Novel trifluoromethylated epoxy based thermosets: synthesis and characterization

Two series of trifluoromethylated crosslinked epoxy‐based polymers with different molecular architectures and fluorine contents (from 1 to 5 wt%) have been investigated. The epoxy monomer was a diglycidyl ether of bisphenol A, and the curing agents were 3‐(trifluoromethyl)aniline and 4,4′‐methylenebis(3‐chloro‐2,6‐diethylaniline). The structural parameters of networks such as gelation and vitrification and the properties of the resulting fluorinated materials were investigated and compared. Final materials showed high transparency with an ultraviolet‐visible absorption cut‐off between 350 and 380 nm, low moisture (0.60 wt%) and a decrease in dielectric constant from 6.3 to 5.2 with increasing fluorine content. Copyright © 2012 Society of Chemical Industry     

Flammability studies of thermally resistant polymers using cone calorimetry

The effectiveness of a set of thermally resistant polymers was evaluated for aircraft applications using the cone calorimeter (ASTM E1354/ISO 5660) under heat fluxes simulating real scale fires. This study included eight developmental and commercial thermally resistant polymers available in the literature and/or marketplace. The polymers included were aromatic polyester, polyetherimide, fluorine‐containing polyetherketone, phosphorus and fluorine‐containing co‐polyetherketone, fluorine and phosphorus‐containing polyether, fluorine‐containing polyester, poly(dimethylsiloxane)etherimide and polysulfone. The effects of fluorine, phosphorus, silicon and sulfone group in polymers were examined. This evaluation was based on time to ignition, peak, average and total heat release rates obtained at an external heat flux of 50 kW/m². Other parameters such as effective heat of combustion, mass loss and rate of smoke and toxic gas evolution were collected during the cone calorimeter test. Copyright © 2000 John Wiley & Sons Ltd.     

Plasma polymer membranes from hexafluoroethane/hydrogen mixtures for separation of oxygen and nitrogen

Thin plasma polymer layers were produced employing feed mixtures of hexafluoroethane and hydrogen in an rf parallel-plate reactor. The layers are intended for use in membrane-based separation of oxygen and nitrogen. The hexafluoroethane-to-hydrogen mixture ratio was varied over a wide range, whereas all other process parameters (power, pressure, substrate temperature, and total gas flow) were held constant. The plasma polymers were examined by scanning electron microscopy, X-ray analysis, quantitative elemental analysis, and X-ray photoelectron spectroscopy. Permeability coefficients of oxygen and nitrogen and selectivities of the pure gases were determined. Pinhole-free plasma polymer films containing different amounts of fluorine, carbon, and hydrogen were formed. The distributions of fluorine and hydrogen in the products reflect their distributions in the feed gas. Traces of oxygen in some of the polymers are explained by the reaction of trapped radicals with atmospheric oxygen on the samples' exposure to air. Fluorine-containing carbon moieties such as CF₃, CF₂, and CF, and carbon moieties with fluorine atoms exclusively in secondary positions are present. A method of calculating crosslink density using the analytical data is described. The oxygen permeability coefficient and the selectivity of the plasma polymers increase as the hexafluoroethane content of the feed gas is raised. This behavior is attributed to growing solubility selectivity as a result of the rising fluorine content of the polymers. Maximum selectivity amounts to 3.4 at an oxygen permeability coefficient of 21 Barrer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1517–1526, 1997     

Synthesis of Some Fluorinated Phenylmethylsiloxane Polymers and Characterization of Their Surface Properties

Conditions have been established for the preparation of three fluorinated phenylmethylsiloxane polymers via syntheses of the appropriate monomers, controlled hydrolyses of these monomers, and polymerization of the resulting oligomers. The polymers thus prepared, in increasing order of fluorine content, were poly(4-fluorophenylmethylsiloxane), poly(3,5-difluorophenylmethylsiloxane), and poly[3,5-bis(trifluoromethyl)phenylmethylsiloxane]. The surface energies of the first two polymers were measured and found to be very similar to those of typical fluorosubstituted polymers that are aliphatic rather than aromatic. This similarity indicates that the bulky phenyl groups do not significantly interfere with migration of the fluorine atoms to the surfaces of these fluorinated phenylmethylsiloxane polymers.     

