EFFECT OF INTRAMOLECULAR REACTION ON THE PROPERTIES OF POLYBUTADIENE-SILANE RUBBERS

Model networks were prepared by the reaction of monodisperse polybutad iene, containing 8% of double bonds in the 1,2 vinyl position, with p- bis(dimethyl silyl) benzene at different stoichiometric imbalances. Sm all strain modulus and measurements of the gel fraction indicate impor tant differences with the predictions from ideal network forming react ions and the molecular theories of rubberlike elasticity. Sol extracti ons are higher than expected and small strain moduli are consistently low. Other macroscopic signs of the departure from ideal behaviour are detected. The onset of the gel point is delayed to a degree that grow s with increasing imbalance of the reactive groups. We consider all th e possible explanations for the observed behaviour, and suggest that t he most likely one is the presence of intramolecular reaction. We also propose a simple theoretical model to confirm that our assumptions ar e consistent with the experimental results. (C) 1998 Elsevier Science Ltd. All rights reserved.