POLYBUTADIENE MODEL NETWORKS - SYNTHESIS, MECHANICAL CHARACTERIZATIONAND COMPARISON WITH RUBBER ELASTICITY MODELS

Model networks of defined crosslink density are prepared via nonradica l statistical crosslinking of polybutadiene in bulk and concentrated s olution using a masked bistriazolinedione as crosslinker. The kinetics of crosslinking is monitored by FT-IR-spectroscopy. The reaction foll ows pseudo-1st-order reaction kinetics. The activation parameter of th e crosslinking reaction is estimated from crosslinking at various temp eratures. Networks of deuterated polybutadiene are prepared by this re action in a wide range of crosslink densities. The stress strain behav ior is analyzed according to the Junction Constraint-Theory of rubber elasticity (JCT) and to the approach introduced by Graessley accountin g for trapped topological constraints. The analysis clearly demonstrat es that trapped entanglements contribute to the mechanically effective cycle rank, i.e., to the modulus in this system in the small and larg e strain limit.