On the Structural and Mechanical Properties of Poly(Phenylacetylene) Truss‐Like Hexagonal Hierarchical Nanonetworks

Abstract

A novel class of hexagonal nanoscale honeycombs made from penta and tetra substituted polyphenlyacetylenes is proposed and modeled as crystalline systems using force‐field based simulations. It is shown that, in‐plane, these systems behave rather similarly to crystalline forms of graphyne, graphdiyne, and other fully substituted equivalents but benefit from the presence of larger pores which makes them less stiff and may enable them to be used in a wider range of applications such as nanofiltration. It is also shown that at large strains these systems have the potential to exhibit auxetic out‐of‐plane behaviour, a property which can be manifested in other triangulated systems and can be explained from buckling of some nanoribs in the systems.

Auxetics and Other Systems of Anomalous Characteristics

“…The theoretical paper presented by the Malta group, 'On the compressibility properties of the wine-rack-like carbon allotropes and related poly(phenylacetylene) systems' [15] looks at a number of carbon-based two-dimensional nano networks, some of which are shown to exhibit more than one negative mechanical property. This work, which extends earlier studies of the same authors, [16,17] shows how some of the networks can be both auxetic and exhibit negative linear compressibility.…”

On the Mechanical Properties of Graphyne, Graphdiyne, and Other Poly(Phenylacetylene) Networks

“…In view of this, an attempt is made to revisit the properties of graphyne, graphdiyne and related sheet‐like systems in an attempt to assess the properties that can be obtained from fully substituted, penta‐substituted, tetra‐substituted and tri‐substituted poly(phenylacetylene) systems shown in Figure in an attempt to identify interesting and anomalous properties that these systems may exhibit. Here it must be noted that depending on the manner of substitution, the systems in Figure result in some very different geometries, where for example, the 1,3,5 tri‐substituted systems and the 1,2,3,4,5 penta‐substituted networks resemble honeycomb‐like structures; the 1,2,4,5 tetra‐substituted networks resemble wine‐rack models whilst the 1,2,3,4‐ tetra‐substituted networks resemble the polytriangles . To simplify discussion a nomenclature system which is based on the manner of substitution of the phenyl rings and the length of the acetylene chains is being proposed, as described in Figure .…”

A Novel Mechanical Metamaterial Exhibiting Auxetic Behavior and Negative Compressibility

“…It is due to these enhanced properties and the wide range of applications that in recent years, there have been various studies which have attempted to design, model, synthesize, manufacture, or characterize materials and metamaterials which exhibit one or more of these anomalous properties. These include zeolites [11][12][13][14], silicates and other minerals [15], and polymeric systems [2,[16][17][18][19][20][21][22] which exhibit negative Poisson's ratios, in addition to metal organic frameworks (MOF) which exhibit negative linear compressibility [23][24][25]. In tandem, there has also been a significant amount of research aimed at exploring new mechanisms leading to anomalous behaviors.…”