mu SR of conducting and non-conducting polymers

mu SR has been used to study a variety of polymers with very different elec tronic properties. In conducting polymers, the muon-generated radical state s take the form of highly mobile polarons. Muon spin relaxation has been us ed to study the mobility of these polarons and to measure the temperature d ependence of their intra-chain and inter-chain diffusion rates. it is found that the transport properties are strongly influenced by the librational r ing modes of the phenylene rings in these polymers. In contrast, the muon-g enerated radical states in non-conducting polymers such as polybutadiene re main localised near the site of the muon. High field muon spin rotation, av oided level crossing resonance and longitudinal relaxation studies have bee n made, using the muon radical state as a probe of the dynamical properties of the polymer. Dramatic changes in the mu SR signals are seen on going th rough the glass-rubber transition, as various dynamical degrees of freedom become frozen out. Additional information about the stability of the muon r adical states on the microsecond timescale has also been obtained using RF muon spin rotation techniques. Using time-delayed RF resonance of the diama gnetic state at the RIKEN-RAL muon facility, the transition rate between pa ramagnetic and diamagnetic states could be studied as a function of tempera ture. (C) 2000 Elsevier Science B.V. All rights reserved.