyelectrolyte adsorption." Cellulose 26, no. 3: 1449-1466.
In polymer nanocomposites, the interface region between the matrix and the fillers has been identified as a key interaction region that strongly determines the properties of the final material. Determining its structure is crucial from several points of view, from modeling (i.e., properties prediction) to materials science (i.e., understanding properties/structure relationships). In the presented paper, a method for characterizing the interface region of polymer nanocomposites is described using molecular dynamics (MD) simulations. In particular, the structure of the polymer within the interface region together with its dimension in terms of thickness were analyzed through density profiles. Epoxy resin nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) were studied using this approach, and the interface region with triple walled carbon nanotubes (TWCNT) and carbon fibers (CF) was characterized. The effect of carbon nanotube diameter, type of hardener, and effect of epoxy resin cross-linking degree on interface thickness were analyzed using MD models. From this analysis no general rule on the effect of these parameters on the interface thickness could be established, since in some cases overlapping effects between the analyzed parameters were observed, and each specific case needs to be analyzed independently in detail. Results show that the diameter has an impact on interface thickness, but this effect is affected by the cross-linking degree of the epoxy resin. The type of hardener also has a certain influence on the interface thickness.
Carlos Sáenz Ezquerro; Manuel Laspalas; Agustín Chiminelli; Francisco Serrano; Clara Valero. Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach. Fibers 2018, 6, 54 .
AMA StyleCarlos Sáenz Ezquerro, Manuel Laspalas, Agustín Chiminelli, Francisco Serrano, Clara Valero. Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach. Fibers. 2018; 6 (3):54.
Chicago/Turabian StyleCarlos Sáenz Ezquerro; Manuel Laspalas; Agustín Chiminelli; Francisco Serrano; Clara Valero. 2018. "Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach." Fibers 6, no. 3: 54.
Carlos Sáenz Ezquerro; Gemma Ibarz Ric; Cristina Crespo Miñana; Javier Sacristán Bermejo. Characterization of montmorillonites modified with organic divalent phosphonium cations. Applied Clay Science 2015, 111, 1 -9.
AMA StyleCarlos Sáenz Ezquerro, Gemma Ibarz Ric, Cristina Crespo Miñana, Javier Sacristán Bermejo. Characterization of montmorillonites modified with organic divalent phosphonium cations. Applied Clay Science. 2015; 111 ():1-9.
Chicago/Turabian StyleCarlos Sáenz Ezquerro; Gemma Ibarz Ric; Cristina Crespo Miñana; Javier Sacristán Bermejo. 2015. "Characterization of montmorillonites modified with organic divalent phosphonium cations." Applied Clay Science 111, no. : 1-9.