Examples of Dendrimers in Separation Processes

The first attempt to prepare essentially water-insoluble, amine-containing dendrimers was realized by conversion of the primary amino groups on the periphery of POPAM dendrimers into amide analogues with long-chain alkyl acid chlorides 

Hydrophobic urea-functionalized dendrimers are readily available by reacHon of POPAM dendrimers with isocyanates [16]. Such polyurea dendrimers with hexyl, octyl and dodecyl alkyl chains (see Fig. 3.7-10) have proved to be efficient carriers for oxoanions. Pertechnetate, perrhenate, and even the highly hydrophilic nucleotide ATP can be extracted from weak acid solution with remarkable efficacy (Fig. 

The extraction of these oxoanions with urea-functionalized dendrimers follows the same behavior as that observed for hydrophobic dendritic amides discussed above. 

Multi-crown dendrimers (Fig. 3.7-12) were found to exhibit good solubihty in solvents of low polarity, making them attractive as extractants for separation processes. The combination of protonated tertiary amine groups as anion binding sites together with cation-active crown ether moieties represents an approach for the simultaneous binding of cations and anions. Extraction studies performed with sodium pertechnetate and mercury(II) chloride have shown that the guest molecules are mainly bound in the interior of the protonated polyamine skeleton [18]. 

Owing to some advantages, in particular low energy requirements and fast reaction kinetics, polymer-supported ultrafiltration is gaining in importance as a pro- 

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