Scaling Analysis and Distribution of the Rotational Correlation Times of a Tracer in Rubbery and Glassy Poly(vinyl acetate):  An Electron Spin Resonance Investigation

• Published in: Macromolecules 1999-03, Vol.32 (6), p.1876-1882
• Main Authors: Faetti, M, Giordano, M, Leporini, D, Pardi, L
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma981178x

We studied by ESR the rotational motion of a paramagnetic tracer (a deuterated 15N-enriched nitroxide) in poly(vinyl acetate) (PVAc). The reorientation of the tracer occurs via jumps of about 50° with a heterogeneous distribution of correlation times. Depending on the temperature range, the average correlation time 〈τ〉 scales as the α, β, and γ relaxation times of PVAc, i.e., 〈τ〉 = C i 〈τ〉 i , i = α, β, γ. On cooling, 〈τ〉 tracks the α relaxation to about the α−β bifurcation temperature and then the β relaxation down to the glass transition. In glassy PVAc 〈τ〉/〈τ〉γ = C γ ≈ 1.