Recently, a new two-dimensional carbon allotrope named biphenylene network (BPN) was experimentally realized. The BPN structure consists of four-, six-, and eight-membered rings of sp²-hybridized carbon atoms. In this work, we carried out fully-atomistic reactive (ReaxFF) molecular dynamics simulations to study the mechanical properties and fracture patterns of non-defective and defective (nanocracks) BPN. Results show that, under uniaxial tensile loading, BPN is converted into four distinct morphologies before fracture starts. This conversion process is dependent on the stretching direction. Some of the formed structures contain mainly eight-membered rings, which have different shapes in each morphology. In one of them, a graphitization process occurs before the complete fracture. Importantly, in the presence of nanocracks, no new morphologies are formed. BPN exhibits a distinct fracture process when contrasted to graphene. After the critical strain threshold, the graphene transitions from an elastic to a brittle regime, while BPN can exhibit different inelastic stages. These stages are associated with the appearance of new morphologies. However, BPN shares some of the exceptional graphene properties. BPN Young's modulus and melting point are comparable to graphene, about 1019.4 GPa and 4024 K, respectively.

The stability of charge carriers in conjugated polymers is investigated in terms of a nonadiabatic evolution method by using an extended version of the Su–Schrieffer–Heeger (SSH) model that includes the effects of an external electric field and temperature. On the basis of this physical picture, different patterns of applied electric field and temperature dependence of polaron and bipolaron kinematics as well as the transitions between different regimes are found. Phase transitions from subsonic to supersonic velocities are also discussed in terms of the system conditions. We were able to describe at which thermal regime each quasi-particle loses its stability and also to determine under which circumstances do the electric field and temperature rise or dampen its motion. The results indicate that thermal effects on polaron and bipolaron stability may provide guidance for improving the charge carrier conduction in organic optoelectronic devices.