Segmented polyurethanes characteristics

FTIR spectroscopy has proven to be particularly useful in gaining an understanding of the biocompatibility phenomenon. It is believed [746, 841, 856, 857] that protein adsorption is the initial step in the interaction of blood with implanted biomaterials, followed by adhesion of cells and subsequent tissue attachment. This implies that the substrate surface characteristics influence the process, which was confirmed by ATR studies of albumin adsorption on calcium phosphate bioceramics and titanium [763] and segmented polyurethane [764], albumin and fibrinogen on acetylated and unmodified cellulose [765, 766], poly(acrylic acid)-mucin bioadhesion [767], polyurethane-blood contact surfaces [768], and other proteins on poly(ester)urethane [769], polystyrene [767, 771] and poly(octadecyl methacrylate) [771] and by IRRAS study of adsorption of proteins on Cu [858]. Another branch of IR spectroscopic studies of protein adsorption relates to microbial adhesion (Section 7.8.3). 

Yang S-H, Lee Y-SJ, Lin F-H, Yang J-M, Chen K-S. Chitosan/poly(vinyl alcohol) blending hydrogel coating improves the surface characteristics of segmented polyurethane urethral catheters. J Biomed Mater Res B Appl Biomater 2007 83B 304-13. 

TABLE 5.2 Porosimetric and modulus data illustrating the effect of changing solvent composition on electrospun segmented polyurethane nanofiber mat characteristics... 

It was determined that a dense physical network having ciosslinking points forming hard domains is characteristic of segmented polyurethane ureas. This physical network limits swelling of SPUU in organic liquids that carmot dissolve hard domains. 

Interesting aspects of the effect of fillers on the relaxation behavior were noted in (158) illustrated by experiments with segmented polyurethanes. In this case the presence of segregations of blocks of different chemical stmcture, typical for blodc-copolymers, causes the appearance in such systems of selective interactions with blocks of different nature, and brings about a complex effect on the temperamre curves of the viscoelastic characteristics, as well as on the modulus-filler concentration curve. 

The ultimate physico-chemical characteristics of a prospective biocompatible polymer is intimately related to the surface chemical composition of the casting material. Several recent studies have shown this to be particularly true of segmented polyurethanes, ie. Biomer and Avcothane. 

Improved polyurethane can he produced hy copolymerization. Block copolymers of polyurethanes connected with segments of isobutylenes exhibit high-temperature properties, hydrolytic stability, and barrier characteristics. The hard segments of polyurethane block polymers consist of 4RNHCOO)-n, where R usually contains an aromatic moiety. 

Polyurethane networks based on triisocyante and diisocyanate connected by segments consisting of polyisobutylene are rubbery and exhibit high temperature properties, hydrolyic stability, and barrier characteristics. ... 

Poly (MDI/EG) hard segments can crystallize, and the development of crystallinity is thought to be part of the driving force for phase separation. The X-ray diffraction characteristics of MDI/EG polyurethanes are now well understood. 

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