Collect. Czech. Chem. Commun. 2005, 70, 1787-1798

Unperturbed Dimensions of Atactic Poly(phenylacetylene)

Dana Rédrováa, Jan Sedláčeka, Majda Žigonb and Jiří Vohlídala,*

a Department of Physical and Macromolecular Chemistry, Laboratory of Specialty Polymers, Faculty of Science, Charles University, Albertov 2030, CZ-128 40 Prague 2, Czech Republic
b National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia


Dilute solution characteristics of atactic (ca. 30% trans) poly(phenylacetylene), PPA, were determined by using the SEC/MALS technique in order to obtain a deeper insight into discrepancy between presumed rigidity of conjugated polyvinylene molecules and their random-coil behavior in solutions resulting from earlier viscometry measurements. PPA was found to exhibit the molecular-weight dependence of the radius of gyration in tetrahydrofuran solution similar to that of atactic polystyrene (saturated analogue of PPA); also unperturbed dimensions of these polymers are almost equal. This rather surprising observation is explained as a consequence of the increased π-π attraction between highly polarizable PPA segments with well-delocalized π-electrons, which compensates the effect of stiffening of these segments due to conjugation. Possible influence of chain branching is also discussed.

Keywords: Polyacetylenes; Polyphenylacetylene; Polyvinylenes; Radius of gyration; Scaling law; Unperturbed dimensions; Polymers; Conformation analysis.

References: 46 live references.