Segmented polyurethanes soft segment chemistry

Wiggins MJ, MacEwan M, Anderson JM, Hiltner A. Effect of soft-segment chemistry on polyurethane hiostability during in vitro fatigue loading. Journal ofBiomedical Materials Research A 2004, 68, 668-683. 

A. Takahara, A.J. Coury, R.W. Hergenrother, S.L. Cooper, Effect of soft segment chemistry on the biostabihty of segmented polyurethanes. 

We have prepared novel polyurethane elastomers with modified soft segment chemistry that has been designed to enhance stability. The new tliermoplastic polyurethanes are based on conventional diisocyanates and chain extenders, but contain macrodiols with a reduced number of ether linkages when compared with PTMO. As part of the development process, improved synthetic procedures involving condensation polymerization were devised (8,9) to prepare the macrodiols, poly(hexamethylene oxide) 1, poly(octamethylene oxide) 2, and poly(decamethylene oxide) 3. 

MICROSTRUCTURE AND BIOSTABILITY OF BIOMEDICAL POLYURETHANE BLOCK COPOLYMERS WITH DIFFERENT SOFT SEGMENT CHEMISTRIES... 

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. 

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. 

Diisocyanate is often used in the chain extension reactions of biopolymers such as PEA, PCL, and their copolymers [97-101]. The combination of hard segment and soft segment may confer the resulting polyurethanes with shape-memory property [100,101]. Polyurethane is an important type of elastomeric polymer for biomedical applications [1,9,11]. Chain extension or cross-linking by diisocyanate can be adapted to many -OH-terminated or H-containing polymers or prepolymers [102]. The convenience of the urethane chemistry has made it into a very popular way of polymer chain extension method in biomaterial designs. 

---