New fluorinated acrylic polymers for improving weatherability of building stone materials

Acrylic polymers are widely used for their suitability to be shaped in different molecular structures. However, while very appropriate for many applications, these materials are characterized by a limited outdoor stability. In order to improve this last characteristic while maintaining the simple and flexible synthetic route, a study was performed based on the preparation of fluorinated polymers from acrylic monomers where several H-atoms in different positions were replaced with F-atoms. The structure design was aimed to optimize (e.g. minimize) the fluorine content of the final material while obtaining improved chemical and photochemical stability, good filmability and limited permeability to condensed water. The preparation of polymers of methacrylates derived from partially fluorinated alcohol by free radical mechanism is described. The fluorine content and distribution in the macromolecules is modulated by selecting different monomers and by copolymerization with nonfluorinated acrylates or vinylethers. The selection of the comonomers and their relative content in the polymer allows to control the glass transition temperature and the filmability as well as the protection efficiency of the coating. Polymers derived from more complex monomers such as -trifluoromethyl-methylacrylate are also described. The suitability of these new materials for protective coating of stones is tested by evaluating their stability to different chemical and physical agents and their selective permeability to water vapour vs. condensed water.     

In situ atomic oxygen erosion study of fluoropolymer films using X‐ray photoelectron spectroscopy

The surfaces of a homologous series of fluoropolymers were characterized in situ using X‐ray photoelectron spectroscopy before and after a 15‐min exposure to the flux produced by a unique hyperthermal atomic oxygen (AO) source, which produces a flux of about of 10¹⁵ atoms cm^?2 s^?1. The linear polymers investigated in this study include high‐density polyethylene (HDPE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVdF), and poly(tetrafluoroethylene) (PTFE). They possess a similar base structure with increasing fluorine‐to‐carbon ratios of 0, 1 : 2, 1 : 1, and 2 : 1, respectively. No interaction of the AO with the nonfluorine‐containing linear polymer HDPE was detected over this short exposure. However, a correlation exists between the chemical composition of the fluorinated polymers and the induced chemical and structural alterations occurring in the near‐surface region as a result of exposure to AO. The data indicate that AO initially attacks the fluorine portion of the polymers, resulting in a substantial decrease in the near‐surface fluorine concentration. The near‐surface fluorine‐to‐carbon ratios of PVF, PVdF, and PTFE decreased during the 15‐min AO exposure by 68, 39, and 18.5%, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1977–1983, 2004     

Free Radicals and ROS Induce Protein Denaturation by UV Photostability Assay

Oxidative stress, photo-oxidation, and photosensitizers are activated by UV irradiation and are affecting the photo-stability of proteins. Understanding the mechanisms that govern protein photo-stability is essential for its control enabling enhancement or reduction. Currently, two major mechanisms for protein denaturation induced by UV irradiation are available: one generated by the local heating of water molecules bound to the proteins and the other by the formation of reactive free radicals. To discriminate which is the likely or dominant mechanism we have studied the effects of thermal and UV denaturation of aqueous protein solutions with and without DHR-123 as fluorogenic probe using circular dichroism (CD), synchrotron radiation circular dichroism (SRCD), and fluorescence spectroscopies. The results indicated that the mechanism of protein denaturation induced by VUV and far-UV irradiation were mediated by the formation of reactive free radicals (FR) and reactive oxygen species (ROS). The development at Diamond B23 beamline for SRCD of a novel protein UV photo-stability assay based on consecutive repeated CD measurements in the far-UV (180–250 nm) region has been successfully used to assess and characterize the photo-stability of protein formulations and ligand binding interactions, in particular for ligand molecules devoid of significant UV absorption.     

Surface Modification of Some Fluorine Polymer Films by Glow Discharges

Extensive study has been made of the effects of various types of glow discharge plasmas on the changes of the surface properties of some fluorine polymers. The properties were investigated as a function of such factors as the exposing period, aging after exposure, type of plasma, and so on.

It was found that the wettability and the critical surface tensions were changed considerably with plasma exposure and that periods of several tens of seconds are long enough to cause changes. The extents of change were not so prominent for fluorine polymers as for polyethylene, and this fact may show the important role of the fluorine atom in the surface properties even after the plasma treatments.     

