Colorless shape memory polyimide (CSMPI) has potential applications in broad fields, especially in advanced optoelectronics due to the excellent optical transparency, shape memory effect and high temperature resistance. In this work, CSMPI prepared by high flexible dianhydrides and fluorine-containing diamines has excellent optical transparency, shape memory properties and high temperature resistance. High flexible dianhydrides that makes the molecule chains more easily twisted and tangled to form physical crosslinking points is favorable for possessing great shape memory property. The fluorine-containing diamines effectively destroyed the highly conjugated molecular structure and inhibited the formation of CTC, ensuring the CSMPI with excellent optical transparency. The effects of monomer ratio and imidization temperature on the molecular structure and properties were discussed. The CSMPI film possesses a higher glass transition temperature (Tg) of 234 °C, compared to the reported transparent shape memory polymers (SMPs). Most importantly, the transmittance of CSMPI film is 87~90% at 450~800nm, meeting the requirements of heat resistance and transmittance of the substrate. Both shape recovery and shape fixity are over 97%. Flexible and colorless CSMPI films has potential applications in broad fields, especially in advanced optoelectronics, such as flexible substrates for OLED and OPV devices, etc.
As smart polymers, shape memory polymers (SMPs) are able to change shape and structure when exposed to an external stimulus, including heating, electrical and magnetic fields, water, light etc. This feature leads to potential for SMPs in many applications such as aerospace, smart textiles, robotics, automobile and biomedical engineering. SMPs can be produced to different forms and structures from nanoscale to macrolevel, including fibers, membranes, particles and foams. SMP foams have been developed due to the light weight, large deformation, etc. However, the fabrication method is too complected and the actuation speed is slow. Herein, to solve these problems, we fabricate a class of shape memory polycaprolactone foams and their composites by microwave, which can also be triggered by microwave. The merits of these foams include fast fabrication (less than 60 s), uniform pores, large compression deformation (80%) and quick shape recovery speed with in 100 s. This approach of using microwave to synthesize shape memory polymer foams in microwave oven would enable the synthesis of a wide variety of novel shape-memory foams. Moreover, microwave actuated shape memory foams can provide higher recovery speed for remote control in various applications.
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