Self-healing polymers based on thermally reversible Diels–Alder chemistry
ABSTRACT The development of self-healing materials has received much research attention in the last two decades. This review paper gathers recent publications on the self-healing polymeric materials with thermally reversible Diels–Alder (DA) chemistry. The DA reaction is a [4 + 2] cycloaddition involving a diene and a dienophile. The self-healing polymers employing the furan group as a diene and the maleimide group as a dienophile have been widely studied. Multifunctional furan and maleimide compounds construct thermally reversible crosslinked networks showing removability and remendability. Self-healing materials have also been utilized as healing agents for conventional thermosets like epoxy resins. Other diene–dienophile pairs, such as anthracene–maleimide and cyclopentadiene–dicyclopentadiene, have also been utilized for the development of thermally induced self-healing materials. Photo-induced self-healing polymers and some novel applications based on DA reactions have been discussed in this review. Moreover, self-healing polymer systems based on other thermally triggered and assisted reactions are also discussed. The discussed publication has provided promising molecular designs and synthetic strategies for the development of high performance self-healing polymers.
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ABSTRACT: New linear polyurethane was synthesized via a Diels-Alder (DA) reaction between a polyurethane prepolymer end-capped with furan groups (MPF) and bismaleimide (BMI). The structure of the linear polyurethane with DA bonds was characterized by 1H NMR, ATI-FTIR, TGA and AFM. The introduction of DA bonds enables the polyurethane thermal reversibility, which was studied thoroughly by 1H NMR, DSC and GPC. Besides, the new linear polyurethane with DA bonds also exhibits self-healing properties under heat treatment, which was observed by polarized optical microscope. The self-healing efficiency determined by the recovery of breaking tensile strength after being damaged and healed can reach up to 80%.RSC Advances 01/2013; 3(35):15475. DOI:10.1039/c3ra42278j
Article: Stimuli-responsive polymer films.[Show abstract] [Hide abstract]
ABSTRACT: Stimuli-responsive polymer films undergo interesting structural and property changes upon external stimuli. Their applications have extended from smart coatings to controlled drug release, smart windows, self-repair and other fields. This tutorial review summarizes non-covalent bonding, reversible reactions and responsive molecules that have played important roles in creating stimuli-responsive systems, and presents the recent development of three types of responsive polymer systems: layer-by-layer polymer multilayer films, polymer brushes, and self-repairing polymer films, with a discussion of their response mechanism. Future research efforts include comprehensive understanding of the response mechanism, producing polymer systems with controlled response properties regarding single or multiple external signals, combining polymer film fabrication with nanotechnology, improving the stability of polymer films on substrates, and evaluating the toxicity of the degradation products.Chemical Society Reviews 06/2013; DOI:10.1039/c3cs60023h
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ABSTRACT: In this work, a novel self-healing system based on the use of polybenzoxazine precursor (PBP) as a healing additive is presented. PBP (Mn = 2300 g/mol, Mw/Mn = 2.6) is facilely synthesized in a reasonable yield by Mannich type polycondensation of bisphenol A, 1,6-diaminohexane with paraformaldehyde. The additive PBP faintly undergoes a thermal ring-opening reaction when contained in polysulfone (PSU) films. Thermal treatment at 160 °C enables PBP to chemically bind to PSU chains and form networks through the Friedel?Crafts reaction, demonstrating a novel self-healing behavior. The extent of the recovery was studied using a stress?elongation (%) test and found to be 55%. Thermal properties of the polybenzoxazine precursor and the healed sample were investigated.Macromolecules 11/2013; 46(22-22):8773-8778. DOI:10.1021/ma4019153