Measurements of persistence length and temperature dependence of the radius of gyration in bulk atactic polystyrene

Measurements of radius of gyration, $\text{〈S}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and persistence length of polymer molecules in bulk atactic polystyrene have been made by means of low angle neutron scattering. The measured values of $\text{〈S}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ lie close to those measured in ?-solvents and have a molecular weight dependence of $\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>+?</mtext>}}$ where ? = 0·04 ± 0·04. The molecular configuration agrees closely with that of a random coil with a persistence length $\text{～ 10}\text{A}\text{?}$. These measurements support the model of an unperturbed Gaussian coil for this polymer. Measurements of $\text{〈S}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ throughout the glass transition region indicate that the overall conformation of the polymer chain does not change on heating through this region.