Secondary relaxations in PVC as studied by phosphorescence decay of grafted luminescent probes

Teyssedre, G.; Reinecke, H.; Corrales, T.; Navarro, R.; Tiemblo, P.
Macromolecules 2005, 38, 10820-10828

Secondary relaxations have been detected in poly(vinyl chloride) (PVC) by measuring the phosphorescence emitted by chromophores present as defects in the polymer chains and in PVC with luminescent probes, pyridine and naphthalene, grafted onto the chain. The measurement of phosphorescence decay with temperature allows to identify the existence of two components in the beta-relaxation of PVC: one at about -40 degrees C and the other at about -60 degrees C. The progressive introduction of luminescent probes grafted on the PVC backbone and the study of such luminescent copolymers permits to attribute the well-known decrease of the beta-relaxation intensity when grafting or plasticizing, to the progressive disappearance of the high-temperature component. The spectral analysis of the mercaptopyridine grafted PVC copolymer (PVC-PYR) in the temperature range -130 to -30 degrees C shows that contiguous modified segments which interact with one another do not relax, while isolated modified segments do relax, either because isolated modified segments display the motions characteristic of the relaxation or because they are sensible to the motions of contiguous unmodified PVC segments