Facile fabrication of fast recyclable and multiple self‐healing epoxy materials through diels‐alder adduct cross‐linker

A reversibly cross‐linked epoxy resin with efficient reprocessing and intrinsic self‐healing was prepared from a diamine Diels‐Alder (DA) adduct cross‐linker and a commercial epoxy oligomer. The newly synthesized diamine cross‐linker, comprising a DA adduct of furan and maleimide moieties, can cure epoxy monomer/oligomer with thermal reversibility. The reversible transition between cross‐linked state and linear architecture endows the cured epoxy with rapid recyclability and repeated healability. The reversibly cross‐linked epoxy fundamentally behaves as typical thermosets at ambient conditions yet can be fast reprocessed at elevated temperature like thermoplastics. As a potential reversible adhesive, the epoxy polymer with adhesive strength values about 3 MPa showed full recovery after repeated fracture‐thermal healing processes. The methodology explored in this contribution provides new insights in modification of conventional engineering plastics as functional materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2094–2103     

Cross‐linking induced thermoresponsive hydrogel with light emitting and self‐healing property

Development of self‐healing hydrogels with thermoresponse is very important for artificial smart materials. In this article, the self‐healing hydrogels with reversible thermoresponses were designed through across‐linking‐induced thermoresponse (CIT) mechanism. The hydrogels were prepared from ketone group containing copolymer bearing tetraphenyl ethylene (TPE) and cross‐linked by naphthalene containing acylhydrazide cross‐linker. The mechanical property, light emission, self‐healing, and thermo‐response of the hydrogels were investigated intensively. With regulation of the copolymer composition, the hydrogels showed thermoresponse with the LCST varied from above to below body temperature. At the same time, the hydrogels showed self‐healing property based on the reversible characteristic of the acylhydrazone bond. The hydrogel also showed temperature‐regulated light emission behavior based on AIE property of the TPE unit. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 869–877     

Time‐dependent morphology development in segmented polyetherurea copolymers based on aromatic diisocyanates

Time‐dependent morphology development in segmented polyureas obtained by the stoichiometric reactions between amine terminated poly(tetramethylene oxide) (PTMO) and aromatic diisocyanates were investigated. Polyureas were prepared by reacting aminopropyl terminated PTMO oligomer (M_n = 1100 g/mol) and various aromatic diisocyanates, such as 1,4‐phenylene diisocyanate (PPDI), 1,3‐phenylene diisocyanate (MPDI), diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI). Time‐dependent FTIR studies were conducted on thin films cast onto KBr discs, which were annealed at 200 °C for 10 min in an air oven. After removing from the oven, samples were placed into the FTIR spectrometer at room temperature, where time‐dependent spectra were recorded until equilibrium was reached. Time‐dependent peak reorganization in 3500–3100 cm^?1 (N? H region), 1750–1450 cm^?1 (C?O region or amide I and amide II regions), and 1180–1020 cm^?1 (C? O? C) were monitored. Depending on the chemical structure and the symmetry of the diisocyanate, major differences were observed in the time needed to reach an equilibrium morphology in these homologous poly(ether urea) copolymers. Symmetric PPDI‐based polyurea reached equilibrium in about 1 h compared with its asymmetric MPDI‐based counterpart, which needed about 150 h. Microphase development of the MPDI urea was also characterized by AFM, which gave similar results. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 471–483, 2009     

Electrically driven self‐healing polymers based on reversible guest–host complexation of β‐cyclodextrin and ferrocene

A multifunctional ferrocene‐modified poly(glycidyl methacrylate) (PGMA‐Fc) and a difunctional β‐cyclodextrin derivative (bis‐CD) has been prepared for the construction of an electrically driven removable and self‐healing polymeric materials based on the complexation reaction between ferrocene and β‐CD groups. The chemical structures of PGMA‐Fc and bis‐CD have been characterized with Fourier transform infrared, ¹H nuclear magnetic resonance, and X‐ray photoelectron spectroscopy. The effects of electrical voltages and medium conductivity on the decrosslinking efficiency of the crosslinked PGMA‐Fc/CD polymer have been examined. The PGMA‐Fc/CD network has shown removable feature and properties for application as a reworkable crosslinked material. Moreover, the crosslinked PGMA‐Fc/CD sample has shown electrically driven self‐healing behavior. The self‐healing performance could be enhanced with wetting the sample to increase the electrical conductivity. As a result, the material could serve as a self‐healing agent for commercial painting products. Preparation and application of a novel and efficient self‐healing polymer have been demonstrated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3395–3403     

