Structural studies on linear polyurethanes. II. Crystal and molecular structures of aliphatic polyurethanes from trimethylene diisocyanate, and tetra- and hexa-methylene glycols

Abstract

The crystal structures of polyurethanes with the formula (Formula Presented) have been determined by X-ray diffraction analysis. Poly(tetramethylene trimethylene dicarbamate) (4,3-polyurethane) crystallizes in the triclinic space group (Formula Presented) with a=5.06Å, b=5.04Å, c(fiber axis)=30.10Å, α=112°C, β=113°C, and γ=110°C. Poly(hexamethylene trimethylene dicarbamate) (6,3-polyurethane) crystallizes in the triclinic space group (Formula Presented), with a=5.04 Å, b=5.04 Å, c=34.65 Å. α=111°C, β=111°C, and γ=111°C. By conformational analysis, we attempted to find structure models that would satisfy the condition of full intermolecular hydrogen bonding. These models were then refined by three dimendional Fourier synthesis to the R values of 0.225 for 4,3- and 0.207 for 6,3-polyurethane. The molecules of both polymers are linked two dimensionally by (Formula Presented) hydrogen bonds. These polymers are the same in structure except for their fiber periods which differ in the length of two methylene groups of the glycols. The hydrogen bonding patterns of these polyurethanes differ from those of other polyurethanes. © 1982 The Society of Polymer Science, Japan. All rights rerserved.