STRONGLY STRETCHED POLYMER BRUSHES

Polymer ''brushes'' are formed when long-chain molecules are somehow a ttached by one end at an interface with a relatively small area per ch ain. Such adsorbed brushes in the presence of solvent may be used to m odify surface properties, stabilize colloidal particles, etc. Strongly segregated block copolymer phases, or interfacial layers of such ''po lymeric surfactants'' may also be modeled in terms of ''melt brushes,' ' (i.e., brushes without solvent). In both cases, when chain attachmen ts are crowded on the interface, the chains stretch out to avoid neigh boring chains. The resulting physical state has properties markedly di fferent from polymer solutions, gels, or weakly adsorbed polymer layer s. When the chains are strongly stretched, their statistical mechanics become simpler, as fluctuations around the set of most probable confo rmations are suppressed. This makes possible many pencil-and-paper cal culations of brush properties, including bending and compressional mod uli, and detailed knowledge of the chain conformations. As a recent ex ample, I will describe calculations of phase diagrams of strongly segr egated block copolymers including bicontinuous double-diamond phases. (C) 1994 John Wiley and Sons, Inc.