Design and development of several polymeric metal–organic frameworks,spectral characterization,and their antimicrobial activity

Coordination polymers were obtained by the reaction of metal acetates, M(CH₃COO)₂·xH₂O {where M = Mn(II), Co(II), Ni(II) and Cu(II)} with AFP ligand (AFP = 5,5'-(piperazine-1,4-diylbis(methylene))bis(2-aminobenzoic acid). The AFP ligand was prepared by the one-pot, two-step reaction of formaldehyde, 2-aminobenzoic acid, and piperazine. Structural and spectroscopic properties have been studied by elemental, spectral (FT-IR, ¹H NMR, ¹³C NMR, and UV–vis), and thermogravimetric analysis. UV–vis spectra and magnetic moment values indicate that Mn(II), Co(II), and Ni(II) polymer–metal complexes are octahedral, while Cu(II) and Zn(II) polymer–metal complexes are distorted octahedral and tetrahedral, respectively. The analytical data confirmed that the coordination polymers of Mn(II), Co(II), Ni(II), and Cu(II) are coordinated with two water molecules, which are further supported by infrared spectra and thermogravimetric analysis data. The prepared polymer–metal complexes showed good antibacterial activities against all tested microorganisms; however, the AFP ligand was also found to be effective, but relatively less than their polymer–metal complexes. Along with antibacterial activity, all the polymer–metal complexes exhibit significant antifungal activity against most of the tested fungal strains. The results of antimicrobial activity reveals that the AFP–Cu(II) showed the highest antibacterial and antifungal activity than other polymer–metal complexes.     

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis,spectral characterization,and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1?:?2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1?:?1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C?min^?1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).     

Soluble metal–polymer catalysts in the hydrogenation of organic compounds

Literature describing the use of soluble metal–polymer catalysts in the molecular hydrogenation of alkenes, alkynes, aromatic and heterocyclic compounds has been reviewed. Special attention has been paid to coordinated metallic and organometallic catalytic systems and highly dispersed colloidal metals stabilized with polymers. The influence of metals, polymers and solvents on the structures of active sites is discussed. The prospects for the application of soluble metal–polymer catalysts in organic synthesis are also considered.     

Interfacial toughness in polymer‐layered laminar composites

The investigation of the interfacial toughness of polymer layered laminar composites with two different approaches produced results differing by up to an order of magnitude and following opposite trends with respect to the strain rates. The flexural modulus and neutral axis of a constrained epoxy‐adhesive layer bound to a painted metal substrate varied with the thickness of the adhesive layer. The adhesion energy depended on the rate at which the force was transmitted to the adhesion bonds—not just on the strength of the adhesion bonds—and on the concomitant strain hardening at high strain rates. As the strain rate and thickness of the polymer layer increased, the transition from a cohesive mode to an adhesive–cohesive (polymer–polymer interface) mode of debonding led to the observed high adhesion energy. The high adhesion energy and increased strain hardening were attributed to the formation of organic–inorganic composites and nanocomposites within the polymer matrix, which evolved as a result of the interactions between the metal oxide pigments and fillers with the polymer matrix during curing. Scission of the polymer chains at the interface was proposed to be the predominant fracture mechanism; it was based on the high relaxation time (～10¹⁷ s) and the high activation energy (～175 kJ mol^?1). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3822–3835, 2004     

Stimuli-responsive polymer/metal composites: From fundamental research to self-regulating devices

The review focuses on stimuli–responsive composite materials consisting of polymers and metals. Special attention is drawn to the conversion of one external stimulus into another one, which leads to a cascade effect on the interaction with the vicinity. Beside fundamental aspects concepts for technical applications of those polymer/metal composites are presented.     

Adhesion of high polymers. I. Influence of diffusion,adsorption, and physical state on polymer adhesion

It is possible to identify three distinct types of polymer adhesion on the basis of the physical state of adhesive and adherend: (1) rubbery polymer–rubbery polymer (R–R adhesion); (2) rubbery polymer–glassy polymer (R–G adhesion); (3) rubbery polymer–nonpolymer (R–S adhesion). Limitations of the diffusion and adsorption theories and their conflicting results are discussed within the framework of the proposed classification. By defining the physical state of the polymer as an adhesive or as an adherend, it is possible to eliminate many of the discrepancies commonly noted in attempted application of the diffusion and adsorption theories. As predicted by the Bueche-Cashin-Debye equation, the diffusion of a polymer into another should be greatly reduced as it changes from the rubbery to the glassy state. For this reason, diffusion, which depends to a great extent on the physical state of the polymer, is actually a limited, selective process. Assuming a 10¹³ poise bulk viscosity at glass temperature, self-diffusion constants of forty polymers were calculated to be 10^?21cm.²/sec. or 10^?5A.²/sec. This slow rate of diffusion is unmeasurable and insignificant. Adsorption, which is less dependent on the physical state of the polymer, is more frequently encountered.     

