Effects of spin-coating speed on the morphology and photovoltaic performance of the diketopyrrolopyrrole-based terpolymer

Polymer solar cells（PSCs） were fabricated by combining a diketopyrrolopyrrole-based terpolymer（PTBT-HTID-DPP） as the electron donor, and [6,6]-phenyl C₆₁ butyric acid methyl ester(PC₆₁BM) as the electron acceptor, and the power conversion efficiency（PCE） of 4.31% has been achieved under AM 1.5 G(100 m W cm^-2) illumination condition via optimizing the polymer/PC₆₁BM ratio, the variety of solvent and the spin-coating speed. The impact of the spin-coating speed on the photovoltaic performance of the PSCs has been investigated by revealing the effects of the spin-coating speed on the morphology and the absorption spectra of the polymer/PC₆₁BM blend films. When the thickness of the blend films are adjusted by spin-coating a fixed concentration with different spin-coating speeds, the blend film prepared at a lower spin-coating speed shows a stronger absorption per unit thickness, and the correspond device shows higher IPCE value in the longer-wavelength region. Under the conditions of similar thickness, the blend film prepared at a lower spin-coating speed forms a more uniform microphase separation and smaller domain size which leads to a higher absorption intensity per unit thickness of the blend film in long wavenumber band, a larger short-circuit current density(J_sc) and a higher power conversion efficiency（PCE） of the PSC device. Noteworthily, it was found that spin-coating speed is not only a way to control the thickness of active layer but also an influencing factor on morphology and photovoltaic performance for the diketopyrrolopyrrole-based terpolymer.     

Thermomechanical properties of cured isophtalic polyester resin modified with poly(ε-caprolactone)

The effect of a low profile additive, poly(ε-caprolactone) (PCL), on the thermal and mechanical properties of unsaturated polyester resins (UP) was investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile tests. The morphology of the systems has been studied by scanning electronic microscopy (SEM). Two PCL molecular mass were selected (PCL2: M _n = 2000 g mol⁻¹ and PCL50: M _n = 50000 g mol⁻¹) to analyze the influence of the molecular mass and the content of PCL on the UP resins and to establish the relation between thermomechanical behavior and morphology. DSC and DMTA glass transition temperatures (T _g) of the UP cured samples containing PCL indicate that PCL2 is miscible with UP whereas for UP + PCL50 system, T _g values are very close to the ones corresponding to neat UP. Besides in UP + PCL2 systems, one phase morphology is observed in which PCL2 would act as solvent of the reacting mixture along curing process; however, UP + PCL50 systems present phase-separated morphology. The presence of PCL2 and PCL50 in UP resin leads to a decrease of the tensile strength and the Young′s modulus as much notorious as the PCL concentration increases. For UP + PCL2 system the elongation at fracture increases in relation to neat UP, increasing as well with the PCL content.     

Determination of percolation threshold electroactivity and phase behavior study on conducting blends of thermotropic polyesters and polyaniline

The new thermotropic polyester/polyaniline (PIn/PAni) blends have been prepared by solution blend of synthesized liquid crystalline poly[4,4′‐bis (ω‐alkoxy) biphenylisophthalate]s having four and six methylene units in spacer (PI4 and PI6) with PAni doped with camphorsolfonic acid (CSA). The percolation threshold electroactivity of prepared blend films has been determined by cyclic voltammetry. The effect of the PAni concentration, solvent nature and polyester structure on the electroactivity of the blends has been investigated. The extremely low percolation threshold of prepared PIn/PAni‐CSA blends from dimethylformamide (DMF) and m‐cresol solution was 3% weight of PAni‐CSA. The amount of conducting polymer necessary to retard the formation of the liquid crystalline (LC) phase is up to 45% by weight. Phase behavior studies by differential scanning calorimetry and polarizing microscopy show that blends with 45% of conducting polymer are both liquid crystal and conductive. The morphology of the blends has been investigated by scanning electron microscopy. Copyright © 2004 John Wiley & Sons, Ltd.     

