We summarize investigations on four different nematic main-chain elastomer systems. In the first part, the synthetic approaches towards nematic elastomers with clearing temperatures suitable for mechanical investigations are described. In the second part, the coupling between the liquid crystalline order and the chain conformation is quantified by the Landau-de Gennes coefficient U. Comparing different types of elastomers shows that the coupling depends on the type of mesogens forming the polymer backbone, and on the elastic modulus of the polymer network. In the third part, we compare the orientation behavior of the different systems under strain.