I'm trying to solvent cast high molecular weight styrene-butadiene-styrene (SBS) block copolymer from a toluene solution. However, I find that it is difficult to obtain a smooth film of uniform thickness. I have tried floating the solution on glycerol and although this reduces cracking and aids in handling, I still get films with poor surface features and undesired dimensions (due to shrinkage).
I have contimplated the idea of sandwiching the toluene solution between two immiscible solvent layers to generate a more uniform film. This would maintain the fluidity required to relieve internal stresses and aid in film extraction, but it would also mitigate toluene evaporation and provide a more equilibrium SBS film.
My question is, does anyone know of a pair of solvents that are (1) immiscible with toluene, styrene, and butadiene, (2) have liquid densities that are greater than and less than that of toluene, and (3) exhibit lower volatility/partial pressures at room temp. than toluene?
Thanks in advance,
Phillip