Buoy regime

If the solvent is nonselective, the anchor has a swollen structure similar to an adsorbed homopolymer. In the case of adsorption of an AB block copol5mier from nonselective solvents there are two possible cases (38) The first is referred to as the buoy regime, in which the anchor are small and adsorption is dominated by repulsive interactions between the buoys. Increasing the length of the anchor will increase the amount adsorbed. The second case is called the anchor regime, in which the anchor layer is saturated and the buoys are small in size. Here, increasing the length of the anchor block will not increase the adsorbed amount. 

Figure 7 shows the results of measurements of adsorption density by Parsonage, etal. [77] on a series of eighteen block copolymers, with poly(2-vinylpyridine) [PVP] anchors and polystyrene [PS] buoys, adsorbed from toluene (selective for PS) of variable molecular weight in each block. The results are presented as the reciprocal square of Eq. 28, that is, as a dimensionless number density of chains ct (d/Rg A)-2. For all but the copolymers of highest asymmetry, Eq. 28 is in good agreement with the data of Fig. 7. The high asymmetry copolymers are in the regime of the data of curves (a) and (c) of Fig. 3 where the large relative size...

In a solvent that selectively solubilizes one of the blocks, when the chain adsorbs, the anchor collapses to form a dense layer, while the buoy stretches out to form a brush-like structure. Adsorption in this case is decided by the competition between van der Waals attraction between the anchor and the substrate and repulsive interactions between the buoys. This is referred to as the van der Waals brush regime (37). 

Van der Waals brush Buoy-controlled regime Anchor-controlled regime... 

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