Silicate coupling layer for metal to polymer adhesion improvement: Physical-chemical fundamentals and technological importance

Silicated metal surfaces may improve the adhesion of polymers to metal surfaces. Two different methods of silicate formation - a flame pyrolysis of orthosilicates and a sol-gel coating based on a Cr^III- doped SiO₂-sol - are proposed. The coupling of the SiO₂-layer on the metal oxide surface, their structure and morphology and, the effect of the silane coupling agent on the adhesion mechanism are discussed. The formation of stable and durable compounds is proved by shear strength measurements and SEM analysis of the interface after boiling tests. Additionally, the adhesion of glued joints between glasses, ceramics and metals is also improved by this method.     

Roles of rhenium diimine complexes as metal‐ion probes and photosensitizers in functional polyurethanes

Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10^?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003     

Molecular and nanoscale factors governing pressure‐sensitive adhesion strength of viscoelastic polymers

Pressure‐sensitive adhesives (PSAs) are finding increasing applications in various areas of industry and medicine. PSAs are a special class of viscoelastic polymers that form strong adhesive joints with substrates of varying chemical nature under application of light external bonding pressures (1–10 Pa) over short periods of time (1–5 s). To be a PSA, a polymer should possess both high fluidity under applied bonding pressure, to form good adhesive contact, and high cohesive strength and elasticity, which are necessary for resistance to debonding stresses and for dissipation of mechanical energy at the stage of adhesive bond failure under detaching force. For rational design of novel PSAs, molecular insight into mechanisms of their adhesive behavior is necessary. As shown in this review, strength of PSA adhesive joints is controlled by a combination of diffusion, viscoelastic, and relaxation mechanisms. At the molecular level, strong adhesion is the result of a narrow balance between two generally conflicting properties: high cohesive strength and large free volume. These conflicting properties are difficult to combine in a single polymer material. Individually, high cohesive interaction energy and large free volume are necessary but insufficient prerequisites for PSA strength. Evident correlations are observed between the adhesive bond strengths of different PSAs, and their relaxation behaviors are described by longer relaxation times. Innovative PSAs with tailored properties can be produced by physical mixing of nonadhesive long‐ and short‐chain linear parent polymers, with groups at the two ends of the short chains complementary to the functional groups in the recurring units of the long chains. Although chemical composition and molecular structure of such innovative adhesives are unrelated to those of conventional PSAs, their mechanical properties and adhesive behaviors obey the same general laws, such as the Dahlquist's criterion of tack. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Underwater adhesive using solid–liquid polymer mixes

Instantaneous adhesion between different materials is a requirement for several applications ranging from electronics to biomedicine. Approaches such as surface patterning, chemical cross-linking, surface modification, and chemical synthesis have been adopted to generate temporary adhesion between various materials and surfaces. Because of the lack of curing times, temporary adhesives are instantaneous, a useful property for specific applications that need quick bonding. However, to this day, temporary adhesives have been mainly demonstrated under dry conditions and do not work well in submerged or humid environments. Furthermore, most rely on chemical bonds resulting from strong interactions with the substrate such as acrylate based. This work demonstrates the synthesis of a universal amphibious adhesive solely by combining solid polytetrafluoroethylene (PTFE) and liquid polydimethylsiloxane (PDMS) polymers. While the dipole-dipole interactions are induced by a large electronegativity difference between fluorine atoms in PTFE and hydrogen atoms in PDMS, strong surface wetting allows the proposed adhesive to fully coat both substrates and PTFE particles, thereby maximizing the interfacial chemistry. The two-phase solid–liquid polymer system displays adhesive characteristics applicable both in air and water, and enables joining of a wide range of similar and dissimilar materials (glasses, metals, ceramics, papers, and biomaterials). The adhesive exhibits excellent mechanical properties for the joints between various surfaces as observed in lap shear testing, T-peel testing, and tensile testing. The proposed biocompatible adhesive can also be reused multiple times in different dry and wet environments. Additionally, we have developed a new reactive force field parameterization and used it in our molecular dynamics simulations to validate the adhesive nature of the mixed polymer system with different surfaces. This simple amphibious adhesive could meet the need for a universal glue that performs well with a number of materials for a wide range of conditions.     

