Molecular‐weight determination of poly(phenylacetylene) by size‐exclusion chromatography/low‐angle laser light scattering. Influence of polymer degradation

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

“…However, indirect evidences of the presence of HH-TT sequences in substituted polyvinylenes were obtained much earlier, from results of the thermal degradation study on ring-substituted PPAs. Blum et al 58 2 ], when kept in THF solution at room temperature in vacuum or exposed to air (unpublished data of the authors) 1,3,5-trisubstituted benzene derivatives. These results were later confirmed by fast pyrolysis gas chromatography 59 , in which the polymer is decomposed at 500°C within ca 0.5 s, and the decomposition products are on-line analyzed by GC/MS.…”

“…Blum et al 58 2 ], when kept in THF solution at room temperature in vacuum or exposed to air (unpublished data of the authors) 1,3,5-trisubstituted benzene derivatives. These results were later confirmed by fast pyrolysis gas chromatography 59 , in which the polymer is decomposed at 500°C within ca 0.5 s, and the decomposition products are on-line analyzed by GC/MS. If a regular HT chain undergoes cyclotrimerization cleavage, only 1,3,5-trisubstituted benzene is formed as the product.…”

“…The observed small configurational defects can be namely ascribed to an additional, rather rapid cis-to-trans isomerization of formed cis-polyvinylene molecules in solution 48,49 , which, undoubtedly, takes also place during polymerization and NMR analysis. The presence of oxygen in the polymerization mixture can further decrease the cis-regularity of the formed polyvinylene molecules because they are often unstable in air undergoing autoxidative degradation [48][49][50][51][52][53] . Their degradation in solution can be so rapid that it even affects the results of the polymer SEC analysis [53][54][55][56] .…”

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

“…[63][64][65][66][67] Probably the first work on this subject was done by Percec and co-workers who described the slow decrease in molecular weight (MW), i.e., degradation, of lower-MW polyphenylacetylene (PPhA) when it was exposed to the atmosphere in the solid state. [55] Results of these studies can be summarized as follows: (i) the degradation is conditioned by the presence of oxygen in the system.…”

Electronic processes in end-functionalized oligomeric poly(diphenylvinylene)s

“…It is notable that, e.g., carotenes, retinals, zeaxanthines and related compounds, which, from the structural viewpoint, are oligomers of substituted acetylenes (oligovinylenes), effectively function as molecular wires in the living matter (photosynthesis systems, vision) for hundreds millions of years. Although high-molecular-weight polyacetylenes show many unique properties [4,5], unfortunately, they are mostly unstable in air [6][7][8][9][10][11][12][13], undergoing autoxidative degradation, which makes their practical applications difficult or even impossible. Nevertheless, polymers of disubstituted acetylenes are practically stable in air [14,15], which, evidently, is due to the absence of main chain vinylic hydrogen and effective protection of their conjugated main chains by substituents.…”