Utilizing Furfural-based Bifuran Diester as Monomer and Comonomer for High-Performance Bioplastics: Properties of Poly(butylene furanoate), Poly(butylene bifuranoate), and their Copolyesters

Two homopolyesters and a series of novel random copolyesters were synthesized from two bio-based diacid esters, dimethyl 2,5-furandicarboxylate, a well-known renewable monomer, and dimethyl 2,2′-bifuran-5,5′-dicarboxylate, a more uncommon diacid based on biochemical furfural. Compared to homopolyesters poly(butylene furanoate) (PBF) and poly(butylene bifuranoate) (PBBf), their random copolyesters differed dramatically in that their melting temperatures were either lowered significantly or they showed no crystallinity at all. However, the thermal stabilities of the homopolyesters and the copolyesters were comparable. Based on tensile tests from amorphous film specimens, it was concluded that the elastic moduli, tensile strengths, and elongation at break values for all copolyesters were similar as well, irrespective of the furan:bifuran molar ratio. Tensile moduli of approximately 2 GPa and tensile strengths up to 66 MPa were observed for amorphous film specimens prepared from the copolyesters. However, copolymerizing bifuran units into PBF allowed the glass transition temperature to be increased by increasing the amount of bifuran units. Besides enhancing the glass transition temperatures, the bifuran units also conferred the copolyesters with significant UV absorbance. This combined with the highly amorphous nature of the copolyesters allowed them to be melt-pressed into highly transparent films with very low ultraviolet light transmission. It was also found that furan–bifuran copolyesters could be as effective, or better, oxygen barrier materials as neat PBF or PBBf, which themselves were found superior to common barrier polyesters such as PET.acceptedVersionPeer reviewe

Charge transfer characteristics of fullerene-free polymer solar cells via multi-state electronic coupling treatment

Recently, non-fullerene (NF) polymer solar cells (PSCs), where new electron acceptor (eA) materials are blended with a donor-acceptor (D-A) copolymer as an electron donor (eD), have shown promising power conversion efficiencies up to 18%. Some of the best-performing NF PSCs use the eD copolymers PBDT-TzBI, PDTB-EF-T, and PBDB-T-2F, and either a D-A copolymer P(NDI2OD-T2) or small molecule acceptors (SMAs) ITIC-4F and ITIC-2Cl as the NF eA compounds. Here we investigate these systems with density functional theory methods and extend our previous study of the multi-state fragment charge difference (FCD) electronic coupling scheme by applying it to the calculations of charge transfer (CT) rates for exciton dissociation and charge recombination (CR) processes at local eD-eA interfaces. Despite similar backbone structures and optical properties, the studied eD copolymers have different conformational, ionization, excitation, and CT characteristics. The electronic couplings and CT rates depend strongly on the relative positioning of the eD and eA compounds in the eD-eA complexes. While the main CT path is from eD to the eA compound, CT from eA to the eD compound is also predicted in the polymer-polymer PBDT-TzBI-P(NDI2OD-T2) system. The multi-state FCD electronic couplings are independent of the number of the excited states included in the calculations when using a dispersion-corrected optimally tuned long-range corrected functional. The calculated CR rates are slower in the polymer-SMA systems than in the polymer-polymer system, which could partly account for their higher experimentally observed efficiencies in devices.publishedVersionPeer reviewe