Synthesis of novel moisture‐curable polyurethanes end‐capped with trialkoxysilane and their application to one‐component adhesives

Novel silane endcappers and novel polyurethanes end‐capped with trimethoxysilane (silylated polyurethanes) were developed as water‐curable materials in which the curing reaction occurred under humid conditions in the presence of dioctyltin diversatate as a curing catalyst. A variety of amine‐terminated trimethoxysilane compounds were synthesized by the Michael addition reaction of commercially available 3‐aminopropyltrimethoxysilane with acrylates, and the resulting silane endcappers were used to react with isocyanate‐terminated polyurethanes, providing the silylated polyurethanes. The moisture‐curable silylated polyurethanes were used for the preparation of novel one‐component and solvent‐free adhesives. The evaluated properties were the curing speed, the tensile shear bond strength, and the adherence to some substrates. The longer alkyl chains of the silane endcappers derived from various acrylates led to a slower curing speed, lower tensile strength at break, and longer elongation at break of the silylated polyurethanes. The tensile shear bond strength of the silylated polyurethane‐based adhesive decreased with decreasing the trimethoxysilane end‐capping ratio, whereas an increase in the adherence was observed. The adherence to the acrylic substrate was improved by changes in the main‐chain structure of the polyurethane based on the composition of poly(propylene oxide) and poly(ethylene oxide). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2689–2704, 2007     

Dual Sulfide–Disulfide Crosslinked Networks with Rapid and Room Temperature Self‐Healability

Polymer‐based crosslinked networks with intrinsic self‐repairing ability have emerged due to their built‐in ability to repair physical damages. Here, novel dual sulfide–disulfide crosslinked networks (s‐ssPxNs) are reported exhibiting rapid and room temperature self‐healability within seconds to minutes, with no extra healing agents and no change under any environmental conditions. The method to synthesize these self‐healable networks utilizes a combination of well‐known crosslinking chemistry: photoinduced thiol‐ene click‐type radical addition, generating lightly sulfide‐crosslinked polysulfide‐based networks with excess thiols, and their oxidation, creating dynamic disulfide crosslinkages to yield the dual s‐ssPxNs. The resulting s‐ssPxN networks show rapid self‐healing within 30 s to 30 min at room temperature, as well as self‐healing elasticity with reversible viscoelastic properties. These results, combined with tunable self‐healing kinetics, demonstrate the versatility of the method as a new means to synthesize smart multifunctional polymeric materials.

     

Synthesis of well‐defined glycidyl methacrylate based block copolymers with self‐activation and self‐initiation behaviors via ambient temperature atom transfer radical polymerization

Well‐defined glycidyl methacrylate (GMA) based di‐ and triblock copolymers, with self‐activation and self‐initiation behaviors by incorporation of 2‐(diethylamino) ethyl methacrylate (DEA) blocks, were synthesized via ambient temperature atom transfer radical polymerization (ATRP). The stability of the GMA pendant oxirane rings in tertiary amine environments at ambient temperature was investigated. More importantly, both self‐activation behavior in oxirane ring opening addition reaction and self‐initiation behavior in post‐cure oxirane ring opening crosslinking of these block copolymers were evidenced by ¹H NMR studies. The results demonstrated that the reactivity of pendent oxirane rings was strongly dependant on the nucleophilicity and steric hindrance of tertiary amine moieties and temperature. This facilitated the synthesis of well‐defined block copolymers of GMA and DEA via sequential monomer addition ATRP, particularly for polymerization of GMA monomer at ambient temperature. Moreover, these one‐component GMA based block polymers have novel self‐activation and self‐initiation properties, rendering some potential applications in both enzyme immobilization and GMA‐based thermosetting materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2947–2958, 2007     

Synthesis of high‐molecular‐weight aliphatic–aromatic copolyesters from poly(ethylene‐co‐1,6‐hexene terephthalate) and poly(L‐lactic acid) by chain extension

