Crystalline morphologies in segmented copolymers with hard segments of uniform length

The crystal morphological properties of segmented poly(ether ester aramide) elastomers with aromatic hard-segment amide units of uniform length were studied. Four samples with hard-segment fractions ranging from 3.4 to 9 wt % were studied by tapping atomic force microscopy (AFM). For one sample, both solution and melt-processed surfaces were examined, and similar crystal morphologies were found. The semicrystalline morphologies of these polymers had some similarities to other low-hard-segment segmented elastomers. The very thin needlelike or ribbonlike crystallites at the surface had a high aspect ratio for all the samples. The main difference observed for the different compositions was a decrease in the surface area density of ribbons with a decrease in the hard-segment fraction. One sample was chosen for in situ AFM studies during film extension. The details of the crystallite orientation and breakup were studied in increments up to 700% elongation (8× stretch ratio) and after relaxation.