Click synthesis and reversible electrochromic behaviors of novel polystyrenes bearing aromatic amine units

Novel electrochromic polymers were prepared by the click postfunctionalization of poly(4‐azidomethylstyrene) with alkyne‐containing aromatic amine units in the presence of Cu(I) catalysts. Two kinds of aromatic amine units, tris(4‐alkoxyphenyl)amine and N,N,N′,N′‐tetraphenyl‐p‐phenylenediamine, were introduced into polystyrene side chains, which were completely characterized by gel permeation chromatography–multiangle light scattering, nuclear magnetic resonance, and infrared spectroscopies, and elemental analysis. Thermal analyses demonstrated the high stability with the decomposition temperatures exceeding 300 °C even after postfunctionalization. The UV–vis absorption spectra of the polymer thin films revealed negligible absorption in the visible region, as reasonably confirmed by visual observation. The polymer thin films were prepared by spray‐coating on an indium tin oxide‐coated glass plate. Cyclic voltammograms of these films exhibited anodic peaks ascribed to the oxidation of the side‐chain aromatic amine moieties. The tris(4‐alkoxyphenyl)amine unit displayed one‐step oxidation at 0.287 V (vs. Ag/AgCl), while the N,N,N′,N′‐tetraphenyl‐p‐phenylenediamine unit showed two‐step oxidations at 0.297 and 0.641 V. These oxidation processes produced new colors of the polymer films. The former triarylamine‐based chromophore provided a blue color after the oxidation, while the latter phenylenediamine‐based chromophore showed a potentially controlled green and dark blue colors. The reversibility and switching behaviors of these color changes were also comprehensively investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effects of packing structure on the optoelectronic and charge transport properties in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole)

Spin-coated poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films of different molecular weights (Mn= 9-255 kg/mol), both in the pristine and annealed state, were studied in an effort to elucidate changes in the polymer packing structure and the effects this structure has on the optoelectronic and charge transport properties of these films. A model based on quantum chemical calculations, wide-angle X-ray scattering, atomic force microscopy, Raman spectroscopy, photoluminescence, and electron mobility measurements was developed to describe the restructuring of the polymer film as a function of polymer chain length and annealing. In pristine high molecular weight films, the polymer chains exhibit a significant torsion angle between the F8 and BT units, and the BT units in neighboring chains are close to one another. Annealing films to sufficiently high transition temperatures allows the polymers to adopt a lower energy configuration in which the BT units in one polymer chain are adjacent to F8 units in a neighboring chain ("alternating structure"), and the torsion angle between F8 and BT units is reduced. This restructuring, dictated by the strong dipole on the BT unit, subsequently affects the efficiencies of interchain electron transfer and exciton migration. Films exhibiting the alternating structure show significantly lower electron mobilities than those of the pristine high molecular weight films, due to a decrease in the efficiency of interchain electron transport in this structure. In addition, interchain exciton migration to low energy weakly emissive states is also reduced for these alternating structure films, as observed in their photoluminescence spectra and efficiencies.     

Tailoring the desired optical and mechanical performance of polyester‐plasticized PVC films: the role of different light stabilizers on the photo‐degradation

Effect of hindered amine light stabilizer (HALS: C944) and ultraviolet absorbers (UVAs: UV326, UV531) on the photo‐stabilities of polyester‐plasticized poly(vinyl chloride) (PVC) and polyester‐plasticized PVC/pigment yellow (PY) films were studied systematically. Both ultraviolet absorbers (UVAs) and hindered amine light stabilizer (HALS) could slow down the discoloration of polyester‐plasticized PVC and polyester‐plasticized PVC/PY films. However, the addition of UVAs protected polyester‐plasticized PVC films from being discolored and its efficiency is higher than HALS. The specific order of stabilizing effect on the photo‐oxidation is UV326 > UV531 > C944. For the optical performance, both UVAs and HALS could help to maintain the transmittance of visible light after photo‐degradation. The former could effectively adsorb ultraviolet (UV) light and resulted in lower transmittance of UV light. For the polyester‐plasticized PVC/PY systems, even though HALS and UVAs cannot help to maintain the shielding ability in high‐energy visible region after UV irradiation, they can help prevent the loss in transmittance of visible light. The surface morphology exhibited small holes on the surface of the films that contain UV531 or UV326; while large and deep holes were observed on the surface of PVC films without additives, C944‐doped and C944/PY‐doped films, indicating the higher UV‐stabilizing effect of UVAs. With regard to mechanical properties, UVAs and HALS can help to prevent the loss. Our present study systematically revealed the role of different stabilizers on the polyester‐plasticized PVC and polyester‐plasticized PVC/PY systems and paved the way to offer PVC materials with functional optical performance and desired long‐term performance using different light stabilizers. Copyright © 2017 John Wiley & Sons, Ltd.     

