Effect of Imidazolium Monomer Structure on Properties of Imidazolium‐Functionalized Self‐Healing UV‐Cured Polymers for Flexible Electronic Devices

Self‐healing UV‐cured polymeric materials based on ionic interactions possess many distinct advantages such as reliability, long lifetime, and green preparation process, and thus obtain great potential development. In this work, a series of UV‐curable imidazolium monomers with different structures are designed and synthesized, and then imidazolium ionic interaction‐based self‐healing materials are prepared through fast and eco‐friendly UV‐curing technology. Also, the structures of imidazolium monomers on properties of self‐healing UV‐cured polymers are investigated. The results show that the structures of imidazolium monomers have no obvious influences on photopolymerization properties of the polymers. The hydroxyl group and polar ether chains in imidazolium monomers can increase the glass transition temperature (T_g) of the polymers. The large substituent at 1‐position of the imidazole ring enhances tensile strain of the polymers due to the reduction of the intermolecular force. The intermolecular forces and content of imidazole ionic groups all affect self‐healing efficiency of the polymers. The polymer containing HD‐IM‐E with a long and nonpolar pendent side chains exhibits an excellent self‐healing efficiency (>90%) and can be healed repeatedly. Importantly, the self‐healing polymer can also be used as a flexible electronic substrate to fabricate a flexible electronic device with good self‐healing function.     

UV‐Induced Frontal Polymerization of a Pt‐Catalyzed Hydrosilation Reaction

The bis(acetylacetonato)platinum(II) is a common thermal catalyst for the hydrosilation reaction, and it is reported to serve also as a photoactivated catalyst for hydrosilation addition of silanes to alkenes and alkynes. In this paper, it is demonstrated that the UV‐activation of hydrosilation reaction proceeds via a thermal‐frontal mechanism. UV light activates the polymerization on the surface of the sample and, subsequently, the heat released by hydrosilation generates a thermal front, converting the UV‐generated homogeneous catalyst to a Pt⁰ heterogeneous catalyst. The UV‐induced frontal polymerization mechanism can exhaustively explain the dark‐curing process observed in the UV‐activated hydrosilation reaction.

     

The Influence of Magnesium Acetate on the Structure Formation of Polystyrene‐block‐poly(4‐vinylpyridine)‐Based Integral‐Asymmetric Membranes

The influence of magnesium acetate on the non‐solvent‐induced phase separation (NIPS) process of amphiphilic polystyrene‐block‐poly(4‐vinylpyridine)s to gain integral‐asymmetric membranes is investigated. Highly uniform pores over the large areas of the membrane can be achieved, and the average pore diameter is adjusted by varying the total molar mass of the block copolymers used. These stimuli‐responsive membranes, which are solution cast in the absence or the presence of small amounts of magnesium acetate, are directly compared, showing a remarkable effect on the pore structures and their openness. Minor salt addition is considered to influence the polarity of the solvents used in a positive manner such that the NIPS process can be improved significantly.

     

UV‐Curable Cycloaliphatic Epoxide Based on Modified Linseed Oil: Synthesis,Characterization and Kinetics

Summary: Linseed oil was derivitized with 1,3‐butadiene via a Diels‐Alder reaction. The cycloaddition adduct was then epoxidized using a hydrogen peroxide/quaternary ammonium tetrakis(diperoxotungsto) phosphate system. The cyclohexene derivitized linseed oil (CLO) and the epoxidized cyclohexene derivatized linseed oil (ECLO) were characterized by ¹H NMR, ¹³C NMR, and FT‐IR. In addition, 2D NMR measurements (COSY) were performed on CLO and ECLO to identify the cyclohexyl structures. Molecular weight was determined by ESI‐MS and GPC. The ECLO was photo‐polymerized using UV‐light, and the kinetics of the photo‐curing reactions was evaluated by real‐time FT‐IR and photo‐DSC. All the characterizations supported the successful introduction of cyclohexyl structure to the backbone of linseed oil directly and indirectly. Real‐time FT‐IR and photo‐DSC indicated the slightly improved reactivity of ECLO.

Ideal structure of cyclohexene linseed oil (CLO).     

