A system of linear polymer liquid crystal (PLC) macromolecules is considered. Each macromolecule constitutes an alternating copolymer of flexible and LC sequences. The macromolecules can be either unconnected or else connected into a PLC network. The system is characterized with respect to local orientation. Competition between energetic effects of anisotropic orienting interactions between LC sequences and entropic effects determined mainly by flexible parts is considered. The Maier and Saupe mean-field approach is assumed for the representation of LC interactions. Types and orders of phase transitions that the system can undergo with respect to local order are discussed in terms of the Landau classification. All transitions are found to be of the first order. Thermodynamical and structural parameters of the system at phase transition points are represented by phase diagrams.