Effect of Solvent on Surface Ordering of Poly(3-hexylthiophene) Thin Films.

Enhancement of charge transport in organic polymer semiconductors is a crucial step in developing optimized devices. A variety of sample preparation conditions, such as film fabrication method, solvent species, and annealing, were found to influence the hole mobility of organic polymers. Despite the fact that many factors can influence their performance, it is believed that polymer surface ordering plays a key role in determining organic polymer function. Here, sum frequency generation (SFG) vibrational spectroscopy was used to nondestructively map the surface/interfacial ordering of poly(3-hexylthiophene) (P3HT) films prepared using different solvents; we believe that solvent interactions determine the degree of surface/interfacial ordering. Both X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM) were used to supplement SFG to systematically study bulk crystallinity and surface morphology. We conclude that SFG is a powerful tool to elucidate the surface/interfacial structural information on polymer semiconducting films. We demonstrate that the solvent composition used to prepare P3HT thin films influences the resulting film surface morphology, surface/interfacial ordering, and bulk crystallinity.

Chain-growth polymerization of aryl Grignards initiated by a stabilized NHC-Pd precatalyst.

An N-heterocyclic carbene-ligated palladium catalyst was discovered to mediate living, chain-growth polymerizations of both phenylene- and thiophene-based monomers. Polymerization of a fluorene-based monomer, on the other hand, did not proceed through a living, chain-growth pathway. Excitingly, block copolymerizations of phenylene and thiophene proceeded via a chain-growth pathway, regardless of the order of monomer addition. Although some chain termination was observed during these copolymerizations, this pathway could be minimized when the second monomer was added shortly after consumption of the first monomer. These results suggest that the catalyst resting-state at the end of polymerization is unstable. As a result, modifications to the NHC-scaffold or the 3-chloropyridine ligand will be necessary to generate an improved catalyst.

100th Anniversary of Macromolecular Science Viewpoint: Redefining Sustainable Polymers.

Although Staudinger realized makromoleküles had enormous potential, he likely did not anticipate the consequences of their universal adoption. With 6.3 billion metric tons of plastic waste now contaminating our land, water, and air, we are facing an environmental and public health crisis. Synthetic polymer chemists can help create a more sustainable future, but are we on the right path to do so? Herein, a comprehensive literature survey reveals that there has been an increased focus on "sustainable polymers" in recent years, but most papers focus on biomass-derived feedstocks. In contrast, there is less focus on polymer end-of-life fates. Moving forward, we suggest an increased emphasis on chemical recycling, which sees value in plastic waste and promotes a closed-loop plastic economy. To help keep us on the path to sustainability, the synthetic polymer community should routinely seek the systems perspective offered by life cycle assessment.