No abstract

Transforming how plastics are made, unmade, and remade through innovative research and diverse partnerships that together foster environmental stewardship is critically important to a sustainable future. Designing, preparing, and implementing polymers derived from renewable resources for a wide range of advanced applications that promote future economic development, energy efficiency, and environmental sustainability are all central to these efforts. In this Chemical Reviews contribution, we take a comprehensive, integrated approach to summarize important and impactful contributions to this broad research arena. The Review highlights signature accomplishments across a broad research portfolio and is organized into four wide-ranging research themes that address the topic in a comprehensive manner: Feedstocks, Polymerization Processes and Techniques, Intended Use, and End of Use. We emphasize those successes that benefitted from collaborative engagements across disciplinary lines.

Cyclic polymers have garnered increasing attention in the materials community as lack of free-chain ends in cyclic polymers results in significant differences in structure, thermodynamics, and dynamics compared to their linear counterparts. Yet, key open questions remain about how cyclic polymer chain conformations and effective interactions in solution change as a function of solvent quality, ring closure chemistry, and the presence/absence of common synthetic impurities. We use coarse-grained molecular dynamics simulations, polymer reference interaction site model theory, and small-angle neutron-scattering experiments on polystyrene in d-cyclohexane to demonstrate how linear and cyclic polymer chain configurations, scaling, and effective interactions are influenced by solvent quality and polymer concentration. We find that the balance between the available intraversus interchain contacts in solution dictate the trends in cyclic polymer size scaling and effective polymer−solvent and polymer−polymer interactions; these results are largely insensitive to the ring closure chemistry and the presence of linear or cyclic dimer impurities. This study provides the broader polymer science and engineering community fundamental insights into how synthesis, purification, and assembly of cyclic polymers in solvent(s) impact the resulting chain structure and polymer solution thermodynamics.

Dodecaphenyltetracene (4), the largest perphenylacene yet prepared, was synthesized from knownt etraphenylfuran, hexaphenylisobenzofuran, and 1,2,4,5-tetrabromo-3,6diphenylbenzene in three steps.The X-ray structure of the deep red, highly luminescent 4 shows it to be aD 2 -symmetric molecule with an end-to-end twist of 978 8.T he central acene is encapsulated by the peripheral phenyl substituents,a nd as aresult, the molecule is relatively unreactive and even displays reversible electrochemical oxidation and reduction.

No abstract