Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 49; no. 12; pp. 890 - 897
• Main Authors: Park, Kiho, Lim, Wan Hee, Ko, Eun-A, Lee, Han Sup
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.06.2011; Wiley
• Subjects: 1,4‐phenylene diisocyanate; 4-phenylene diisocyanate; Applied sciences; Diisocyanates; Exact sciences and technology; Grain boundaries; Hydrogen bonding; Molecular structure; Organic polymers; Orientation; phase separation; Physicochemistry of polymers; Polyurethane resins; preferential domain orientation; Properties and characterization; Reproduction; Segments; Structure, morphology and analysis; phase separation; Organic diisocyanate; Domain structure; preferential domain orientation; Segmented polymer; Supramolecular structure; Small angle X ray scattering; Experimental study; 1,4-phenylene diisocyanate; Etherurethane polymer; Comparative study; Hydrogen bond
• ISSN: 0887-6266; 1099-0488; 1099-0488
• DOI: 10.1002/polb.22264

Three diisocyanate units having different linearity and planarity on the basis of the arrangement of constituent aromatic rings are used to synthesize three polyurethanes (PUs) and the effects of the molecular structure of the diisocyanate units on phase separated morphologies of PUs have been studied. The linear and planar diisocyanate unit allows good packing of the hard segments in the hard domain by extensive intersegmental hydrogen bonding, and it forms a well ordered, long hard domain. However, the nonlinear and noncoplanar diisocyanate unit shows a lesser degree of hydrogen bonding in the short hard domain. Strong preferential orientation of the rigid/long hard domains inside a macroscopic grain boundary has been observed with the polarizing optical microscope especially for the PU based on the rigid diisocyanate. It was concluded that the molecular structure of the diisocyanate unit in PU plays an important role in determining the interchain interaction, the detailed phase‐separated domain structure, and local domain orientation in each grain boundary. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 The mechanical properties of polyurethanes are largely determined during the microphase separation process that forms the heterogeneous microphase‐separated morphology of hard and soft domains. Using polarizing optical microscopy, the molecular structure of the diisocyanate unit in polyurethane is shown to play an important role in determining the interchain interaction, chain packing, and local domain orientation in each grain boundary, thus determining the microphase‐separated and macroscopic grain structure of the material.