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Self-healing polymers (SHP), inspired by nature, are materials that have the ability to recover themselves from various physical damages in the presence of different inducing environments. The self-recovering property indicates the capability to heal the cracks in their very nascent stage at their micro or nano-level size and provides a door to prevent them from any major catastrophic failure. In this article, a comprehensive review with updated reported work on various types of self-healing mechanisms and their advantages and limitations has been discussed, along with their applications. The main focus of the review has been aligned with the challenges and future scopes associated with the exploration of self-healing concepts for industrial coating applications. The different extrinsic, intrinsic, and combined healing mechanisms have been explained, along with their application in coating. Finally, the recent status of healing technology and future research trends has been discussed in this review article. [ABSTRACT FROM AUTHOR]

Statistical copolymers of norbornene (NBE) with cyclopentene (CP) were prepared by ring-opening metathesis polymerization, employing the 1st-generation Grubbs’ catalyst, in the presence or absence of triphenylphosphine, PPh3. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT, which evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data by integrating a given copolymerization equation in its differential form. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Finally, the effect of triphenylphosphine on the kinetics of copolymerization, the reactivity ratios, and the kinetics of thermal decomposition were examined.

Reaction of commercial ruthenium complexes M31 and M20 with 2-nitrostyrene gave a new nitroso-chelated cyclic η 1 -acyl ruthenium(II) complexes Ru-4 and Ru-6 respectively instead of expected Hoveyda-Grubbs type (pre)catalyst Ru-3 . New complexes were characterized by means of standard analytical techniques and their crystallographic structure has been confirmed by X-ray structural analysis. It was found that Ru-4 and Ru-6 do not exhibit any activity in standard metathesis reactions. However, a dramatic increase of activity was observed upon treatment with (trimethylsilyl)diazomethane, allowed for the successful application of Ru-4 in ROMP of endo, exo -bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid dimethyl ester. Moreover, such complexes can be effective catalysts of transfer hydrogenation of ketones as well as cycloisomerization reactions. [ABSTRACT FROM AUTHOR]

A series of crosslinked poly(norbornene-dicarboximide)s have been prepared by ring opening metathesis polymerization. Increasing quantities of a bifunctional norbornene-dicarboximide crosslinker was doped into a high T g cyclohexyl-substituted norbornene-dicarboximide monomer before polymerization. The wt% of the crosslinker was increased from 0.00 to 4.40 wt%, after which the polymers became gelated. Polymer molecular weights increased drastically from 23,500 to 2,135,000 g/mol, the polydispersities increased from 1.18 to 73.47 and the viscosities increased from 5.27 to 538.7 mPa·s as the wt% of the crosslinker was increased. The trans : cis vinylene ratio remained constant at 1:0.18 as well as the T g and T d with average values of 210 °C and 392 °C being measured. Five of the crosslinked polymers and the reference homopolymer were utilized as hosts for the high activity tert -butyldiphenylsilyl substituted FTC chromophore guest. The polymer host containing 1.96 wt% crosslinker was found to have a maximum r 33 of 78 pm/V when polled at 150 °C with an electric field strength of 100 V/μm. The r 33 increased linearly from 63 to 78 pm/V as the wt% of the crosslinker was increased from 0.00 to 1.96 wt%. The thermal and temporal stability was found to increase slightly with the 0.00 wt% polymer exhibiting a stability of 77%, while the 1.96 wt% polymer exhibited a stability of 79% when both were heated to 85 °C and aged for 500 h in air. [ABSTRACT FROM AUTHOR]

A latent Ru olefin metathesis catalyst bearing a chelating ligand with an azoxybenzene fragment was obtained and characterized. The complex was inactive in the ring closing metathesis (RCM) reaction of a standard test diene: diethyl diallylmalonate at room temperature but can be subsequently activated by elevated temperature (up to 100 °C). The lack of activity of this azoxy catalyst in RCM of dienes containing terminal C-C double bonds at room temperature and high activity in ring opening metathesis polymerization (ROMP) of bicyclo [2.2.1]hept-2-ene (norbornene, NBE) permitted the ROMP of the challenging monomer: 5-vinyl-2-norbornene yielding soluble polymers with cyclopentenylenevinylene chains with vinyl pendant groups. [ABSTRACT FROM AUTHOR]