Influence of solvents properties on morphology of electrospun polyurethane nanofiber mats

Segmented polyurethane (SPU) nanofiber mats were prepared by electrospinning technique using the combination of four different solvents viz. tetrahydrofuran, N,N′‐dimethyl formamide, N,N′‐dimethyl acetamide, and dimethyl sulfoxide. Morphology of the electrospun nanofibers was examined by field emission scanning electron microscope. Experimental results revealed that the morphologies of polyurethane nanofiber mats have been changed significantly with the solvent selection for the electrospinning. It was observed that the diameters and morphology of the SPU nanofibers were influenced greatly by the use of combination of solvents. The uniform polyurethane nanofibers without beads or curls could be prepared by electrospinning through the selection of combination of good conductive and good volatile solvent viz. 7.5 wt/v% of SPU in N,N′‐dimethyl formamide/tetrahydrofuran (30 : 70 v/v) solutions at 20 kV applied voltages and volume flow rate of 1 ml/min. On the basis of the results obtained from this investigation, it has been established that solvent selection is one of the driving factors for controlling the morphology of the polyurethane electrospun nanofiber mats. The well‐controlled morphology of electrospun polyurethane nanofiber mats could be useful for many potential industrial applications such as in biomedical, smart textiles, nanofiltration, and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

Stable PZT sol for preparing reproducible high-permittivity perovskite-based thin films

Results are reported on the development of high-K dielectric material using sol-gel chemistry. High permittivity thin film capacitor have been developed based on lead-zirconate-titanate (PbZr _x Ti_1−x O₃, PZT) ferroelectric ceramic layers deposited on to 6″ platinized silicon wafer using the spin-coating technique. Selecting a diol-based solvent as diluting medium, a PZT solution with remarkable shelf life up to 1 year has been prepared. To synthesize such a reproducible and time-stable solution, a ripening step before dilution has been introduced. The deposition process has been also optimized to reduce the required number of coatings and to avoid intermediate high-temperature annealing. By carefully controlling environmental parameters, the as-developed PZT solution leads to reproducible high-performance thin film capacitor, enabling an industrial use. Thus, 200-nm thick PZT layers with permittivity as high as 900, capacitance as high as 40 nF/mm2 and breakdown voltage up to 30 V have been obtained.     

Layered self-organized structures on poly(3-octylthiophene) thin films studied by scanning probe microscopy

The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the preparation conditions, that is, spin-coating or drop-casting, of the solvent concentration or of the type of substrate. Using the drop-casting method for sample preparation these layered structures are hardly visible due to the high surface roughness, while using spin-coating these structures are the main topographic feature on the surface. These structures have typically one or two layers, even though occasionally up to four layers have been observed. Each layer has a height of 4-5 nm, which is associated to crystalline P3OT domains and lay on the polymer film. The size of these structures increases with increasing concentration of the P3OT in the solvent. We find well differentiated morphological, electrostatic as well as mechanical properties for the self-assembled structures as compared to the rest of the polymer film. Finally, the growth rate of these structures has been studied.     

Electrospinning of supramolecular polymer complexes

Supramolecular polymer complexes with small molecules are self-assembled through non-covalent interactions and have been proposed for a wide variety of applications in materials science and nanoscience.Our research group has recently shown the possibility of forming highly ordered nanofibers of supramolecular complexes in their thermodynamically stable state using the electrospinning technique.The ultrafast solvent evaporation rate of electrospinning made possible the in-depth characterization of complexes that had never been prepared in their pure state before because of kinetic issues associated with their formation by conventional approaches.The improved understanding of the formation mechanism allowed us to extend the concept to other techniques featuring a fast solvent evaporation rate,such as electrospray and spin-coating.In this article,we review our most significant contributions in this research field.     

