Maarten Maesen

Every twig and splinter used Plant-based production of commodity chemicals faces steep competition from fossil resources, which are often cheaper and easier to partition. Sustainable use of renewable resources requires strategies for converting complex and recalcitrant biomolecules into streams of chemicals with extraordinary efficiency. Liao et al. developed a biorefinery concept in which wood is eventually fully converted into useful chemicals: phenol, propylene, pulp amenable to ethanol production, and phenolic oligomers that can be incorporated into ink production (see the Perspective by Zhang). A life-cycle assessment and techno-economic analysis highlight the efficiency of the process and reveal the potential for such biorefinery strategies to contribute to sustainable chemicals markets. Science , this issue p. 1385 ; see also p. 1305

A series of chiral, substituted conjugated polymers containing the cyclopenta[2,1-b:3,4-b‘]dithiophene unit were synthesized: poly(cyclopenta[2,1-b:3,4-b‘]dithiophene)s, poly(thieno[3,2-b]thiophene-alt-cyclopenta[2,1-b:3,4-b‘]dithiophene)s and poly(thiophene-alt-cyclopenta[2,1-b:3,4-b‘]dithiophene)s. The polymers were prepared by a Stille-coupling reaction and their (chir)optical properties were investigated in solution as well as in film. UV−vis and fluorescence spectroscopy indicated that the polymers are present as rigid, highly conjugated strands in solution. Although the homopolymers (poly(cyclopenta[2,1-b:3,4-b‘]dithiophene)s) do not self-assemble in solution as well as in film, the alternating copolymers (chirally) stack upon transition to nonsolvents and solid state. The (chir)optical properties in film appeared to depend on the annealing conditions: initially, the chiroptical response increases, but at higher temperatures, the Cotton effects irreversibly disappear. Moreover, the CD spectra of films of poly(thieno[3,2-b]thiophene-alt-cyclopenta[2,1-b:3,4-b‘]dithiophene)s with chiral substituents on the thieno[3,2-b]thiophene moiety appeared to be a superposition of two effects, which had a different annealing dependency. In poly(thiophene-alt-cyclopenta[2,1-b:3,4-b‘]dithiophene)s, only chiral exciton coupling was found to be present.