A side chain EO copolymer series has been synthesized by ROMP using the Grubbs 3rd generation initiator and quenched with ethyl vinyl ether. The copolymers were prepared by combining two norbornene-dicarboximide monomers, one with a cyclohexyl substituent and another substituted with an FTC chromophore. The mol% of the chromophore-substituted monomer was varied from 0.00 mol% to 22.92 mol%, all polymers were obtained in a yield of between 83 and 92% and a purity of between 97 and 98%. The cis : trans vinylene ratio remained constant at 1:1, confirming the polymers were amorphous. Peak molecular weights increased from 29,541 g/mol to 142,113 g/mol and the PDI increased from 1.36 to 4.01 respectively. Glass transition and thermal decomposition temperatures decreased from 206 °C to 168 °C and 433 °C to 382 °C as the mol% of the chromophore-substituted monomer was increased. UV–vis absorbance spectroscopy was used to quantify the chromophore content. A close correlation (68–95%) between the measured and calculated absorbance was found. The polymer containing 22.92 mol% of the chromophore-substituted monomer had a maximum r 33 of 70 pm/V when polled at an optimum field of 60 V/μm at a polling temperature of 200 °C. This equates to a high polling efficiency of 1.16. High current flow in this polymer film at elevated field strength caused a breakdown of the electrode, preventing access to an elevated electro-optic coefficient. This polymer was found to have an excellent stability of 76% when aged at 85 °C for 1000 h in air. [ABSTRACT FROM AUTHOR]

Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. Subsequent ring opening metathesis polymerization (ROMP) of the macromonomers using ruthenium catalysts (Grubbs catalysts of the 1st, 2nd and 3rd generations) afforded the corresponding polymacromonomers. The effects of the macromonomer molecular weight, the type of the catalyst, the nature of the solvent, the monomer concentration and the polymerization temperature on the molecular characteristics of the branched polymers were examined in detail. The crystallization behavior of the macromonomers and the corresponding polymacromonomers were studied by Differential Scanning Calorimetry (DSC). The thermal stability and the kinetics of the thermal decomposition of the samples were also studied by Thermogravimetric Analysis (TGA). The activation energies of the thermal decomposition were analyzed using the Ozawa-Flynn-Wall and Kissinger methodologies. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of synthetic polymer aerogels based on dendritic-type urethane-norbornene monomers. The core of those monomers is based either on an aromatic/rigid (TIPM/Desmodur RE), or an aliphatic/flexible (Desmodur N3300) triisocyanate. The terminal norbornene groups (three at the tip of each of the three branches) were polymerized via ROMP using the inexpensive 1st generation Grubbs catalyst. The polymerization/gelation conditions were optimized by varying the amount of the catalyst. The resulting wet-gels were dried either from pentane under ambient pressure at 50 °C, or from t-butanol via freeze-drying, or by using supercritical fluid (SCF) CO2. Monomers were characterized with high resolution mass spectrometry (HRMS), 1H- and solid-state 13C-NMR. Aerogels were characterized with ATR-FTIR and solid-state 13C-NMR. The porous network was probed with N2-sorption and SEM. The thermal stability of monomers and aerogels was studied with TGA, which also provides evidence for the number of norbornene groups that reacted via ROMP. At low densities ( 90%), mostly macroporous materials; aerogels based on the aliphatic/flexible core were fragile, whereas aerogels containing the aromatic/rigid core were plastic, and at even lower densities (0.03 g cm−3) foamy. At higher densities (0.2–0.7 g cm−3) all materials were stiff, strong, and hard. At low monomer concentrations all aerogels consisted of discrete primary particles that formed spherical secondary aggregates. At higher monomer concentrations the structure consisted of fused particles with the size of the previous secondary aggregates, due to the low solubility of the developing polymer, which phase-separated and formed a primary particle network. Same-size fused aggregates were observed for both aliphatic and aromatic triisocyanate-derived aerogels, leading to the conclusion that it is not the aliphatic or aromatic core that determines phase separation, but rather the solubility of the polymeric backbone (polynorbornene) that is in both cases the same. The material properties were compared to those of analogous aerogels bearing only one norbornene moiety at the tip of each branch deriving from the same cores.

