Unperturbed chain dimensions of polyethylene in theta solvents

The theta temperatures for linear polyethylene in diphenyl, diphenyl methane, and diphenyl ether were determined by the precipitation temperature measurements. The unperturbed mean‐square end‐to‐end distance (R₀²) and its temperature variation d In (R₀²)/dT were estimated from direct intrinsic viscosity measurements in these three theta solvents: <R₀²/nl² (where n is the Dumber of bonds, and l is the bond length) in diphenyl, diphenyl methane, and diphenyl ether was 7.10 at 127.5°C, 6.99 at 142.2°C, and 6.80 at 163.9°C., respectively. These numerical values gave d In <R₀²/dT = −1.21 × 10⁻³ deg.⁻¹. The results obtained here were in good agreement with those reported by Flory^1,2 and Chiang,³ and in support of the theoretical calculation by Hoeve⁴ and Nagai⁵.