THERMODYNAMICS OF FORMATION OF POROUS POLYMERIC MEMBRANE BY PHASE-SEPARATION METHOD .2. PARTICLE SIMULATION APPROACH BY MONTE-CARLO METHOD AND EXPERIMENTAL-OBSERVATIONS FOR THE PROCESS OF GROWTH OF PRIMARY PARTICLES TO SECONDARY PARTICLES

An attempt was made (1) to establish a theory on particle growth durin g the membrane formation by the phase separation method with an aid of computer simulation technique, and (2) to compare results of the comp uter simulation with those of actual experiments. In the particle simu lation, primary particles consisting of polymer-rich phase are generat ed at random position in a hypothetical space, and moving velocity v1 was given to them, assuming Brownian movement in a solution of polymer -lean phase. If a distance between the centers of gravity of two arbit rary chosen particles is less than the summation of their radii, they are considered to have collided, yielding a new larger particle. The s imulation reveals that the growth rate of particles is theoretically e xpected to be larger when the phase separation occurs under the condit ions of lower concentration (i.e., lower viscosity) of polymer-lean ph ase and of smaller two phase volume ratio R(= V(1)/V(2); V(1) and V(2) are the volumes of polymer-lean and -rich phases, respectively). The lower viscosity yields lager velocity and the smaller R gives larger c ollision frequency. Particle size distribution N(S) and the number-ave rage radius of growing particles SBAR were evaluated by dynamic light scattering measurement on systems of polymer solution/coagulating solu tion, i.e., cellulose cuprammonium solution/acetone-ammonia-water solu tion and cellulose cuprammonium solution/sodium hydroxide-water soluti on and it is experimentally confirmed that the primary particles grow by amalgamation and under some conditions, their radii approach an asy mptotic value, which is the radius of the secondary particle S2.