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    4D-printable thermo- and light-responsive triple-shape memory polymer nanocomposites containing titanium nitride nanoparticles
    (Elsevier Sci Ltd, 2025) Tekay, Emre; Aybakan, Betul; Aslan, Vahap Uygar
    In this work, novel light-responsive nanocomposites were developed by incorporating varying amounts (1-3-5 phr) of titanium nitride nanoparticles (TiN-NP) into a ternary polymer blend consisting of 30 wt% of maleic anhydride grafted SEBS (SEBS-MA), 40 wt% of ethylene vinyl acetate copolymer (EVA), and 30 wt% of butyl methacrylate/isobutyl methacrylate copolymer (PBMA-PiBMA), that exhibits thermally induced triple-shape memory properties. In the nanocomposite containing 1 phr TiN nanoparticles (1-TiN), a core-shell morphology was observed, with the fillers selectively localizing within the SEBS-MA phase. The presence of TiN filler did not have a significant effect on the thermal transition temperatures of the polymer components. An increase in TiN content resulted in enhanced elastic modulus values for the composites, with a notable 138 % rise observed in the composite that included 5 phr filler relative to the blend. The best heat responsive shape memory performance was observed in the 1-TiN composite, with the first and second shape fixation ratios of 91.6 % and 83.4 %, respectively, and the first and second shape recovery ratios of 90.8 % and 100 %, respectively. The 1-TiN composite underwent photothermal heating under 808 nm NIR light, reaching 40 degrees C and 80 degrees C at light intensities of 48 mW/cm2 and 158 mW/cm2, respectively, demonstrating light-responsive triple-shape memory effect. The filament of the same nanocomposite was produced, and 4D-printed objects were created using an FDM-type 3D printer for various applications. Moreover, the 4D-printed objects fabricated using the nanocomposite filament exhibit triple-shape recovery under NIR light with an intensity of 48 mW/cm2 and 161 mW/cm2.
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    Design of thermally triggered triple-shape memory ternary polymer blends for 4D printing applications
    (Elsevier, 2025) Tekay, Emre; Aybakan, Betul; Aslan, Vahap Uygar
    4D printing represents an emerging technology that has developed from the combination of shape memory polymers (SMPs) with additive manufacturing techniques. Shape memory polymers are members of the smart materials family and have the capability to change their shape in response to a stimulus. Thermo-responsive triple-SMPs possess the capability to maintain two distinct temporary shapes and can transition between these shapes when exposed to heat. This study introduces novel ternary polymer blends incorporating ethylene vinyl acetate copolymer (EVA), maleic anhydride grafted poly(styrene-b-ethylene-butylene-b-styrene) (SEBS-MA), and poly(butyl-co-isobutyl methacrylate) (PBMA-PiBMA) polymers, which exhibit thermo-responsive triple-shape memory properties at 40 degrees C and 80 degrees C. The SEBS-MA/EVA/PBMA-PiBMA ternary blend with 30/40/30 composition showed optimal triple-shape memory performance, exhibiting 92.3 % first shape fixing, 88.0 % second shape fixing, 90.5 % first shape recovery and 100 % second shape recovery ratios. The same blend also demonstrated a dual shape memory effect at 80 degrees C, achieving a shape fixing ratio of 98.6 % and a shape recovery performance of 100 %. Filament of the polymer blend was produced to be used in 3D printers. Using this filament, a hinge, a daisy, a stent, and a robotic gripper were created for use in different 4D printing applications. The 4D-printed objects produced from the ternary blend filament show two-way shape recovery at 40 degrees C and 80 degrees C.
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    Development of Near Infrared Light and Electrically Responsive Shape Memory Polymer Composites Based on Copolyester Thermoplastic Elastomer/Polycaprolactone Blend and Carbon Nanotubes
    (Wiley, 2025) Tekay, Emre; Aslan, Vahap Uygar; Orhun, Tuana; Sen, Sinan; Aybakan, Betul
    Carbon nanotubes (CNTs) are carbon-based materials that not only exhibit excellent electrical and thermal conductivity but also possess the ability to absorb light, thereby providing a photothermal effect. Due to these characteristics, when utilized in conjunction with a thermally sensitive shape memory polymer (SMP) matrix, a multi-stimuli responsive shape memory effect (SME) can be achieved. In this study, a thermally responsive SMP blend composed of a copolyester thermoplastic elastomer (COPE) and polycaprolactone (PCL) was transformed into electroactive and light-responsive shape memory polymer composites by incorporating multi-walled carbon nanotubes (MWCNTs) at loadings of 3, 5, 10, and 20 phr. The composite containing 20 phr CNT achieved an electrical resistance of 2.03 Omega cm. Under a voltage of 4 V, the same composite performed Joule heating, resulting in an electroactive shape recovery of 95.67%. It was observed that the light-responsive shape memory effect is more advantageous at lower filler loadings. The composite with 3 phr filler achieved complete shape recovery under NIR light with a wavelength of 808 nm and an intensity of 108 mW/cm(2). The produced composites exhibit multifunctional properties, making them promising candidates for advanced applications including sensors, actuators, responsive smart textiles, and innovative 4D printing technologies.
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    Heat-responsive poly(styrene-block-ethylene-butylene-block-styrene)/poly (butyl methacrylate-co-isobutyl methacrylate) blends and their applications in 4D printing
    (Elsevier Science Sa, 2025) Tekay, Emre; Aybakan, Betul; Aslan, Vahap Uygar
    Recent advancements in additive manufacturing technology have also introduced new research areas in materials science. The processing of shape memory polymers (SMPs) using 3D printers has led to the emergence of 4D printing technology. The present study focused on the creation of new polymer blends that incorporate maleic anhydride grafted SEBS (SEBS-g-MA) alongside poly(butyl methacrylate-co-isobutyl methacrylate) (poly(BM-coiBM)) in diverse compositions, aimed at facilitating advancements in 4D printing technologies. In the formulation with a weight ratio of SEBS-g-MA to poly(BM-co-iBM) of 6/4 (60S-40B), a co-continuous morphology was detected. With a rising concentration of SEBS-g-MA in the polymer blends, the Tg of the poly(BM-co-iBM) phase exhibited an upward shift. Dynamic mechanical analysis results indicate that the poly(BM-co-iBM) polymer within the blends transitioned from a glassy state to a rubbery state before reaching 55 degrees C, which resulted in a pronounced reduction in the storage modulus at this temperature. On the other hand, with an increase in the amount of poly(BM-co-iBM) in the blend, there was a corresponding increase in the elastic modulus values, while the elongation at break values diminished. The results from the thermo-responsive shape memory analysis demonstrated that the 60S-40B blend provided the most favorable performance. A filament suitable for 4D printing was developed from this blend for application in fused deposition modeling printers. Employing the filament, objects produced via 4D printing were developed for applications such as lifting devices, stents, door closers, cogwheels, and robotic grippers, and their shape memory properties were evaluated.