Irradiation osmometry

Changes in molar mass of irradiated polymers were measured by viscosity, gel permeation chromatography, osmometry and light scattering. G (scission) and G (cross-link) values can be derived from gel contents if cross-linking predominates (3) and a GPC technique requiring only 50 mg of polymer, which could be in the form of powder, was developed for this purpose (4). 

Solvent 1 1 benzene-isopropanol or 1 1 benzene-ethanol or 1 1 tetrahydrofuran-isopropanol or isopropanol irradiation under nitrogen atmosphere Fischer-Black-Ray long-wavelength UV-lamp molecular weights are determined by vapor pressure osmometry in benzene. 

Re-investigation of the radio lysis of poly isobutene was undertaken more recently by Turner [388]. Irradiations were performed in vacuo at 25°C. The Gcs determined by viscosimetry and osmometry was 4.1 and the G for total unsaturation was 5.3. Hydrogen and methane were found with G values of 1.3—1.6 and 0.8—0.5. On lowering the temperature to 77°K, the scission yield decreased by a factor of about 2—3 whereas the gas yield was unchanged. 

The same group has also prepared chiral dimeric cycloalkynes that are linked by an azo group [66]. A separate synthesis of both the trans-177 and cis-177 derivatives was required due to an inability to isomerize the macrocyclic species using either heat or irradiation. Variable temperature CD and NMR spectroscopy indicated that both isomers formed aggregates in solution. Vapor pressure osmometry and GPC were used to provide an estimate of the molecular weights of the aggregates. Interestingly, it was found that while the trans-isomer forms strictly bimolecular... 

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