No abstract

No abstract

No abstract

The excited state reaction of 1,4,7-tris-(5-methylene-8-hydroxyquinoline)-1,4,7-triazacyclononane was studied in solution. The intramolecular-π-stacked tripod shows pH-dependent eximer emission and dual fluorescence due to intermolecular π-stacking.

Hydroxy-terminated polybutadiene (HTPB) prepolymer prepared by freeradical mechanism at Chemical Engineering Complex, Vikram Sarabhai Space Center, Thiruvananthapuram was reacted with toluene diisocyanate (TDI), a curative at varying stoichiometric ratios (r ϭ [NCO]/[OH]) equal to 0.7, 0.8, 0.9, 1.0, and 1.1 at a constant temperature of 70°C. The increased rate of viscosity of polyurethane networks formed was used to calculate the rate constant. Similarly, the rate of change of viscosity of curing networks at different r values (0.7-1.1) and temperature intervals (30 -70°C) was used to calculate activation energy. The results of the curing networks showed that the rate constant at r Ͼ 0.9 is constant and the rate of decrease of activation energy is lower at r Յ 1; thereafter, it becomes quite significant.