Photomobile Polymer Materials: Photoresponsive Behavior of Cross‐Linked Liquid‐Crystalline Polymers with Mesomorphic Diarylethenes

Cross‐linked liquid‐crystalline (LC) polymers with a mesomorphic diarylethene were prepared to demonstrate a versatile strategy for cross‐linked photochromic LC polymers as photomobile materials. Upon exposure to UV light to cause photocyclization of the diarylethene chromophore, the cross‐linked polymer films bend toward an actinic light source. By irradiation with visible light to cause a closed‐ring to open‐ring isomerization, the bent films revert to the initial flat state. Without visible‐light irradiation, the bent films remain bent even at 120 °C, indicating high thermal stability of the cross‐linked diarylethene LC polymers.     

Photolabile carboxylic acid protected terpolymers for surface patterning. Part 1: Polymer synthesis and film characterization

We present the synthesis and characterization of a series of photolabile phenacyl derivative polymers and their subsequent thin film preparation. These systems are composed of up to three methacrylate units: a photolabile component including a p-methoxyphenacyl moiety which after selective irradiation (UV/laser) can provide free carboxylic groups in specific areas for further modification; an anchoring unit, trimethoxysiloxane or glycidyl methacrylate derivative, which allows the covalent attachment of the polymer to the substrate; and a spacer, methyl methacrylate or styrene, which in the appropriate proportion ensures the formation of films with good quality. Structural and thermal properties of these materials have been analyzed by means of NMR, FTIR, elemental analysis, UV, gel permeation chromatography, differental scanning calorimetry, and thermogravimetric analysis. The polymers have been subsequently processed by spin coating to render ultrathin films (<50 nm). Topographic and structural characterization studies of the films have been carried out with atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. The extent of the substrate attachment of the polymers depending on the nature of the anchoring groups have been studied by ellipsometry and FTIR.     

Labile hyperbranched polymers used as nanopore-forming agents in polymeric dielectrica

Hyperbranched polyesters containing labile triazene units in the main chain have been synthesized and characterized. These structure decompose photochemically upon UV irradiation and thermally above 160°C. Homogeneous incorporation of these globular, functional polymers in thermostabile polymer matrices (polyimides and BCB polymers) was possible. Smooth films from blends of thermolabile matrix and up to 50% hyperbranched polymers could be prepared and have been studied as insulating material in microelectronic multilayer applications.     

Functionalized conducting polymers for chemical sensors – an in situ ESR/UV‐Vis‐NIR voltammetric study

The redox and optical properties of various well defined polymer and copolymer films containing pyrrole or thiophene units were studied. The in situ ESR/UV‐Vis‐NIR spectroelectrochemistry was applied to investigate polymers and copolymers deposited both electrochemically or by a special chemical procedure using adhesion promoter onto the optically transparent indium‐tin‐oxide (ITO) electrodes. The spectroelectrochemical responses of chemically and electrochemically prepared polythiophenes on ITO were compared and the electronic structures of both polymers found to be similar. In situ ESR/UV‐Vis‐NIR voltammetric studies on electrochemically prepared copolymers containing pyrrole units and various N,N′‐ethylene‐bis(salicylidenimine) (salen) transition metal complexes indicate the presence of both polysalen and polypyrrole redox active centers in the copolymer.     

Electrical conductivity of partly oxidized aromatic and heteroaromatic polymers

The electrical conductivity of aromatic and heteroaromatic polymers as well as polymers with aromatic, heteroaromatic and vinylene units in the main chain, can be enhanced by oxidation. In a single electron transfer reaction, a polymer with a salt structure (“doped polymer”) can be formed. Such polymers can also be prepared in a one-step reaction from low-molecular weight compounds by oxidants, as well as by electrochemical reaction. Electrochemically produced samples have higher electrical conductivities (as high as 6298K = 0,5 Ω⁻¹ · cm⁻¹) than samples made by chemical oxidation from the same starting material.     