Effect of preparation conditions on properties of polylactide and polystyrene and their composite microparticles made by emulsion solvent evaporation method

In this study, polylactide and polystyrene microparticles have been prepared by emulsion solvent evaporation method. Effects of polymer nature, stirring speed, emulsifier, and concentration of the components on the size, size distribution and morphology of polymeric microparticles have been investigated. 11-Acryloyl-aminoundecanoic acid and its polymer poly(11-acryloyl-aminoundecanoic acid) were tested for comparison with traditional emulsifiers such as sodium dodecylsulfate. Interfacial tension measurement was applied to compare these emulsifiers. Dynamic light scattering and scanning electron microscopy were used to analyze microparticles. Polylactide/polystyrene composite microparticles have been prepared as well; their surface morphology has been studied.     

Thermal induced mobility of self-assembled platelets of polyethylene-block-poly(ethylene oxide) in liquid precursors of unsaturated polyester thermoset

We report the variation of the molecular assembly and crystallinity of polyethylene-block-poly(ethylene oxide) (EEO, 1400 g mol⁻¹) in a non initiated liquid resin of unsaturated polyester (UP). We particularly focus on the driving force that governs the variation of the molecular assembly of the block copolymer in the UP resin upon heating. For this purpose, we performed a set of experiments combining time resolved in situ SAXS and WAXS measurements upon heating and cooling. Upon heating, SAXS shows that the inter-distance of the EEO domains decreases dramatically for temperature above 75 °C (between 90 and 30 nm for the initial system at room temperature vs 9 nm at 110 °C) suggesting that the initially homogeneously dispersed EEO domains undergo aggregation. This is consistent with the macroscopic phase separation observed in such temperature range. In situ WAXS shows that the onset of the aggregation coincides with the melting of the PE domains suggesting that the flexibility of the platelets plays an important role in their aggregation. Upon cooling, peculiar behaviour is observed for the systems with higher EEO content, with an irreversible structure formation leading to macroscopic EEO rich domains dispersed in continuous UP rich phase.     

Morphology of poly(p‐oxybenzoyl) prepared in perfluoropolyether

Solvent effect on the morphology of poly(p‐oxybenzoyl) (POB) prepared by the reaction‐induced phase separation of oligomers was examined by the polymerization of p‐acetoxybenzoic acid in perfluoropolyether Aflunox^TM (AFL2507 and AFL606). Polymerization was carried out at 320°C for 6 hr. POB microspheres were formed in AFL2507 by the liquid–liquid phase separation of oligomers due to the low miscibility of oligomers in AFL2507. The molecular weight of the solvent influenced the morphology, and the polymerization in AFL606 of which the molecular weight was lower than AFL2507 yielded whiskers formed by crystallization of oligomers induced by the increase in miscibility compared with that in AFL2507. The solvent structure and its molecular weight influenced the miscibility of oligomers and ultimately controlled the morphology from whisker to microsphere. Copyright © 2004 John Wiley & Sons, Ltd.     

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin for selective extraction of di(2‐ethylhexyl) phthalate in environmental waters

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin were prepared as solid‐phase extraction column sorbents for specific recognition and sensitive detection of di(2‐ethylhexyl) phthalate in water samples. The morphology and composition of synthesized sorbents were characterized by scanning electron microscopy, thermo‐gravimetric analysis, Raman spectroscopy, and Fourier‐transform infrared spectroscopy. The conditions affecting the performance of extraction procedures such as desorption solvent types and volume, sample pH and volume were investigated. The loading capacity (8.2 μg/mg) of the prepared sorbents increased eight times after modification with β‐cyclodextrin. The developed extraction procedures coupled to high‐performance liquid chromatography exhibited good linearity (0.2–500 μg/L), low limit of detection (0.052 μg/L), and good precision (relative standard deviation?5.7%) under optimized conditions. The developed solid‐phase extraction technique with prepared sorbents has been successfully applied in extracting trace di(2‐ethylhexyl) phthalate from real natural waters with high efficiency, good selectivity, and desirable recoveries.     

