Unperturbed Dimensions of Atactic Poly(phenylacetylene)

Abstract

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.

Synthesis and Spectral Properties of Novel Poly(disubstituted acetylene)s

“…The value of σ = 0.80 obtained for P4 thus confirmed the enhanced rigidity of P4 chains in THF. The rigid conformation of poly(disubstituted acetylene)s with bulky substituents (that can be assumed from the covalent structure of these polymers) was confirmed for several polymers of this type by intrinsic viscosity vs. molecular weight measurements 71–74…”

(η4-Tetrafluorobenzobarrelene)-η1-((tri-4-fluorophenyl)phosphine)-η1-(2-phenylphenyl)rhodium(I): A Catalyst for the Living Polymerization of Phenylacetylenes

“…Based on the kinetics, the expected M n after 90 min would be 9130. Assuming polystyrene standards are appropriate for PPhC 2 H, 39 the theoretical and observed M n 's correspond to an IE of 0.87. To demonstrate the potential to prepare new AB diblock copolymers via sequential monomer addition, we next conducted a self-blocking experiment to confirm the retention of chain-end activity and to examine the crossover (reinitiation) efficiency.…”

Characterization of substituted polyacetylene microstructure by pyrolysis gas chromatography

“…Less reliable information of this kind can be obtained from IR spectra of these polymers [6]. Since changes in cisoid and transoid configurations of single bonds in conjugation corresponds to conformational transitions of saturated chains, this feature of polyacetylenes can be roughly ascertained, as an average torsion angle, from unperturbed dimensions of a particular polyacetylene of the known contents of cis and trans units [7,8]. Methods for a reliable characterization of H-T isomerism of polyacetylenes have not yet been developed.…”