Fabrication of Thermoplastic Polyurethane/Polycaprolactone Multilayered Composites with Confined Distribution of MWCNTs for Achieving Tunable Thermo- and Electro-Responsive Shape-Memory Performances

Abstract

Multilayered shape-memory composites composed of multiwalled carbon nanotube (MWCNT)-filled thermoplastic polyurethane (TPU) (denoted as cTPU) and polycaprolactone (PCL) were prepared through layer-multiplying coextrusion. The phase interfaces and conductive pathways in the multilayered structure which can be tailored by layer-multiplying endowed the materials with tunable thermo-and electro-responsive shapememory effects (TSME and ESME). Compared with the conventional blending composite having the same compositions, the cTPU/PCL multilayered system with high phase continuity and abundantly continuous interfaces exhibited better TSME, which could be further enhanced with increasing the layer number. It was revealed that the strain energy stored in cTPU layers would be balanced by adjacent PCL layers via interfacial shearing effect so that each domain could endow the maximum contribution to the shape-memory performance. Besides, the confined layer space allowed for a more compact connection between the MWCNTs than in the blending composite, while the original conductive network formed in cTPU tended to be gradually broken up during layer multiplying. Moreover, an excessive conductivity may induce local overheating and even the melting of permanent domains, leading to undesired deformation. Accordingly, the multilayered composite with a proper layer number which exhibited suitable conductivity and efficient TSME achieved balanced ESME with quick recovery speed, excellent recovery ratio, and good appearance retention. This work opened an avenue in preparing outstanding shape-memory materials with both thermal and electrical actuations, which showed great potential in applications of sensors, actuators, self-deployable devices, and so forth.

UV Reconfigurable Shape Memory Polyurethane with a High Recovery Ratio under Large Deformation

“…As shown in Figure 1b, the chemical shifts at 1 (δ = 1.36), 2 (δ = 1.65), 3 (δ = 2.29), and 4 (δ = 4.05) can be attributed to the protons in the methylene of the PCL soft segment, while the chemical shifts at 5 (δ = 3.70), 6 (δ = 7.04), and 7 (δ = 7.2) can be attributed to the protons from MDI. Moreover, the characteristic peaks (8,9,10,11) in the range of δ = 7.40−8.44 were assigned to the aromatic protons from anthracene groups, and the chemical shifts at 12 (δ = 4.6) and 13 (δ = 2.9) were attributed to the protons from BHEAA, indicating the successful synthesis of the AN-TPU. When the feed molar ratio (MDI/BHEAA/PCL) was 2:1:1, the HS (hard segment) content and the AN content were calculated by eqs S1 and S2, respectively, which were 28.4 and 10.2%, as shown in Table 1.…”

“…The thermoplastic polyurethane (TPU) with shape memory properties has attracted much attention due to the high elongation, adjustable moduli, and transition temperature, giving it extensive application scope. − Most polyurethanes generally exhibit phase-separated structures, in which the hard segments form the hard domains via hydrogen bonds as the stable phase, and play an important role in shape recovery, while soft segments, usually including polyether or polyester, aggregate into soft domains as the reversible phase that absorb external stress and provide elasticity and changeability. , …”

Carbon Nanotubes-Coated Conductive Elastomer: Electrical and Near Infrared Light Dual-Stimulated Shape Memory, Self-Healing, and Wearable Sensing

“…Except for the NIR light stimulation, electrical stimulation gradually attracts the attention on account of the accessibility of remote control and easy operation. ,, Since CNTs can effectively convert electrical energy into heat, which infers that CNTs/CHSMP composites may probably possess the electricity-actuated shape memory capacity. An experiment concerning electrothermal performance of CNTs/CHSMP composites at different external voltages (3–20 V) was first conducted to find a suitable external voltage for triggering shape memory manifestation (Figure a).…”

“…Conductive elastomeric composite materials have recently drawn significant interest due to their excellent stretchability, flexibility, and specific electrochemical performance, which show promising applications in flexible wearable electronics, battery, artificial skin, soft robotics, and biosensing. − To satisfy the requirements of various functional applications, nanosized conductive fillers, such as carbon nanotubes (CNTs), − carbon back, , carbon fiber, metal nanoparticles, and graphene, , have been employed to construct conductive elastomeric composites. Among them, CNTs have aroused particular attention due to unique electrical and mechanical properties with low percolation threshold, and the physical blending and swelling/permeating method were the common strategies to processing CNT-containing composites. ,, In recent years, the surface coating of CNTs on the polymer substrate was also developed as an easy, economical, and scalable way to achieve CNT-based elastomeric composites with continuous conductive networks. , …”

Deployment Analysis of Aramid Fiber Reinforced Shape-Memory Epoxy Resin Composites

“…[1][2][3][4][5] Thus, SMPs are widely used in electronics, aircraft, and aerospace fields, such as in actuators and self-deployable space structures. [6][7][8][9][10] An SMP shifts between rigid and elastic states through thermal stimuli at the critical temperature (T c ). 11 The polymer is deformed to a desired shape at a temperature above T c .…”