Polyurethanes microphase-separated structure

K. Kojio, S. Nakashima and M. Furukawa, Microphase-separated structure and mechanical properties of norbornane diisocyanate-based polyurethanes . Polymer, 2007, 48, 997-1004. 

Rueda L, Fernandez d Arias B, Corcuera MA, Eceiza A. Biostability of polyurethanes. Study from the viewpoint of microphase separated structure. Polym Degrad Stab 2014 108 195-200. 

Huang SL, Chao MS, Ruaan RC, Lai JY. Microphase separated structure and protein adsorption of polyurethanes with butadiene soft segment Eur Polym J 2000 36(2) 285-94. 

Polyurethane thermoplastic elastomers (PTE) are characterized by microphase separation into an SS microphase and HS microdomains. In fact, the versatile physical and thermomechanical properties of TPE, which make them attractive for several technological applications, are based on their microphase-separated structure. The glass transition temperature, Tg, of the amorphous SS microphase is typically below 0°C, so that at room temperature the material behaves as an elastomer. At high temperatures (typically above 100°C), dissociation of the physical bonds occurs, the HS microdomains are destroyed and the material flows as a linear polymer. In addition to microphase separation, intermolecular hydrogen bonding and partial crystallization of the SS microphase often contribute to the thermoplastic elastomeric behavior of PTE. 

Table 9. DSC data and the parameters of the microphase-separated structure of the polyurethane ionomers W2 is the HS weight fraction, the melting temperature of the SS-rich phase, Tg s the glass transition temperature of the SS-rich phase, AT the width of the glass transition temperature of the SS-rich phase, T the calculated glass transition temperature of the sample using Fox s equation, A the specific heat capacity jump at Tg, Wi the overall weight fraction of the SS-rich phase, Wj the weight fraction of the SS component in the SS-rich phase, and Wj j, the weight fraction of the HS component in the SS-rich phase 65 ...

Table 10. SAXS-based parameters of the microphase-separated structure of the acid polyurethanes of Table 9. Dj and are values of the interdomain spacing, the calculated thickness of the HS lamellar-like microdomains, and the HS length [65]...

Ishida M and Yoshinaga K (1996) Solid-state C NMR analyses of the microphase-separated structure of polyurethane elastomer, Macromolecules 29 8824-8829. 

The variation of Tg of the soft matrix in segmented polyurethanes as a function of composition or segmental chemical structure has been monitored and used as an indicator of the degree of microphase separation. Factors influencing the phase-separation process in these MDI-based polyurethanes have been summarized by Aitken and Jeffs (69) as follows (a) crystallization of either component, (b) the steric hin-... 

Microdomain size in phase-separated copolymers plays a fundamental role in determining various macroscopic physical properties in the solid state. The difference in segmental mobility between the hard and soft domains governs the physical properties of microphase-separated polyurethane elastomers [7]. In this respect, the development of structure-property relations at the molecular level which relate directly to macroscopic behavior is the focus of this sub-section. One can exploit the well-documented difference between domain mobility [7-10] and the i3C NMR chemical shift distinction between the 0 .H2 resonances in the hard and soft segments to probe the microdomain morphology of polyether-... 

Chu B, et al. Microphase separation kinetics in segmented polyurethanes effects of soft segment length and structure. Macromolecules 1992 25(21) 5724—9. 

Krakovsky, L, Urakawa, H., Kajiwara, K. (1997), Inhomogeneous structure of polyurethane networks based onpoly(butadiene)diol 2. Time-resolved SAXS study ofthe microphase separation. Polymer, 38, 3645-53. 

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