Preparation and Gas Separation Properties of Triptycene‐Based Microporous Polyimide

Polyimides with intrinsic microporosity (PIM‐PIs) are widely regarded as one of the most promising next‐generation membrane materials to simultaneously achieve high permeability and selectivity. Despite the fact that tremendous microporous polyimides have been synthesized, only cost‐ef?cient PIM‐PIs have the potential to be used in industrial applications. In this work, a PIM‐PI is prepared by using the commercial and inexpensive planar pyromellitic dianhydride (PMDA) as the dianhydride monomer, and 2,6‐diaminotriptycene as the diamine monomer. The CO₂ permeability of PMDA‐DAT is ≈23‐fold higher than that of Kapton, one of the commercially available polyimide membranes also made from PMDA, and with almost the same CO₂/CH₄ selectivity. In addition, no plasticization phenomenon is observed for PMDA‐DAT membrane even at a CO₂ pressure up to 15 atm. The good plasticization resistance performance of PMDA‐DAT can be mainly attributed to the formation of pseudo‐physical crosslinking by interlocking and π–π interactions in triptycene moieties.     

Counter‐Anion Effect on the Properties of Anion‐Conducting Polymer Electrolyte Membranes Prepared by Radiation‐Induced Graft Polymerization

Graft‐type anion‐conducting polymer electrolyte membranes (AEMs) are prepared by the radiation‐induced graft polymerization of chloromethylstyrene into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) films and subsequent quaternization with trimethylamine. AEMs in the hydroxide form (AEM‐OH) are prepared by immersing the chloride form (AEM‐Cl) in 1 M potassium hydroxide (KOH) solution, followed by KOH and washing with nitrogen‐saturated water to prevent bicarbonate formation (AEM‐HCO₃). The AEM‐OH shows conductivity and water uptake four and two times higher than AEM‐Cl and ‐HCO₃ and is thermally and chemically less stable, resulting in the tendency to absorb water and to convert to the bicarbonate form.

     

The First Vanadium‐Oxide‐Based UHMWPE Catalyst Supported on Chemically Modified Silica Gel

Novel vanadium‐oxide‐based catalysts supported on alumina, zirconia, or titania‐modified silica, which are able to synthesize ultrahigh molecular weight polyethylene (UHMWPE), are successfully developed. Compared with the unmodified silica supported catalyst, the activities of the modified catalysts are substantially enhanced. By changing the polymerization temperature (T _p) from 90 to 60 °C, the molecular weight of the produced UHMWPE can be easily regulated from 2 × 10⁶ to more than 6 × 10⁶ g mol⁻¹. It is the first time that chloride‐free nonsingle site catalysts have been developed to synthesize UHMWPE within such a broad range of T _p. Catalyst characterization by NH₃‐temperature‐programmed desorption and pyridine‐Fourier transform infrared spectroscopy reveals that the modified catalysts have increased acidity derived from both Lewis and Brønsted acid sites. The X‐ray photoelectron spectroscopy characterization indicates that the vanadium on the modified catalysts is more electron deficient. Thus, the acidity of the catalysts and the electronic state of the vanadium play a critical role in determining the activity of the vanadium active sites for ethylene polymerization.

     

A Novel Characterization Method for Graft‐Polymer Structures Chemically Attached on Thermally Stable Polymer Films

Most polymer grafts in grafted polymer films obtained by radiation‐induced solid graft polymerization are not analyzed in detail due to difficulties in isolation of the grafts without structural decomposition. Herein, a novel structural and molecular weight characterization method is reported for polymer grafts that are chemically attached to thermally and chemically stable polymer substrates, based on a swelling‐induced graft detachment in hot water. Polymer grafts prepared by the radiation‐induced polymerization of alkyl acrylate into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) followed by a sulfonation reaction are found to have a ternary copolymer structure whose monomer units contain –COOH or –SO₃H groups, or both.     

Synthesis and Photopolymerization of Thiol‐Modified Triazine‐Based Monomers and Oligomers for the Use in Thiol‐Ene‐Based Dental Composites

Thiol‐ene photopolymerizations combine the unique features of step‐growth reactions and photoinitiated polymerizations, so that they experience a growing interest for applications such as coatings or dental restoratives. Most studies have making use of a relatively flexible ester and the hydrolytically labile derivative pentaerythritoltetra(3‐mercaptopropionate) ( PETMP ) as the thiol component in common. In this study, the performance of hydrolytically stable 1,3,5‐tris(3‐mercaptopropyl)‐1,3,5‐triazine‐2,4,6‐trione ( 4a ), 1,3,5‐tris(2‐methyl‐3‐mercapto‐propyl)‐1,3,5‐triazine‐2,4,6‐trione ( 4b ), and oligomers thereof in thiol‐ene photopolymerizations is investigated. The oligomers are prepared via thiol‐Michael or thiol‐isocyanate additions by using 4a and suitable diacrylates or diisocyanates containing a rigid core structure. Compared with PETMP , the thiol derivative 4a shows better flexural strength and modulus of elasticity in thiol‐ene photopolymerizations with 1,3,5‐triallyl‐1,3,5‐triazine‐2,4,6‐trione ( TATATO ) as the‐ene derivative. This phenomenon becomes especially evident after storage in water at 37 °C for 24 h. Furthermore, the performance regarding the flexural strength, the Young's modulus of elasticity, the polymerization shrinkage stress of 4a , and the polyadducts thereof in dental filling composites is evaluated and discussed.

