Yinwen Li

Efficient monochromatic red-light-emitting PLEDs based on a series of nonconjugated Eu-polymers containing a neutral terpyridyl ligand

Three novel Eu-polymers containing hole transporting units and light-emitting units in the main chain have been designed and synthesized via radical copolymerization of N-vinylcarbazole and polymerizable Eu(TTA)3vinyl-tpy, where TTA is 2-thenoyltrifluoroacetonate. The chemical structure and composition of the Eu-polymers were characterized by FTIR, UV-vis, 1H NMR, 13C NMR spectroscopy, GPC, ESI-MS, and elemental analysis. The geometry of the polymerizable monomer Eu(TTA)3vinyl-tpy was predicted using the Sparkle/PM6 model and suggested to be in a chemical environment with very low symmetry around the Eu3+ ions (C1), in agreement with the fluorescence spectrum. All Eu-polymers exhibited good solubility, as well as good thermal stability and high glass transition temperatures. The photoluminescence (PL) properties of the copolymers in solution and in the solid state were investigated in detail. Intramolecular energy transfer from the carbazole groups to the europium complexes occurred even in diluted solutions. The efficiency of this process also depended on the composition of the Eu-polymers. In the solid state, emission from the carbazole groups was suppressed and the absorbed excitation energy was transferred effectively to the europium complexes in the Eu-polymers. Most importantly, the EL performances of eight pure red-emission PLEDs based on P1, P2, and P3 as the emitting layer have been studied in detail. Bright electroluminescence with a maximum luminance of 68.2 cd m−2 from the double-layer devices of P1 was demonstrated. Although the EL performance was only the third-best among those of the Eu-chelated polymers reported so far, to the best of our knowledge, this is the first example of electroluminescent devices of Eu-polymers based on tpy as a neutral ligand. These results illustrate the potential application of polymerizable tpy ligands in high performance EL Eu-chelated polymers.

Synthesis of copolymers with cyclodextrin as pendants and its end group effect as superplasticizer

In this paper, the efficient approach for the synthesis of β-cyclodextrin (CD) based functional monomers was described. Based on the monovinyl β-CD monomer (GMA-EDA-CD), a new type poly(AA-co-GMA-EDA-CD) (PCDs) copolymer bearing pendent CD groups was synthesized and used as superplasticizer. Their chemical compositions were characterized by FT-IR, NMR, MALDI-TOF and GPC. The effects of PCDs on dispersion and adsorption in cement mortars were detailed discussed. The results indicated that PCD copolymers behaved excellent dispersion ability and strong retarding effect. PCD2 with molar ratio (%) for monomer (AA:GMA-EDA-CD=80:20) had the best dispersion and dispersion maintaining abilities, which were mainly attributed to the synergistic effects of steric hindrance and electrostatic repulsive force, and the retarding effect of PCD copolymers resulted from steric hindrance repulsion of CD pendants and the large number of hydroxyl groups, which affected the hydration reaction of cement.

Pseudo-graft polymer based on adamantyl-terminated poly(oligo(ethylene glycol) methacrylate) and homopolymer with cyclodextrin as pendant: its thermoresponsivity through polymeric self-assembly and host–guest inclusion complexation

A series of well-defined adamantyl-terminated thermally responsive copolymers (Ad-POEGMAs) were synthesized by atom transfer radical polymerization (ATRP), in which 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA) served as the thermosensitive building blocks. Moreover, cyclodextrins (CDs) as bulky pendant grafted polymers (PGCD) were synthesized by homopolymerization of aminoethyl methacrylate β-cyclodextrin (GCD). The thermal-responsive behaviors were investigated by a combination of 1H NMR, UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). In comparison to other thermal-responsive copolymers based on POEGMAs, Ad-POEGMAs exhibited unusual thermally induced aggregation processes. The Ad group assembled and POEGMA chains associated to produce stable water-soluble nano-aggregates, followed by a rearrangement process at the second thermal transition. Moreover, it was found that a noncovalently connected supramolecular pseudo-graft polymer was formed via inclusion complexation in aqueous solution. This pseudo-graft polymer underwent a reversible temperature-induced transition from solution to micelle under suitable conditions. The cyclodextrin (CD) moiety attached to the main chain played two roles. As supramolecular host moieties, CDs formed inclusion complexes with guest-ended polymers, leading to graft-like polymers. As bulky hydrophilic moieties, CDs stabilized the micelles induced by the coil-to-globule transition of POEGMA segments.

Synthesis and self-assembly of well-defined binary graft copolymer and its use in superhydrophobic cotton fabrics preparation

We have synthesized and characterized a series of functional binary graft copolymers PGMA-g-(PHFBMA-r-POEGMA)s(BGCs). First, PHFBMA–CCH, POEGMA–CCH and P(GMA-N3) were synthesized via sequential atom transfer radical polymerization (ATRP). BGCs were prepared by grafting of alkyne-end poly(hexafluorobutyl methacrylate) (PHFBMA–CCH) and poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA–CCH) onto poly(3-azide-2-hydroxypropyl methacrylate) (P(GMA-N3)) via click chemistry. The self-assembly behaviors were investigated by combination of dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Since POEGMA was soluble in water while PHFBMA was insoluble, BGCs self-assembled and produced stable PHFBMA-centered nano-micelles; then BGCs were used to fabricate hydrophobic cotton fabrics. While the PHFBMA block provided low surface free energy, the POEGMA block served as an anchor with cotton fibers, the modified cotton fabrics showed excellent superhydrophobic property. The results confirmed that fluorinated surface was formed onto substrate without changing the transparency and bulk composition of the cotton fabrics. Moreover, SEM and AFM analysis indicated that nano- and microscale roughness were created by combining BGC-based nano bumps onto surfaces of micro-sized cotton fabrics.