The accomplishments in the copolymerization of ethylene with cyclic olefins such as norborn-2-ene or cis-cyclooctene via tandem ring-opening metathesis polymerization (ROMP) - vinyl insertion polymerization (VIP) are outlined. This approach provides polyolefins with high molecular weight (600,000 < Mn < 4,500,000 g mol−1) and substantial amounts of double bonds along the polymer main chain. Olefinic moieties in ROMP-derived polymers can be converted into hydroxyl, amino, silyl, ester, or carboxylate groups by different means including controlled radical polymerization-based grafting. The underlying concept for the switch in polymerization mechanism, the resulting pre-catalyst requirements, limitations and challenges and the chemistry developed for functionalizing unsaturated polymers are outlined in detail. [ABSTRACT FROM AUTHOR]

Statistical copolymers of norbornene (NBE) with cyclopentene (CP) were prepared by ring-opening metathesis polymerization, employing the 1st-generation Grubbs' catalyst, in the presence or absence of triphenylphosphine, PPh3. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT, which evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data by integrating a given copolymerization equation in its differential form. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Finally, the effect of triphenylphosphine on the kinetics of copolymerization, the reactivity ratios, and the kinetics of thermal decomposition were examined. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have reviewed N-donor heterocycles as sensitizers of lanthanide ion emission. [•] Terpyridine-based sensitizers are among the most studied and the published work deals increasingly with applications in bioimaging and sensing. [•] Work published with other N-donor ligands still involves mostly exploratory structure-property research. [Copyright &y& Elsevier]

In this article we present a review of our recent results in one area of research we are involved in. All research efforts in our group focus on functional polymers and new ways of gaining higher levels of control with regard to the placement of functional groups within these polymers. Here, the living ring opening metathesis polymerization (ROMP) will be reviewed for which end-functionalization methods had been rare until very recently. Polymers carrying particular functional groups only at the chain-ends are, however, very interesting for a variety of industrial and academic applications. Polymeric surfactants and polymer–protein conjugates are two examples for the former and polymer-?-sheet-peptide conjugates one example for the latter. The functionalization of macroscopic or nanoscopic surfaces often relies on mono-end functional polymers. Complex macromolecular architectures are often constructed from macromolecules carrying exactly one functional group at their chain- end. The ring opening metathesis polymerization is particularly interesting in this context as it is one of the most functional group tolerant polymerization methods known. Additionally, high molecular weight polymers are readily accessible with this technique, a feature that living radical polymerizations often struggle to achieve. Finding new ways of functionalizing the polymer chain-end of ROMP polymers has therefore been a task long overdue. Here, we present our contribution to this area of research.

Nanocomposite polyHIPE foams with open-cellular morphology were obtained using nanoparticles (γFe2O3/Fe3O4), surfactant (Pluronic L121) or nanoparticle/surfactant stabilized dicyclopentadiene high internal phase emulsions (DCPD HIPEs). Upon curing, cavity sizes were found to vary drastically between 950 ± 360 μm down to 7 ±3 μm depending on the HIPE formulations. As-obtained nanocomposite polyHIPE foams were functionalized using elemental bromine in THF. Upon bromination the nanoparticles are moved from the cavities surfaces into the bulk phase of the polymer scaffold, which affects the inductive-heating capability of the magnetic nanocomposite foams decreasing it by the factor of 2. [ABSTRACT FROM AUTHOR]

Copolymerization represents a modular synthetic strategy toward optochemical sensors by disassembling small molecule probes and recombining them to screen various fluorophore-quencher combinations, instead of synthesizing individual sensor molecules. To demonstrate this, a polymerizable, fluorescent 1,6,7,12-tetrachloroperylene-3,4:9,10-bis(dicarboximide) derivative with a norbornene ester side chain is prepared and copolymerized with a tertiary-amine-bearing monomer, as well as an oligo-glycol-bearing monomer, via ring-opening metathesis polymerization (ROMP). In this manner, water-soluble optical pH sensor polymers (with apparent p ka values of 6.4-7) are obtained. The effect of the macromolecular architecture on the sensing performance is evaluated, whereby a diblock copolymer structure made of an oligoglycol segment and a segment containing the secondary amine and the fluorescent moiety is identified as being most favorable for pH sensing. Similarly, profluorescent polymers are obtained by employing nitroxides instead of secondary amines, which allows detection of ascorbic acid (with a detection limit of 0.1 × 10−3 m) in water. [ABSTRACT FROM AUTHOR]