Construction of diads and triads copolymer systems containing perylene,porphyrin, and/or fullerene blocks

A series of conjugated copolymers containing perylene, porphyrin, and/or fullerene units on the main chain have been synthesized. The structures and photophysical properties of polymers were characterized by FTIR, NMR, UV–vis, and fluorescence spectroscopy, gel permeation chromatography, and cyclic voltammetry. The photoinduced charge transfer properties of the films were also measured by a three‐electrode cell technique. A rapid, steady, and reproducible cathodic photocurrent response for each polymer was produced when the film was irradiated by a white light. The SEM and TEM images displayed the aggregation superstructures of the polymers. In chloroform, polySPeZnP₂F could form a large quantity of spherical nanoparticles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5863–5874, 2006     

Low Band Gap Donor–Acceptor Conjugated Systems Based on 3‐Alkoxy or 3‐Pyrrolidino‐4‐cyanothiophene and Benzothiadiazole Units

3‐Hexyloxy‐4‐cyanothiophene, 3‐pyrrolidil‐4‐cyanothiophene, and 3,4‐ethylenedioxythiophene (EDOT) units are used with benzothiadiazole as building blocks for the development of three new conjugated donor–acceptor–donor (DAD) derivatives. The DAD molecules have the central acceptor part, which is formed by combining electron‐withdrawing cyano groups and the benzothiadiazole moiety, in common. Theoretical calculations and UV/Vis and electrochemical data reveal the key role of the end‐capped donor to tune the electronic properties of the derivatives. A study of the electropolymerization process of the three derivatives shows the strong influence of the donor parts on both the reactivity of the precursors and the electronic properties of the resulting polymers. Derivatives end‐capped with pyrrolidinocyano thiophene or EDOT units lead to films of polymers presenting low band gaps of around 0.9–1.4 eV. Upon oxidation, the two polymers present different behavior. In the presence of the pyrrolidinocyano thiophene moieties, oxidation leads to a blueshift of the absorption bands, whereas with EDOT units a classical redshift, giving high absorption in the near‐IR region, is observed for the oxidized states.     

Preparation of conducting copolymers by oxidative electropolymerization of 2,2′-bithiophene with pyrrole

Various feed ratios of 2,2′-bithiophene (BT) and pyrrole (PY) were electropolymerized to low conversion and the polymers analyzed for their mer ratios. The polymeric product was rich in polypyrrole (PPY), but the composition could be varied by control of the electrode potential. The increase in BT content is not linear with composition, and the physical evidence indicates oxidative copolymerization and not the formation of the two homopolymers. The data can be interpreted on a copolymerization equation despite the absence of steady state conditions. Sets of reactivity ratios were determined for the polymers formed at two potentials. The electrical efficiencies for polymer formation approach stoichiometric values for oxidative polymerization.     

Structure-property relationships for novel wholly aromatic polyamide-hydrazides containing various proportions of para-phenylene and meta-phenylene units: I. Synthesis and characterization

A series of novel wholly aromatic polyamide-hydrazides was synthesized by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl chloride (TCl), isophthaloyl chloride (ICl), or mixtures of various molar ratios of TCl and ICl in anhydrous N,N-dimethylacetamide (DMAc) as a solvent. Polymer structures were identified by elemental analysis and infrared spectroscopy. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. The content of para- and meta-phenylene moieties was varied within this series so that the changes in the latter were 10 mol % from polymer to polymer, starting from an overall content of 0-100 mol %. The prepared polymers were characterized for their properties in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as solubility, intrinsic viscosity, moisture regain, mechanical properties and thermal as well as thermo-oxidative stability. The polymers were readily soluble in several organic polar solvents such as DMAc, N,N-dimethylformamide, dimethyl sulphoxide, N-methyl-2-pyrrolidone and hexamethyl phosphoramide and could be cast into flexible films. Their solubilities were found to increase remarkably with introduction of meta-phenylene moieties into the polymer chains. Their intrinsic viscosities ranged from 0.73 to 4.83 dl g⁻¹ in DMAc at 30 °C and increased with the increase of para-phenylene units content. Mechanical properties of the films produced from these polymers are improved markedly by substitution of para-phenylene units for meta-phenylene units. Thermogravimetric studies revealed that the completely para-oriented type of polymer has better thermal and thermo-oxidative stability relative to that of the other polymers. Moreover, the results reveal that the prepared polymers have a great affinity to water sorption. The hydrophilic character increases as a function of meta-oriented phenylene rings incorporated into the polymer chains.     