High thermo-responsive shape memory epoxies based on substituted biphenyl mesogenic with good water resistance

In this work, a novel epoxy monomer denoted as 3,5′-di-t-butyl-5,3′-dimethyl biphenyl diglycidyl ether (t-BuMBPDGE) was synthesized and applied into in situ composites with 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether (TMBPDGE), accompanied with curing agent aromatic amines. The liquid crystalline phase structure and the crosslink density of substituted biphenyl epoxies were determined by polarized optical microscopy, wide angle X-ray diffraction measurements and dynamic storage moduli data. The samples showed good mechanical properties and could recover quickly from a second state to their initial states with a shape fixity ratio higher than 98% and shape recovery ratio higher than 99%, owing to the oriented structure and increased crosslink network density caused by the orientation of biphenyl mesogenic. The high glass transition temperatures ranging from 160 to 178 °C and good water resistance could contribute to a stable fixed shape. The water resistance is analyzed by contact angles test. The samples exhibited contact angles of 92–98 degrees, which indicated that the water resistance was apparently better than that of conventional epoxy systems.

Synthesis and encapsulation of an amphiphilic thermoresponsive star polymer with β-cyclodextrin and hyperbranched poly(oligo(ethylene glycol)methacrylate) as building blocks

Novel macromolecular star polymers with triazole and cyclodextrin (CD) segments as branch points and poly(oligo(ethylene glycol)methacrylate) (POEGMAs) as dense hydrophilic branches were synthesized via a combination of azide–alkyne click chemistry and atom transfer radical polymerization (ATRP). Firstly, a tetrafunctional linking agent (PETP) was prepared by the reaction of pentaerythritol (PE) and propargyl bromide, and then a four arm β-CD terminated star polymer (PE-CD) was obtained through the click chemistry reaction. Finally, thermally-responsive star polymers (PE-CD–POEGMAs) with PE as the central core, triazole and CD segments as branch points, and POEGMAs as side branches were synthesized by the ATRP of MEO2MA and OEGMA using PE-CD terminated with bromines as macroinitiators. A study on the thermoresponsivity and morphology of PE-CD–POEGMAs indicated that polymeric nano-aggregates existed as multimolecular micelles and behaved with tunable thermosensitivity, which were driven by the strong hydrophobic–hydrophilic interactions in the inner core and outer shell. The encapsulation capacities towards multi-guest molecules were investigated and the results indicated that water soluble guests could be encapsulated by PE-CD–POEGMAs, and the guest encapsulation capacities were derived from the special star molecular structure properties of PE-CD–POEGMAs and the synergistic encapsulation phenomenon of different guest molecules. This unique amphiphilic star polymer illustrated the potential applications in supramolecular science, drug delivery and other nanotechnology applications.

Inhibitory Action of Funtumia elastica Extracts on the Corrosion of Q235 Mild Steel in Hydrochloric Acid Medium: Experimental and Theoretical Studies

The inhibiting effect of aqueous extracts of Funtumia elastica (FE) on mild steel corrosion in 1 M HCl solution was investigated using electrochemical and surface characterization techniques. The results revealed that FE effectively inhibited the corrosion reaction. Polarization data reveal that the extract functioned as a mixed-type inhibitor, while impedance results show that the extract organic matter gets adsorbed on the metal/solution interface. Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy results confirmed the formation of a protective layer of extract adsorbed on the mild steel surface. Adsorption of some organic constituents of FE on mild steel was theoretically described by quantum chemical computations and molecular dynamics simulations, in the framework of the density functional theory. GRAPHICAL ABSTRACT

Low formaldehyde emission urea-formaldehyde resins modified by 2,4,6-trimethylolphenate and physical properties of its impregnated papers

The objective of this study is using 2,4,6-trimethylolphenate (TMP) as modifier to prepare stable TMP-Urea-Formaldehyde resins (TMPUF) with low formaldehyde emission and using TMPUF to improve mechanical properties and water resistance of the common filter paper. The prepared TMPUF was characterized by IR, DSC and POM. The results indicated that as the mass ratio of TMP/U was increased, the free formaldehyde concentration of the TMP modified UF resins was decreased. Curing temperature of TMPUF was increasing with the decreasing of free low formaldehyde and POM analysis showed that the crystalline structure of TMPUF is destroyed with the adding of TMP. In addition, mechanical properties, thermal stability and water absorption of TMUF impregnated papers have been studied. The results showed that both mechanical properties and water absorption of TMPUF impregnated papers can be improved in the experimental range. However, all TMPUF impregnated paper shows little difference in thermal stability. These results indicated that TMP as a kind of phenol-formaldehyde intermediate is a useful alternative to formaldehyde and phenol to reduce environmental pollution. This work provides a method of preparing stable TMPUF adhesives with low formaldehyde emission used for wood adhesives and paper impregnating applications.

Preparation and Application of New Polycarboxylate Superplasticizers with Mild Retarding Performance Based on Monovinyl β-Cyclodextrin Monomer

Based on monovinyl β-CD monomer (GCD), random copolymers (PTCDs) were first synthesized by AA, TPEG, and GCD, and characterized by FTIR and GPC. The application performances of PTCDs as superplasticizers in cement and concrete were investigated considering dispersion, adsorption, setting times, and compressive strength. The results indicated that PTCDs had more excellent applied performance compared with AA-co-GCD copolymers, and the outstanding feature is that PTCDs had a mild tunable retarding effect. When with certain amount of CD pendants and PEO side chains, PTCD2 had the best dispersion and mild retarding performances, which were mainly attributed to the joint steric hindrance effect provided by CD pendants and PEO side chains. This study offers a new type of superplasticizer from CD and its derivatives with excellent dispersion and retarding performances to concrete engineering.