Pressure-inducedcis totrans isomerization of aromatic polyacetylenes prepared using a Rh complex catalyst: A control of ?-conjugation length

SEC/DAD and1H NMR Study of Molecular Weight and Configurational Stability of Poly(2,4-difluorophenylacetylene) and Polyphenylacetylene Prepared with Rh Catalyst

“…Let us now assume the cis-to-trans isomerization proceeding (at least partly) via the rotational scission of the mainchain double bonds that leads to the increase of the content of unpaired electrons on the isomerized polymer chains [69][70][71][72][73]86] as it is known from the pressure-induced cis-to-trans isomerization of polyarylacetylenes. Assuming that the degradation of PdFPhA and PPhA is initiated by reaction of O 2 with the unpaired electrons on polymer chains, the isomerized cis/trans macromolecules should be more prone to the degradation compared to the high-cis microstructurally unperturbed macromolecules with a lower unpaired electrons content.…”

“…Isomerization proceeding by itself should lead to formation of more conjugated cis/trans main-chain sequences that should be manifested by a red shift in the visible spectrum. [69][70][71][72][73] If both processes proceed simultaneously and if the increase in conjugation due to cisto-trans isomerization overwhelms the declension in conjugation due to degradation the red shift in the visible spectrum may be expected.…”

“…The subject of particular interest in this field has been the pressureinduced cis-to-trans isomerization of these polymers in the solid state. [69][70][71][72][73][74] This phenomenon is manifested by (i) red shift in the UV-Vis spectra due to the increase in the effective conjugation length and (ii) a significant increase in the concentration of mobile unpaired electrons (solitons) on the polymer chains. [69] Since this process usually leads to the decrease in polymer solubility no reliable data is available on the eventual changes in MW accompanying cis-to-trans isomerization.…”

Molecular Shapes of Monosubstituted Polyacetylenes in their Liquid Crystalline Phases

“…For example, poly(phenylacetylene) and its derivatives initiated by organorhodium complexes are often cis-dominant, and in some cases the cis-content has even been measured as 100%. [28,29] On the other hand, trans-dominant MSPA can be obtained with W-based metathesis catalysts. It is worth noting that MSPAs are usually soluble in ordinary solvents.…”

Copolymers of phenylacetylene and para‐nitrophenylacetylene with nonlinear optical properties: Further insight on the conformational structure

“…In our previous research,16–19 we showed that cis‐to‐trans isomerization of polyphenylacetylenes bearing different substituents in the phenyl group could be induced by compression. A series of experiments on para ‐nitrophenylacetylene ( p NPA) polymers were performed to attain the designed trans configuration; particularly, the compression of the polymer to induce cis‐to‐trans isomerization was investigated 19.…”