The doctoral thesis covers a theoretical study of three cases of symmetry breaking phenomenon for applicative purposes. We focus on possible applications in liquid crystals, which combine a unique combination of optical anisotropy, the partial character of the liquid and the "softness". The latter describes the possibility of a relatively strong macroscopic response to relatively small external perturbations. First, we consider the use of phase change materials in construction composites. With numerical simulations, we show that phase change materials can decrease room temperature fluctuations and thereby improve the thermal stability of the room. In the latter, the phase transition temperature has a key role. Furthermore, we present two possible improvements. The first improvement is a combination of two different phase change materials that undergo phase transitions at different temperatures, which prolongs the time constant of the heat stabilization. The second improvement is the manipulation of the phase transition temperature with external perturbations. For liquid crystals enclosed in a cell, we show that the phase transition temperature depends on the characteristic length of the cell. The following can be manipulated by external perturbations, for example, the external electric field. With proposed improvements, we expand the optimal operation interval of innovative composites with phase change materials. The second symmetry breaking application is an electrocaloric effect. In the doctoral thesis, we study electrocaloric effect in liquid crystals near the phase transitions and near the critical point by the addition of nanoparticles. For a theoretical study, we use the Landau-de Gennes-Ginzburg model at the mesoscopic scale. Numerical results reveal that by approaching the phase transition temperature from an isotropic to a nematic phase, the electrocaloric response of the system increases because of the increase in the orientational entropy change. We prove that the electrocaloric response increases for a direct phase transition between the isotropic and the smectic A phase both analytically and numerically. In the latter, the smectic ordering effectively acts as an external electric field. Consequently, it can enhance the electrocaloric response, which strongly depends on the intensity of discontinuous transitions between the competing phases. The phase behaviour is controlled by the coupling strength between the orientational and the translational order. In addition, we present an electrocaloric based cooling system and an active regenerator, which can increase performance and cooling power yield per mass. We analyse the electrocaloric effect near a critical point by randomly distributing different concentrations of nanoparticles in the liquid crystal system. Numerical simulations are based on Lebwohl Lasher model at a semi- microscopic scale. We reveal that the presence of nanoparticles does not contribute to an increase in electrocaloric response. The reasoning behind this is a decrease in the electrically induced change in orientational entropy, which prevails over the possible increase due to the critical point. The third symmetry breaking application is the detection of nanoparticles. The presence of nanoparticles in a nematic liquid crystal cell causes frustration, which results in a local biaxiality. At varying external conditions such as the external electric field, temperature, and position of the nanoparticle, we obtain qualitatively different configurations, which can be used to detect nanoparticles. The results of the doctoral thesis contribute to a better understanding of the behaviour of the liquid crystal system in the vicinity of phase transitions under the influence of external factors.

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