Abstract: Porous polymers with well-defined porosities and high specific surface areas in the form of monoliths, films, and beads are being used in a wide range of applications (reaction supports, separation membranes, tissue engineering scaffolds, controlled release matrices, responsive and smart materials) and are being used as templates for porous ceramics and porous carbons. The surge in the research and development of porous polymer systems is a rather recent phenomenon. PolyHIPEs are porous emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). HIPEs are highly viscous, paste-like emulsions in which the major, “internal” phase, usually defined as constituting more than 74% of the volume, is dispersed within the continuous, minor, “external” phase. This review focuses upon the recent advances in polyHIPEs involving innovations in polymer chemistry, macromolecular structure, multiphase architecture, surface functionalization, and nanoparticle stabilization. The effects of these innovations upon the natures of the resulting polyHIPE-based materials (including bicontinuous polymers, nanocomposites, hybrids, porous ceramics, and porous carbons) and upon the applications involving polyHIPEs are discussed. The advances in polyHIPEs described in this review are now being used to generate new families of porous materials with novel porous architectures and unique properties. [Copyright &y& Elsevier]

Highlights: [•] The main backbone is produced using ROMP of various oxanorbornene monomers. [•] The PMMA, PEG and PCL are grafted to the main backbone via quadruple click reactions. [•] The click reactions are thiol-ene, Diels–Alder, CuAAC and NRC. [Copyright &y& Elsevier]

PolyHIPE materials have been prepared by Ring Opening Metathesis Polymerisation (ROMP) of dicyclopentadiene. Two characteristic features for successful stabilization of high internal phase emulsions (HIPEs) were tuned in order to achieve improvements regarding mechanical properties of polyHIPEs. Mechanical properties of the new materials were related to variations of the surfactant concentration and the volume ratio of the internal phase in HIPEs. Values for Young's moduli were about a hundred times higher than in standard polyHIPE materials with the same level of porosity, which represents a major improvement for highly porous cellular polymeric materials. Moreover, fully interconnected macroporous morphology was found for polyHIPEs, where respective HIPEs were stabilized with only 0.25 v% of surfactant. [ABSTRACT FROM AUTHOR]

In this study, an equimolar mixture of oxanorbornenyl-anthracene (ONB-anthracene), oxanorbornenyl-bromide (ONB-Br), and oxanorbornenyl tosylate (ONB-OTs) was polymerized via ring opening metathesis polymerization using the first generation Grubbs' catalyst in CH2Cl2 at room temperature to form poly(ONB-anthracene- co-ONB-Br- co-ONB-OTs)10 copolymer as a main backbone. Next, this main backbone was sequentially clicked with a furan protected maleimide-terminated poly(methyl methacrylate), 2,2,6,6-tetramethyl-1-piperidinyloxy-terminated poly(ethylene glycol), and alkyne-terminated poly(ε-caprolactone) (PCL20-alkyne) via Diels-Alder, nitroxide radical coupling, and copper-catalyzed azide-alkyne cycloaddition, respectively, to yield a poly(ONB- g-PMMA- co-ONB- g-PEG- co-ONB- g-PCL)10 heterograft brush copolymer © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

A new ligand, methyl 2,3,5,6-tetrafluoro-4-oxybenzoate (C8H3F4O3), combining an electron withdrawing group (C6F4) to tune the reactivity with an anchor group (CO2Me) for immobilization on supports, was used to prepare four new ruthenium initiators, viz. Ru(C8H3F4O3)2(=CHPh)(3-Br–C5H5N)(H2IMes) and Ru(C8H3F4O3)2XL, where X = C,N-(=CHCH2CH2-2-C5H4N) and L = PiPr3, PCy3 or H2IMes. The new ligand greatly reduced the reactivity of the ruthenium centre at room temperature. The 1H NMR and DSC investigation for the ROMP of norbornene dicarboximide monomers clearly demonstrated that the Ru(C8H3F4O3)2XL initiators were inactive at room temperature and required elevated temperatures for their activation. [ABSTRACT FROM AUTHOR]

Abstract: This article features the current state of research in olefin metathesis polymerization techniques towards the synthesis of functional polymeric materials. Emphasis is laid on work making use of ring opening metathesis polymerization (ROMP) initiated by ruthenium complexes published in the last five years. Other techniques such as alternating diene metathesis polymerization (ALTMET) are only covered when appropriate. A survey on polymer architectures accessible via olefin metathesis is presented and illustrated with manifold examples from research fields like life science, optics and electronics, sensorics or energy storage. Important new developments such as end-group functionalization or stereoselective polymerization are addressed. A chapter on using alternative and green solvents in ROMP is disclosed as well as an overview on the use of olefin metathesis polymerization using sustainable substrates. Applications in material science such as porous, liquid crystal or self-healing materials close the work. [Copyright &y& Elsevier]