Characteristics and Bond Performance of Wood Adhesive Made from Natural Rubber Latex and Alkaline Pretreatment Lignin

The aim of this study was to characterize an aqueous polymer isocyanate (API) type adhesive made from natural rubber latex (NRL) and lignin as base polymers, and to evaluate bond performance of the adhesive as laminated wood adhesive. The base polymers of the adhesive were prepared by blending NRL, polyvinyl alcohol (PVA), and lignin isolated from black liquor of alkaline pretreatment of oil palm empty fruit bunch (OPEFB) and sugarcane bagasse (SB) with compositions of 25/25/0, 25/20/5, 25/15/10, 25/10/15, 25/5/20, and 25/0/25 (w/w/w). The isocyanate crosslinker was added at the level of 15% of the weight of base polymer. The glass transition temperature (Tg), heat degradation, and the homogenity of the adhesive blend were analyzed. The adhesive was used for producing laminated wood (20×8 cm²). Results showed that the addition of lignin in the base polymer blends of API adhesive did not significantly affect the Tg of the adhesives. However, it affected the thermal decomposition and bond performance of the adhesives. There were more residues and less homogenous adhesive solution due to the addition of lignin in the base polyemr blends of API adhesives. The addition of lignin in the base polymer blends caused significant decrease in bond performance of the adhesive applied in glue laminated wood.     

The MX2Lx matrices,with M = Zn2+, Cd2+, Hg2+, X = Cl−, Br−, I− and L = pyrazine,quinoxaline, phenazine

Three structures combining the ditopic organic ligand quinoxaline with divalent metal halides MX₂, with M = Cd²⁺ and Hg²⁺, are reported. All three structures are coordination polymers, with the quinoxaline ligand acting as organic linker between metal centers. In two structures, with M = Hg²⁺ and X = Cl^? or Br^?, the formation of a 1-D, halide-bridged polymer in addition to the quinoxaline coordination polymer increases the dimensionality of the structure to 2-D, while in the case of M = Hg²⁺ and X = Cl^?, the formation of two halide-bridged polymers along with the coordination polymer results in the creation of a 3-D structure. Structural trends are identified, and the templating effect of the organic ligand is highlighted, through horizontal and vertical comparisons of these structures with related structures reported in the literature obtained upon combining the said metal halides with the related organic ligands pyrazine, quinoxaline, and phenazine, presented as the resulting matrices of structures.     

Metal ion-induced capacitance modulation in near-isostructural complexes-derived electrochromic coordination polymers

Coordination polymers and metal–organic frameworks have attracted immense attention across different fields of science as materials with numerous functional applications. Herein, we report the use of coordination polymers obtained from near-isostructural metal (Mn²⁺, Fe²⁺, and Co²⁺) bipyridine complexes as electrode materials in a symmetric supercapacitor test cell. The variation in the central metal ion (Mn²⁺ vs. Fe²⁺ vs. Co²⁺) in these nearly identical coordination complexes was found to dictate the capacitive performance of the coordination polymers obtained via Pd(II) cross-linking. The central metal ion not only influences the porosity, Brunauer–Emmett–Teller (BET) surface area (6.5 (Mn), 10.4 (Fe), and 29.7 (Co) m²/g), and the areal capacitance, but also the performance parameters such as the cycling stability and charge–discharge kinetics as well as the charge transfer mechanism. A 3:4:5 ratio for the areal capacitance values (9.1 (Mn), 12.2 (Fe), and 15.4 (Co) mF cm^?2 at a scan rate of 5 mV/s) corroborates the modulative effect of the metal center. The cycling stabilities of these coordination polymers also followed the same order. At higher current densities (>0.50 mA cm^?2), the supercapacitors fabricated from the Mn-coordination polymer were found to charge and discharge at faster rates, whereas those fabricated from Fe- or Co-coordination polymers continued to discharge at similar rates, indicating similar pore volumes for the latter as confirmed by BET surface area measurements. Although the materials used in this study resulted in modest capacitive performance, the possibilities to enhance their surface area and crystallinity is envisaged to result in the development of new, multifunctional non-carbon electrode materials with efficient electrochemical storage characteristics and tunable electro-optical properties.     