New sulfonated engineering polymers via the metalation route. II. Sulfinated/sulfonated poly(ether sulfone) PSU Udel and its crosslinking

New mixed sulfinated/sulfonated polysulfone PSU Udel has been produced by partial oxidation of sulfinated PSU with NaOCl. From the mixed sulfinated/sulfonated PSU, thin crosslinked polymer films have been produced by S-alkylation of the residual sulfinate groups with α,ω-diiodoalkanes having 4–10  (CH₂) units. The advantages of the partial oxidation process using NaOCl are as follows: (1) The desired oxidation degree can be adjusted finely. (2) No side reactions take place during oxidation. (3) The partially oxidized polymers is stable at ambient temperature. By variation of the oxidation degree of the sulfinated/sulfonated prepolymer and by variation of the chain length of the diiodo crosslinker, crosslinked membranes with a large range of properties in terms of ionic conductivity, swelling, and permselectivity have been produced. The partially oxidized polymers have been characterized by redox titration, ¹H-NMR, and FTIR. The crosslinked membranes have been characterized in terms of ionic conductivity (resistance), permselectivity, and swelling in dependence on ion-exchange capacity and oxidation degree of the prepolymers. In addition, the thermal stabilities of the membranes have been determined by TGA, and FTIR spectra have been recorded on the crosslinked films. Selected membranes show low ionic resistances, low swelling, and good temperature stability which makes them promising candidates for application in (electro)membrane processes. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1441–1448, 1998     

Synthesis and characterization of new,soluble polyazomethines bearing fluorene and carbazole units in the backbone and solubility‐improving moieties in the side group

A series of novel, soluble polyazomethines bearing fluorene and carbazole moieties in the main chain and solubility‐improving moieties in the side group (dibutyl, ethylhexyl, thienylethyloxy, furyl, and fluorenyl) were synthesized. Good‐quality films of these polymers were prepared through the conventional solution‐casting and drying processes. Depending on the polymer structure, some polymers showed a glass‐transition temperature (107–167 °C) and others showed a melting temperature (285–341 °C). The temperature of 5% weight loss under nitrogen atmosphere of the polymers ranged from 370 to 464 °C. The results indicated that the side groups incorporated into the polyazomethine structure in this work improved the polymer solubility without sacrificing thermal stability. Depending on the polymer structure, some of the polymers were crystalline whereas others were amorphous. All the polyazomethines were solution‐processable and thermally stable, making them potential candidate materials for applications in microelectronics and aerospace. Moreover, the features in the UV–visible spectra of the polyazomethines were redshifted as compared with those of the monomers from which the polymers were synthesized, indicating that these polymers, if combined with an appropriate doping agent to improve the light‐emitting and conducting abilities, may be good candidate materials for optoelectronic devices. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 825–834, 2004     

Synthesis of a soluble pyrrole copolymer with phenetidine

A new series of copolymers was synthesized through the oxidative polymerization of pyrrole (PY) and o‐phenetidine (PHT) with inorganic oxidants in acidic media. The polymerization parameters including the mixing method of the oxidant with the comonomer, the comonomer ratio, the time, the temperature, the oxidant, the organic medium, and the acid were systematically optimized for the synthesis of copolymers with high yields, intrinsic viscosities, and solubility. The resultant copolymers were characterized by elemental analysis, infrared, ultraviolet–visible, solution high‐resolution ¹H NMR and solid‐state high‐resolution ¹³C NMR, circular dichroism spectroscopy, and cyclic voltammetry. The results showed that the PY observed content in the copolymers was much higher than the PY feed content. The regular variation of the polymerization yield, intrinsic viscosity, solubility, macromolecular structure, and electroactivity of the resulting polymers with the comonomer ratio, together with the complete solubility of a PY/PHT (10/90) polymer in highly polar solvents, indicated the formation of real random copolymers containing both PY and PHT units rather than a mixture of two homopolymers. However, the polymers containing more than 59 mol % PY were not homogeneous copolymers consisting of soluble and insoluble parts. A semiquantitative relationship between the polymerization yield or solubility of the copolymers and the polarity index of the organic solvents was examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2073–2092, 2004     

Anisotropic optical properties in electroluminescent conjugated polymers based on grazing angle photoluminescence measurements

Grazing angle photoluminescence (GPL) originates from a waveguided light emitted at grazing angle to the substrate due to the total internal reflections, and the light emission is polarized with enhanced intensity at selective mode wavelength. GPL measurements reveal the optical anisotropy of luminescent conjugated polymers, in particular, the alignment of emitting dipoles from which emission occurs, in contrast to spectroscopic ellipsometry measurements that give the anisotropy in the absorption. Based on the GPL emission intensities and spectra, we investigate the anisotropic optical properties in electroluminescent poly(9,9'-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) conjugated polymer thin films of different molecular weights (M(n) = 9-255 kg/mol), both in the pristine and annealed states. The optical anisotropy in F8BT films generally increases with molecular weight, suggesting that higher molecular weight polymers with longer chains are more likely to lie in-plane to the substrate. Upon annealing, high molecular weight F8BT films show even a higher degree of anisotropy, in contrast to low molecular weight F8BT films that become more isotropic. Annealing causes the polymer chains to rearrange and adopt a configuration in which the interchain exciton migration to better ordered low energy (LE) emissive states is strongly suppressed. We observe that the emissive states in F8BT are strongly affected by the local polymer chain arrangement, producing the less ordered high energy (HE) emissive states near the substrate interface where there is a higher degree of chain disorder and the LE states in the bulk of the film. When spin coated onto a quartz substrate precoated with a poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) layer, films of F8BT show severe luminescence quenching near the PEDOT:PSS interface for both the LE and HE emissive states, but a selective quenching of the LE states in the bulk of the film. These observations have important implications for fabricating efficient electronic devices using conjugated polymers as an active material, since the performance of these devices will strongly depend on anisotropic optical properties of electroluminescent conjugated polymers.     