     

Thermo‐Responsive Nanogels Based on Poly[NIPAAm‐graft‐(2‐alkyl‐2‐oxazoline)]s Crosslinked in the Micellar State

Graft copolymers with thermo‐sensitive PNIPAAm backbone and hydrophilic PEtOxa graft chains demonstrated typical amphiphilic behavior. For specific compositions stable micelle‐like aggregates were formed depending on the temperature. Applying long polyoxazoline side chains ( > 120), stable reversible micelle‐like aggregates with hydrodynamic radii of 30–40 nm could be obtained between 33 and 55 °C. These graft copolymers have been successfully crosslinked by electron‐beam irradiation in the micellar state yielding core/shell type nanogels with thermo‐reversible swelling behavior. The temperature dependent volume change of the new thermo‐responsive nanogels due to the phase transition of the PNIPAAm core has been verified by DLS.

     

Preparation of Polybenzimidazole/Lithium Hydrazinium Sulfate Composite Membranes for High‐Temperature Fuel Cell Applications

PBI‐LiHzS composite membranes were prepared by casting N,N'‐DMAc solutions containing PBI and LiHzS, where the LiHzS contents in the membranes were between 2.5 and 10 wt.‐%. LiHzS was obtained by reacting hydrazine sulfate and lithium carbonate in water. PBI‐LiHzS composite membranes were thermally stable up to approximately 300 °C and their acid‐absorbing capabilities were comparable to those of the pure PBI membranes. The proton conductivity of PBI‐LiHzS composite membranes (2.12 × 10^?2 S · cm^?1 at 180 °C and 0% RH) was higher than that of pure PBI membranes when used at the same acid doping levels. The mechanical stability of the composite membranes having less than 5 wt.‐% of LiHzS was found to be close to that of pure PBI membranes.

     

Effect of Solvent–Nonsolvent Miscibility on Morphology and Electrochemical Performance of SiO2/PVdF‐HFP‐Based Composite Separator Membranes for Safer Lithium‐Ion Batteries

As a new approach to improve the thermal stability of separator membranes crucially affecting the internal short‐circuit failures of lithium‐ion batteries, we develop a new composite separator membrane. The composite separator membrane is prepared by introducing microporous composite coating layers onto both sides of a polyethylene (PE) separator membrane. The composite coating layers consist of silica (SiO₂) nanoparticles and gel‐type polymer electrolytes (PVdF‐HFP, polyvinylidene fluoride‐hexafluoropropylene). The microporous morphology of composite coating layers is determined by controlling the phase inversion, more specifically the solvent–nonsolvent miscibility in the coating solutions. To induce the phase inversion, three different nonsolvents are chosen in the decreasing order of solubility parameter (δ) difference against the solvent (acetone, δ = 20 MPa^1/2); the non‐solvents are water (δ = 48 MPa^1/2), ethanol (δ = 26 MPa^1/2), and isopropyl alcohol (δ = 24 MPa^1/2). The microporous structure of composite coating layers becomes more developed with the increase of not only the nonsolvent content, but also the solubility parameter difference between acetone and the nonsolvent. Based on this understanding of the phase inversion, the influence of the morphological variation on the thermal shrinkage and electrochemical performance of the composite separator membranes is quantitatively identified.

     

Multifunctional BSA Scaffolds Prepared with a Novel Combination of UV‐Crosslinking Systems

This study presents the hydrogelation of bovine serum albumin by using a natural‐derived photo‐initiator system based on riboflavin and l ‐arginine that ensures the preparation of biocompatible hydrogels. Fourier transform infrared spectroscopy reveals that the synthesis conditions do not induce protein denaturation and confirms the potential UV‐crosslinking mechanism for albumin hydrogels realization. Thermal and morphological characterization indicates the formation of thermodynamically stable hydrogels with interconnected inner structure which presents a riboflavin concentration‐dependent porosity. The evolution of the hydrogel's decomposition products is analyzed by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectrometry and reveals a degradation pathway characterized by deamination of unreacted amino moieties and peptide ? NH? groups, condensation, decomposition of the condensation products, and oxidation of N‐containing residues. The kinetics and pH‐responsive behavior of hydrogels are investigated by water uptake dynamics revealing a swelling mechanism which can be switched from a less Fickian to a non‐Fickian process by varying the crosslinker concentration. In vivo tests prove the high degree of biocompatibility of the new hydrogels, after oral administration in mice.     

