| Autor: |
de Ruijter, Christiaan, F. Jager, Wolter, Li, Liangbin, J. Picken, Stephen |
| Zdroj: |
Macromolecules; June 2006, Vol. 39 Issue: 13 p4411-4417, 7p |
| Abstrakt: |
We present results of the phase behavior in sulfuric acid and a structural investigation in the solid state by DSC and SAXS of a series of rod−coil multiblock copolymers comprised of alternating poly(p-phenylene terephthalamide) (PPTA) and polyamide 6,6 (PA 6,6) blocks. These polymers were synthesized via a low-temperature polycondensation reaction as described in the first paper of this series. Concentrated solutions of the copolymers in sulfuric acid show a liquid crystalline phase if the mole fraction of PPTA exceeds 0.5. The critical concentration for the transition from the isotropic to the liquid crystalline state increases with increasing amount of flexible PA 6,6 segments. Comparison of the phase behavior of the copolymer with that of PPTA provides strong evidence that the coils in the copolymer are significantly stretched in the nematic solutions. Without solvent, DSC experiments show that the crystallization of the PA 6,6 is to a large extent suppressed by the presence of PPTA, but the degree of crystallization increases upon annealing. SAXS experiments revealed that, although some block copolymers show a peak in the SAXS data, there is no evidence for long-range lamellar order in any block copolymer due to the absence of higher order peaks. |
| Databáze: |
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