Dependence on pressure of the diffusion coefficients of low molecular weight particles in a polymer

• Published in: Polymer science USSR 1983, Vol.25 (11), p.2664-2673
• Main Authors: Kovarskii, A.L., Aliyev, I.I.
• Format: Article
• Language: English
• ISSN: 0032-3950; 1878-268X
• DOI: 10.1016/0032-3950(83)90342-8

An analysis has been made of the pressure dependence of the rotatory and translational diffusion coefficients of spin probes—stable nitroxyl radicals in polydimethylsiloxane, polyisobutylene and PE. It is shown that deviation from linear relations in the coordinates log D= f( p) is due to change in the modulus of volumetric compression with pressure. An equation is obtained describing the pressure dependence of the diffusion coefficients of low molecular weight particles: D=D' exp (—p V K 0 ∗/K)/RT where K 0 is the value of the bulk modulus of compression K at p a ̊ 0 . From the equation it is possible without the pVT-diagram to determine simultaneously from the functions log D=f(p) both the activation volumes V ∗ depending on the structure of the particle and the type of molecular movement and the value K 0 K characterizing the polymer matrix. The parameters of the equations of state of polymers are calculated from the diffusion data.