Exponential function in Simscape

I wanted to know how can I input an exponential function in simscape syntax. When I tried to enter exp(-Ea/(R*Tc)) I got the following error message: No matching signature found for exp. exp takes one dimensionless argument. Argument 1 = {[1x1 double], 's^2*mol*J/m^2/kg/K^2'} Ea = {[1x1 double], 'J'} R = {8.3140, 'm^2*kg*K/s^2/mol'} Tc = {[1x1 double], 'K'}