A series of shape memory nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) E51/methylhexahydrophthalic anhydride (MHHPA)/multiwalled carbon nanotube (MWCNT) with various stoichiometric ratios (rs) of DGEBA/MHHPA from 0.5 to 1.2 and filler contents of 0.25 and 0.75 wt % are fabricated. Their morphology, curing kinetics, phase transition, mechanical properties, thermal conduction, and shape memory behaviors are systematically investigated. The prepared materials show a wide range of glass transition temperatures (Tg) of ca. 65–140 °C, high flexural modulus (E) at room temperature up to ca. 3.0 GPa, high maximum stress (σm) up to ca. 30 MPa, high strain at break (εb) above 10%, and a fast recovery of 32 s. The results indicate that a small amount of MWCNT fillers (0.75 wt %) can significantly increase all three key mechanical properties (E, σm, and εb) at temperatures close to Tg, the recovery rate, and the repetition stability of the shape memory cycles. All of these remarkable advantages make the materials good candidates for the applications in aerospace and other important fields.Keywords: carbon nanotube; curing; epoxy; nanocomposite; shape memory polymer

This work examines the effects of carbon black (CB) nanoparticles on two-way, reversible shape memory cycles in crosslinked polyethylene. The two-way shape memory effect is characterized by mechanical measurements, thermal analysis, and X-ray diffraction. For the first time, it is shown that there is an optimal loading of CB particles that maximizes the actuation ratio (Ra ≡ (ɛ2 – ɛ1) × 100%), where ɛ1 is the initial strain under load above the crystal melting temperature and ɛ2 is the strain following crystallization under load. Adding a small volume fraction of CB particles (νCB = 0.5 to 1.0 vol. %) enhances Ra by more than a factor of 1.5. Through swelling experiments and mechanical testing, the CB nanoparticles are shown to act as physical crosslinkers, significantly decreasing ɛ1. However, the observed ɛ2 is barely affected by small amounts of CB, which are insufficient to disrupt the formation of highly oriented crystals. In contrast, the two-way shape memory effect is greatly reduced with higher CB loading (νCB = 20 vol. %), which decreases both ɛ2 and Ra. Addition of a small amount of CB is also shown to provide a simple means to lower the response temperature range of polyethylene-based shape memory polymers.

In this work, electrically and thermally actuated triple shape memory polymers (SMPs) of chemically cross-linked polycyclooctene (PCO)–multiwalled carbon nanotube (MWCNT)/polyethylene (PE) nanocomposites with co-continuous structure and selective distribution of fillers in PCO phase are prepared. We systematically studied not only the microstructure including morphology and fillers’ selective distribution in one phase of the PCO/PE blends, but also the macroscopic properties including thermal, mechanical, and electrical properties. The co-continuous window of the immiscible PCO/PE blends is found to be the volume fraction of PCO (vPCO) of ca. 40–70 vol %. The selective distribution of fillers in one phase of co-continuous blends is obtained by a masterbatch technique. The prepared triple SMP materials show pronounced triple shape memory effects (SMEs) on the dynamic mechanical thermal analysis (DMTA) and the visual observation by both thermal and electric actuations. Such polyolefin samples with well-defined microstructure, electrical actuation, and triple SMEs might have potential applications as, for example, multiple autochoke elements for engines, self-adjusting orthodontic wires, and ophthalmic devices.Keywords: co-continuous structure; electrical actuation; nanocomposites; polyolefins; selective distribution; triple shape memory effects