Polymer/filler interactions have been found to affect the performance of tire tread, sidewall, innerliner, or carcass and other industrial rubber products that are all based on filled elastomers. Identification of types of various polymer/filler interactions and ranking of their impacts have been elusive. Isobutylene-based polymers have relatively saturated structures and contain very low concentrations of functional group. Examples are BIMS (a brominated isobutylene/p-methylstyrene copolymer) containing p-bromomethylstyrene and p-methylstyrene; bromobutyl rubber containing -Br and olefin; chlorobutyl rubber containing -CI and olefin; and butyl rubber containing olefin. On the other hand, high diene rubbers, such as polybutadiene rubber, polyisoprene rubber, and styrene/butadiene rubber, have unsaturated backbones and high olefin contents. Hence, different types and extents of interaction with reinforcing fillers, such as carbon black (CB) or silica, are expected in these two classes of elastomer. This work employs bound rubber (solvent extraction), viscoelasticity, stress-strain measurements, and solid state NMR to identify, differentiate, and scale polymer/filler interactions in unvulcanized BIMS/CB, BTMS/silica, SBR/CB, and SBR/silica composites, where SBR denotes a styrene/butadiene rubber. Four different types of CB and one type of silica have been studied. (c) 2006 Wiley Periodicals, Inc.