Polylactide (PLA)-based covalent adaptable networks (CANs) that combine biodegradability with self-healing capability are promising environmentally benign materials; however, the influence of the number and type of dynamic covalent bonds on their properties remains poorly understood. In this study, PLA-based network polymers containing triple dynamic imine, disulfide, and phenol–carbamate bonds were prepared by reacting a hydroxy-terminated four-armed star-shaped PLA oligomer, a vanillin-derived bisphenol containing imine bonds and polyether segments, and bis(2-hydroxyethyl) disulfide with 1,5-pentamethylene diisocyanate. The resulting networks (HDB-411, HDB-433, and HDB-455) were compared with analogous PLA networks containing dual dynamic imine and phenol-carbamate bonds (HDH-455), a single dynamic disulfide bond (HPB-455), and no dynamic covalent bonds (HPH-455). FT-IR spectroscopy and gel fraction measurements confirmed successful network formation through urethanization. Increasing the contents of the imine-containing bisphenol and disulfide compound decreased the crosslinking density, glass transition temperature, tensile modulus, and tensile strength of the triple-dynamic networks. HPH-455 exhibited no detectable self-healing, whereas all network films containing dynamic covalent bonds exhibited self-healing after annealing at 120 °C for 3 h. Furthermore, repeated healing experiments revealed that the healing efficiency generally decreased in the order HDB-455 > HDH-455 > HPB-455. These results demonstrate the essential role of dynamic covalent bonds in enabling self-healing and indicate that the incorporation of multiple dynamic covalent bond types is beneficial for the self-healing performance of biodegradable and partially bio-based PLA-based associative CANs.
Poly(3,4-ethylenedioxythiophene) (PEDOT) is the most researched conducting polymer, yet the oxidative polymerization of its monomer EDOT in aqueous emulsion remains poorly understood. In particular, the influence of oxidant concentration on polymerization kinetics and the resulting structure–property relationship has not been quantitatively established. Here, a quantitative 1H NMR (q-NMR) protocol was developed, that enables direct time-resolved measurement of EDOT conversion during emulsion polymerization with an anionic surfactant.By coupling q-NMR with kinetic modelling, EDOT consumption is described by apparent pseudo-first-order kinetics, with the apparent rate constant increasing with FeCl3 concentration, consistent with EDOT oxidation by Fe3+ as the dominant chemical step under the investigated conditions.Structural and electronic characterization reveals that slower polymerization at lower oxidant ratios promotes less surfactant enrichment and enhanced electrical conductivity in PSS-free PEDOT. This work aims to establish a quantitative link between oxidant-controlled reaction rate, structural organization, and conductivity in PEDOT synthesized in emulsion, leading to an improved understanding and optimization for conductive PEDOT materials.
Highly efficient and controllable synthesis of ultrahigh-molecular-weight poly(α-olefin)s (UHMWPAOs) via coordination polymerization remains a formidable challenge. Herein, the fluorenylamidotitanium-catalyzed (co)polymerization of higher α-olefins was reported to exhibit unprecedented catalytic behavior. The Ti-[Ph3C][B(C6F5)4]/iBu3Al system exhibited a record high activity to produce UHMWPAOs (Mw of up to 2.65 × 106 g mol−1), and the propagation rate enhanced remarkably according to the chain length of higher α-olefins with the highest TOF (4930 min−1) achieved in 1-octadecene polymerization at 0 °C, which can be attribute to a more open η3 coordination model, the efficient separation of the active ion pair, and also the probable influence of long-chain α-olefin monomers on the coordination mode of titanium catalytic centers. Copolymerization of different α-olefins was conducted for the first time, providing atactic UHMWPAOs with longer chain lengths, lower crystallinity, and enhanced molecular chain flexibility. This work establishes a transformative paradigm for synthesizing high-performance UHMWPAOs via metallocene-titanium-mediated copolymerization, highlighting potential applications in advanced oil drag-reduction technology.