A series of aliphatic–aromatic multiblock copolyesters consisting of poly(ethylene‐co‐1,6‐hexene terephthalate) (PEHT) and poly(L ‐lactic acid) (PLLA) were synthesized successfully by chain‐extension reaction of dihydroxyl terminated PEHT‐OH prepolymer and dihydroxyl terminated PLLA‐OH prepolymer using toluene‐2,4‐diisoyanate as a chain extender. PEHT‐OH prepolymers were prepared by two step reactions using dimethyl terephthalate, ethylene glycol, and 1,6‐hexanediol as raw materials. PLLA‐OH prepolymers were prepared by direct polycondensation of L ‐lactic acid in the presence of 1,4‐butanediol. The chemical structures, the molecular weights and the thermal properties of PEHT‐OH, PLLA‐OH prepolymers, and PEHT‐PLLA copolymers were characterized by FTIR, ¹H NMR, GPC, TG, and DSC. This synthetic method has been proved to be very efficient for the synthesis of high‐molecular‐weight copolyesters (say, higher than M_w = 3 × 10⁵ g/mol). Only one glass transition temperature was found in the DSC curves of PEHT‐PLLA copolymers, indicating that the PLLA and PEHT segments had good miscibility. TG curves showed that all the copolyesters had good thermal stabilities. The resulting novel aromatic–aliphatic copolyesters are expected to find a potential application in the area of biodegradable polymer materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5898–5907, 2009     

Coordination Bonds and Diels–Alder Bonds Dual Crosslinked Polymer Networks of Self‐healing Polyurethane

A dual crosslinked self‐healing polyurethane was prepared with robust mechanical properties through the dynamic reversible pyridine‐Fe³⁺ coordination bonds and Diels–Alder (DA) covalent bonds dual crosslinking strategy. Moreover, the mechanical properties and self‐healing ability of polyurethane can be tuned readily by different ratio of the coordination bonds and DA bonds. Under external load, the coordination bonds serve as sacrificial bonds are broken to dissipate energy, the DA bonds can keep the shape of sample. With the coordination bonds participation, the damaged samples can be healed under moderate heating treatment or with the aid of FeCl₃ solution. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2228–2234     

Imine‐based dynamic polymer networks as photoprogrammable amine sensing devices

Here, we describe a “smart” polymeric material, which is able to readily detect and discriminate amine vapors. The dynamic imine‐based network can be conveniently prepared by mixing a commercially available, amino‐functionalized polysiloxane with small amounts of a diarylethene dialdehyde. The photoswitchable crosslinker allows for reversible imprinting of custom‐designed patterns on the polymer surface with (sun)light and thus enables noninvasive information storage in the material, which before, during, and after amine exposure can readily be decoded with commonly used smartphone apps. This feature along with the self‐healing nature of the dynamic polymer, an easy recycling and manufacturing procedure, and the overall low cost and toxicity render this material advantageous to develop low‐cost and practical amine sensing devices for the broad public. © 2019 The Authors. Journal of Polymer Science Part A: Polymer Chemistry published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2378–2382     

Effects of external donors and hydrogen concentration on oligomer formation and chain end distribution in propylene polymerization with Ziegler‐Natta catalysts

The effect of type and concentration of external donor and hydrogen concentration on oligomer formation and chain end distribution were studied. Bulk polymerization of propylene was carried out with two different Ziegler‐Natta catalysts at 70 °C, one a novel self‐supported catalyst (A) and the other a conventional MgCl₂‐supported catalyst (B) with triethyl aluminum as cocatalyst. The external donors used were dicyclopentyl dimethoxy silane (DCP) and cyclohexylmethyl dimethoxy silane (CHM). The oligomer amount was shown to be strongly dependent on the molecular weight of the polymer. Catalyst A gave approximately 50 % lower oligomer content than catalyst B due to narrower molecular weight distribution in case of catalyst A. More n‐Bu‐terminated chain ends were found for catalyst A indicating more frequent 2,1 insertions. Catalyst A also gave more vinylidene‐terminated oligomers, suggesting that chain transfer to monomer, responsible for the vinylidene chain ends, was a more important chain termination mechanism for this catalyst, especially at low hydrogen concentration. Low site selectivity, due to low external donor concentration or use of a weak external donor (CHM), was also found to increase formation of vinylidene‐terminated oligomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 351–358, 2010     

Synthesis,self‐assembly and reversible healing of supramolecular perfluoropolyethers

The synthesis and thermomechanical properties of a novel class of self‐healing perfluoropolyethers (PFPEs) is reported. By decoration of 2‐ureido‐4[1H]‐pyrimidone end groups on the termini of low molar mass PFPE, the formation of supramolecular polymers and networks held together via hydrogen bonding associations was achieved. These novel supramolecular polymer materials exhibit a combination of enhanced modulus and elasticity, along with self‐healing properties, where rapid self‐healing time was demonstrated using dynamic rheological measurements. These types of supramolecular PFPEs are anticipated to be useful for a number of emerging areas in lubrication. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3598–3606     

