New Design Strategy for Reversible Plasticity Shape Memory Polymers with Deformable Glassy Aggregates

Reversible plasticity shape memory (RPSM) is a new concept in the study of shape memory performance behavior and describes a phenomenon in which shape memory polymers (SMPs) can undergo a large plastic deformation at room temperature and subsequently recover their original shape upon heating. To date, RPSM behavior has been demonstrated in only a few polymers. In the present study, we implement a new design strategy, in which deformable glassy hindered phenol (AO-80) aggregates are incorporated into an amorphous network of epoxidized natural rubber (ENR) cured with zinc diacrylate (ZDA), in order to achieve RPSM properties. We propose that AO-80 continuously tunes the glass transition temperature (<i>T</i>_g) and improves the chain mobility of the SMP, providing traction and anchoring the ENR chains by intermolecular hydrogen bonding interactions. The RPSM behavior of the amorphous SMPs is characterized, and the results demonstrate good fixity at large deformations (up to 300%) and excellent recovery upon heating. Large energy storage capacities at <i>T</i>_d in these RPSM materials are demonstrated compared with those achieved at elevated temperature in traditional SMPs. Interestingly, the further revealed self-healing properties of these materials are closely related to their RPSM behavior

Polyphenol-Reduced Graphene Oxide: Mechanism and Derivatization

In this work, tea polyphenols (TPs) were employed as an environmentally friendly and highly efficient reducer and stabilizer for graphene oxide (GO). The results from XPS, Raman, and conductivity studies of reduced graphene indicated the efficient deoxidization of GO. The adsorption of oxidized TPs onto graphene supplies steric hindrance among graphene sheets to keep them individually dispersed in water and some solvents. To investigate the reduction mechanism, epigallocatechin gallate (EGCG), the primary component of TPs, was used as a model. Characterization by ¹H NMR and FTIR spectroscopies indicated that the gallic units in EGCG were converted to galloyl-derived orthoquinone and the flavonoid structure survived during the reduction. To further enhance the organosolubility of the resultant graphene, derivatization of the graphene was conducted by galloyl-derived orthoquinone–thiol chemistry. The successful derivatization was found to greatly improve the organosolubility of graphene in solvents with low boiling points

Malleable, Mechanically Strong, and Adaptive Elastomers Enabled by Interfacial Exchangeable Bonds

Reinforcement, recycling, and functional applications are three important issues in elastomer science and engineering. It is of great importance, but rarely achievable, to integrate these properties into elastomers. Herein, we report a simple way to prepare covalently cross-linked yet recyclable, robust, and macroscopically responsive elastomer vitrimers by engineering exchangeable bonds into rubber–carbon nanodot (CD) interphase using CD as high-functionality cross-linker. The cross-linked rubbers can rearrange the network topology through transesterification reactions in the interphase, conferring the materials the ability to be recycled, reshaped, and welded. The relatively short chains bridging adjacent CD are highly stretched and preferentially rupture to dissipate energy under external force, resulting in remarkable improvements on the mechanical properties. Moreover, the malleable and welding properties allow the samples to access reconfigurable/multiple shape memory effects

Interphase Percolation Mechanism Underlying Elastomer Reinforcement

Glassy interphase has been claimed to be of vital importance for mechanical reinforcement of elastomer nanocomposites (ENCs), but the evolution of interphase topology in correlation to reinforcement percolation remains uncertain. Here, an accurate interfacial regulation strategy upon implementing an interphase percolation mechanism is exploited to realize percolation of mechanical performance toward striking elastomer reinforcement. Architecture design of interfacial metal–ligand bridges accomplishes firm anchoring between elastomer skeleton and carbon nanodots, leading to the formation of interfacial metal-enriched regions. The volume fraction of the interfacial region systemically enlarges upon increase of interfacial bridges, which finally overlaps with neighboring domains to form a penetrating interphase. The topological evolution of the interfacial region is quantitatively monitored upon small-angle X-ray scattering and dielectric measurements, which exhibits a similar percolation behavior in sync with that of macroscopic mechanical performance. Furthermore, the interphase exhibits much slower relaxation dynamics than in bulk polymer, which significantly improves the network rigidity and hence accounts for the prominent elastomer reinforcement. This investigation corroborates that the formation of penetrating interphase may be an executable mechanism to induce the reinforcement percolation of ENCs. We further envision that the implementation of interphase percolation mechanism can be a universal avenue to afford rationalized optimization of ENCs

Malleable, Mechanically Strong, and Adaptive Elastomers Enabled by Interfacial Exchangeable Bonds

Reinforcement, recycling, and functional applications are three important issues in elastomer science and engineering. It is of great importance, but rarely achievable, to integrate these properties into elastomers. Herein, we report a simple way to prepare covalently cross-linked yet recyclable, robust, and macroscopically responsive elastomer vitrimers by engineering exchangeable bonds into rubber–carbon nanodot (CD) interphase using CD as high-functionality cross-linker. The cross-linked rubbers can rearrange the network topology through transesterification reactions in the interphase, conferring the materials the ability to be recycled, reshaped, and welded. The relatively short chains bridging adjacent CD are highly stretched and preferentially rupture to dissipate energy under external force, resulting in remarkable improvements on the mechanical properties. Moreover, the malleable and welding properties allow the samples to access reconfigurable/multiple shape memory effects