Two‐Dimensional ATR FT‐IR Spectroscopic Study on Glycol Diffusion in a Cured Epoxy Membrane

Summary: A novel experimental approach, that is, two‐dimensional (2D) correlation analysis based on time‐resolved attenuated total reflection (ATR) FT‐IR spectroscopy, has been used to study the diffusion behavior of ethylene glycol molecules into EP and EPB (novolac epoxy resins cured with novolac resin or novolac butyrate resin, respectively). The diffusion behavior of ethylene glycol into these systems is discussed and compared with that of water. Ethylene glycol absorbed in EP can be classified into two types (free and bound types), while in EPB a third type (referred to as “specific” type) is also observed, which differs from water sorption behavior. In particular, it is interesting to find that the hydrogen bonding of specific ethylene glycol involves two hydroxyl groups rather than one hydroxyl group and polar group in epoxy networks (carbonyl group), a similar example of which has not been previously observed. In addition, in both EP and EPB, bound ethylene glycol molecules diffuse faster than any other types.

Asynchronous 2D correlation spectra of ethylene glycol in the two resins studied here. Positive peaks are unshaded, whereas negative peaks are shaded.     

Organic‐Inorganic Hybrid Membranes for Removal of Benzene from an Aqueous Solution by Pervaporation

Summary: Preparation of organic‐inorganic hybrid membranes and their pervaporation permeation and separation characteristics for an aqueous solution of 0.05 wt.‐% benzene are described. In this study, we prepared organic‐inorganic hybrid membranes by the sol‐gel reaction of tetraethoxysilane (TEOS) as an inorganic component with poly(methyl methacrylate‐co‐vinyltriethoxysilane) (P(MMA‐co‐VTES)) and poly(butyl methacrylate‐co‐vinyltriethoxysilane) (P(BMA‐co‐VTES)) as organic components. When an aqueous solution of dilute benzene (0.05 wt.‐%) was permeated through the P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes, the benzene concentration in the permeate through all hybrid membranes was higher than that in the feed solution. This result demonstrates that these hybrid membranes are benzene selective for an aqueous solution containing dilute benzene. The benzene/water selectivity of the P(BMA‐co‐VTES)/TEOS hybrid membrane was about 20 times higher than that of the P(MMA‐co‐VTES)/TEOS hybrid membrane. Specifically, the P(BMA‐co‐VTES)/TEOS hybrid membrane with a TEOS content of 75 mol‐% showed the highest benzene/water selectivity. The benzene/water selectivity of the hybrid membranes depended significantly on the cross‐linked structures formed by the sol‐gel reaction of VTES and TEOS.

Effects of the TEOS content on the sorption selectivity (○) and the diffusion selectivity (?) for an aqueous solution of 0.05 wt.‐% benzene through P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes at 40 °C.     

Branched Base‐Amplifying Oligomers Enhancing UV‐Curing of Epoxy Resins

This paper describes the preparation and the enhancing effect on anionic UV‐curing of epoxy resins of three and four‐armed oligomers bearing 9‐fluorenylmethyl carbamate residues, which displayed the autocatalytic formation of primary amino residues triggered by a photogenerated amine. The branched oligomers were readily synthesized by the Michael addition of the corresponding polythiol with 9‐fluorenylmethyl 2‐acryloyloxyethylcarbamate, which were obtained from 9‐fluorenylmethanol and commercially available 2‐isocyanatoethyl acrylate. Films of poly(glycidyl methacrylate) and a glycidylated novolac resin doped with a photobase generator exhibited boosted photosensitivity leading to photoinsolubilization in the presence of the base‐amplifying oligomers. The more marked effect of the branched oligomers on UV‐curing of epoxy resins was demonstrated by using films of a fluid epoxy, which were converted into hard films after UV exposure and post‐exposure baking, whereas no hardening occurred in the absence of the oligomers.

