Attractive grafting surfaces

Other effects of an interacting surface on the brush structure have also been studied using a SCF approach and MC simulations. Both treatments find that in the presence of an attractive surface (within the brush regime), the brush height decreases as h/ho = (1 - A), where ho is the brush height for a neutral surface and A is a measure of the strength of 

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All these factors combined are of great importance when considering PE adsorption to charged surfaces. We distinguish between physical adsorption, where chain monomers are attracted to surfaces via electrostatic or nonelectrostatic interactions, and chemical adsorption, where a part of the PE (usually the chain end) is chemically bound (grafted) to the surface. In all cases, the long-ranged repulsion of the dense layer of adsorbed PEs and the entropy associated with the counterion distribution are important factors in the theoretical description. 

PEG is very attractive for surface modification since it can simultaneously impart biocompatibility and lubricity to materials. The grafting of PEG chains onto polymeric surfaces can be achieved... 

The diseussion has so far assumed that all monomers of a polymer are alike and therefore show the same tendency to adsorb to the substrate siuface. For industrial and technological applications, one is often interested in end-functionalized polymers. These are polymers which attach with one end only to the substrate, as is depicted in Fig. 3b, while the rest of the polymer is not particularly attracted to (or even repelled from) the grafting surface. Hence, it attains a random-coil structure in the vicinity of the siuface. Another possibility of block copolymer grafting (Fig. 3c) will be also briefly discussed. 

In cases when the two surfaces are non-equivalent (e.g., an attractive substrate on one side, an air on the other side), similar to the problem of a semi-infinite system in contact with a wall, wetting can also occur (the term dewetting appHes if the homogeneous film breaks up upon cooHng into droplets). We consider adsorption of chains only in the case where all monomers experience the same interaction energy with the surface. An important alternative case occurs for chains that are end-grafted at the walls polymer brushes which may also undergo collapse transition when the solvent quality deteriorates. Simulation of polymer brushes has been reviewed recently [9,29] and will not be considered here. 

The preparation of polymer brushes by controlled radical polymerization from appropriately functionalized polymer chains, surfaces or particles by a grafting from approach has recently attracted a lot of attention.742 743 The advantages of growing a polymer brush directly on a surface include well-defined grafts, when the polymerization kinetics exhibit living character, and stability due to covalent attachment of the polymer chains to the surface. Most work has used ATRP or NMP, though papers on the use of RAFT polymerization in this context also have begun to appear. 

In all cases, the cloud-point temperature was slightly dependent on polymer concentration for a given copolymer it increased with decreasing concentration. This effect is enhanced with increasing number of PEO grafts per chain. Also, the PNIPAM collapse seemed to be less abrupt with decreasing concentration. Upon dilution of the solution the distance between polymer chains increases, which favours intrapolymeric interactions over in-terpolymeric attractions. Dilution also enhances the surface stabilisation of the polymer particles by PEO. 

Most of published results deal with very high graft yield and consequently the bulk properties of the base polymer are altered by grafting. In principle, graft polymerization is an attractive method to impart a variety of surface properties on the condition... 

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