A Comparative Study of Microphase Separation of Polyurethane Multiblock Copolymers with Different Soft Segment Chemistries.

We focus in this study on three series of chemically well-defined polyurethanes (PUs) with the same hard segments (MDI-BDO) but different soft segment chemistries of interest in biomedical applications: 1000 g/mol aliphatic polycarbonate, polytetramethylenoxide and a mixed macrodiol of polydimethylsiloxane (PDMS) and polyhexamethylenoxide. Using quantitative small-angle X-ray scattering we demonstrate that the degree of hard/soft segment demixing varies greatly between the materials. For example, the PDMS-based copolymers exhibit a three phase, core-shell morphology, while the other copolymers exhibit a typical two phase structure. Additional analysis was conducted with a number of experimental probes including FTIR to assess inter- and intracomponent hydrogen bonding, and tapping mode AFM to characterize the nanoscale morphology.