     

Studies on Preparation and Fluorescent Properties of a Novel Photo‐Sensitive Nanoparticle Composed of Europium Ion and Cinnamic Acid Derivative

A novel fluorescent and photo‐sensitive nanoparticle was self‐assembled from an europium‐based random copolymer, europium coordinated poly(methylacrylic acid)‐co‐poly(cinnamyl acrylate) (PMCFA‐Eu³⁺), which was synthesized from methylacrylic acid (MAA), and Eu³⁺‐cinnamyl acrylate derivative (CFA) by radical polymerization. DLS and TEM results indicated the formation of spherical nanoparticles with 120 nm in diameter. The PMCFA‐Eu³⁺ complex showed stronger fluorescence than Eu³⁺, indicating the effective energy transferred from the ligand to Eu³⁺. Moreover, the photo‐crosslinking of the cinnamate groups induced a decrease in the diameter and an increase in the fluorescent properties of the PMCFA‐Eu³⁺ nanoparticles. This functional nanoparticle might be useful as a carrier and a fluorescence probe in biomedical and fluorescent fields.

     

A New Approach for the Synthesis of pH‐Responsive Cross‐Linked Micelles from a Poly(glycidyl methacrylate)‐Based Functional Copolymer

An amphiphilic poly(ethylene glycol)methyl ether‐block‐poly(glycidyl methacrylate) (MPEG‐b‐PGMA) diblock copolymer is first synthesized via atom transfer radical polymerization. Epoxy groups of this precursor block copolymer are converted to hydroxyl and tertiary amine residues by reacting with diethyl amine over a ring‐opening reaction. The resulting diblock copolymer is poly(ethylene glycol)methyl ether‐block‐poly(3‐diethylamino‐2‐hydroxypropyl methacrylate) (MPEG‐b‐PDEAHPMA). Micellar solution of this diblock copolymer is prepared at pH 12.0 in aqueous media. At high pH (12.0), core – shell micelles are formed with PDEAHPMA‐core and MPEG‐shell. PDEAHPMA blocks have both hydroxyl and tertiary amine groups that provide reactivity against divinyl sulfone (DVS) and a response to solution pH, respectively. Cross‐linking of hydroxyl groups of PDEAHPMA chains in the micelle core is successfully achieved by adding DVS. At pH 2.0, the DEAHPMA‐core of core cross‐linked (CCL) micelles becomes protonated and hence swelling is observed. The effect of varying the DVS concentrations is also studied. The micelle formation of diblock copolymer and its response to solution pH are investigated by using surface tensiometer, ¹H NMR spectroscopy, and dynamic light scattering (DLS) techniques. CCL micellar structure and its response to solution conditions are investigated with transmission electron microscopy and DLS studies, respectively.

     

One‐Component Intrinsic Self‐Healing Coatings Based on Reversible Crosslinking by Diels–Alder Cycloadditions

Terpolymers containing functional moieties for reversible crosslinking by DA reaction are synthesized for application as self‐healing coatings. The polymers are based on a methacrylate backbone containing furan as well as maleimide units in the side chains. No additional crosslinker is required to obtain a self‐healing polymeric material. After damage, the material can be heated to a temperature at which the retro‐DA reaction takes place. Subsequent cooling to room temperature leads to a healing of the scratch due to the coupling of the two reactive functional groups. This healing process can be repeated multiple times. The polymers are characterized by means of ¹H NMR spectroscopy, size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, thermogravimentric analysis, and differential scanning calorimetry. The self‐healing properties are studied using atomic force microscopy, scanning electron microscopy, and nanoindentation.

     

Effects of Cross‐Link Density on Structures and Properties of Dual‐Sensitive Semi‐Interpenetrating Polymer Networks Hydrogel Microspheres

Semi‐interpenetrating polymer network (semi‐IPN) strategy is employed to fabricate uniform microspheres with temperature and pH dual‐responsive behavior, which is composed of poly(N‐isopropylacrylamide) and poly(acrylic acid) in the presence of N ,N ′‐methylenebisacrylamide (MBA) as the cross‐linker. The influences of MBA amount (M _m) on the structures and properties of the microspheres are investigated in terms of particle size, surface morphology, pH sensitivity, and thermo‐sensitivity with low critical solution temperature in the range M _m = 2.5–15%. Additionally, functional group distributions in the microspheres are probed by titration and employing the Henderson–Hasselbalch equation. The results show that all the properties strongly change depending on M _m. Based on transmission electron microscopy and confocal laser scanning microscopy measurements, and these properties, the M_m‐induced changes in the structures of the semi‐IPN microspheres are discussed.