Series of thiophenes containing mesogenic side chains at the 3^rd position are synthesized. The thermal transitions and thermal stability of the synthesized monomers and polymers are studied. The polarizing microscopic studies of synthesized monomers showed nematic liquid crystalline phase and these mesophases further confirmed by differential scanning calorimetric study. The obtained melting and the isotropic temperatures decrease linearly with the increase of aliphatic chain length. The transition temperatures determined from DSC analysis, overlap well with the temperatures obtained from optical microscopy studies. Thermal stability of the compounds is analysed using thermogravimetric studies. Thermal stability of monomers and polymers has been determined by calculating IPDT values. Structural influence on thermal degradation patterns of monomers and polymers are also discussed.