Synthesis,spectroscopy, and electrochemical investigation of new conjugated polymers containing thiophene and 1,3,4-thiadiazole in the main chain

Novel photoluminescent donor–acceptor poly(p-phenylenevinylene)-type conjugated polymers containing thiophene and 1,3,4-thiadiazole units in the main chain were synthesized from 2,5-bis(5-bromomethyl-2-thienyl)-1,3,4-thiadiazole and 1,3/1,4-benzenedialdehyde by Wittig–Horner reaction. The synthesized polymers were characterized by the use of thermal analysis and spectroscopic (infrared, UV-visible absorption, and photoluminescence) measurement. The resultant material exhibited bluish green, green, and orange fluorescence in their solution and thin film and solid forms, respectively. The redox property of the polymers has also been studied by cyclic voltammetry. The optical and electrochemical studies reveal that these novel polymers are new promising materials for the development of efficient polymer light-emitting diodes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influences of the substrate temperature on the films plasma-polymerized at the low system pressure

Summary Influences of the substrate temperature and the system pressure on the plasma polymerization were investigated from a viewpoint of the chemical composition of the deposited polymers. Both parameters influenced the plasma polymerization of tetrafluoroethylene (TFE). The deposition at the high substrate temperature as well as at the low system pressure led to the formation of plasma polymers being poor in fluorine moieties. This result indicates that the chemical composition of the deposited plasma polymers may be determined by interactions of activated molecules with substrate surfaces.     

Synthesis,characterization, and study of antibacterial activity of homopolymers and copolymers of 4-benzyloxyphenylacrylates for pressure-sensitive adhesive application

Poly(4-benzyloxyphenylacrylate) and its copolymers with glycidyl methacrylate were synthesized from the monomer, 4-benzyloxyphenylacrylate (4-BOPA) by free radical solution polymerization. The synthesized homopolymers and copolymers were characterized by UV, FTIR, ¹H-NMR, and ¹³C-NMR spectroscopic techniques. The thermal stability of the polymers was performed by thermogravimetric analysis in inert atmosphere. The glass transition temperatures of the polymers were determined by differential scanning calorimeter. The lap shear strength of the polymers was determined by Universal testing machine. The antibacterial activities of the polymers were also studied by UV spectroscopy. The results of the TGA analysis showed that the polymers possess good stability even beyond 250°C. Different concentrations of the polymer solutions were prepared and tested for their adhesive strength by applying them between leather strips. Thus, the results of the study reveal that the poly(4-benzyloxyphenylacrylate-co-glycidyl methacrylate) has good adhesive strength compared with poly(4-BOPA), which can be used for its adhesive property suitable for high temperature applications, which can also resist the bacterial growth on the applied surface of the material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PHOTO-DEGRADATION OF HYDROPHOBIC DERIVATIVES OF PYRIDINECARBOXYLIC ACID AS COPPER EXTRACTANTS FROM CHLORIDE MEDIA

ABSTRACT

The photo-stability of 2-ethylhexyl pyridine-3-carboxylate and N,N′-di(2-ethylhexyl)pyridine-3,5-dicarboxamide as the model extractants of copper from chloride media were studied and compared with the photo-stability of di(2-ethylhexyl) pyridine-3,5-dicarboxylate, N,N,N′,N′-tetrahexylpyridine-3,5-dicarboxamide and the hydroxyoxime copper extractants. Also the resistance against the UV light the copper(II) complexes of tested extractants were done. The obtained results of photo-degradation indicate that the UV light degraded amide derivatives and esters of pyridine-3,5-dicarboxylic acid and pyridine-3-carboxylic acid. A comparison of the photo-stability of oximes and derivatives of pyridine-3,5-dicarboxylic acid and pyridine-3-carboxylic acid indicates that all tested derivatives of pyridinecarboxylic acid are more stable than hydroxyoxime copper extractants. The copper complexes of derivatives of pyridinecarboxylic acid are less stable than the copper complexes of hydroxyoxime.     

