Copolyurethanes

For polyurethane production, Donnelly [109] has carried out the synthesis of copolyurethanes based on mixtures of commercial poly(THF diol)s with glucose. Complex products resulted, which can be represented by mono- or bis(glucoside) structures. From a variety of polyol blends, solid polyurethanes were prepared which ranged from linear, soluble, weak elastomers to polymers of higher transition temperature and stiffness, low solubility, and low extension under tensile load [110]. 

Copolyurethanes based on L-arabinitol and 2,2 -dithiodiethanol have been obtained by polyaddition reaction of mixtures of 2,2 -dithiodiethanol (DiT) and 2,3,4-tri-O-methyl-L-arabinitol (9) or 2,3,4-tri-O-benzyl-L-arabinitol (11) to 1,6 hexamethylene diisocyanate (HDI) [118]. 

The same concept was used in polycondensation systems for the preparation of branched and cross-linked polymers [121]. Copolyurethanes 73 were prepared from tetra(ethylene glycol), bis(5-hydroxymethyl-l,3-phenylene)-32-crown-10 (74)... 

Comparative studies are presented that demonstrate that homopolyurethane and segmented copolyurethane elastomers and plastics and rubber-modified polyurethane glasses with properties similar to counterparts formed from oil-... 

Both series of polyurethanes were prepared using a prepolymer technique in which reactants were mixed at 70 °C/1 hour, cast into molds at 105 °C/2 hours, and cured at 80 °C/14 hours. The BD/MDI hard segment contents ranged from 0% (transparent, colorless homopolyurethanes) to 30% w/w (opaque, white copolyurethanes). All elastomers were characterized using DSC, dynamic mechanical, and tensile stress-strain measurements. 

These observations were confirmed by DSC data (4) obtained from samples quench-cooled from temperatures above 200 °C that gave T -values of about 80 and 60 °C, respectively, for myrcene- and butadiene-copolyurethanes. Corresponding T -values, -57 and -81 °C, from DSC were almost identical to the T -values reported in Table III for the parent polyols and confirm that phase... 

Figure 5. Dynamic shear modulus-temperature behavior (torsion pendulum, 1 Hz) of 50% w/w HS copolyurethanes based on diisocyanates FDI-a (F) and MDI (M). Soft segment glass transition and hard-segment melting are in the temperature regions indicated, respectively, by and Tm.

Pure liquid diisocyanates can be synthesized from the renewable resource furfural, and used with low and high molar mass diols also derived from furfural to form block copolyurethanes. 

The urea segments and interfacing urethane linkage were modeled by an alternating copolyurethane-urea synthesized from methylene bis(4-phenylisocyanate),... 

While AB block copolymers are known to phase separate into relatively pure two-phase morphologies, multiple block copolymers such as these block copolyurethanes may not necessarily have such a complete phase separation. 

The surface morphologies of these block copolyurethanes differ from their bulk morphologies (4-6). Because the surface controls the interaction of a vascular implant with blood, the surface structure and its relation to the bulk structure of the same material was determined also. Originally, ESCA was explored to study the surface structure because the depth of penetration was within the first 100 A. The low surface depth of penetration and subtle shifts in binding energies that result in peak splittings of the elemental spectra appeared to make this an attractive method to study the chemical and bonding environments of the elements (40). 

In summary, the surface chemical and morphological structures of block copolyether-urethane-ureas may be determined by ESCA and FTIR coupled with internal reflectance techniques to probe the surface and bulk structures. These ESCA and FTIR data are being used to model the domain-interface structure of these copolyurethanes and their interaction with blood protein. 

To understand the interaction of LiBr with the copolyurethanes and the resulting morphological changes, nonextracted samples of PEUU 700 were studied, because this copolyurethane exhibited the largest variation in water absorption and tensile strength as a function of salt concentration. 

Thus, the addition of LiBr to the copolyurethane casting solution does allow the formation of films having morphologies that cause these hydro-phobic polymers to form hydrogels. 

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