Synthesis of a novel fluorene-based conjugated polymer with pendent bulky caged adamantane moieties and its application in the detection of trace DNT explosives

A novel fluorene-based conjugated polymer with phenylene spacers and steric bulky adamantane moieties in side chains has been synthesized by palladium-catalyzed Suzuki coupling reactions. This design strategy offers several advantages for the detection of trace 2,4-dinitrotoluene (DNT) vapor. The incorporation of the two groups into polymer side chains could retain an effective conjugation length and prevent the π-stacking of polymer chains. The detection of DNT vapor indicated that the polymer displayed higher fluorescence quenching sensitivity toward the explosives in films compared to reference polymers. The fluorescence quenching efficiency of the fluorescent polymer achieved 33.3% in 10 s and 71.1% in 60 s. The pathways or cavities generated by the two spacers are beneficial for the rapid diffusion of explosive vapor into the film interiors and increase the fluorescence quenching efficiency of the film.     

Surface‐tethered conjugated polymers created via the grafting‐from approach

Polyacrylate brushes with pendent terthiophenes [poly(terthiophene methyl methacrylate) (PTTMM)] were successfully grown from indium tin oxide and gold with surface‐initiated atom transfer radical polymerization. The films formed on both substrates were characterized by ellipsometry and Fourier transform infrared spectroscopy. Using cyclic voltammetry, we electrochemically crosslinked the PTTMM brush to form a conjugated polymer network. The conjugation lengths in the film were increased as evidenced by ultraviolet–visible spectroscopy. Additionally, an atomic force microscopy study on the surface‐modified solid substrate revealed the formation of a smooth and uniform polymer brush with a low surface roughness, even after electrochemical crosslinking. These uniformly grafted conducting polymer brushes may find use in photovoltaic devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41363.     

Effect of film thickness, blending and undercoating on optical detection of nitroaromatics using fluorescent polymer films

In this work, using a fluorescent poly(phenylene ethynylene) containing the rigid pentiptycene and large cholesteryl ester pendent groups, the fluorescence quenching properties of the polymer thin films in response to vapor of 2,4-dinitrotulene (DNT) have been investigated by varying the film thickness, applying an undercoating and blending with another polar polymer. A significant change in fluorescence intensity (51% in 60 s) in response to DNT vapor exposure at ambient temperature was achieved when the polymer film coated on glass plate was about 2 nm in thickness. In comparison with the film of polymer alone, the film undercoated with (3-aminopropyl)triethoxysilane and the film of polymer blend containing a non-fluorescent polymer showed additional 18.5% (in 20-s exposure) and 18.7% (in 5-min exposure) decrease in fluorescence intensity, respectively. The use of polymer or polymer blend coated on optic-fiber tip for detection of DNT vapor has also been demonstrated.     

Synthesis of new ionic crosslinked polymer hydrogel combining polystyrene and poly(4‐vinyl pyridine) and its self‐healing through a reshuffling reaction of the trithiocarbonate moiety under irradiation of ultraviolet light

A new ionic crosslinked polymer hydrogel was achieved by the strategy of ionically crosslinking α,ω‐dibromide terminated polystyrene (Br‐PS‐Br) with poly(4‐vinyl pyridine) (P4VP) which was synthesized by reversible addition‐fragmentation chain transfer polymerization using a chain transfer agent containing a trithiocarbonate moiety. The moiety of trithiocarbonate was introduced into the crosslinked network to show the self‐healing characteristics. The chain structure and components of Br‐PS‐Br and P4VP were characterized through ¹H NMR, gel permeation chromatography, Fourier transform IR spectroscopy and elemental analysis. The P4VP (M_n = 25 300 g mol^?1) chains were crosslinked with Br‐PS‐Br (M_n = 2000 g mol^?1) through the quaternization reaction to form a polymer network which was further crosslinked in acetonitrile by irradiation of UV light to fabricate a hydrogel. Such a hydrogel of P4VP/Br‐PS‐Br cut by a razor blade can be rapidly (1 h) and repeatedly (three times) healed through a reshuffling reaction of the trithiocarbonate moiety under irradiation by UV light. © 2018 Society of Chemical Industry     

Polystyrene‐block‐polylactide obtained by the combination of atom transfer radical polymerization and ring‐opening polymerization with a commercial dual initiator

