0000000000759293
AUTHOR
L. De Lucca Freitas
Polybutadiene model networks —synthesis, mechanical characterization and comparison with rubber elasticity models
Model networks of defined crosslink density are prepared via nonradical statistical crosslinking of polybutadiene in bulk and concentrated solution using a masked bistriazolinedione as crosslinker. The kinetics of crosslinking is monitored by FT-IR-spectroscopy. The reaction follows pseudo-1st-order reaction kinetics. The activation parameter of the crosslinking reaction is estimated from crosslinking at various temperatures. Networks of deuterated polybutadiene are prepared by this reaction in a wide range of crosslink densities. The stress strain behavior is analyzed according to the Junction Constraint-Theory of rubber elasticity (JCT) and to the approach introduced by Graessley accounti…
Hydrogen bonds in unpolar matrix — Comparison of complexation in polymeric and low molecular-weight systems
By ene-reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with double bonds, polar 4-phenyl-1,2,4-triazolidine-3,5-dione (phenyl urazole) groups are introduced into unpolar matrices. Hydrogen-bond complexes are formed between two amide-like units. The temperature dependence of complex formation in dilute hydrocarbon medium is obtained from remperature-dependent IR spectra in the region of the C=O stretching vibration. Results obtained for a low molecular-weight model system are compared with modified polybutadienes, where the groups are attached statistically along the polymer backbone. The enthalpy and the entropy of complex formation (ΔH f =−28.6 kJ/mol; ΔS f =−52 J/mol K−1) obtained for the…