REPTATION TIME, TEMPERATURE, AND COSURFACTANT EFFECTS ON THE MOLECULAR INTERDIFFUSION RATE DURING POLYSTYRENE LATEX FILM FORMATION

The interdiffusion of polymer chains during film formation from direct mini-emulsified deuterated and protonated polystyrenes (DPS = mol wt 150 000 and 185 000; HPS = mol wt 150 000 and 200 000) was characteriz ed by small-angle neutron scattering (SANS) and tensile strength measu rements. Films containing 6 mol % deuterated particles were annealed a t several temperatures above T-g for various periods of time. The aver age interpenetration depth of deuterated polystyrene chains depended o n the one-fourth power of the annealing time up to the reptation time, tau, shifting to the one-half power after the reptation time. The cen ter of mass diffusion coefficients from the SANS data were 2.4 x 10(-1 6) cm(2)/s for M(2) = 150 000 and 1.5 x 10(-16) cm(2)/s for M(n) = 185 000 at an annealing temperature of 135 degrees C. The diffusion activ ation energies of the present system were 52 +/- 4 kcal/mol for the te mperature range 125 less than or equal to T less than or equal to 155 degrees C. Full tensile strength was achieved at a penetration depth o f 90-100 Angstrom, which is comparable to 0.81 times the radius of gyr ation of the whole polystyrene chain (86 Angstrom for M(n) 150 000) pr edicted theoretically. Finally, latex samples containing 1.5 wt % cosu rfactants showed a faster interdiffusion rate especially at t > tau an d a smaller activation energy than the corresponding pure latex sample .