A polystyrene (PS)‐b‐polylactide (PLA) block copolymer was prepared from the combination of atom transfer radical polymerization and ring‐opening polymerization with commercially available 2,2,2‐tribromoethanol as a dual initiator in a sequential two‐step procedure. Hydroxyl‐terminated polystyrene (PS‐OH)s with various molecular weights were first prepared with polydispersity indices lower than 1.3; these provided valuable macroinitiators for the polymerization of D,L ‐lactide. A block copolymer with a composition allowing the formation of hexagonally packed PLA cylinders in a PS matrix was then obtained. The PS‐b‐PLA thin films revealed, after vapor solvent annealing, a hexagonally packed organization of the PLA cylinders, which was oriented perpendicularly to the surface of the film. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of conducting composites of polypyrrole using supercritical carbon dioxide

Supercritical carbon dioxide, saturated with pyrrole, was brought into contact with oxidant‐impregnated films of poly(chlorotrifluoroethylene) (PCTFE), crosslinked poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and porous crosslinked polystyrene (PS) in order to form conducting composites via the in situ polymerization of pyrrole. The two nonporous hosts—PCTFE and crosslinked PDMS—did not form conducting composites with polypyrrole (PPy). On the other hand, the electrical conductivity of the PPy composites with carbon dioxide‐swollen PMMA and porous PS ranged from 1.0 × 10^?4 S/cm to 3.0 × 10^?5 S/cm. In these two cases, the level of pyrrole polymerized on the surface or in the pores of the host polymer was sufficient to attain the interconnected conducting polymer networks necessary for electrical conductivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1113–1116, 2003     

Annealing‐promoted unidirectional migration of organic‐modified nanoparticles embedded two‐dimensionally in polymer thin films

The spatial structures of oleic acid‐modified CeO₂ nanoparticles in polystyrene (PS) thin films spin‐coated on silicon substrates were observed by transmission electron microscopy, when the films underwent thermal annealing above the glass‐transition temperature of PS. Before annealing, the nanoparticles have segregated to the surface of the films, and formed two‐dimensional spatial structures in the PS films. Then, the nanoparticles migrated away from the film surface to the substrate/film interface during thermal annealing, maintaining the two‐dimensional spatial structures. In addition, we demonstrated that such unidirectional migration of nanoparticles across the PS film occurs regardless of the characteristics of the substrate surface, the concentration of nanoparticles, and the thickness of the films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42760.     

Physical and electrochemical characterizations of poly(vinylidene fluoride‐co‐hexafluoropropylene)/SiO2‐based polymer electrolytes prepared by the phase‐inversion technique

Highly porous poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF–HFP)‐based polymer membranes filled with fumed silica (SiO₂) were prepared by a phase‐inversion technique, and films were also cast by a conventional casting method for comparison. N‐Methyl‐2‐pyrrolidone as a solvent was used to dissolve the polymer and to make the slurry with SiO₂. Phase inversion occurred just after the impregnation of the applied slurry on a glass plate into flowing water as a nonsolvent, and then a highly porous structure developed by mutual diffusion between the solvent and nonsolvent components. The PVdF–HFP/SiO₂ cast films and phase‐inversion membranes were then characterized by an examination of the morphology, thermal and crystalline properties, absorption ability of an electrolyte solution, ionic conductivity, electrochemical stability, and interfacial resistance with a lithium electrode. LiPF₆ (1M) dissolved in a liquid mixture of ethylene carbonate and dimethyl carbonate (1:1 w/w) was used as the electrolyte solution. Through these characterizations, the phase‐inversion polymer electrolytes were proved to be superior to the cast‐film electrolytes for application to rechargeable lithium batteries. In particular, phase‐inversion PVdF–HFP/SiO₂ (30–40 wt %) electrolytes could be recommended to have optimum properties for the application. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 140–148, 2006     

Poly(hydroxybutyrate‐co‐hydroxyvalerate) and bovine serum albumin blend prepared by electrospinning

Electrospinning is a method for the preparation of nanosized polymer fibers. Here, electrospinning is used to prepare a blend of a polyester, poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), and a globular protein, bovine serum albumin (BSA). The electrospun blend film is compared with a solution‐cast blend film and with single‐component electrospun films made of PHBV and BSA. In the electrospun blend films, BSA manifests itself as flat ribbons and a fine network formed from fibers less than 50 nm in diameter. The dissolution rate of BSA from the electrospun blended film is lower than from the solution‐cast one. The films are characterized using scanning electron microscopy, differential scanning calorimetry, and contact‐angle measurements. The obtained PHBV+BSA blend films have several emergent properties: a slow BSA dissolution rate, a fine BSA network, and unusual thermal behavior. Thus, the PHBV+BSA blend films introduce a new class of polymer–protein blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45090.     

