Optical and shape memory properties of semicrystalline poly(cyclooctene) upon cold-drawing

Semicrystalline thermoplastic poly(cyclooctene) (PCO) shows significant improvement in transparency when cold-drawn at room temperature, unlike other semicrystalline polymers whose fibrillated chains cause crazing upon cold-drawing, making the polymers opaque to visible light. Upon heating, transparent cold-drawn PCO recovers its original opacity as well as its undeformed shape. In situ wide- and small-angle X-ray diffraction and polarized Fourier transform infrared analyses show that molecular density differences between the PCO crystalline and amorphous phases were reduced due to strain-induced crystallization and that fibrillated chains and voids, an indication of craze, were not observed due to chain entanglements concentrated in trans double-bond regions. These two factors explain the unique optical properties of PCO. Finally, it is demonstrated that crosslinked PCO enhanced optical and shape memory recovery without deterioration of the transparency of the polymer. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017