The phase properties of polydimethylsiloxane (PDMS) and low molecular weight liquid crystals (LMWLCs) with different size and architecture of the polymer are investigated. An oligomer of molecular weight 800 g/mol and two linear polymers of molecular weight 5500 and 45000 g/mol are considered. Electron beam cured PDMS/4-cyano-4'-n-pentyl-biphenyl (5CB) mixtures in which the polymer is a crosslinked network are also investigated. Experimental phase diagrams are established using polarized optical microscopy (POM) and analyzed using classical theories for the free energy of isotropic mixing, network elasticity and nematic order.