Low‐oxidation‐potential conducting polymers derived from 3,4‐ethylenedioxythiophene and dialkoxybenzenes

Monomers derived from 3,4‐ethylenedioxythiophene and phenylenes with branched or oligomeric ether dialkoxy substituents were prepared with the Negishi coupling technique. Electrooxidative polymerization led to the corresponding dialkoxy‐substituted 3,4‐ethylenedioxythiophene–phenylene polymers, with extremely low oxidation potentials (E_1/2,p = ?0.16 to ?0.50 V vs Ag/Ag⁺) due to the highly electron‐rich nature of these materials. The polymers were electrochromic, reversibly switching from red to blue upon oxidation, with bandgaps at about 2 eV. The electrochemical behavior of the oligomeric ether‐substituted polymer was investigated in the presence of different metal ions. Films of the polymer exhibited electrochemical recognition for several alkali and alkaline‐earth cations with selectivity in the order Li⁺ > Ba²⁺ > Na⁺ > Mg²⁺. Cyclic voltammetry showed a decrease in the oxidation potential and an improvement in the definition of the voltammetric response, as well as an increase in the overall electroactivity of the polymer films when the concentration of the cations in the medium was increased. These results are discussed in terms of the electrostatic interactions between the complexed cation and the redox center, as well as the diffusion of the ionic species into the polymer matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2164–2178, 2001     

Separation and quantification of quantum dots and dissolved metal cations by size exclusion chromatography–ICP-MS

The prevalence of engineered metallic nanoparticles within electronic products has evoked a need to assess their occurrence and fate within environmental systems upon potential release of these nanoparticles. Quantum dots (QDs) are mixed-metal nanocrystals with the smallest of particle sizes (2–10 nm) that readily leach heavy metal cations in water, potentially creating a co-occurrence of nanoparticulate and dissolved metal pollutants. In this report, we develop a size exclusion chromatography–inductively coupled plasma–mass spectrometry method (SEC-ICP-MS) for the rapid separation and quantification of ~5-nm-sized CdSe/ZnS QDs and dissolved Cd²⁺ and Zn²⁺ cations in water. The SEC-ICP-MS method provided a wide chromatographic separation of CdSe/ZnS QDs and dissolved Cd²⁺ and Zn²⁺ cations only when using the smallest SEC column pore size available and an eluent composition that prevented loss of metals to column polymer surfaces by using a surfactant to ensure elution of QDs (ammonium lauryl sulfate) and a complexing ligand to ensure elution of metal cations (ethylenediaminetetraacetate). Detection limits were between 0.2 and 2 µg L^–1 for Cd²⁺ and Zn²⁺ among dissolved cation and QD phases, and ranges of linearity covered two to three orders of magnitude. Gold nanoparticles of sizes 5, 10, 20 and 50 nm were also effectively separated from dissolved Au³⁺ cations, illustrating the method applicability to a wide range of nanoparticle sizes and compositions. QD and dissolved metal concentrations measured by SEC-ICP-MS were comparable to those measured using the more conventional method of centrifuge ultrafiltration on split samples for dissolved and total metals. The applicability of the SEC-ICP-MS method to environmental systems was verified by measuring QDs and dissolved metals added to samples of natural waters. The method was also applied to monitoring CdSe/ZnS dissolution kinetics in an urban river water. The SEC-ICP-MS developed here may offer improved automation for characterising heterogeneous suspensions containing >1 µg L^–1 heavy metals.     

An SKP and EIS investigation of amine adsorption on zinc oxide surfaces

A metal/oxide/polymer ‘interphase’ with mixed organic–inorganic nature insures the high stability and the strength of the adhesive joints in a variety of corrosive environments. To model the interaction of epoxy resin with a metal surface, the interaction of amines of different structure with oxidized zinc surfaces was studied by Scanning Kelvin Probe (SKP), FTIR microscopy in atmospheric conditions, and a.c. and d.c. electrochemical techniques in the aqueous electrolyte. It was shown that bidentate ligand‐ethylendiamine, forming stable chelate complexes reacts with zinc oxide with redeposition of the interphase. In air and water electrolyte, this ligand shifts the potential of Zn/ZnO electrode to the level of the oxide‐free zinc. The amines with low chelating property show low effect on the potential of Zn/ZnO. The SKP was used to measure the potential drop at epoxy resin/zinc interface. On this basis, SKP is proposed as a sensitive nondestructive technique to characterize in situ the interaction of the resin with the metal and the subsequent formation of the interphase in the metal–polymer joints. Copyright © 2010 John Wiley & Sons, Ltd.     