Long‐range‐ordered,hexagonally packed nanoporous membranes from degradable‐block‐containing diblock copolymer film templates

Polystyrene (PS)‐b‐polylactide (PLA) diblock copolymers with different molecular weights and fractions were synthesized through a combination of living anionic polymerization and controlled ring‐opening polymerization. Then, the PS–PLA films were guided to phase‐separate by self‐assembly into different morphologies through casting solvent selection, solvent evaporation, and thermal and solvent‐field regulation. Finally, perpendicularly oriented PS–PLA films were used as precursors for PS membranes with an ordered periodic nanoporous structure; this was achieved by the selective etching of the segregated PLA domains dispersed in a continuous matrix of PS. Testing techniques, including IR, ¹H‐NMR, gel permeation chromatography, scanning electron microscopy (SEM), and atomic force microscopy (AFM), were used to determine the chemical structure of the PS–PLA copolymer and its film morphology. AFM images of the self‐assembled PS‐PLA films indicate that vertical tapers of the PLA domains were generated among PS continuum when either toluene or tetrahydrofuran was used as the annealing solvent. The SEM images certified that the chemical etching of the PLA component from the self‐assembled PS–PLA films led to a long‐range‐ordered array of hexagonally packed nanoporous membranes with a diameter about 500 nm and a center‐to‐center distance of 1700 nm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39638.     

Energy‐transfer method to study vapor‐induced latex film formation

Nonradiative energy transfer method was used to study latex film formation induced by organic solvent vapor. Seven different films with the same latex content were prepared separately from poly(methyl methacrylate) (PMMA) particles and exposed to ethyl benzene, toluene, chloroform, dichloromethane, tetrahydrofuran, and acetone vapor in seven different experiments. Energy‐transfer experiments were carried out between PMMA‐bound naphthalene (N) and pyrene (P) during vapor‐induced film formation. Latex films were prepared from equal amounts of N‐ and P‐labeled latex particles, and steady state spectra of N and P were monitored during film formation. It was observed that the P to N intensity ratio, I_P/I_N, increased as the vapor exposure time increased. The Prager–Tirrell (PT) model was employed to obtain back‐and‐forth frequencies, ν, of the reptating PMMA chains during latex film formation induced by solvent vapor. ν values were obtained and found to be correlated with the solubility parameter, δ. Polymer interdiffusion obeyed the t^1/2 law during film formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 632–645, 2002; DOI 10.1002/app.10346     

Single Solvent‐Based Film Casting Method for the Production of Porous Polymer Films

A single solvent‐based film casting process for fabricating porous polymer films is developed in this study. The porous film is produced by mixing concentrated polylactic acid (PLA)/chloroform solution (20 wt%) and fresh chloroform solvent is followed by film casting. The average pore sizes of the films produced are seen to increase from 2.1 (±0.1) µm to 6.4 (±0.2) µm with increasing ratio of concentrated PLA solution and fresh solvent from 1:2 to 1:4. Functional groups of PLA after casting into porous film are confirmed via Fourier transform infrared spectroscopy analysis. Cytocompatibility studies (via Alamar Blue assessment) utilizing MG‐63 cells on the porous PLA films reveal an increase in cell metabolic activity up to 8 d postseeding. In addition, these direct cell culture studies show that the porous membranes support cell adhesion and growth not only on the surface but also through the porous structures of the membrane, highlighting the suitability of these porous films in tissue engineering applications.     

Superhydrophobic and Low‐k Polyimide Film with Porous Interior Structure and Hierarchical Surface Morphology

Porous interior structured polyimide (PI) films with a hierarchical surface are fabricated from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 4,4′‐oxydianiline by a water vapor induced phase separation process under a humid environment. Superhydrophobic properties with a water contact angle of 161° are obtained using the hierarchical surface morphology, which can be adjusted from flower‐like to wrinkle‐shape particles facilely by changing the relative humidity. The dielectric constant (k) of the PI film decreases sharply from 2.8 (film prepared under dry conditions) to ≈1.9 (film prepared under humid conditions) because of the interior porous structure and fluorine‐containing framework. Both a low‐k and superhydrophobicity are very important parameters for PI films in microelectronic and insulating applications.     

