Chain Extender-induced Hydrogen Bonding Organization Determines the Morphology and Properties of Thermoplastic Polycarbonate Polyurethane

Thermoplastic polycarbonate polyurethanes (PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders (CE) involved in the composition of the hard segments of PCU. However, limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties. To investigate this problem, a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol (BDO), aminoethanol (MEA), ethanediol (EO) as three kinds of chain extenders. Tiny differences in the CE chemical structure results in remarkable variations in phase separation, condensed morphologies, thermal and mechanical properties, which are characterized by Fourier transform infrared spectrometer, atomic force microscopy, small-angle X-ray scattering, differential scanning calorimetry, and tensile tests. The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide- and small-angle X-ray diffraction. Symmetry of CE can improve the organization of the hydrogen bonding. The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.

Automated summary

This study investigates the effect of the chemical structure of chain extenders on the hydrogen bonding and mechanical properties of PCUs by synthesizing PCUs with different types of chain extenders. The results show that even minor differences in the chain extender's chemical structure can result in significant variations in phase separation, condensed morphologies, thermal and mechanical properties. The symmetry of the chain extender improves the ordering of the hydrogen bonding, and the coherence strength of the urethane/urea group also plays a key role in the polymer's properties.