Block copolyurethanes

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. 

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). 

For the DBDI-based material and its corresponding homopolyurethane [EG-DBDI]n (curve 2) the crystallization did not disappear with the inclusion of the HS in the block copolyurethane elastomeric matrix, indicating the appearance of more or less phase separations associated with the formation of crystalline hard domains. As seen, curve (2) for the material with molar ratio EG/PEA = 3, was very similar with curve (1) corresponding to the homopolymer, and proportional to HS... 

The results which are portrayed in Fig. 3.17 and 3.18 show the dependence of thermomechanical properties on the sequential ordering of the block copolyurethane blocks. As seen in Fig. 3.17 in the case of PUs based on PTHF soft segments, the course of the thermal creep curves achieved on original PU as obtained after synthesis did not depend essentially on the sequential block ordering. 

An alternate approach to increase compliance of urethane block copolymers is to vary the structure of the soft polyether block to lower the initial modulus. In our analysis of structure-property relationship of the block copolyurethanes, it would appear that a polyether segment based on a... 

Ryan, A. J., Macosko, C. W., Bras, W. (1992), Order-disorder transition in a block copolyurethane. Macromolecules, 25,6277-83. 

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