Hydrogen-bond complexes poly derivatives

Series of various mono,- bi-, and poly-(thio)urea-functionalized (poly)saccha-rides have already been synthesized and studied for molecular recognition of, e.g., dimethyl and phenylphosphate as model compounds for monoanionic and polyanionic phosphate esters, respechvely [111]. Thiourea derivatives such as 195-197 were analyhcally identified to provide double hydrogen bonding mediated host-guest complexes of well-defined dimension and orientations and were also reported to serve as phosphate binders even in the hydrogen bonding environment of water (Figure 6.57) [111]. 

The formation of the polymer complex was observed between poly-VAd and natural RNA. In order to get better information about the specific interaction between poly-VAd and RNA, further studies on the interaction of N-methyl and N,N-dimethyl derivatives of poly-VAd with RNA were carried out. It was found that mono- or dimethylation of the 6-amino group of poly-VAd depresses the specific polymer-polymer interaction, and no polymer complex was formed between the N,N-dimethyl derivative of poly-VAd and RNA. This fact suggests that the interaction between poly-VAd and RNA was caused by hydrogen bonding between the complementary nucleic add bases. 

The hydrogen bonding between carboxylic acid and imidazole is also useful. A complex derived from poly(acrylic acid) and bis(imidazolyl)biphenyls forms a smectic A phase [89]. 

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