Abstract: Two norbornene derivatives bearing phenantroimidazole dyes, namely endo/exo-11-(4-(1H-phenanthro[9,10-d]imidazol-2-yl)phenoxy) undecylbicyclo[2.2.1] hept-5-ene-2-carboxylat (5) and 11-(4-(1-Methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenoxy) undecylbicyclo[2.2.1]hept-5-ene-2-carboxylate (6) were synthesized. 5 and 6 were used to prepare statistical copolymers with endo,exo-bicyclo[2.2.1.]hept-2-ene-5,6-dicarboxylic acid dimethylester (7) via ring opening metathesis polymerization. The photophysical properties of the monomers and polymers and to what extent polymerization and substitution patterns influence the photophysical properties were investigated. Furthermore, the optical response upon addition of acid was investigated. The emission of monomer 5 shows a small bathochromic shift of 13nm upon protonation while the emission of the resultant polymer poly5/7 exhibits a large red shift of 62nm. In contrast, the according methylated monomer 6 and the resulting polymer poly6/7 gave similar absorption and emission characteristics. The differences were attributed to an increased tendency of the non-methylated dyes to interact when brought in close proximity in the polymer. [Copyright &y& Elsevier]

Abstract: Until now niobium compounds have been very rarely applied for the polymerization of olefins, notwithstanding their moderate cost, limited toxicity and the large availability of stable oxidation states, which makes them versatile precursors. The data reported to date on ethylene and norbornene polymerization catalysts are discussed, with particular reference to the evolution of the approach to the design of these systems, starting from isoelectronic, isolobal or isostructural relationships with Group 4 metallocene catalysts. The catalytic performances in ethylene and norbornene polymerization of the niobium precursors with cyclopentadienyl, diene, amido, amidinate, pyrazolylborate ligands have been compared. The most recent results have been discussed, comparing the reported activities for complexes with phenolate, bis(imino)pyridine and N,N-dialkylcarbamate ligands. Significant improvements in norbornene ROMP have been recently achieved, whilst for ethylene polymerization the process of optimization of the niobium-based catalytic systems still needs hard work. [Copyright &y& Elsevier]

The use of electro-induced Mo and W-based catalysts has been investigated in the ring opening metathesis polymerization (ROMP) of 1,3,5,7-cyclooctatetraene (COT). The soluble and conjugated polyacetylene (PA) was obtained under ambient temperature and pressure without employing any secondary reagent (comonomer, chain transfer agent) or substituted monomer (R-COT). NMR analysis results show that the electrochemical Mo-based system leads to a completely (100%) trans product, however, mainly (80%) trans polymer was obtained with W-based analogue for PA. [ABSTRACT FROM AUTHOR]

Abstract: A set of poly(norbornenes) was prepared using ring opening metathesis polymerization (ROMP) and used as matrix material for the preparation of optical oxygen sensor layers based on platinum tetrakis(pentafluorophenyl)porphyrin (PtTFPP) as the sensitive dye. Different polymers were prepared and investigated in order to retrieve information on the influence of the anchor group and the side chain attached to the polymer backbone on their performance as matrix material for the dye. Bulky side groups increased the oxygen permeability through ROM polymer layers, especially when the bulky group was directly attached via an anchor group to the polymer backbone without any aliphatic spacer in between. Sensor layers made of poly(endo,exo[2.2.1]bicyclo-5-heptene-2,3-dicarboxyclic acid di-tert-butylester) and PtTFPP exhibited the highest τ 0/τ ratio and responded strongly to small amounts of oxygen. [Copyright &y& Elsevier]

Abstract: The ring opening metathesis polymerization (ROMP) of cycloocta-1,5-diene (COD) is mediated by a series of six well-defined ruthenium-based indenylidene catalysts. The polymerization kinetics are monitored and compared with three generations of Grubbs’ catalyst. Moderate control over the polymerizations was observed for both benzylidene and indenylidene-based catalysts. [Copyright &y& Elsevier]

Carbocationic polymerization of N- ortho/meta/para tolyl-exo-norbornene dicarboximide (nadimide) was carried out using Pd(II) catalyst. Under similar conditions of polymerization, poly(N- m-tolyl nadimide) showed higher molecular mass compared to poly(N- p-tolyl nadimide) and poly(N- o-tolyl nadimide). Thermal stability of these polymers was evaluated by dynamic thermogravimetry in nitrogen atmosphere. The polymers were stable up to 460°C and lost mass above this temperature in a single step. The characteristic decomposition temperature and char yield of these polymers were higher than the polymers prepared by using ring opening metathesis polymerization. The difference has been attributed to the presence of rigid bicyclic ring structure in these polymers. [ABSTRACT FROM AUTHOR]