Synthesis of phenanthroline‐terminated polymers and their Fe(II)‐complexes

Well‐defined mono‐ and bifunctional, phenanthroline‐terminated poly(ethylene glycol) and polyisobutylene capable of polymer network formation were synthesized. The starting materials mono‐ and bi‐phenanthroline‐ (phen) terminated poly(ethylene glycols) (mPEG‐phen, phen‐PEG‐phen) and polyisobutylenes (PIB‐phen, phen‐PIB‐phen) were prepared by the Williamson synthesis and characterized by means of ¹H NMR and MALDI‐TOF mass spectrometry. According to UV–Vis spectrophotometry and ESI‐TOF mass spectrometry, the phenanthroline‐terminated polymers underwent quantitative complex formation with ferrous ions in solution. The aqueous solution of mPEG‐phen shows self‐assembly behavior. Important parameters, such as critical micelle concentration and hydrodynamic radius of the aggregates were also determined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2709–2715, 2010     

Evaluation of peroxide initiators for radical polymerization‐based self‐healing applications

The suitability of various peroxide initiators for a radical polymerization‐based self‐healing system is evaluated. The initiators are compared using previously established criteria in the design of ring opening metathesis polymerization‐based self‐healing systems. Benzoyl peroxide (BPO) emerges as the best performing initiator across the range of evaluation criteria. Epoxy vinyl ester resin samples prepared with microcapsules containing BPO exhibited upwards of 80% healing efficiency in preliminary tests in which a mixture of acrylic monomers and tertiary amine activator was injected into the crack plane of the sample after the initial fracture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2698–2708, 2010     

Temperature‐induced self‐assembly and metal‐ion stabilization of histidine functional block copolymers

Histidine functional block copolymers are thermally self‐assembled into polymer micelles with poly‐N‐isopropylacrylamide in the core and the histidine functionality in the corona. The thermally induced self‐assemblies are reversible until treated with Cu²⁺ ions at 50 °C. Upon treatment with 0.5 equivalents of Cu²⁺ relative to the histidine moieties, metal‐ion coordination locks the self‐assemblies. The self‐assembly behavior of histidine functional block copolymers is explored at different values of pH using DLS and ¹H NMR. Metal‐ion coordination locking of the histidine functional micelles is also explored at different pH values, with stable micelles forming at pH 9, observed by DLS and imaged by atomic force microscopy. The thermal self‐assembly of glycine functional block copolymers at pH 5, 7, and 9 is similar to the histidine functional materials; however, the self‐assemblies do not become stable after the addition of Cu²⁺, indicating that the imidazole plays a crucial role in metal‐ion coordination that locks the micelles. The reversibility of the histidine‐copper complex locking mechanism is demonstrated by the addition of acid to protonate the imidazole and destabilize the polymer self‐assemblies. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1964–1973     

Theoretical consideration and modeling of self‐healing polymers

Bioinspired self‐healing polymers have attracted more and more interests. Imparting self‐healing ability to existing polymers or developing new polymeric materials capable of self‐healing is considered to be a solution for improving their long term stability and durability. This article reviews achievements in the field of theoretical researches on re‐establishment of bonding between broken surfaces of self‐healing polymers from microscopic and macroscopic point of view. Chains interaction, mechanical models related to healing procedures and effect of healing, design of novel self‐healing composite systems, and so forth are summarized and analyzed in detail. Both thermoplastics and thermosets are included to offer a comprehensive knowledge framework of the smart function. The scientific challenges are also highlighted, which are related to the production of more advanced self‐healing polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Multiblock Copolymer‐Based Dual Dynamic Disulfide and Supramolecular Crosslinked Self‐Healing Networks

A new multiblock copolymer self‐healing strategy is reported that centers on the synthesis of block copolymers designed with different self‐healing motifs incorporated into individual blocks. As a proof of concept, a novel pentablock copolymer (ABCBA) consisting of a poly(ethylene glycol) middle block and self‐healable symmetric blocks of a polymethacrylate with pendant disulfide linkages and carboxylic acids is synthesized by a combination of consecutive controlled radical polymerization with hydrolytic cleavage. Disulfide exchange reactions of pendant disulfide linkages and metal–ligand interactions of pendant carboxylic acids with ferric ions allow for the formation of dual crosslinked networks with dynamic disulfide and supramolecular crosslinkages. The resultant networks possessing self‐healing viscoelasticity enable self‐healing on macroscale damages through supramolecular metal–ligand interactions and disulfide exchange reactions at room or moderate temperatures. These preliminary results suggest that the strategy can offer the versatility in the development of multifunctional self‐healable materials in dual or multiple self‐healable mechanisms.

