Control over grafting density

Control over grafting density is essential for regulation of the number of polymer brushes on the surface. This can be achieved by using a mixture of active and inactive ( dummy ) initiators to functionalize the substrate surface. The number of active ATRP initiators, and thus the number of polymer chains on the surface, is varied by controlling the corresponding fraction of active initiators in the mixture. Scheme 10b illustrates this strategy. 

Spite of the simplicity of the copolymerization process, more tunable properties of the functionalized material can be achieved using grafting techniques, as they allow the independent tuning of the support characteristics and of the grafting points. Moreover, the control over the density of the grafted brushes can also be achieved by tuning the initial density of the initiator on the grafting surface. 

In recent years, much attention has been paid to the use of controlled/ living polymerizations from flat and spherical surfaces [121,122],because this allows better control over the MW and MWD of the target polymer. By using these techniques, a high grafting density and a controlled film thickness can be obtained, as such brushes consist of end-grafted, strictly linear chains of the same length and the chains are forced to stretch away from the flat surface. Several research... 

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