Abstract
AbstractWe report the results of a combined study of the local structure and the reorientation dynamics in a series of five amorphous polymers of different fragility: cis‐trans‐1,4‐poly(butadiene) (c‐t‐1,4‐PBD), cis‐1,4‐poly(isoprene) (cis‐1,4‐PIP), poly(isobutylene) (PIB), poly(vinyl methylether)(PVME) and poly (propylene glycol) (PPG) by using two different probe methods. The reorientation dynamics of the molecular spin probe 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) from electron spin resonance (ESR) is related to the annihilation behaviour of the atomic ortho‐positronium (o‐Ps) one as obtained by positron annihilation lifetime spectroscopy (PALS). It was found that a slow to fast transition in the spin probe rotation mobility at the operationally defined spectral temperature parameter, T50G, is connected with the mean o‐Ps lifetime, τ3 (T50G) = (2.04 ± 0.26) ns. Consequently, using the free‐volume concept of the o‐Ps annihilation in terms of a quantum‐mechanical model of o‐Ps lifetime this transition can be connected with the occurrence of the mean free volume hole, Vh (T50G) = (102 ± 17) Å3, nearly independent of the chemical composition and the basic structural relaxation parameters of the amorphous polymers investigated. Finally, the free volume hole distribution aspect of the slow to fast transition indicates the presence of a sufficient free volume fluctuation at T50G for both typical fragile PVME and strong PIB polymer and emphasizes the essential role of free volume in the spin probe dynamics.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
