Multifunctionality by Polymer Analogous Reactions

Multifunctionality can be introduced not only through copolymerization but also by polymer analogous reactions in a postpolymerization modification step, often in combination with the introduction of additional comonomers during the polymerization process. Well-known technical examples are copolymers of polyvinyl alcohol and polyvinyl acetate with different amounts of vinyl acetate (see Section 3.1.3), which all derive from homopoly(vinyl acetate) and are the result of acetate hydrolysis to a different extent. The content of remaining vinyl acetate groups defines the hydrophilicity/hydrophobicity of the copolymer and thus the amphiphilic and stabilizing character of the material. 

A famous example of multifunctionality in polymeric materials for biomedical applications is the concept of polymer-drag conjugates as introduced by Ringsdorf in 1975 [3] (Fig. 5.2). The various functionalities are introduced by a combination of copolymerization and polymer analogous reactions. It has to be noted that for drug delivery carrier polymers, not only the functionality but also the molar mass are of high importance for the apphcation since it defines not only the solubihty but also the half-life time in blood and the uptake in specific cells and the excretion from the kidneys. 

FIGURE 5.3 Schematic representation of a dendritic multifunctional carrier molecule. 

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