Autoxidative Degradation of Poly(phenylacetylene)

Abstract

Autooxidative degradation of high molecular-weight poly(phenylacetylene) (PPhA) in solid state and in solution was studied using the size exclusion chromatography (SEC) and UV, IR, and EPR spectrometry. No degradation was observed on PPhA stored in vacuum, whereas the polymer exposed to air was found to degrade without any induction period. No evidence of a cross-linking of oxidized PPhA was observed. The degradation of PPhA was found to be: (i) practically non-influenced by an ambient, diffuse day-light; (ii) of the random type (i.e. each main-chain bond of PPhA has the same probability of being ruptured); and (iii) fast enough to influence the results of SEC measurements.

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

“…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] .…”

Molecular weight and configurational stability of poly(phenylacetylene) prepared with Rh catalyst

“…In the FTIR spectra of F2 and F3 a new weak band was distinguishable at about 1730 cm À1 . This band can be ascribed to carbonyl groups that are considered as products of oxidative degradation of polyacetylenes [57,66,86]. Position and relative intensities of all the other bans did not alter with MW and configuration of individual fractions and well corresponded to bands described in IR spectra of PPhAs prepared with Rh catalysts [91].…”

“…2 also shows the a vs. t plot (parameter a is defined as follows: a ¼ 1/(X n ) t -1/(X n ) 0 where (X n ) 0 and (X n ) t stand for the number-average degree of polymerization at the onset of ageing and in time t, respectively). The non-linearity of a vs. t plot demonstrates that the degradation of high-cis PPhA under given conditions is not of the random character [57]. This finding is in accord with reports of our and other groups describing the non-randomness of oxidative degradation of various high-cis Ageing time dependences of parameter a, (X w ) t /(X w ) 0 and (X n ) t /(X n ) 0 resulting from the experiments in which non-fractionated PPhA (dissolved in THF-d 8 ) was allowed to age in contact with the atmosphere and diffuse daylight at room temperature.…”

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.…”