     

Synthesis and healing properties of poly(arylene ether sulfone)‐poly(alkyl disulfide) multiblock copolymers

A multiblock copolymer consisting of hard (poly(arylene ether sulfone)) and soft (poly(alkyl disulfide)) segments was successfully synthesized by oxidative coupling of the corresponding thiol‐terminated oligomers. Its structure was confirmed by ¹H and ¹³C NMR spectroscopy. The GPC data (M_w = 82,000, M_w/M_n = 2.7) and inherent viscosity (0.67 dL g⁻¹) indicated the formation of a high‐molecular‐weight multiblock copolymer, while AFM and DSC indicated a microphase‐separated morphology. Tensile testing of the multiblock copolymer films showed a large elongation at break, which is characteristic of microphase‐separated hard/soft multiblock copolymers. Over 90% of the elongation at break of damaged samples (notched or cut) was recovered by UV irradiation. The elongation recovery was proportional to the UV irradiation energy, and the high recovery was achieved by relatively weak irradiation (<170 J cm⁻²). The high content of disulfide bonds in the multiblock copolymer resulted in a lower self‐healing energy. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1358–1365     

Supramacromolecular self‐assembly: Chain extension,star and block polymers via pseudorotaxane formation from well‐defined end‐functionalized polymers

Dibenzo‐24‐crown‐8‐terminated polystyrene ( 5 ) was chain extended to “dimeric” 8 by pseudorotaxane formation with a ditopic guest, α,ω‐bis[p‐(N‐benzylammoniomethyl)phenoxy]heptane bis(hexafluorophosphate) ( 7 ). The three‐armed star polymer 11 was similarly formed by complexation of the dibenzo‐24‐crown‐8‐terminated polystyrene ( 5 ) with a tritopic secondary ammonium salt, 1,3,5‐tris[p‐(benzylammoniomethyl)phenyl]benzene tris(hexafluorophosphate) ( 10 ). Another three‐armed star polymer 13 was self‐assembled from dibenzo‐24‐crown‐8‐terminated polystyrene ( 5 ) and a tetratopic paraquat compound, 1,2,4,5‐tetrakis{p‐N‐[(N′‐methyl‐4,4′‐bipyridinium)methylphenyl]}benzene octakis(hexafluorophosphate) ( 12 ). The above chain extension and star polymer formation processes seemed to be cooperative; that is, the second and third complexation steps proceed with stepwise higher efficiencies than statistically expected. Dibenzo‐24‐crown‐8‐terminated polystyrene ( 5 ) was chain extended with secondary ammonium terminated polystyrene 14 , forming 16 , and also self‐assembled with a secondary ammonium ion terminated polyisoprene 15 to form supramolecular block copolymer 17 . These processes were examined by NMR, mass spectrometry and viscometery. Thus, although binding in these systems is not particularly strong (association constants <10⁴ M^?1), these examples provide proof‐of‐principle that pseudorotaxane formation is a viable concept for chain extension and self‐assembly of novel types of block copolymers and star polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3518–3543, 2009     

Exploring novel poly(thiophene‐3‐yl‐amine) through facile self acid assisted‐polycondensation

Aromatic moieties of benzene and pyridine as side chains for poly(thiophene‐3‐yl‐amine) are rationally designed and synthesized by facile self acid‐assisted polycondensation (SAAP). Nitrogen atom is the key atom to form ammonium cation which guarantees SAAP success while other aromatic moieties are chosen carefully to attach on N atom to functionalize poly(thiophene‐3‐yl‐amine) matrix. Our results indicate that thiophene‐3‐yl‐amine is an excellent platform to construct plenty of functionalized monomers candidates for SAAP. Our study would push SAAP or AAP scope forward and pave the way to explore much more polythiophene derivatives. Furthermore, DFT calculation is carried out to deep understand AAP mechanism. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 4003–4012