Aromatic triblock polymers from natural sources as protective coatings for stone surfaces

Aromatic triblock polymers were synthesized, characterized, and tested as protective coatings for stone surfaces. Syntheses were carried out by a ring opening polymerization process from specifically synthesized monomers ((3S)‐6‐methyl‐3‐phenyl‐1,4‐dioxan‐2,5‐dione or 1,4‐benzodioxepin‐3‐methyl‐2,5‐dione) and a perfluoropolyether diol (Fluorolink D10‐H), as chain initiator. Polymers were characterized through spectroscopic and analytical techniques while their stability under photo‐oxidative conditions was tested using a Solar Box. An excellent stability to environmental conditions was noticed with very low degradation during accelerated aging tests up to 1000 h, as detected by FTIR, molecular weight, DSC and weight loss. Furthermore, these polymers formed an excellent protective coating on the stone surface as shown by capillary water absorption test. Finally, as expected, very stable coatings were obtained as shown by aging tests. The stone surface showed negligible changes of color and a good hydrorepellency confirming a good durability of treatments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43377.     

Calorimetric determination of the heat and products of detonation of an Unusual CHNOFS Explosive

The heat of detonation of an explosive is determined by its chemical structure and the nature of the products that are formed during detonation. Most explosives contain the elements CHNO and, because plastic bonded explosives often include stable halocarbon polymers, the elements fluorine and/or chlorine may also be present. However, little is known about the effect of the combination of fluorine and sulfur on heat of detonation, specifically the SF₅ group. Detonation calorimetry was the experimental technique used to determine the heat and very unusual products of detonation of tris-(fluorodinitroethyl) pentafluorothio ethylorthocarbonate.     

Synthesis of new organic semiconductors based on poly(2‐anilinoethanol) doped with different acids and investigation of their electro‐optical properties

The polyaniline (PANI) was synthesized using different dopant acids (iminodiacetic, methanesulfonic, phosphoric, and boron trifuoride) using oxidative polymerization method. These obtained new polymers were characterized by using spectrophotometric methods such as FTIR, UV–vis. The calculated value of the optical energy gap for the doped investigated polymer was reached to 3.70 eV for PANI‐OH doped by boron trifuoride. The conductivity of the polymers was also investigated. The direct current (dc) conductivity as a function of temperature for the doped polymers has been studied. The results show increase in the conductivity with increase in temperature. Also, the value of dc conductivity at room temperature was found to be greater than that of the undoped PANI by nearly one to four orders of magnitude with respect to the used dopant acid. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Surface fluorination of transparent polymer film

Transparent polymer film was fluorinated by contacting with fluorine gas. The fluorinated layer depth was determined from the visual spectrum. The relation between fluorinated depth d and reaction time t was represented by d = k·t^½. This result indicates that fluorine diffusion plays a predominant role in forming the diffusion profile. The apparent activation energy of fluorine gas diffusion into polystyrene (PS) and polycarbonate (PC) was 2.8 kcal/mole and 6.6 kcal/mole, respectively. The refractive index distribution from surface to center, which corresponds to the fluorine content in the layer, was determined by interference microscopy. PS and PC showed nearly stepwise change of refractive index. On the other hand, poly(methyl methacrylate) showed a gradual change. These results are compatible with fluorine analysis data and IR spectra of the fluorinated polymers. On the basis of these results, antireflecting layers on plastic lens or plate, plastic optical fiber, or fiber sheet were formed.     

Synthesis and evaluation of a metal‐complexing imprinted polymer for Chinese herbs quercetin

In this study, a metal‐complexing imprinted polymer has been prepared using the complex of Quercetin and Co(II) (Qu‐Co(II)) as template (Quercetin is a kind of flavonoid, which is a class of important active ingredients of Chinese herbs.). The polymers were synthesized in the mixed solution of methanol and tetrahydrofuran by photo‐ and thermal‐initiated polymerization, respectively. The complex ratio between Qu and Co(II), as well as the ternary complexation of Qu, Co(II), and acrylamide, was assessed in differential UV absorption spectrometry. Fourier transform infrared spectra (FTIR) were useful to verify whether the polymers prepared in two ways had the same molecular structure. The effect of initiation mode was studied by the transmission electron microscopy (TEM) and equilibrium binding experiments. Isothermal adsorption and selectivity experiments showed that molecularly imprinted polymers exhibited high affinity and specific recognition for Qu by introducing cobalt ion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bis(thien-2-yl)-2,1,3-benzothiadiazole-diketopyrrolopyrrole-based acceptor–acceptor conjugated polymers: Design,synthesis, and the synergistic effect of the substituent on their solar cell properties

