Dependence of Polymer Thin Film Adhesion Energy on Cohesive Interactions between Chains

Abstract

The adhesion of supported polymer thin fi lms is predominantly infl uenced by the substrate-fi lm interfacial properties. Utilizing steered molecular dynamics simulations, here we uncover that the cohesive noncovalent forces between polymer chains in the fi lm also have a signifi cant effect on the adhesive properties of supported fi lm. We demonstrate that weaker interchain interactions, all else being the same, can induce higher adhesion energy within the interface. Three different adhesion regimes in the substrate-fi lm interaction strength profi le can be characterized by a nonlinear scaling relationship that earlier theoretical predictions currently do not capture. In the weak substrate-fi lm interaction regime, the adhesion energy of the fi lms exhibits near independence of cohesive forces, and entropic contributions to the surface free energy are consequential. In the intermediate regime, weaker fi lm cohesive forces achieve higher adhesion energy due to the ability of polymer chains to pack more effectively in the interfacial region, thereby increasing the adhesive interaction density. In the strong interaction regime, the adhesion energy increases linearly with the adhesive interaction strength because of saturation of local packing in the interfacial region. These fi ndings corroborate recent polymer wetting observations that have hinted on the importance of local relaxation and packing effects on interfacial properties.

Moisture effect on interfacial integrity of epoxy-bonded system: a hierarchical approach

“…To simulate the film-substrate interaction, an energetic implicit wall representing a typical substrate in the experiment (such as the silica) is introduced at the bottom surface, which interacts with the epoxy thin film by using a truncated Lennard-Jones (LJ) 12-6 potential, as shown in equation 1, where z denotes the distance from the atom to the wall, z c is the cutoff distance of the interaction between the film and substrate, with a value of 10 Å, σ sub is the distance from the substrate at which the potential energy E sub crosses the zero axis, and ε sp denotes the film-substrate interaction strength, which affects the depth of the potential well. Here, σ sub has a value of 4.0 Å, which is close to the value of the polymersubstrate interaction in various studies [15,[42][43][44][45]. Meanwhile, in order to observe a clear substrate effect, ε sp is chosen with a value of 3.0 kcal mol −1 , which leads to a surface energy of around 100 mJ m −2 that can be obtained for the atomically smooth surfaces, including the silica surface [46,47].…”

Traction–separation laws and stick–slip shear phenomenon of interfaces between cellulose nanocrystals

“…These CG models will improve computational efficiency of molecular simulations and will open the door for studying new polymer-CNC bionanocomposites. Specifically, these CG models can be used to simulate the effect of CNCs within these bionanocomposites due to the development of interphase regions that have a pronounced effect on properties such as the glass-transition temperature and elastic modulus (Dong et al, 2012;Xia et al, 2014)_ENREF_62. These efforts will allow for an enhanced materials-by-design approach for CNC hierarchical materials that will help to improve upon the current shortcomings in the performance of these materials.…”

Electrically conductive nanocomposite adhesives based on epoxy or chloroprene containing polyaniline, and carbon nanotubes

“…They offer some potential advantages such as lower temperature processing, reducing the weight and cost, more flexible, simpler processing, higher stiffness and load transmission, and environmentally friendly in comparison to traditional tin/lead solder alloys [1][2][3][4][5]. In this respect, electrically conductive adhesives (ECAs) have recently received a lot of attention, on the basis of their importance in basic scientific research and potential industrial applications.…”