Molecular Dynamics in the Rod-like Liquid Crystal 4-(trans-4-Pentylcyclohexyl) Benzonitrile (PCH5) Probed by Muon Spin Resonance Spectroscopy

Two types of muoniated spin probes were produced by the addition of muonium (Mu) to the phenyl ring of the rod-like liquid crystal 4-(trans-4-pentylcyclohexyl)benzonitrile (PCH5). Avoided level crossing muon spin resonance spec-troscopy was used to characterize the muoniated spin probes and to probe dynamics of PCH5 at the molecular level. The methylene proton hyperfine coupling constant (hfcc) of one of the muoniated spin probes shift in the nematic phase due to the dipolar hyperfine coupling, the ordering of the molecules along the applied magnetic field and fiuctuations about the local director. The amplitude of these fluctuations in PCH5 is determined from the temperature dependence of the methylene proton hfcc.