Thermally conductive composites are witnessing expanding applications in electronics, energy and aerospace sectors. However, the development of eco-friendly, durable and high-performance thermally conductive materials remains a key challenge. To address this challenge, we rationally designed and fabricated a cardanol-derived non-isocyanate polyurethane (NIPU). Boron nitride nanosheets (BNNSs) and diphenyl chlorophosphate (DCP) were incorporated into the NIPU matrix to improve its thermal conductivity and flame-retardant performance. Moreover, dynamic disulfide bonds were rationally incorporated into the system, endowing the NIPU composites with efficient and reliable self-healing capabilities. Consequently, benefiting from the continuous thermally conductive pathways established by BNNSs, the 20% NIPU-2 N sample exhibited a striking 270% enhancement in through-plane thermal conductivity at a BNNSs loading of 20 wt%, reaching a final thermal conductivity of 1 W·m−1·K−1. Additionally, the 20% NIPU-2 N achieved efficient self-healing at 100 °C within 3 h, with a tensile-strength recovery of 95.5%, and attained a V-0 flame retardancy rating. This fabrication strategy, leveraging the nano-reinforcing effect of BNNSs, offers a scalable approach that integrates green synthesis, efficient thermal management, and prolonged service life, demonstrating outstanding application potential in flexible printed circuits and wearable sensors.
It remains a challenge to design and prepare polylactic acid (PLA) composites with a well-balanced combination of flame retardancy and mechanical performance. In this work, a nanohybrid flame retardant (HNTs-P@ZIF-67) was prepared by employing an interface-engineered strategy of nanocavity confined encapsulation and surface in-situ growth. Specifically, diphenylphosphinic acid (DPPA) was encapsulated inside the halloysite nanotubes (HNTs), and zeolitic imidazolate framework (ZIF-67) was in-situ grown on the outer surface. Benefiting from the reinforced phosphorus-containing crosslinked char layer contributed by HNTs, combined with the catalytic and adsorption effects of ZIF-67, PLA composites achieved a limiting oxygen index (LOI) of 27.2% and obtained a V-0 rating in the UL-94 test at an addition of 8%. Moreover, both the peak heat release rate (pHRR) and total heat release (THR) were reduced compared to those of control PLA. Owing to a pre-stretch strategy applied to PLA, together with the strong interfacial adhesion and excellent dispersion of HNTs-P@ZIF-67 within the PLA matrix, the PLA composites exhibited higher tensile strength and elongation at break than control PLA. This work provided a reference for developing PLA materials with high fire safety and enhanced mechanical performance, laying a foundation for their future widespread application as bio-based and biodegradable materials.
Due to the exceptional nonvolatility, high ionic conductivity, wide electrochemical window, and extreme-environment adaptability, self-healing ionogels have emerged as promising soft materials for next-generation flexible electronics, advanced energy storage systems, soft robotics, and smart technologies. The self-healing mechanism relies on dynamic bonding interactions, ranging from reversible noncovalent associations to dynamic covalent chemistries. Self-healing ionogels are being tailored for practical applications, offering superior mechanical robustness, extreme-temperature tolerance, underwater adhesion and self-healing, optical transparency, antibacterial ability, and full-lifecycle recyclability. This review presents a critical and systematic analysis of the structure–property–healing relationships in self-healing ionogels, with a particular emphasis on synergistic design strategies that reconcile conflicting performance requirements. The recent progress on self-healing ionogels in their dynamic bonding mechanisms, synergistic design strategies, performance optimization, and cutting-edge applications is systematically summarized. Subsequently, the design strategies of self-healing ionogels, involving multiple dynamic bonds, covalent/noncovalent dual-network, multiphase architectures, nanofillers, microphase separation, and bioinspired sustainable motifs, are comprehensively discussed. Moreover, recent advancements in utilization of self-healing ionogels in solid-state electrolytes, flexible strain sensors, triboelectric nanogenerators, ionic thermoelectric devices, electrochromic smart windows, soft robotic actuators, gas separation membranes, and underwater communication interfaces are also elaborated upon extensively. Finally, critical challenges and future directions for ionogels are thoroughly discussed. Our analysis reveals that the future of self-healing ionogels lies in the rational integration of dynamic chemistry, bioinspired architectures, and sustainable manufacturing, rather than in isolated material improvements.
