The crosslinking reaction of polyisoprene with the radical forming dicumyl peroxide (DCP) is studied, in an in situ small angle neutron scattering study and, a transient dynamical mechanical experiment in shear on an isotopic HDH triblock copolymer. Both experiments are closely identical in time as well as temperature profile which was chosen to simulate typical conditions of peroxide cross-linking Oscillatory shear data Provided typical, easily amenable parameters which were, physically probed. at, the molecular level by the parallel SANS experiment. A scisioning side reaction as proposed earlier was confirmed in detail. No sign of this chain degradation could be detected in the theological response except for times exceeding the typical reaction time. The data agree with a theoretical description in the random phase approximation for the formed networks, necessary to describe the quenched correlation hole effect due to the crosslinking reaction of the triblock copolymer.