We have investigated thermo-mechanical properties and optical birefringence of the V3 cross-linker liquid single crystal elastomers (V3LSCEs) with different concentrations of the flexible tri-functional cross-linker as a function of temperature. The length of V3LSCEs along the director (n) over cap shrinks on heating while it expands perpendicular to (n) over cap. Drastic length changes as well as large variations in the optical birefringence, Delta n, are observed near T-c. The maximum contraction increases with increasing cross-linking concentration. When the anisotropy of the shape change is plotted as a function of Delta n, a linear dependence is observed only deep in the nematic phase for larger cross-linking concentrations. (c) 2005 Elsevier B.V. All rights reserved.