Developing novel chemically recyclable polymers that are degradable under mild conditions is essential to mitigating plastic waste and advancing sustainability. Herein, we report the preparation of poly(thioether-alt-ester)s (PTEs) via Sb2O3-catalyzed polycondensation of AB-type thioether ester monomers. These monomers were synthesized from bioderived cinnamate via thio-Michael addition with two ω-mercapto alcohols, namely mercapto ethanol and mercapto propanol, respectively. The resulting PTEs materials are non-crystalline and soluble in common organic solvents such as THF, DMF, DMSO and EA. When treated with organic base catalysts (DBU or TBD), the PTEs underwent efficient chemical degradation (100 mol% DBU) back to their constituent monomers within 0.5 h at room temperature in dilute solution. Unlike previously reported PTEs that degrade at ester site, the obtained PTEs in the present study degrade through two distinct pathways: ester alcoholysis and thioether cleavage. The recovered monomers can subsequently be repolymerized to reproduce identical PTE polymers. Remarkably, PTE-3 displays strong, durable adhesion to metal substrates, with a maximum bonding strength of 3.45 MPa. After seven repeated adhesion cycles, its adhesive strength remains as high as 3.00 MPa, demonstrating that the material is fully recyclable and reusable as an adhesive.
In the search of new molecular switches structurally related to Green Fluorescent Protein (GFP) chromophore and based on a 3-phenylbenzofulvene scaffold, we found that some of them were stable in the ordered crystalline state, but in the disordered amorphous state, PEGylated derivative ethyl (E)-6-[2-[4-(2,5,8,11,14,17,20,23,26,29-decaoxatriacontyl)-1H-1,2,3-triazol-1-yl]ethoxy]-1-(2-oxopyrrolidin-3-ylidene)-3-phenyl-1H-indene-2-carboxylate [(E)-VC1801] underwent spontaneous polymerization leading to random co-polymer materials with molecular oxygen, but containing homo-polymer sequences. Thus, NMR spectroscopy and dynamic light scattering techniques were employed to gain information about the self-assembly process of (E)-VC1801 in the relatively disordered state in which polymerization occurs, and the results highlighted the importance of the aromatic specific interaction in the aggregation process. Very interestingly, the study of the interaction of benzofulvene derivative (E)-VC1801 with light revealed that UV excitation could induce photochemical reactions in the solid state with the formation of new species showing increased emission features. The analysis of the irradiated films showed that along with the photoisomerization reaction of (E)-VC1801 into the corresponding (Z)-VC1801, also a polymerization process occurred. Intriguingly, the polymerization reaction was more efficient in the presence of atmospheric oxygen than in the sample irradiated under reduced oxygen content, and the photophysical features of the corresponding polymeric materials were significantly different. These differences in the emission features supported the existence of differences in the composition of the samples such as their content in homo-polymer sequences.
The conversion of biobased fatty acids and waste cooking oil (WCO) into chemically recyclable polyesters provides a promising strategy for designing sustainable polyethylene-like materials. We use coarse-grained modeling to elucidate how branching architecture influences crystallization and melting in polyesters composed of WCO-derived branching diols, linear diols, and diesters. We identify the effects of branching on crystallization and melting temperatures and ordering of both the backbone and the side chains during cooling. We quantify the disruption in backbone ordering due to increasing branching content and ordering of the longer side chains. We find that branching content modulates the net effect of the branch length. At lower branching content the backbone ordering dominates, yielding similar behavior for different branch lengths, while at higher branching content, polyesters with longer branches exhibit higher crystallinity and increased melting and crystallization temperatures. These results provide a predictive framework for designing sustainable polyesters with tunable crystallization behavior.