In vitro antibacterial and antifungal assay of poly‐(ethylene oxamide‐N,N′‐diacetate) and its polymer–metal complexes

A new polyester, poly‐(ethylene oxamide‐N,N′‐diacetate) (PEODA), containing glycine moiety was synthesized by the reaction of oxamide‐N,N′‐diacetic acid and ethylene glycol and its polymer–metal complexes were synthesized with transition metal ions. The monomer oxamide‐N,N′‐diacetic acid was prepared by the reaction of glycine and diethyl oxalate. The polymer and its metal complexes were characterized by elemental analysis and other spectroscopic techniques. The in vitro antibacterial activities of all the synthesized polymers were investigated against some bacteria and fungi. The analytical data revealed that the coordination polymers of Mn(II), Co(II) and Ni(II) are coordinated with two water molecules, which are further supported by FTIR spectra and TGA data. The polymer–metal complexes showed excellent antibacterial activities against both types of microorganisms; the polymeric ligand was also found to be effective but less so than the polymer–metal complexes. On the basis of the antimicrobial behavior, these polymers may be used as antifungal and antifouling coating materials in fields like life‐saving medical devices and the bottoms of ships. Copyright © 2007 John Wiley & Sons, Ltd.     

Silica Polyamine Composites: New Supramolecular Materials for Cation and Anion Recovery and Remediation

Summary: The surface coverage of amorphous silica gels used in the synthesis of silica polyamine composites has been investigated by ²⁹Si NMR. By diluting the polyamine anchor silane, chloropropyl trichlorosilane, with methyl trichlorosilane it was found that surface coverage could be markedly improved for a range of amine polymers after grafting to the silica surface. The commensurate decrease in the number of anchor points and increase in the number of free amines results in an increase in metal capacity and/or an improvement in capture kinetics. Solid state CPMAS-¹³C NMR has been employed to investigate the structure and metal ion binding of a series of these composite materials. It is reported that the highly branched polymer, poly(ethyleneimine) (PEI) exhibits much broader ¹³C NMR resonances than the linear polymers poly(allylamine) (PAA) and poly(vinylamine) (PVA). These results are understood in terms of the low energy conformations calculated from molecular modeling studies. Three new applications of the technology are also presented: 1) separation of lanthanides as a group from ferric ion and all other divalent ions; 2) a multi step process for recovering and concentrating the valuable metals in acid mine drainage; 3) a process for removing low level arsenic and selenium in the presence of sulfate using immobilized cations on the composite materials.     

Temperature compensation of dye doped polymeric microscale lasers

In this article, a new technique for building temperature compensated microscale lasers that are based on the morphology dependent resonances phenomenon is presented. The dome shaped resonator is made with a mixture of NBA 107 UV curable polymer and rhodamine 6 g dissolved in ethanol solution. Since polymers usually exhibit linear thermal expansion and thermo‐optic coefficients that are opposite in sign but similar in order of magnitude, it is possible to compensate for temperature over the dome shaped resonator by tuning the dye concentration and the ratio between the polymer and dye solution. Experiments with dye concentration between 10^?2 to 10^?3 M and polymer and dye solution ratios between 1:1 and 4:1 are conducted. The sensitivity for all cases is presented, and the quality factor Q is investigated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 789–792     

polyMOFs: A Class of Interconvertible Polymer‐Metal‐Organic‐Framework Hybrid Materials

Preparation of porous materials from one‐dimensional polymers is challenging because the packing of polymer chains results in a dense, non‐porous arrangement. Herein, we demonstrate the remarkable adaptation of an amorphous, linear, non‐porous, flexible organic polymer into a three‐dimensional, highly porous, crystalline solid, as the organic component of a metal–organic framework (MOF). A polymer with aromatic dicarboxylic acids in the backbone functioned as a polymer ligand upon annealing with Zn^II, generating a polymer–metal–organic framework (polyMOF). These materials break the dogma that MOFs must be prepared from small, rigid ligands. Similarly, polyMOFs contradict conventional polymer chemistry by demonstrating that linear and amorphous polymers can be readily coaxed into a highly crystalline, porous, three‐dimensional structure by coordination chemistry.