Semicrystalline segmented polyurethanes based on hydrogenated polybutadiene soft segments (H-PBD) and butanediol (BDO) as chain extender were synthesized in bulk. Because of the initial immiscibility of the reactants, macroscopic phase separation occurs during a two-step polymerization in bulk. As a previous work on the same materials prepared in polar solvent has shown the high level of microphase separation with such polymers, the challenge of the present work is also to obtain a high level of microphase separation for bulk-prepared polyurethanes. For this purpose the synthesis of polyurethanes in bulk is carried out in the presence of different emulsifiers to minimize the effects of the premature macrophase phenomenon. The morphology of such polyurethanes with non-polar soft segments can be well characterized by dielectric measurements. The dielectric relaxations confirm the thermal behaviour and also the presence of a mixed interfacial region. The addition of emulsifiers to bulk samples decreases the number of short isolated or amorphous hard segments, as shown by size exclusion chromatography results, and suppresses the related conduction process appearing in the dielectric measurements. The results show the control of the structures by appropriate synthesis and the monitoring of phase separation using dielectric spectroscopy.
Посилання на статтю:
Synthesis and properties of polyurethanes based on polyolefin: 3. Monitoring of phase separation by dielectric relaxation spectroscopy of segmented semicrystalline polyurethane prepared in bulk by the use of emulsifiers / Gisele Boiteux and Leon Cuve and Jean-Pierre Pascault // Polymer. – 1994. – Vol 35. – P. 173-178.
Synthesis and properties of polyurethanes based on polyolefin: 3. Monitoring of phase separation by dielectric relaxation spectroscopy of segmented semicrystalline polyurethane prepared in bulk by the use of emulsifiers - Завантажити.