Two-stages of thermal and photo curing reactive polymer network from bio-based precursors

Abstract

Shape memory polymers (SMP) are a class of smart materials that can be fixed in a temporary shape and regain its permanent shape upon stimulus. Bio-based polymer with shape memory effect can overcome environmental and economic issues. It can be used as actuator, sensor and for drug delivery system in medical area. Two stages curing reactive bio-based polyester network namely, poly(octanediol-co-dodecanedioate-co-citrate-co-itaconate) were synthesized. The produced samples were formulated as PCxIytz, where x represented molar ratio of citric acid, y represented molar ratio of itaconic acid, and z represented photo-curing duration which varies from 0 to 60 min. In the first curing stage, prepolymer of PCxIy was thermally crosslinked. At later time, a second curing was completed through photo initiated free-radical polymerization. From Fourier-transform infrared spectra of PCxIytz, the intensity of the absorption bands at 660 cm-1 and 700 cm-1 were found decreased with increasing photocuring time. Swelling ratio of bio-based polyester was decreased from 2750 % to 250 % after exposed under UV light for 60 min. All of the synthesized bio-based polymers existed as a semi-crystalline polymer with melting-transition temperature and crystallization-transition temperature vary with photocuring time. Based on X-ray diffraction analysis, the polymer crystallinity of the bio-based polymer decreased with time of photocuring. The Young’s modulus of PCxIytz decreased with increasing photocuring time which may be due to increase in elasticity and softness upon second curing. Shape-recovery temperature of all of the PCxIytz was found around 37 °C. Two formulations of PCxIytz were successfully synthesized with excellent shape memory effect (SME). Therefore, this bio-based polymer with shape memory property can be potentially explored in bio-3D printing and medical industry as a printing and an adhesive material respectively.