Positron annihilation and relaxation dynamics from dielectric spectroscopy and nuclear magnetic resonance: Cis–trans-1,4-poly(butadiene)

10 paginas, 7 figuras, 1 tabla.-- et al.We report a joint analysis of positron annihilation lifetime spectroscopy (PALS), dielectric spectroscopy (BDS), and nuclear magnetic resonance (NMR) on cis–trans-1,4-poly(butadiene) (c–t-1,4-PBD). Phenomenological analysis of the orthopositronium lifetime τ3 − T dependence by linear fitting reveals four characteristic PALS temperatures: Tb1G = 0.63Tg PALS , Tg PALS , Tb1L = 1.22Tg PALS , and Tb2L = 1.52Tg PALS . Slight bend effects in the glassy and supercooled liquid states are related to the fast or slow secondary β process, from neutron scattering, respectively, the latter being connected with the trans-isomers. In addition, the first bend effect in the supercooled liquid coincides with a deviation of the slow effective secondary βeff relaxation related to the cis-isomers from low-T Arrhenius behavior to non-Arrhenius one and correlates with the onset of the primary α process from BDS. The second plateau effect in the liquid state occurs when τ3 becomes commensurable with the structural relaxation time τα(Tb2). It is also approximately related to its crossover from non-Arrhenius to Arrhenius regime in the combined BDS and NMR data. Finally, the combined BDS and NMR structural relaxation data, when analyzed in terms of the two-order parameter (TOP) model, suggest the influence of solidlike domains on both the annihilation behavior and the local and segmental chain mobility in the supercooled liquid. All these findings indicate the influence of the dynamic heterogeneity in both the primary and secondary relaxations due to the cis–trans isomerism in c–t-1,4-PBD and their impact into the PALS response.This work was supported by the VEGA Agency, Slovakia under Grants No. 2/0014/09 (J.B.) and 2/0099/10 (O.Š.) and byMAT2007–63681 (Spanish Ministry of Education), IT- 436–07 (Basque Government) and Project 2007SK0008 between Slovak Academy of Sciences (SAS) and Spanish Research Council (CSIC).Peer reviewe