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Crystalline phase transition can be used to detect changes in the solid state properties of materials. Here, the authors describe the mechanical response of a crystal composed of ferrocene-containing rotaxane to laser irradiation.

“Cycloparaphenylenes consisting of are cyclic π-conjugated structures presetting interesting physical properties upon functionalization. However, the ring strain and steric hindrance of the substituents hamper the functionalization of small sized cycloparaphenylenes. Here, the authors describe a [6]cycloparaphenylene with twelve methoxy units employed to form a rotaxane with in-plane aromaticity upon oxidation.”

Vinylcycloalkanes with 12-, 15-, and 21-membered rings were synthesized from commercially available cycloalkanones or cycloalkyl carboxylic acids derived from malonate and ω-bromo-α-alkenes. Pd complexes with diimine ligands promoted the isomerization polymerization of vinylcycloalkanes with 15- and 21-membered rings to afford polymers having cycloalkylene groups in the main chain. Vinylcycloheneicosane with a 21-membered ring afforded polymers with M_n up to 9700, whereas vinylcycloalkanes with smaller ring sizes (8- and 12-membered rings) yielded oligomers with M_n = 720–1600.

Pd complexes with diimine ligands promote controlled cyclopolymerization of 1,6-dienes and 1,6,11-trienes to afford the polymers containing 1,2-trans-cyclopentane groups with well-regulated stereochemistry. Copolymerization of the dienes with ethylene and α-olefins also proceeds to give functionalized polyolefins. The polymerization of the monomers with oligomethylene spacer yields the polymers with five-membered rings in accurate density and distribution along the polymer chain. 4-Alkylcyclopentenes and alkenylcyclohexanes also get polymerized by the Pd complex to afford polymers with 1,3-trans-cyclopentane groups and 1,4-trans-cyclohexane groups, respectively. Isotactic polymer of 4-alkylcyclopentenes show liquid crystalline properties.

Direct arylation polycondensation has been investigated to develop efficient synthetic methods of conjugated polymers for use in optoelectronic applications. The optimization of reaction conditions achieved high molecular weights and minimal structural defects in the recurring structures. The optimized direct arylation method has several advantages over conventional methods, e.g., fewer synthetic steps, and high-molecular-weight and high-purity polymer. The high-quality polymeric materials exhibited superior performance to those obtained using a conventional method when used in organic photovoltaics and field-effect transistors.