“…From a macroscopic structure standpoint, SMPs typically consist of a stationary phase with an elastic restoring force and a reversible phase that maintains deformation 1,13 . Thus, the simplest polymer combination systems, (such as, a crosslinked amorphous or crystalline polymer) will exhibit the shape‐memory behavior.…”
Section: Introductionmentioning
confidence: 99%
“…However, it has a narrow processing window, poor high-temperature thermal stability, and a brittle texture. 14,15 Therefore, it is necessary to find a polymer that can not only improve the overall performance of PHB but also act as a reversible phase in the PHB-based blend. Among many kinds of polymers, polycaprolactone (PCL) has outstanding toughness and a high thermal decomposition temperature.…”
Shape‐memory polymers have attracted attention as smart implant materials in recent years because they are lightweight, low‐cost, easily processable, and because they undergo large deformation. Here, cellulose nanofibers (CNFs) were used as a reinforcement for polyhydroxybutyrate (PHB)/polycaprolactone (PCL) composites to improve mechanical properties. The composites were investigated by rheological tests, differential scanning calorimetry, dynamic mechanical analysis, mechanical property tests, and shape‐memory tests. The printability of PHB/PCL/CNFs composites was demonstrated by using them to print interconnected porous structures with a gyroid surface. The results showed that the PHB/PCL (80:20) composites with 1 wt% CNF displayed the best comprehensive mechanical and shape‐memory properties. As a functional verification, a model of the self‐opening hand was fabricated by 3D printing, and its deformation and recovery capabilities were evaluated.
“…From a macroscopic structure standpoint, SMPs typically consist of a stationary phase with an elastic restoring force and a reversible phase that maintains deformation 1,13 . Thus, the simplest polymer combination systems, (such as, a crosslinked amorphous or crystalline polymer) will exhibit the shape‐memory behavior.…”
Section: Introductionmentioning
confidence: 99%
“…However, it has a narrow processing window, poor high-temperature thermal stability, and a brittle texture. 14,15 Therefore, it is necessary to find a polymer that can not only improve the overall performance of PHB but also act as a reversible phase in the PHB-based blend. Among many kinds of polymers, polycaprolactone (PCL) has outstanding toughness and a high thermal decomposition temperature.…”
Shape‐memory polymers have attracted attention as smart implant materials in recent years because they are lightweight, low‐cost, easily processable, and because they undergo large deformation. Here, cellulose nanofibers (CNFs) were used as a reinforcement for polyhydroxybutyrate (PHB)/polycaprolactone (PCL) composites to improve mechanical properties. The composites were investigated by rheological tests, differential scanning calorimetry, dynamic mechanical analysis, mechanical property tests, and shape‐memory tests. The printability of PHB/PCL/CNFs composites was demonstrated by using them to print interconnected porous structures with a gyroid surface. The results showed that the PHB/PCL (80:20) composites with 1 wt% CNF displayed the best comprehensive mechanical and shape‐memory properties. As a functional verification, a model of the self‐opening hand was fabricated by 3D printing, and its deformation and recovery capabilities were evaluated.
“…4 d). The sericin's α-helices, that are arranged in coiled-coil architectures, undergo continuous structural transition into metastable β-sheets when load is applied [ 40 ], and this reversible transition could be restored in response to hydration, probably endowing the shape-memory properties to CNTs-SS. Fig.…”
“…While a metal coordination of carboxymethyl cellulose derivatives [ 12 , 13 ] contains bio-polymer-based switching segments, the so-formed temporary net points do not occur in nature in this way. In contrast, several proteins have been used as components or blueprints in shape-memory polymers, e.g., the switch between α-helical and β-strand conformations upon water uptake and at different strain was utilized in keratin-based materials [ 14 ]. The pH-dependent switching between an unordered and a β-strand conformation of a 20mer peptide was employed to form temporary net points in acrylate copolymers with grafted peptide groups [ 15 ].…”
Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) α,ω-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27–23 kPa and Young’s moduli of 215–360 kPa at 4 °C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 °C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates Rr close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.
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