A joint study of the spin probe TEMPO dynamics by ESR and the annihilation rate of ortho-positronium by PALS in four short-and medium-sized n-alkanes is presented. In addition to the usually observed changes in both the reorientation dynamics and size of free volumes at the temperature of melting, T-m, and solid-solid phase transition, T-ss, an additional coincidence between the characteristic ESR and PALS temperatures T-x1(fast) congruent to T-b1(sol)< T-m, T-ss was found. The phenomenological analysis of the viscosity data of n-alkanes using the power law equation indicates a presence of locally disordered regions in which the dynamic change occurs at the crossover temperature T-x congruent to T-x1(fast )congruent to T-b1(sol). (C) 2018 Elsevier B.V. All rights reserved.