A New Approach to Enhance the Force Distribution and Viscoelastic Properties of ENR Compounds via In Situ Mercaptosilane-Modified Pseudopolyrotaxane

A hybrid supramolecular–covalent strategy via in situ mercaptosilane-modified pseudopolyrotaxane was investigated for effects on force redistribution and viscoelastic balance in uncured epoxidized natural rubber (ENR). ATR-FTIR and multidimensional NMR were consistent with the formation of pseudopolyrotaxane, consisting of α-cyclodextrin rings threaded onto a PEG axle. Structural analysis indicated a sparsely threaded structure, suggesting the pseudopolyrotaxane functions as a localized dynamic modifier rather than a slide-ring network across the ENR matrix. The addition of 1 phr mercaptosilane raised Mooney viscosity by around 25–35% and improved stress relaxation rate at short time scales, consistent with stress redistribution that may arise from movable supramolecular junctions rather than stiff network formation. The RPA results showed higher low-frequency storage modulus and lower tan δ, indicative of increased elastic constraint and dynamic junction mobility. At greater mercaptosilane contents (≥2 phr), plasticization became more pronounced in the rheological response. The similar patterns seen in both large- and small-strain rheological tests are broadly consistent with the proposed hybrid interaction mechanism. These findings suggest that the regulated integration of movable supramolecular structures with reactive silane chemistry may provide a potential strategy for manipulating prevulcanization rheology and dynamic force-transfer behavior in uncured ENR compounds.