Electroactive shape memory polyurethane composites reinforced with octadecyl isocyanate-functionalized multi-walled carbon nanotubes

Abstract

Shape memory polymers (SMPs) have a wide range of potential applications in many fields. In particular, electrically driven SMPs have attracted increasing attention due to their unique electrical deformation behaviors. Carbon nanotubes (CNTs) are often used as SMP conductive fillers because of their excellent electrical conductivities. However, raw CNTs do not disperse into the polymer matrix well. This strictly limits their use. In this study, to improve their dispersion performance characteristics in the polymer matrix, hydroxylated multi-walled carbon nanotubes (MWCNT-OHs) were functionalized with octadecyl isocyanate (i-MWCNTs). Polyurethane with shape memory properties (SMPU) was synthesized using polycaprolactone diol (PCL-diol), hexamethylene diisocyanate (HDI), and 1,4-butanediol (BDO) at a 1:5:4 ratio. Then, electroactive shape memory composites were developed by blending SMPU with i-MWCNTs to produce SMPU/i-MWCNTs. The functionalized i-MWCNTs exhibited better dispersibility characteristics in organic solvents and SMPU composites than the MWCNT-OHs. The addition of i-MWCNTs reduced the crystallinity of SMPU without affecting the original chemical structure. In addition, the hydrogen bond index and melting temperature of the SMPU soft segment decreased significantly, and the thermal decomposition temperatures of the composites increased. The SMPU/i-MWCNT composites exhibited conductivity when the i-MWCNT content was 0.5 wt%. This conductivity increased with the i-MWCNT content. In addition, when the i-MWCNT content exceeded 1 wt%, the composite temperature could increase beyond 60°C within 140 s and the temporary structure could be restored to its initial state within 120 s using a voltage of 30 eV. Therefore, the functionalized CNTs exhibit excellent potential for use in the development of electroactive shape memory composites, which may be used in flexible electronics and other fields.

4D Printing of Electroactive Triple-Shape Composites

“…For the unfilled blend, no peaks associated with crystalline PLA were observed. The most noticeable change was a characteristic peak associated with the MWCNTs at 2θ = 26° [ 51 ]. While, as before, all crystalline polymer peaks disappeared at 55 °C, the MWCNT peak remained, as expected.…”

Effect of Particle Functionalization on Structural and Dielectric Properties of Flexible TPU/BaTiO3/MWCNTs Composite Films

“…Differently, by using functionalized fillers, hydrogen bonds can be established at the polymer‐particle interface, thus reducing the tendency of the chain to segregate from the particles. [ 18 ]…”

“…Differently, by using functionalized fillers, hydrogen bonds can be established at the polymer-particle interface, thus reducing the tendency of the chain to segregate from the particles. [18] DSC heating curves recorded for the pure TPU and its composite films are shown in Figure 4. The existence of two glass transition temperatures can be observed: the lower glass transition T g1 is related to the SS, and the higher glass transition T g2 is ascribable to the HS of TPU.…”

Advances in Graphene‐Reinforced Polyurethane Nanocomposites: An Advanced Shape Memory Material

“…By incorporating Gr, SMPs can exhibit improved thermal conductivity, which can be beneficial for applications that involve efficient heat transfer, such as thermal actuators or shape memory materials used in heat management systems. [111][112][113] Gr is an excellent conductor of electricity, and incorporating Gr into SMPs can result in nanocomposites with improved electrical properties. This can enable the development of smart SMPs with electrical sensing, actuating, or communication capabilities.…”

“…Several Gr‐based active responsive materials have been modified with functional groups via covalent or non‐covalent bonds to enable the conversion of one or more environmental stimuli, such as electrical, light, thermal, or chemical energy, to mechanical energy. By incorporating Gr, SMPs can exhibit improved thermal conductivity, which can be beneficial for applications that involve efficient heat transfer, such as thermal actuators or shape memory materials used in heat management systems [111–113] . Gr is an excellent conductor of electricity, and incorporating Gr into SMPs can result in nanocomposites with improved electrical properties.…”