Spin-Probe Investigation of the Dynamic Behavior of Low Molecule Additive in Polyvinylchloride

Abstract

The three kinds of TEMPO radical derivatives (TEMPO (-H), TEMPOL (-OH), TEMPOAM (-NH₂) ) having different substituents in the molecule as the spin probe agents were added to the poly(vinyl chloride) (PVC) including dioctyl phthalate (DOP) as plasticizer, and the rotational correlation times τ_c^(m) of the radical derivatives were obtained in the temperature range of 90-180°C by the ESR measurement. The values of τ_c^(m) for each radical decreased by increasing the quantity of DOP added to PVC. Similarly, the values of τ_c^(m) decreased by increasing the temperature. The decrease of τ_c^(m) may be explained by the decrease of the density of the PVC resin and, thus, the decrease of the viscosity of PVC resin, due to the addition of DOP and the increase of the temperature. It has been cleared that the value of τ_c^(m) varies depending on the kinds of functional groups (-H, -OH, -NH₂) in TEMPO radical derivatives, indicating the existence of the interaction between the PVC molecule and the functional groups (-H, -OH, -NH₂) in TEMPO derivatives. The energies of the above interactions were calculated with the UHF-PM3 method by using the MOPAC 93 program. TEMPO derivativesand DOP increases in the order of TEMPO<TEMPOL =DOP<TEMPOAM. Low stabilization energy was obtained for the TEMPO derivatives, which show fast rotation motion in PVC resin.