Single and double poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) macromonomers having a norbornenyl polymerizable group were prepared by conventional Ring Opening Polymerization (ROP). These macromonomers were further subjected to ring opening metathesis polymerization (ROMP) reactions in order to produce double polymer brushes consisting of PLLA or PCL side chains on a polynorbornene (PNBE) backbone. Statistical or block ring opening metathesis copolymerization of the PLLA and PCL macromonomers afforded the corresponding random and block double brushes. Sequential ROMP of the single PLLA, PCL and PLLA macromonomers resulted in the synthesis of the corresponding triblock copolymer brush. The molecular characteristics of the macromolecular brushes were obtained by 1H-NMR spectroscopy and Size Exclusion Chromatography. The thermal properties of the samples were studied by thermogravimetric analysis, TGA, Differential Thermogravimetry, DTG and Differential Scanning Calorimetry, DSC. [ABSTRACT FROM AUTHOR]

In this review, molecular brushes and other macromolecular architectures bearing a bottlebrush segment where the main chain is synthesized by ring opening metathesis polymerization (ROMP) mediated by Mo or Ru metal complexes are considered. A brief review of metathesis and ROMP is presented in order to understand the problems and the solutions provided through the years. The synthetic strategies towards bottlebrush copolymers are demonstrated and each one discussed separately. The initiators/catalysts for the synthesis of the backbone with ROMP are discussed. Syntheses of molecular brushes are presented. The most interesting properties of the bottlebrushes are detailed. Finally, the applications studied by different groups are presented. [ABSTRACT FROM AUTHOR]

We induced a terpyridine moiety into a norbornene-based polymer to demonstrate its self-healing property, without an external stimulus, such as light, heat, or healing agent, using metal–ligand interactions. We synthesized terpyridine incorporated norbornene-based polymers using a ring-opening metathesis polymerization. The sol state of diluted polymer solutions was converted into supramolecular assembled gels, through the addition of transition metal ions (Ni2+, Co2+, Fe2+, and Zn2+). In particular, a supramolecular complex gel with Zn2+, which is a metal with a lower binding affinity, demonstrated fast self-healing properties, without any additional external stimuli, and its mechanical properties were completely recovered. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of synthetic polymer aerogels based on dendritic-type urethane-norbornene monomers. The core of those monomers is based either on an aromatic/rigid (TIPM/Desmodur RE), or an aliphatic/flexible (Desmodur N3300) triisocyanate. The terminal norbornene groups (three at the tip of each of the three branches) were polymerized via ROMP using the inexpensive 1st generation Grubbs catalyst. The polymerization/gelation conditions were optimized by varying the amount of the catalyst. The resulting wet-gels were dried either from pentane under ambient pressure at 50 °C, or from t-butanol via freeze-drying, or by using supercritical fluid (SCF) CO2. Monomers were characterized with high resolution mass spectrometry (HRMS), 1H- and solid-state 13C-NMR. Aerogels were characterized with ATR-FTIR and solid-state 13C-NMR. The porous network was probed with N2-sorption and SEM. The thermal stability of monomers and aerogels was studied with TGA, which also provides evidence for the number of norbornene groups that reacted via ROMP. At low densities (<0.1 g cm−3) all aerogels were highly porous (porosity > 90%), mostly macroporous materials; aerogels based on the aliphatic/flexible core were fragile, whereas aerogels containing the aromatic/rigid core were plastic, and at even lower densities (0.03 g cm−3) foamy. At higher densities (0.2–0.7 g cm−3) all materials were stiff, strong, and hard. At low monomer concentrations all aerogels consisted of discrete primary particles that formed spherical secondary aggregates. At higher monomer concentrations the structure consisted of fused particles with the size of the previous secondary aggregates, due to the low solubility of the developing polymer, which phase-separated and formed a primary particle network. Same-size fused aggregates were observed for both aliphatic and aromatic triisocyanate-derived aerogels, leading to the conclusion that it is not the aliphatic or aromatic core that determines phase separation, but rather the solubility of the polymeric backbone (polynorbornene) that is in both cases the same. The material properties were compared to those of analogous aerogels bearing only one norbornene moiety at the tip of each branch deriving from the same cores. [ABSTRACT FROM AUTHOR]