Backbone Chemical Composition and Monomer Sequence Effects on Phenylene Polymer Persistence Lengths

Multiscale Analyses of Strain-Enhanced Charge Transport in Conjugated Polymers

The advancement of flexible and wearable electronics relies on semiconducting polymers that can endure mechanical deformation while maintaining high electrical performance under strain. In this study, we demonstrate that fine-tuning backbone rigidity through the molecular design of donor moieties significantly enhances both the mechanical and charge transport properties of diketopyrrolopyrrole (DPP)-based polymers. Specifically, the flexible DPP-4T (quaterthiophene) exhibited a persistence length of 20.4 nm in solution, while DPP-DTT (dithienothiophene) showed a longer persistence length of 32.8 nm due to its stiff backbone, as confirmed by small-angle neutron scattering and Monte Carlo simulations. This flexibility enabled DPP-4T to achieve a crack-onset strain exceeding 100% via the film-on-elastomer method and a fracture strain of over 30% in quasi-free-standing films. Additionally, DPP-4T demonstrated a 180% increase in hole mobility at 80% strain, driven by strain-induced chain alignment and backbone planarization. Utilizing a range of characterization techniques, including ultraviolet-visible (UV-vis) spectroscopy, grazing incidence X-ray diffraction (XRD), and Raman spectroscopy, we characterized structural changes at multiple length scales under applied tensile strain. Notably, strain induced a transformation in chain conformation from a twisted to a flat structure, reducing the hopping energy barrier and enhancing charge transport. These structural rearrangements are crucial for sustaining efficient charge transport and ensuring the reliability of electronic performance under mechanical stress.

Virtual Screening for Organic Solar Cells and Light Emitting Diodes

The field of organic semiconductors is multifaceted and the potentially suitable molecular compounds are very diverse. Representative examples include discotic liquid crystals, dye-sensitized solar cells, conjugated polymers, and graphene-based low-dimensional materials. This huge variety not only represents enormous challenges for synthesis but also for theory, which aims at a comprehensive understanding and structuring of the plethora of possible compounds. Eventually computational methods should point to new, better materials, which have not yet been synthesized. In this perspective, it is shown that the answer to this question rests upon the delicate balance between computational efficiency and accuracy of the methods used in the virtual screening. To illustrate the fundamentals of virtual screening, chemical design of non-fullerene acceptors, thermally activated delayed fluorescence emitters, and nanographenes are discussed.

Rigidification of Poly(p-phenylene)s through ortho-Phenyl Substitution

A sterically π-congested ortho-phenylated poly(p-phenylene) (PPP) has been synthesized with unprecedentedly high molecular weights up to 29 kDa after fractionation, as confirmed by gel permeation chromatography coupled with a multiangle laser light scattering detector. The chain translation diffusion coefficient obtained from dynamic light scattering experiments displayed strong scaling (∼L_w^–0.8) to the chain contour length, indicating a rodlike shape with remarkably high rigidity of this novel PPP. These results provide an interesting insight into the relationship between the structure and the chain stiffness of PPP-based polymers and challenge the validity of the existing diffusion models in polymer physics.