Morphology of poly(styrene‐block‐dimethylsiloxane) copolymer films

The morphologies of poly(styrene‐block‐di‐methylsiloxane) (PS‐b‐PDMS) copolymer thin films were analyzed via atomic force microscopy and transition electron microscopy (TEM). The asymmetric copolymer thin films spin‐cast from toluene onto mica presented meshlike structures, which were different from the spherical structures from TEM measurements. The annealing temperature affected the surface morphology of the PS‐b‐PDMS copolymer thin films; the polydimethylsiloxane (PDMS) phases at the surface were increased when the annealing temperature was higher than the PDMS glass‐transition temperature. The morphologies of the PS‐b‐PDMS copolymer thin films were different from solvent to solvent; for thin films spin‐cast from toluene, the polystyrene (PS) phase appeared as pits in the PDMS matrix, whereas the thin films spin‐cast from cyclohexane solutions exhibited an islandlike structure and small, separated PS phases as protrusions over the macroscopically flat surface. The microphase structure of the PS‐b‐PDMS copolymer thin films was also strongly influenced by the different substrates; for an asymmetric block copolymer thin film, the PDMS and PS phases on a silicon substrate presented a lamellar structure parallel to the surface at intervals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1010–1018, 2007     

Aryl acrylate porous functional polymer supports from water‐in‐oil‐in‐water multiple emulsions

Porous functional polymer supports are a class of material of wide interest due to the possibility of immobilising reactive species. A simplified procedure was applied for the preparation of porous polymer supports using a water‐in‐oil‐in‐water multiple emulsion. The primary emulsion was a high internal phase emulsion, having a volume fraction of water phase up to 95%. Two reactive acrylates, namely 4‐nitrophenyl acrylate and 2,4,6‐trichlorophenyl acrylate, were (separately) incorporated in the oil phase in order to obtain porous reactive polymer supports. Both acrylates were crosslinked with either divinylbenzene or ethylene glycol dimethacrylate, and beads of size ca 60 µm were obtained after the polymerisation of droplets suspended into the secondary aqueous phase. In the case of 4‐nitrophenyl acrylate and divinylbenzene as a crosslinker, particles with a star shape, the core being ca 60 µm in diameter and the arms ca 180 µm in length, were obtained. The polymers were functionalised with morpholine, tris(2‐aminoethyl)amine, piperidine or piperazine yielding supports with loadings of reactive groups of between 2.6 and 6.6 mmol g^?1. The results show that multiple emulsions can be precursors for porous polymer preparation. Copyright © 2007 Society of Chemical Industry     

Study of film formation from PS latex/TiO2 nanocomposites; Effect of latex size and TiO2 content

In this work, we investigated the film formation from polystyrene (PS) latex/TiO₂ nanocomposites using the steady state fluorescence (SSF) and UV–vis (UVV) techniques depending on PS particle size and TiO₂ content. The structural properties of films were characterized by scanning electron microscope (SEM). The films were prepared from pyrene (P)‐labeled PS particles (SmPS:203 nm; LgPS:382 nm) by covering them with different layers of TiO₂ by dip‐coating method and then annealed at elevated temperatures. Two film series (SmPS/TiO₂ and LgPS/TiO₂) were prepared and seven different films were studied in various TiO₂ contents for each series. Scattered (I_sc), fluorescence (I_P), and transmitted (I_tr) light intensities were measured after each annealing step to monitor the stages of film formation. Results showed that, SmPS/TiO₂ films undergo complete film formation independent of TiO₂ content. However, no film formation occurs above a certain TiO₂ content in LgPS/TiO₂ films. SEM images showed that SmPS/TiO₂ films have highly well‐ordered microporous structures with increasing TiO₂ content after extraction of PS polymer whereas LgPS/TiO2 composites show no porous structure for high TiO₂ content. Our experiments also showed that porous TiO₂ films with different sizes could be successfully prepared using this technique. POLYM. COMPOS., 35:2376–2389, 2014. © 2014 Society of Plastics Engineers     

