Rheology of rod/random coil polymer systems, and interpenetrating networks
Poly({gamma}-benzyl-L-glutamate) (PBLG), a synthetic {alpha}-helical rodlike polypeptide, and aqueous solutions of cetyltrimethylammonium chloride (CTAC), a surfactant that forms rodlike colloids, were used to study the properties of rod polymer solutions. Interpenetrating networks of PBLG and acrylic polymers were prepared and studied rheologically. The rheology of PBLG solutions in toluene and dimethyl formamide (DMF) was studied in the dilute, semi-dilute, and concentrated regimes. Steady shear results fit well to a theory recently proposed, but not to older theories in the literature. The rheology and morphology of viscoelastic solutions of CTAC were studied using steady and oscillatory shear measurements, and transmission electron microscopy. By titrating a fixed CTAC concentration with salicylate the surfactant solution changed from the Newtonian behavior of spherical micelles 5 nm in diameter to viscoelastic solutions of entangled rodlike micelles as long as several micrometers. The phase diagram was determined for the three component system PBLG, polystyrene (PS), DMF system at {approximately}23 C. The results did not fit the athermal theory for rod/random coil systems. However, the addition of enthalpic terms brings theoretical predictions in general agreement with experimental results. The kinetics of PBLG/DMF gelation were studied rheologically. Solutions of PBLG/DMF were observed using oscillatory shear as they were cooled below the gel point, and on heating from the gel to the solution phase. The results support the hypothesis that gelation occurs as a result of the kinetics of phase separation; however, the mechanism is unproven. The rheological properties of interpenetrating networks (IPNs) prepared from rod and random coil polymers were studied. Rod/random coil IPNs were prepared by polymerizing the diluent around an isotropic solution of rods, and by polymerizing the diluent around a microphase separated rod polymer gel.
- Research Organization:
- Minnesota Univ., Minneapolis, MN (United States)
- OSTI ID:
- 111310
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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