On the "tertiary structure" of poly-carbenes; self-assembly of sp3-carbon-based polymers into liquid-crystalline aggregates.

The self-assembly of poly(ethylidene acetate) (st-PEA) into van der Waals-stabilized liquid-crystalline (LC) aggregates is reported. The LC behavior of these materials is unexpected, and unusual for flexible sp(3)-carbon backbone polymers. Although the dense packing of polar ester functionalities along the carbon backbone of st-PEA could perhaps be expected to lead directly to rigid-rod behavior, molecular modeling reveals that individual st-PEA chains are actually highly flexible and should not reveal rigid-rod induced LC behavior.

Synthesis of functional 'polyolefins': state of the art and remaining challenges.

Functional polyolefins (i.e., polyethene or polypropene bearing functional groups) are highly desired materials, due to their beneficial surface properties.

A different route to functional polyolefins: olefin-carbene copolymerisation.

Copolymerisation of carbenes and olefins (ethene), mediated by Rh-based catalyst precursors, is presented as a new, proof-of-concept methodology for the controlled synthesis of functional polymers. The reactions studied show that olefin-carbene polymerisation reactions provide a viable alternative to more traditional olefin polymerization techniques. Rh(III)-catalyst precursors, while active in the homopolymerisation of either olefins or carbenes, proved to be virtually inactive in olefin-carbene copolymerization.

Propagation and termination steps in Rh-mediated carbene polymerisation using diazomethane.

Rh-mediated carbene (co)polymerisation of diazomethane works best in the presence of Rh(III) catalyst precursors, the use of which leads to a significant increase in polymer yield and molecular weight. Chain termination via β-hydride elimination is severely suppressed for these species, although this process does still occur leading to unsaturated chain ends. Subsequent chain walking leading to the formation of branched polymers seems not to occur.