Irreversible adsorption from concentrated polymer solutions

Abstract

\nWe study the adsorption of concentrated Poly(dimethylsiloxane) (PDMS) solutions in Dichloromethane on porous silica. We vary the plymerization index $N$ and the chain volume fraction $\\Phi$ from the overlap concentration to the melt. The adsorption of PDMS on silica by hydrogen bonding is very strong and a large amount of polymer remains bound to the surface after the washing of the silica with a good solvent of the chains. We measure this quantity $\\Gamma$ by small angle neutron scattering. If there is no chain desorption, $\\Gamma$ represents the weight of polymer attached to the solid in the initial solution, which varies as the product $N^{1/2} \\Phi^{7/8}$ according to a recent prediction. This relation of proportionality indeed interprets our experimental results. When the size of the chains is comparable to the pore diameter (either 500, 1 200, or 3 000 Å depending on the samples) we observe confinement effects which lower the adsorbed amount.\n