Experimental studies have shown that nanoparticles play an important role on the rotator phase transitions of n-alkanes. A phenomenological model for predicting the R-II - R-I - R-V phase transitions in mixtures of alkanes and nanoparticles has been proposed by combining Flory-Huggins free energy of isotropic mixing and Landau free energy. The impact of nanoparticles on the R-II - R-I - R-V phase transitions and their transition temperatures is discussed by means of phenomenological theory. The possibility of the tricritical behavior of the R-I - R-V phase transition in the mixtures of alkanes and nanoparticles is discussed. The theoretical predictions are in good qualitative agreement with available experimental results. (C) 2017 Elsevier B.V. All rights reserved.