1993

4-(4-Carboxyphenyl)-3,5-dioxo-1,2,4-triazolidin-1-yl moieties resulting from 4-(3,5-dioxo-1,2,4-triazolin-4-yl)benzoic acid (U4A) randomly attached to 1,4-polybutadiene form supramolecular aggregates which act as effective junction zones in new thermoplastic elastomers. Deuteron nuclear magnetic resonance (2H NMR) spectroscopy was used to investigate the molecular dynamics of the polymer backbone and the junction zones in selectively labelled samples. The spectra show motional heterogeneity along the polymer chain as well as in the supramolecular domains. Polybutadiene segments which are adjacent to these polar clusters are restricted in their mobility, even at temperatures 100 K above the …

1995

Supramolecular structures based on 4-(3,5-dioxo-1,2,4-triazolidin-4-yl) benzoic acid (U4A) units act as effective junction zones in functionalized polybutadienes, resulting in the formation of thermoplastic elastomers. The dynamics on a molecular scale of the phenyl rings have been probed by 2H-NMR. In the polymeric system, there are three spatially separated environments, which are reflected in the mobility of the polar units. Phenyl rings which are incorporated in the structures are either rigid or undergo 180° phenyl flips. The small fraction of free functional groups move isotropically and their mobility is coupled to the dynamics of the polybutadiene matrix. In two model compounds, whe…

Orientation of polybutadiene chains in a thermoplastic elastomer

1996

The orientation of polybutadiene chains in thermoplastic elastomers based on hydrogen bonding complexes is investigated under uniaxial deformation by two-dimensional small-angle neutron scattering (SANS), deuteron magnetic resonance spectroscopy (2H-NMR), optical birefringence and infrared dichroism spectroscopy (FTIR-D). While SANS probes orientation on the length scale of the radius of gyration,2H-NMR, birefringence and FTIR-D monitor orientation on a segmental scale. The deformation of the elastomer chains appears to be affine on the different length scales.

Junction Dynamics in Telechelic Hydrogen Bonded Polyisobutylene Networks

1996

4-Urazoylbenzoic acid groups are attached to the chain ends of polyisobutylene. The cooperative assembling process of these polar groups is studied by DSC and dielectric and dynamic mechanical spectroscopy. The melting of the ordered clusters occurs in the temperature range 380-390 K. Distortions within the U4A clusters (Σ process) are monitored below the melting temperature T m with dielectric spectroscopy. On a larger length scale, these distortions also lead to stress relaxation which can be probed by dynamic mechanical measurements. Near T m , the relaxation ofU4A multiplets (α* relaxation) is detected with dielectric spectroscopy. In this temperature range, dynamic mechanical measureme…