The preparation of non-extractable methylphenylpolysiloxane stationary phases for capillary column gas chromatography

Summary The synthesis of methylphenylpolysiloxane polymers and their use in the preparation of crosslinked, non-extractable stationary phases for fused-silica capillary columns are described. By preparing more viscous phenyl-containing polymers than are commercially available, stationary phase films of these polymers could be efficiently coated on fused-silica capillary columns and stabilized by a free radical crosslinking mechanism using peroxides. Four methylphenylpolysiloxane polymers containing different phenyl concentrations were prepared. These included three polymers containing 50% phenyl and one polymer containing 70% phenyl. Two of the 50% phenyl polymers had one phenyl and one methyl group attached to each silicon atom. One of these also had 1% vinyl incorporated. The third 50% phenyl polymer was synthesized in such a way that one half of the silicon atoms had two phenyl groups attached while the rest contained dimethyl groups. The 70% phenyl polymer also had 4% vinyl incorporated. Due to the intrinsic thermal stability of these phenyl phases and the enhanced film stability achieved by crosslinking, the 70% phenyl phase could be utilized up to 400 °C. Using the methods described in this paper, highly efficient and thermally stable fused silica capillary columns coated with crosslinked methylphenylpolysiloxane stationary phases can be successfully prepared.     

Synthesis and photochromism of polymer-bound phenoxyquinone derivatives

Acrylate- and styrene-derived polymers having pendant phenoxyquinones for photochromism were prepared by 2,2′-azoisobutyronitrile (AIBN)-initiated radical polymerization. Synthesis of the monomers were straightforward and the polymers were obtained in high yields in spite of the quinone moieties presented in the monomers, which usually can function as radical scavengers and/or catalysts poison. Photo-induced rearrangement from the “trans”-quinone forms to the “ana”-quinone forms readily occurred when the polymer films were irradiated with UV light.     

Photolysis of polymeric organosilicon systems. III. Synthesis and photochemical behavior of polysiloxanes containing phenyldisilanyl units

The synthesis and photochemical behavior of three types of polysiloxanes containing phenyldisilanyl units as chromophore have been reported. Irradiation of thin liquid films of the polymer (2) prepared from copolymerization of octamethylcyclotetrasiloxane and 1,3,5-triphenyl-1,3,5-tris(trimethylsilyl)cyclostrisiloxane (1) with a 500-W Xe-Hg lamp afforded transparent solid films which are insoluble in common organic solvents. Similar irradiation of thin liquid films of polysiloxane (8) containing both phenyldisilanyl units and vinyl groups resulted in formation of crosslinked solid films. When thick films of the polymers 2 and 8 were irradiated with a Xe-Hg lamp, crosslinking occurred only on the surface of the films, but inside remained as liquid. Irradiation of the films prepared from the polysiloxane involving the phenyldisilanyl units and butenyl groups, however, gave crosslinked solid films, whatever thickness of the films. The mechanism of photochemically induced crosslinking of the copolymers is discussed on the basis of the results obtained from the photolysis of 1,1-bis(trimethylsiloxy)-1-phenyl(trimethyl)disilane as a model compound.     

Photochemistry of polymeric systems. II. Photocrosslinking of polymers and copolymers containing various aromatic N-oxide groups

2-Methyl-5-vinylpyridine-N-oxide, 4-vinylquinoline-N-oxide. 9-vinylacridine-N-oxide, p-N,N-dimethylaminostyrene-N-oxide units were introduced in polymeric chains as homopolymers or/and as styrene copolymers to study their photocrosslinking. The method used for characterization of photocrosslinked films was a “photoresist test” described in Part I of this series. The photosensitivity of the different chromophores bound to the different polymer has also been studied by UV, IR, and fluorescence spectrophotometries. The use of aromatic amine N-oxide groups in polymers seems to be a general means to produce their photocrosslinking by radical reactions. Among the different polymeric materials prepared, 4-vinylpyridine-N-oxide and 4-vinylquinoline-N-oxide are the most photosensitive.