Effects of Mechanical Deformation on the Opto-Electronic Responses, Reactivity, and Performance of Conjugated Polymers: A DFT Study

Abstract

The development of polymers for optoelectronic applications is an important research area; however, a deeper understanding of the effects induced by mechanical deformations on their intrinsic properties is needed to expand their applicability and improve their durability. Despite the number of recent studies on the mechanochemistry of organic materials, the basic knowledge and applicability of such concepts in these materials are far from those for their inorganic counterparts. To bring light to this, here we employ molecular modeling techniques to evaluate the effects of mechanical deformations on the structural, optoelectronic, and reactivity properties of traditional semiconducting polymers, such as polyaniline (PANI), polythiophene (PT), poly (p-phenylene vinylene) (PPV), and polypyrrole (PPy). For this purpose, density functional theory (DFT)-based calculations were conducted for the distinct systems at varied stretching levels in order to identify the influence of structural deformations on the electronic structure of the systems. In general, it is noticed that the elongation process leads to an increase in electronic gaps, hypsochromic effects in the optical absorption spectrum, and small changes in local reactivities. Such changes can influence the performance of polymer-based devices, allowing us to establish significant structure deformation response relationships.

Structural Insights into Conjugated Polymers for Stretchable Organic Transistors

“…Mechanical deformation causes multiscale structural changes in polymer films, including the formation of cracks and defects within the polymer (Figure b). , The phenomenon of multiscale structural changes within CP chains under mechanical deformation is fascinating yet complex. This process can be visualized as a chain of paper clips being pulled, with each link undergoing alterations; however, it is far more intricate.…”

Mechanical stability ofcis,trans-poly(p-phenylene vinylenes)

“…transistors, diodes, resistors, capacitors) need to be mechanically robust to extension and flexing and the performance of these devices must be stable under repeated mechanical deformation. 23 Semiconducting polymers often do not exhibit the same mechanical strength and toughness of traditional engineering polymers as they have rigid planar backbones that are ordered in the solid state but are surrounded by long, flexible side chains to enhance solubility, reducing the cohesive forces within thin films of these materials. 24 Although the thickness of the active semiconducting layer of most flexible electronic devices is more than an order of magnitude less than that of other layers, mechanical change or damage within these layers leads to dramatic changes in device performance.…”