Size Exclusion Chromatography of Substituted Acetylene Polymers: Effect of Autooxidative Degradation of the Polymer During the Analysis

Vohlı́dal, Jiřı́; Kabátek, Zdeněk; Pacovská, Marta; Sedláček, Jan; Grubisic-Gallot, Z.

doi:10.1135/cccc19960120

Cited by 25 publications

(20 citation statements)

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“…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] . It is important that autoxidative degradation of cis-transoid polymers is faster than that of the irregular or the trans-rich ones 52,53 .…”

Section: Isomerism Of Polyvinylene Macromoleculesmentioning

confidence: 99%

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Sedláček¹,

Vohlı́dal²

2003

Collect. Czech. Chem. Commun.

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101

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In the last fifteen years, a large variety of specialty polymers of diverse chemical structure and functionality have been synthesized with the rhodium-based catalysts. The high tolerance to the reaction medium and functional groups of monomers, as well as ability to control various structure features of the polymer formed are typical properties of these catalysts. In addition, some rhodium catalysts can be anchored to inorganic or organic supports or dissolved in ionic liquids to form heterophase polymerization systems, which opens the way to pure, well-defined polymers free of the catalyst residues, as well as to recycling rhodium catalysts. This review provides a survey on the polymerization reactions induced with rhodium-based catalysts, in which one or more structure attributes of the polymer formed are subject to control. The structure attributes considered are (i) sequential arrangement of monomeric units along polymer chains; (ii) head-tail isomerism of polymer molecules; (iii) configurational structure of polymer molecules; (iv) conformation of polymer molecules; and (v) molecular weight and molecular-weight distribution of the polymer formed. A review with 188 references.

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Section: Isomerism Of Polyvinylene Macromoleculesmentioning

confidence: 99%

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Sedláček¹,

Vohlı́dal²

2003

Collect. Czech. Chem. Commun.

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101

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“…It is thus obvious that from a value of ν the half-time of a degrading macromolecule with DP equal to Χ, τ(Χ), can be easily calculated: τ(Χ) = In2/v(X-\). Taking the value of ν = 2-10" 6 rnin 1 found for PPA/W in stabilized THF (16) and assuming an autoxidatively de grading macromolecule of X = 5 000, then the macromolecule half-time τ(Χ) is about 70 minutes only. Within that time just one half of original macromolecules remain intact the other being disrupted to fragments.…”

Section: Influence Of Polymer Degradation On Results Of Sec Analysismentioning

confidence: 99%

“…As it can be seen, the MW distribution of PPA/W sample remains unimodal dur ing entire process. All three kinetic plots according to equations 3 to 5 are linear and yield almost identical values of the degradation rate constant: ν = (2.5 ± 0.2)· 10" 6 min" 1 for the degradation in non-stabilized THF (26) and ν = (2.0 ± 0.2)· 10" 6 min" 1 for the degradation in THF stabilized by 2,6-ditert.butyl-4-methylphenol (0.025 weight %) (16). In summary, the autoxidative degradation of PPA/W suits the laws of the random polymer degradations.…”

Section: Time Of Degradation (In Solution) In Hoursmentioning

confidence: 95%

“…Using three types of experimental ap proaches and PPA/W as the model polymer (16) has proved the degradation of oxy gen-sensitive polymer inside SEC column: a) Comparison of results of SEC analyses performed in THF saturated with argon and air, respectively In the first experiment, a sample of PPA/W was, under the argon at mosphere, dissolved in THF saturated with argon. This THF was also used as eluent in the subsequent SEC analysis.…”

Section: Experimental Evidence For the Polymer Degradation During Secmentioning

confidence: 99%

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Degradation of Substituted Polyacetylenes and Effect of This Process on SEC Analysis of These Polymers

Vohlı́dal

Sedláček

1999

ACS Symposium Series

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Survey of advances in the fields of: (i) spontaneous autoxidative degradation of substituted polyacetylenes, and (ii) effect of this process on SEC analyses of these polymers, involving already published and new original results is presented. The degradation is shown to be, essentially, of the random type but accompanied by the enhanced low-MW species elimination in case of high-cis polymers. These species are suggested to be formed in the reactive relaxation of excited ends of primary fragments resulting from the random oxidative cleavage of macromolecules. The degradation proceeds even in SEC columns and distorts results of the polymer SEC analysis. Theoretical treatment and computer simulation of such analyses provided information on the results' distortion extent and showed that systematically biased MW averages provide plausible degradation rate constants.Size partitioning of macromolecules in SEC columns is more or less perturbed by various hydrodynamic and thermodynamic effects that do not alter a constitution of analyzed macromolecules (1-3). Only in case of very long macromolecules, typically with MW above 5-10 6 , the degradation induced by hydrodynamic shear forces can occur in SEC columns (4,5). This process has been reported for various high-MW polymers like poly(styrene), polyethylene, poly(methyl methacrylate), poly(isoprene), poly(oxyethylene) and poly(isobutylene) (4-15) so that it is well established and known,.nowadays. On the other hand, little is yet known on the effect of chemically induced degradation in the polymer SEC analysis that was recently demonstrated in the case of poly(phenylacetylene) (16) which undergoes rather fast oxidative degradation in soluSupported by the Ministry of Education of the Czech Republic, Project VS 97103.

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“…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.…”

Section: Introductionmentioning

confidence: 99%