Rotational mobility of the radical probe in butadiene-nitrile rubbers

The difference in co-monomer composition of the disordered phase of butadiene-nitrile rubbers of BNKS and SKN grades is determined by EPR spectroscopy. The degree of aggregation of fragments consisting of alternating units and looseness of the disordered rubber phase in the case of BNKSs are shown to be higher than those of SKNs. The rotational mobility of the radical-probe indicates the lowering of the straight chain flexibility to be more pronounced in the case of BNKS rubbers. This phenomenon is due to the more large-size nanostructures if compared to the ones in SKNs.