Polymer-filler coupling compounds with the formula B-A-Sx—N are claimed. In these compounds, B is an azaheterocyclic oxygen or sulfur containing moiety, or an allyltin moiety; Sx is a polysulfide, where x is between 2 and about 10; A is a linking atom or group that forms a bridge between B and Sx; and N is a blocking group. Sx can be a disulfide. N can be a conventional blocking group or other group such as -A-B. Methods for using the polymer-filler coupling compounds to modify polymers containing unsaturated carbon-carbon bonds and promote filler dispersion are also claimed. Additionally, vulcanizable rubber compositions containing the polymer-filler coupling compounds and methods for making vulcanized rubber compositions using the polymer-filler coupling compounds are also claimed.