Hard segment chemistry isocyanates

This paper will describe the reactions of ketene aminals, 1, more highly activated electron-rich alkenes, with isocyanates to again afford amide products. We shall initially discuss the chemistry of the ketene aminal/isocyanate reaction, the preparation of these activated monomers and sane properties of solution-derived model "hard segments". 

In spite of polyurethane is a hazardous polymer, it can be modified through the basic chemistry of polyurethanes, which can modify a wide variety of soft and hard segments, morphological features, thermic and mechanical properties of structures, just by changing several conditions, such as the ratio NCO/OH, the aliphatic or aromatic isocyanate, the molecular weight, and the ester or ether form of the polyol, but especially the nature of the monomer, whether synthetic or natural. Among the natural options than can be used for synthesis are oil, polysaccharides, and amino acids. 

Braatz et al.- studied the adsorption of proteins on polyurethane surfaces. They coated silica and silicone tubing with a variety of chemistries. Although they found differences, the polyuretlianes demonstrated minimal protein adsorption given sufficient coating thickness. Correlations between the relative number of hard (isocyanate) and soft (glycol) segments were drawn. More soft segments resulted in less adsorption. 

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