A method of chemically crosslinking side-chain liquid crystal polymers at carefully controlled temperatures with variable crosslinking densities in the bulk phase is described. The nematic-isotropic phase transition temperatures of the resulting liquid crystal elastomers are found to show a marked dependence on the history of the sample. In particular, crosslinking a polymer in the nematic phase results in an elastomer in which the nematic phase shows an enhanced stability. The results are compared with theoretical expectations, and related to the coupling between the mesogenic units and the polymer backbone.