Crosslinking mechanisms, structure and glass transition in phthalonitrile resins: Insight from computer multiscale simulations and experiments

Abstract

The influence of crosslinking process on the resulting structural properties of phthalonitrile matrices is studied through theoretical and experimental investigations. Multiscale procedure for generating fully atomistic phthalonitrile networks with simulation of radical polymerization reactions and specific reactions of triazine formation at the mesoscale level is presented and applied to the case of phthalonitrile resin based on low-melting monomer bis(3-(3,4-dicyanophenoxy)phenyl)phenyl phosphate. The structural properties of the generated networks of various conversions and with various amount of triazine are analyzed using the dissipative particle dynamics and atomistic molecular dynamics. Triazine-containing networks are much sparser in comparison with triazine-free ones in terms of simple cycle size. The values of density, coefficients of linear thermal expansion and glass transition temperatures (T g s) agree with obtained experimental data, and are very similar for different crosslinking mechanisms. The dependence of T g on conversion correlates well with the sol-gel transition in network structure.

Multiscale Simulations Approach: Crosslinked Polymer Matrices

“…On the second stage we perform extensive topological analysis of the networks, first proposed by Khalatur in [3]. This stage is important to refine the adaptive model: (a) to optimize the set of DPD parameters for generation of polymer matrix with correct topology [5], and (b) to modify the network by removing "wrong" bonds leading to internal stresses.…”

“…Then, we construct fully atomistic models of crosslinked samples using an automatic reverse mapping procedure. This procedure extracts the coordinates of all DPD beads and their topological connections, and replaces the beads with the corresponding molecular fragments according to coarse-graining scheme (see details in [5]). The restored matrix may contain the so-called "spearing" monomers.…”

“…During the last decade, we developed a multiscale simulation methodology that makes it possible to predict various physical properties of highly crosslinked polymer materials [2][3][4][5][6]. In this work, we summarize our simulations methodology combining coarse-grained MSC technique with full atomistic modelling.…”

“…In this work, we summarize our simulations methodology combining coarse-grained MSC technique with full atomistic modelling. Here, we apply it to generate fully atomistic model of highly crosslinked networks of phthalonitrile resin, based on the monomer bis(3-(3,4-dicyanophenoxy) phenyl) phenyl phosphate (DPPPP) and the initiator 1,3-bis(4-aminophenoxy)benzene (APB) [5], and to predict their physical properties (see Fig. 1a).…”

Interfacial Characteristics of Boron Nitride Nanosheet/Epoxy Resin Nanocomposites: A Molecular Dynamics Simulation

“…Through the above process, the uncross-linked model was obtained. The force field of this molecular dynamics (MD) simulation is universal force field (UFF), and the method of thermostat and barostat is Andersen and Berendsen, respectively [56].…”