Molecular Dynamics Simulation of the Formation of Polymer Networks

Abstract

The random end linking of different amounts of trifunctional crosslinkers with 3 000 prepolymer linear chains, with length varying from 10 to 30 monomers, to form networks at different system number densities was dynamically simulated by the molecular dynamics method. Investigation of the crosslinking kinetics shows that, with a stoichiometric number of crosslinkers present, the time evolution of free ends fraction decays as a power law in time t−3/4. This scaling behavior is different from the one in a dense polymer melt. Structural analyses of the resulting networks indicate that the imperfections of the network structure strongly depend on the initial synthesis conditions including the initial system number density and the ratio of crosslinkers to precursor polymer chain ends.magnified image

Analysis of the Gel Point of Polymer Model Networks by Computer Simulations

“…Yang et al 28 study network formation using Molecular Dynamics simulations. Apparently, not all of the presented data seem to be consistent and thus, need to be considered with care.…”

Impact of precursor size on the chain structure and mechanical properties of solvent-swollen epoxy gels

“…The capture radius is dependent on the length of the precursor chain and therefore a shorter precursor will have a smaller capture radius, resulting in a larger fraction of loop defects consistent with computational models of network formation. 27,40,41 The addition of solvent will increase the loop defect formation by further diluting the bulk concentration of reactive functional groups, resulting in the decreasing probability of a secondary chain being present in the capture radius. 41,42 The loop defect formation can also be influenced by a change in reactivity of the tetrafunctional cross-linker as a result of increased steric hindrance with extent of reaction.…”

“…27,40,41 The addition of solvent will increase the loop defect formation by further diluting the bulk concentration of reactive functional groups, resulting in the decreasing probability of a secondary chain being present in the capture radius. 41,42 The loop defect formation can also be influenced by a change in reactivity of the tetrafunctional cross-linker as a result of increased steric hindrance with extent of reaction. 43 The increasing scaling factors observed with increasing amine precursor molecular weight involves a competition between several effects.…”

“…(ii) Loop formation decreases with increasing molecular weight of the difunctional epoxide (PPGDE), consistent with previous work attributed to an increased capture radius. 27,40,41 (iii) Loop formation increases with increasing diamine precursor molecular weight (a tetrafunctional monomer due to the reactive capability of each amine hydrogen) attributed to the molecular structure which consists of two difunctional groups separated by a non-reactive spacer. When the molecular weight of the spacer is increased the local concentration of each difunctional group remains consistent while the bulk functional density is decreased, similar to dilution.…”

A study of highly crosslinked Epoxy Molding Compound and its interface with copper substrate by molecular dynamic simulations

“…Several authors have proposed methodologies of building atomistic network structure for thermosetting polymers. Some of these methods [2][3][4][5][6][7][8][9][10] involve a polymerization molecular dynamics simulation starting from either crystalline [3,6] or amorphous [2,4,5,[7][8][9][10] mixtures of separated monomers. Covalent bonds formation between reactive sites followed by relaxation of the system proceeds cyclically, leading to the final crosslinked model with relatively high conversion.…”