A Micromechanical Study of Interactions of Cyanate Ester Monomer with Graphene or Boron Nitride Monolayer

Abstract

Polymer composites, hailed for their ultra-strength and lightweight attributes, stand out as promising materials for the upcoming era of space vehicles. The selection of the polymer matrix plays a pivotal role in material design, given its significant impact on bulk-level properties through the reinforcement/polymer interface. To aid in the systematic design of such composite systems, molecular-level calculations are employed to establish the relationship between interfacial characteristics and mechanical response, specifically stiffness. This study focuses on the interaction of fluorinated and non-fluorinated cyanate ester monomers with graphene or a BN monolayer, representing non-polymerized ester composites. Utilizing micromechanics and the density functional theory method to analyze interaction energy, charge density, and stiffness, our findings reveal that the fluorinated cyanate-ester monomer demonstrates lower interaction energy, reduced pull-apart force, and a higher separation point compared to the non-fluorinated counterpart. This behavior is attributed to the steric hindrance caused by fluorine atoms. Furthermore, the BN monolayer exhibits enhanced transverse stiffness due to increased interfacial strength, stemming from the polar nature of B-N bonds on the surface, as opposed to the C-C bonds of graphene. These molecular-level results are intended to inform the design of next-generation composites incorporating cyanate esters, specifically for structural applications.

Keywords: cyanate-ester; density functional theory; elastic stiffness; graphene; pull-apart.

Figure 1

Molecular Representation of (a) AroCy-F10 (Fluorinated) and (b) Primaset PT-30 (Non-Fluorinated) Cyanate Ester Resin Monomers: Ball and Stick Models with Ester and Fluorine Groups Highlighted. Color codes: C—grey, H—white, N—blue, F—green, O—red.

Figure 2

A workflow diagram describing the steps taken to determine the equilibrium structure of the monomer/graphene complex. Color codes: C—grey, H—white, N—blue, F—green, O—red.

Figure 3

The calculated interaction energy of the ester resins: AroCy-F10 (fluorinated cyanate ester), labeled as F-CE, and Primaset PT-30 (non-fluorinated cyanate ester), labeled as NF-CE. G refers to graphene, and BN refers to a boron nitride monolayer.

Figure 4

Calculated force vs. transverse strain curve of the ester/monolayer; AroCy-F10 (fluorinated cyanate ester) labeled as F-CE and Primaset PT-30 (non-fluorinated cyanate ester) labeled as NF-CE. G refers to graphene, and BN refers to a BN monolayer.

Figure 5

Calculated mechanical response and the interaction energy of the ester complexes; AroCy-F10 (fluorinated cyanate ester) labeled as F-CE and Primaset PT-30 (non-fluorinated cyanate ester) labeled as NF-CE. Also, G refers to graphene, and BN refers to a BN monolayer.