Oil absorbents based on styrene–butadiene rubber

Four oil absorbents based on styrene–butadiene (SBR)—pure SBR (PS), 4‐tert‐butylstyrene–SBR (PBS), EPDM–SBR network (PES), and 4‐tert‐butylstyrene‐EPDM‐SBR (PBES)—were produced from crosslinking polymerization of uncured styrene–butadiene rubber (SBR), 4‐tert‐butylstyrene (tBS), and ethylene–propylene–diene terpolymer (EPDM). The reaction took place in toluene using benzoyl peroxide (BPO) as an initiator. Uncured SBR was used as both a prepolymer and a crosslink agent in this work, and the crosslinked polymer was identified by IR spectroscopy. The oil absorbency of the crosslinked polymer was evaluated with ASTM method F726‐81. The order of maximum oil absorbency was PBES > PBS > PES > PS. The maximum values of oil absorbency of PBES and PBS were 74.0 and 69.5 g/g, respectively. Gel fractions and swelling kinetic constants, however, had opposite sequences. The swelling kinetic constant of PS evaluated by an experimental equation was 49.97 × 10^?2 h^?1. The gel strength parameter, S, the relaxation exponent, n, and the fractal dimension, d_f, of the crosslinked polymer at the pseudo‐critical gel state were determined from oscillatory shear measurements by a dynamic rheometer. The morphologies and light resistance properties of the crosslinked polymers were observed, respectively, with a scanning electron microscope (SEM) and a color difference meter.     

Preparation of polystyrene/poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] fluorescent microspheres by miniemulsion polymerization

Fluorescent microspheres have great potential for use as probes in biological diagnostics. In this context, poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] (MEH‐PPV), a conjugated polymer which has high quantum yield, controllable emitting wavelength and facile processing in manufacture, was used as a fluorescent material for the preparation of polystyrene (PS)/MEH‐PPV fluorescent microspheres via miniemulsion polymerization. We demonstrate that the emitting wavelength of the PS/MEH‐PPV fluorescent microspheres can be regulated by changing the amount of azobisisobutyronitrile initiator in the polymerization process. Using acrylic acid comonomer, poly[styrene‐co‐(acrylic acid)]/MEH‐PPV fluorescent microspheres with functional carboxyl groups were also prepared. All the microspheres were characterized using transmission electron microscopy, scanning electron microscopy, fluorescence microscopy and fluorescence spectrophotometry. The functional carboxyl groups were characterized using Fourier transform infrared spectroscopy. This work provides a novel platform for the preparation of conjugated polymer fluorescent microspheres for biological applications. © 2012 Society of Chemical Industry     

Synthesis of a photo‐crosslinked stable nonlinear optical polymer and application to external electro‐optic measurement

A photo‐crosslinked side‐chain second‐order nonlinear optical polymer was synthesized with bis‐phenol‐A as the polymer backbone, p‐nitroaniline as the chromophore and cinnamyl group as the photo‐sensitizer. The characterization of the polymer was made by nuclear magnetic resonance, infrared, ultraviolet‐vis, and dynamic mechanical analysis methods. An electro‐optic film was obtained by spin coating of the polymer and corona poling then photo‐crosslinking reaction. An external electro‐optic measurement system was established based on the film and reflective light path configuration, and successfully applied to measure the electrical signals propagating on the under‐test circuits. The poled and crosslinked film showed high glass transition temperature (160°C) and improved chromophore orientation stability. The measuring principle was analyzed by electro‐optic tensor matrix and index ellipsoid methods. The results showed that the designed polymer film had the linear electro‐optic effect, the voltage sensitivity of the system was measured to be 5 mv/ at the condition of 1 kHz input signal. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1506–1512, 2000     

Dielectric and mechanical optimization properties of porous poly(ethylene‐co‐vinyl acetate) copolymer films for pseudo‐piezoelectric effect

In this article, the authors present a porous copolymer film with pseudo‐piezoelectric effects as a new candidate material for sensing applications. Porous films of poly(ethylene‐co‐vinyl acetate) (EVA) with a thicknesses ranging from 160 to 310 μm are fabricated by a coextrusion chemical foaming process and charged using a high‐voltage contact charging process. Output performances (piezoelectric constant and relative permittivity) with related thermal/mechanical stability are specifically studied as a function of the film porosity and of the electrical charging process. The piezoelectric constant d₃₃ increases with the cell porosity and an interesting piezoelectric constant close to 5.1 pC/N is achieved with a porous EVA film containing 65% of porosity. Actual results are then discussed using a theoretical solid–gas multilayer model to describe and predict the pseudo‐piezoelectric effect of porous polymer materials. The originality of this work lies in the fact that all the steps leading to optimize pseudo piezoelectric films are included, and also in the use of EVA which is not a standard piezoelectric material. Therefore, this work is a contribution in the development of low‐cost piezoelectric materials with potential applications as sensor in different fields such as medical, security, environment, sport, and transport. POLYM. ENG. SCI., 59:1455–1461 2019. © 2019 Society of Plastics Engineers