Unveiling the Enzymatic Degradation Process of Biobased Thiophene Polyesters

In the past 20 years, scientific research focused on the identification of valid alternatives to materials of fossil origin, in particular, related to biobased polymers. Recently, the efforts led to the synthesis of thiophene-based polymers (TBPs), a new class of polyesters based on 2,5-thiophenedicarboxylic acid (TPCA) that can be industrially produced using biomass-derived molecules. In this study, TBPs were synthesized using diols with different chain length (from C4 to C6) leading to poly(butylene 2,5-thiophenedicarboxylate) (PBTF), poly(pentamethylene 2,5-thiophenedicarboxylate) (PPeTF), and poly(hexamethylene 2,5-thiophenedicarboxylate) (PHTF), respectively, that were processed to thin films. To investigate enzymatic hydrolysis of these polymer films, cutinase 1 (Thc_cut1) and cutinase 2 (Thc_cut2) from Thermobifida cellulosilytica were recombinantly expressed in the host E. coli and purified. After 72 h of incubation at 65°C with 5 µM Thc_cut1, weight loss and HPLC analysis indicated 9, 100, and 80% degradation of PBTF, PPeTF, and PHTG with a concomitant release of 0.12, 2.70, and 0.67 mM of TPCA. The SEM analysis showed that tiny holes were formed on the surface of the films and after 72 h PPeTF was completely degraded. The LC-TOF/MS analysis indicated that Thc_cut2 in particular released various oligomers from the polymer during the reaction. In addition, the FTIR analysis showed the formation of novel acid and hydroxyl groups on the polymer surfaces. The results showed that the two used thermostable cutinases are promising biocatalysts for the environmentally friendly degradation of TPCA-based polyesters, in view of a possible sustainable recycling of plastic waste through resynthesis processes.

Improvement of poly(3-hexylthiophene-2,5-diyl) electron mobility through complete elimination of regioregularity defects

The improvement of electron transport in polymer semiconductors is highly desirable for realizing robust, large-area and low-cost organic integrated circuits. This work investigates the effect of regioregularity on the intrinsic hole and electron transport characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) using current-voltage (I-V) measurements in metal/polymer/metal sandwich structures. Through a direct comparison between 93% regioregular P3HT (EG-P3HT) and 100% regioregular defect-free poly(3-hexylthiophene-2,5-diyl) (DF-P3HT), it is found that the elimination of regioregularity defects improves the electron mobility of DF-P3HT (1.05 × 10-7 cm2 V-1 s-1) by three orders of magnitude compared to the 93% regioregular EG-P3HT sample (1.82 × 10-10 cm2 V-1 s-1). Quantum chemical calculations indicate that the improvement of electron mobility in DF-P3HT can be associated to the lower degree of disorder in these samples that tends to increase the transfer angle between the lowest unoccupied molecular orbitals of adjacent chains. At the same time, the lower dipole moments produced by the defect-free polymer molecules also appears to play an important role in decreasing the susceptibility of charge transport to environment-induced electron traps. The obtained results provide a strong evidence that the elimination of regioregularity defects is an effective technique to improve electron transport and restore the symmetry between hole and electron mobility in P3HT as well as other thiophene-based polymers.

Supramolecular Thiophene-Based Materials: A Few Examples of the Interplay between Synthesis, Optoelectronic Properties and Applications

Supramolecular nanostructured thiophene based materials with optoelectronic functions are of wide current interest and are playing a crucial role in different fields of nanoscience and nanotechnology. This short review gives a concise report of some particularly interesting examples from our own work concerning thiophene-based supramolecular architectures at multiple length scales, their function and application in devices. We start with some general considerations on the great chemical diversity of thiophene derivatives and their supramolecular architectures. Then we focus on how the supramolecular organization of specific thiophene derivatives may generate nanostructures that enable new functions and applications in devices. For each example, we report the synthesis of the corresponding thiophene derivatives.1. Introduction2. Supramolecular Organization may Impart New Functions to the System3. Supramolecular and Optoelectronic Properties of Oligothiophene-S,S-dioxides4. Colloidal Nanoparticles formed by Self-Assembly of Thiophene-Based Polymers5. Conclusions and Outlook