Isotactic polystyrene characterization by gel permeation chromatography in tetrahydrofuran

Abstract

SynopsisIsotactic polystyrene fractions were characterized by gel permeation chromatography (GPC) in tetrahydrofuran (THF) a t 25OC. From the universal calibration method, a viscosity law has been established allowing determination of the correspondence between the molecular weight GPC calibration laws for APS and IPS. The validity of characterization of IPS by this method was confirmed with light scattering and osmometry.

Thermoreversible gelation of isotactic polystyrene: thermodynamics and phase diagrams

“…Molecular weights and molecular weight distributions were determined from gel permeation chromatography in tetrahydrofuran at 25 °C with columns calibrated by means of atactic polystyrene standards. 7 The results are l3C NMR experiments carried out in chlorobenzene at 50 °C7 have shown the degree of stereoregularity of these samples to be over 97% isotactic.…”

Neutron scattering investigation of the chain trajectory in thermoreversible gels

“…The scattered intensity then reads as in relation 5 except that Mw must be replaced by NCMW, Nc being the number of chains in the cluster, and P(q) by Pc(q). Pc(q) stands for the cluster form factor and can be expressed as a function of the single-chain form factor provided that the chain conformation is not perturbed by the clustering:13 PM = P(q)/N2[2Pnn(q) -NJ*(q) -2P(q) + JVC][1 -P(q)]~2 (8) It can be easily shown that at larger q, the single chain behavior is retrieved since Pc(q) = P(q)/Nc for qR > 1.…”

Polymer‐Solvent Molecular Compounds: A Brief Presentation

“…The fibrillar structure, which gives rise to thermoreversible gels is obtained through the helix stabilization of the polymer chain as shown by neutron scattering both for isotactic polystyrene (iPS) and syndiotactic polystyrene (sPS). [10,[12][13] Other surface morphologies are observed, especially with samples prepared by exposing solid sPS to vapours or liquid. [14,15] These are not welldefined, in the sense that no fibrils nor spherulites can be identified beyond doubt.…”

“…the chain persistence length enhancement, which in turns results from the formation of the compound. [10,12,13] Indeed, the helical structure of the polymer is stabilized thanks to the solvation process which prevents the chain from folding. As a result, chainfolded crystals cannot be formed, and correspondingly no spherulitic structure can be obtained.…”