Abstract
In solutions of ABA-triblock copolymers in a poor solvent for A thermoreversible gelation can occur. A three-dimensional dynamic network may form and, given the polymer and the solvent, its structure will depend on temperature and polymer mass fraction. The zero-shear rate viscosity of solutions of the triblock-copolymer polystyrene-polyisoprene-polystyrene in n-tetradecane was measured as a function of temperature and polymer mass fraction, and analyzed; the polystyrene blocks contained about 100 monomers, the polyisoprene blocks about 2000 monomers. Empirically, in the viscosity at constant mass fraction plotted versus inverse temperature, two contributions could be discerned; one contribution dominating at high and the other one dominating at low temperatures. In a comparison with theory, the contribution dominating at low temperatures was identified with the Lodge transient network viscosity; some questions remain to be answered, however. An earlier proposal for defining the gelation temperature Tgel is specified for the systems considered, and leads to a gelation curve; Tgel as a function of polymer mass fraction.
Original language | Undefined |
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Pages (from-to) | 559-574 |
Number of pages | 16 |
Journal | Rheologica acta |
Volume | 30 |
Issue number | 6 |
DOIs | |
Publication status | Published - 1991 |
Keywords
- zero shear-rate viscosity
- IR-85759
- Triblock-copolymer solution
- METIS-129228
- gelation temperature
- thermo-reversible gelation
- dynamic network