CONTROLLED SWELLING OF POLYMER BRUSHES

Very long chains with molecular weights up to 600000 can be grafted on a solid surface. We discuss here some specific features of these graf ted systems : a) the climbing of a liquid along a vertical plane cover ed with long grafted polymer chains : because of a minute difference i n chemical potential, the brushes can show color variations over an al titude approximately 1 cm ! b) swelling of brushes by elongated solven t molecules : this type of solvent can induce swelling in the isotropi c phase, but when they become cooperatively ordered (nematic) we usual ly expect a collapse of the brush.