Malleable, Mechanically Strong, and Adaptive Elastomers Enabled by Interfacial Exchangeable Bonds

Reinforcement, recycling, and functional applications are three important issues in elastomer science and engineering. It is of great importance, but rarely achievable, to integrate these properties into elastomers. Herein, we report a simple way to prepare covalently cross-linked yet recyclable, robust, and macroscopically responsive elastomer vitrimers by engineering exchangeable bonds into rubber–carbon nanodot (CD) interphase using CD as high-functionality cross-linker. The cross-linked rubbers can rearrange the network topology through transesterification reactions in the interphase, conferring the materials the ability to be recycled, reshaped, and welded. The relatively short chains bridging adjacent CD are highly stretched and preferentially rupture to dissipate energy under external force, resulting in remarkable improvements on the mechanical properties. Moreover, the malleable and welding properties allow the samples to access reconfigurable/multiple shape memory effects

New Design of Shape Memory Polymers Based on Natural Rubber Crosslinked via Oxa-Michael Reaction

Shape memory polymers (SMPs) based on natural rubber were fabricated by crosslinking epoxidized natural rubber with zinc diacrylate (ZDA) using the oxa-Michael reaction. These SMPs possessed excellent shape fixity and recovery. The glass transition largely accounted for the fixing of the SMPs temporary shape. Increasing the ZDA content allowed the trigger temperature (20–46 °C) and recovery time (14–33 s) of the SMPs to be continuously tuned. Nanosized silica (nanosilica) was incorporated into the neat polymers to further increase the flexibility and tune the recovery stress. The nanosilica–SMPs exhibited exceptionally high strength in a rubbery state (>20 MPa). The nanosilica–SMPs exhibited high transparency, making them suitable in visible heat-shrinkable tubes

Enabling Design of Advanced Elastomer with Bioinspired Metal–Oxygen Coordination

It poses a huge challenge to expand the application gallery of rubbers into advanced smart materials and achieve the reinforcement simultaneously. In the present work, inspired by the metal–ligand complexations of mussel byssus, ferric ion was introduced into an oxygen-abundant rubber network to create additional metal–oxygen coordination cross-links. Such complexation has been revealed to be highly efficient in enhancing the strength and toughness of the rubbers. Significantly, such complexation also enables the functionalization of the rubber into highly damping or excellent multishape memory materials. We envision that the present work offers an efficient yet facile way of creating advanced elastomers based on industrially available diene-based rubber

Sustainable Carbon Nanodots with Tunable Radical Scavenging Activity for Elastomers

The application of polymers as an essential class of material was greatly inhibited due to the aging failure of these versatile materials during normal use. Hence, it is generally recognized that stabilization against thermo-oxidative aging is indispensable to extend the service life of polymers for long-term applications. However, toxicity and pollution of the state-of-the-art antiaging technologies have long been puzzles in the polymer industry. Herein, sustainable carbon nanodots (CDs), synthesized by facile and cost-effective microwave-assisted pyrolysis, are used for first time as radical scavengers to resist the thermo-oxidative aging of elastomers. We have demonstrated that incorporation of the resultant CDs could be green and generic radical scavengers toward highly aging-resistant elastomers. Furthermore, by controlling the photoluminescent quantum yield of the CDs with various passivated agents, tunable radical scavenging activity was achieved. We established for the first time that the aging resistance originates from the prominent reactive radical scavenging activity of the CDs, which was rationally controlled by their photoluminescent quantum yield

Stronger and Faster Degradable Biobased Poly(propylene sebacate) as Shape Memory Polymer by Incorporating Boehmite Nanoplatelets

Boehmite (BM) nanoplatelets were adopted to compound with fully biobased poly­(propylene sebacate) (PPSe) to form the shape memory composites. The PPSe/BM composites kept excellent shape memory properties as previously reported PPSe. Compared to neat PPSe, the composites possess much higher mechanical properties above the melting point and faster biodegradation rate, which was demonstrated via tensile test at elevated temperature and in vitro degradation experiments in phosphate buffer saline (PBS), respectively. The obviously improved mechanical properties at elevated temperature are attributed to the uniform dispersion of the reinforcing boehmite nanoplatelets, which was facilitated by the interfacial interaction between BM and PPSe as revealed by FTIR, XPS, and XRD results. The faster degradation is correlated to accelerated hydrolysis by basic boehmite with surface aluminols. The potential biocompatibility, as substantiated by the outstanding cell viability and cell attachment, together with the realization of transformation temperature close to body temperature makes the PPSe/BM composites suitable for the biomedical applications, such as stents, in human body