Effect of soft segment length on properties of hydrophilic/hydrophobic polyurethanes

Polyurethanes (PUs) were prepared from 4,4′‐diphenylmethane diisocyanate and various molecular weights of poly(tetramethylene glycol) and polydimethylsiloxane. The physical properties of these polymers were determined using Fourier transform infrared spectroscopy and through calculation of their swelling ratios. The thermal properties were investigated through thermogravimetric analysis and dynamic mechanical analysis. The blood compatibility of each polymer was determined by calculating its relative index of platelet adhesion (RIPA). Domain separation of the resulting PUs occurred during polymerization because of the immiscibility of the hydrophilic and hydrophobic polyols. The hydrophilic/hydrophobic domain‐separated structure affected the surface tension through the formation of hydrophilic and hydrophobic domains of the PU, which reduced the adhesion of blood platelets onto the materials. The PU(PDMS/PTMO1000) = 75/25 sample, with its RIPA of 0.34, appears to be suitable for biomedical applications as a blood‐compatible material. Copyright © 2007 Society of Chemical Industry