Three acceptor–acceptor conjugated copolymers ( TBT-DPP , FTBT-DPP , and HFTBT-DPP ) with different substituent groups have been synthesized with palladium-catalyzed Stille coupling condensation polymerization assisted with microwave. Polymer solar cells (PSCs) based on these copolymers as the electron donors and PC71BM as the acceptor have been fabricated. The synergistic effect of the substituent between two fluorine atoms and hexyl alkyl chains in bis(thien-2-yl)-2,1,3-benzothiadiazole fragment on their solar cell properties has been investigated. Both the fluorine atoms and the synergistic effect can improve the solubility of the polymers effectively while the excellent thermal stability properties are still retained. Two fluorine atoms (polymer FTBT-DPP ) increased the power conversion efficiency of the PSCs twice compared with TBT-DPP (without substituent). The synergistic effect (polymer HFTBT-DPP ) decreased that seriously to zero. Density function theory calculations showed that the conjugation level of the polymer backbone is one of key factors. It demonstrates that the synergistic effect of fluorine atoms and alkyl chains in the same fragment does not always work well in improving the PSCs performance.     

Synthesis and characterization of fluorinated polyacrylate–cellulose acetate butyrate interpenetrating polymer networks

Fluorinated polyacrylates are highly hydrophobic and oleophobic. However, their poor mechanical properties prevent their development in many applications. Combination of a fluorinated polyacrylate network with a rigid cellulose acetate butyrate (CAB) network in an interpenetrating polymer network (IPN) architecture is an effective method for improving the mechanical properties of fluorinated polyacrylates. IPNs combining poly(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate) (polyAcRf6) with CAB were prepared according to an in situ polymerization/crosslinking synthesis. CAB was crosslinked by addition between unmodified hydroxyl groups and the isocyanate of a pluri‐isocyanate crosslinker. The fluorinated network was obtained through free‐radical copolymerization of 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate with poly(ethylene glycol dimethacrylate). The rates of formation of both networks were followed using Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) of IPNs show a single glass transition temperature and a single mechanical relaxation temperature, which are characteristic of a high degree of interpenetration between the partner networks. The mechanical properties of IPNs are greatly improved compared with those of the single fluorinated network. CAB/polyAcRf6 IPNs were prepared, and characterized using DSC and DMTA as well as contact angle measurements for their surface properties. As hoped, the mechanical properties of such materials are much improved compared with those of the fluorinated partner alone. Copyright © 2010 Society of Chemical Industry     

Synthesis of functionalized polyolefins with novel applications as protective coatings for stone Cultural Heritage

Ethylene copolymers were synthetized for application as protective coatings for stone surface monuments. An increased compatibility of the apolar polyethylene with inorganic materials was obtained by introducing some oxydril and ester groups in the polymers. Two different copolymerizations of ethylene were followed: with 10-undecen-1-ol (UDO) and 7-methyl-1,6-octadiene (MOD) catalyzed by Ziegler–Natta metallocene/methylaluminoxane (MAO) catalyst. In the first case the polar comonomer UDO was reacted with MAO prior to copolymerization to improve its compatibility with the catalyst. Residual double bonds in the copolymerization with MOD were hydroesterificated/hydrogenated. Some synthesis were performed in the presence of hydrogen as chain transfer agent to reduce molecular weights and increase solubility of the products. The polyolefins were characterized by analytical and spectroscopic techniques and their photochemical stability in environmental conditions was tested through an accelerated ageing chamber. Polyolefins were applied on stone specimens showing a slight chromatic change of the surfaces, not perceptible by naked eye. The protection performances were also evaluated in terms of water repellency, photo-oxidative stability and colour change of the treated stone surfaces in comparison with Paraloid B-72, an acrylic resin widely applied in the field of conservation. Ethylene/10-undecen-1-ol copolymer kept its protective efficiency after the ageing cycles thanks to its good stability to photo-oxidative degradation.