A new room-temperature deposition technique for optical coatings

We describe a new coating method Laminar Flow Coating (LFC) technique developed to obtain highly reflective (HR) laser damage resistant sol-gel multidielectric coatings. Such coatings are used in high-power lasers for inertial confinement fusion experiments (ICF). This technique uses substrates in an upside-down position and a travelling wave of coating solution is transported with a laminar motion under the substrate surface with a tubular dispense unit. This creates a thin-film coating by solvent evaporation. Satisfactory results have been obtained on 20-cm square glass substrates regarding the optical performances, the thickness uniformity, the edge-effects and the laser damage resistance. This deposition technique combines the advantages of both classical techniques: the non-exclusive substrate geometry such as in dip-coating and the small solution consumption such as in spin-coating.The association of sol-gel colloidal suspensions and LFC coating process has been demonstrated as a promising way to produce inexpensive specific optical coatings [1].     

Nanostructure evolution in high-temperature perfluorosulfonic acid ionomer membrane by small-angle X-ray scattering

The high-temperature morphology of supported liquid membranes (SLMs) prepared from perfluorinated membranes such as Nafion and Hyflon and hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-TFSI) has been investigated by small-angle X-ray scattering (SAXS). Proton conductivity results of SLMs before and after leaching show an increase in conductivity with temperature up to 160 °C in an anhydrous environment. DSC results show that crystallites within perfluorinated membranes are thermally stable up to 196 °C. High-temperature SAXS results have been used to correlate structure and morphology of supported liquid membranes with high-temperature conductivity data. The ionic liquid essentially acts as a proton solvent in a similar way to water in hydrated Nafion membranes and increases size of clusters, which allow percolation to be achieved more easily. The cation of the ionic liquid interacts with sulfonate groups within ionic domains through electrostatic interactions and displaces protons. Protons can associate with free anions of the ionic liquid, which are loosely associated with cations and can transport by hopping from anion sites within the membrane. The ionic liquid contributes to proton conductivity at high temperature through achievement of long-range ordering and subsequent percolation.     

离子液体中聚(3-溴噻吩)的电化学合成和电色效应研究

以1-丁基-3-甲基咪唑六氟磷酸盐离子液体[BMIM]PF₆既作为溶剂又作为支持电介质, 通过恒电流、循环伏安等方法制备聚(3-溴噻吩)(PBrT)膜. 采用红外光谱(FT-IR)和扫描电子显微镜(SEM)对PBrT膜的结构和形貌进行表征, 用热重和差热分析法(TG-DTA)研究聚合膜的热稳定性, 并利用紫外-可见光谱(UV-Vis)、计时电流和计时吸收曲线研究该聚合膜电化学和电致变色的特性. 研究结果表明, 与传统方法比较, 在离子液体[BMIM]PF₆中制备的PBrT膜更致密、光滑, 具有良好的氧化还原可逆性和充放电能力, 电活性高, 热稳定性好. 以该方法制备的PBrT膜颜色变化明显, 响应时间快(0.5 s), 同时由于离子液体具有电位窗宽、导电率高、可循环利用等优点, 因此在电化学聚合等方面具有良好的应用前景.     

Ionic Liquid Iodinating Reagent for Mild and Efficient Iodination of Aromatic and Heteroaromatic Amines and Terminal Alkynes

Hexamethylene bis(N-methylimidazolium) bis(dichloroiodate) (HMBMIBDCI), an ionic liquid iodinating reagent, have been prepared and characterized. Its ability to perform iodination reactions with a variety of substrates has been explored. In general, iodination reactions of aromatic and heteroaromatic amines proceed with good yields in the absence of solvent. Reactions of terminal alkynes in the presence of 1,8-diazabicyclo [5.4.O] undec-7-ene and tetrahydrofuran have been investigated as well.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Tailoring poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) microstructure and physicochemical properties by exploring its binary phase diagram with dimethylformamide

Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) (PVDF‐CTFE) membranes were prepared by solvent casting from dimethylformamide (DMF). The preparation conditions involved a systematic variation of polymer/solvent ratio and solvent evaporation temperature. The microstructural variations of the PVDF‐CTFE membranes depend on the different regions of the PVDF‐CTFE/DMF phase diagram, explained by the Flory‐Huggins theory. The effect of the polymer/solvent ratio and solvent evaporation temperature on the morphology, degree of porosity, β phase content, degree of crystallinity, mechanical, dielectric, and piezoelectric properties of the PVDF‐CTFE polymer were evaluated. In this binary system, the porous microstructure is attributed to a spinodal decomposition of the liquid‐liquid phase separation. For a given polymer/solvent ratio, 20 wt % , and higher evaporation solvent temperature, the β phase content is around 82% and the piezoelectric coefficient, d₃₃, is ? 4 pC/N © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 761–773     

Dual‐emissive polydiphenylsilane nanocomposite: effect of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine‐Zn complex

The fluorescence properties of polysilane can be strongly influenced by creating new excited states that involve electronic transitions and the relaxation to the ground state. This work presents the optical effects obtained by doping a specially designed polydiphenylsilane copolymer with Zn complex of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine. The nanocomposites have been prepared in solution by mixing the polymer with low amounts of Zn–salophen and using tetrahydrofuran as solvent. The ultraviolet–visible spectrum has shown the occurrence of an intermolecular charge transfer between polysilane and the metal complex. Photoluminescence studies have revealed an interesting dual emission profile of nanocomposite. The origin of this phenomenon has been evidenced by molecular modeling and simulation of the electronic transitions. The modeling results have unveiled a new low‐lying excited state due to intermolecular interactions. The thin films of nanocomposites have been drop‐casted from solutions. The obtained films have been studied by Transmission Electron Microscopy (TEM)‐Scanning Transmission Electron Microscopy (STEM)‐Energy Dispersive X‐ray analysis (EDX) to gain information on the film‐forming capacity and surface morphology. The results have revealed a high potential of such materials for fluorescence sensing applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation and properties of solution-processed zinc tin oxide films from a new organic precursor

Transparent,smooth and dense zinc tin oxide (ZTO) thin films have been successfully produced by using a new precursor solution,zinc acetate and tin(II) 2-ethylhexanoate mixed with 2-ethanolamine in methoxyethanol.The ZTO films have been prepared by spin-coating,followed by thermal treatment in oxygen atmosphere.The morphology,composition,crystallinity and band gap energy (Eg) of the ZTO thin films have been characterized by Atomic Force Microscopy (AFM),Atomic Emission Spectrometry (AES),X-ray Diffraction (...     

Intercalation of solvent and polymer in galleries of mobile clay platelets by a Monte Carlo simulation

The intercalation of solvent particles and polymer chains of concentration C_w = 0.2 and C_p = 0.2, respectively, in a layer of (4) clay platelets is studied by a Monte Carlo simulation on a cubic lattice. Polymer chains and platelets are modeled by bond fluctuations. Besides the excluded volume, a set of polymer-clay (cs) and solvent-clay (ws) interactions with (i) cs = 1, ws = −2, (ii) cs = −2, ws = 1 and (iii) cs = ws = −2 are considered. The global dynamics of platelets is constrained due to the presence of three components, i.e., solvent, polymer, and platelets, which retain their interstitial spacing with well-defined galleries. Intercalation of solvent particles and polymer chains (low molecular weight) occurs with their attractive interaction with the platelets, which further reinforces the layered clay morphology. The density profiles of the solvent particles are similar to previous studies with platelets in a mobile solvent. The density profile of polymer chains differs considerably from the platelets in a polymer matrix alone, particularly with its attractive interaction (ii). For the same attractive interaction of solvent and polymer chains with the clay platelets (iii), the solvent particles (the smallest constituents) intercalate the fastest in the clay galleries, whereas the intercalation of polymer chains decreases with their molecular weight. The polymer density profiles, both longitudinal (x) and transverse (y), show maxima peaks around outer platelets (surface) of the layer and decay sharply both in the adjacent galleries and in the bulk. The amplitude of oscillation in the transverse density profiles, a measure of the degree of intercalation, decreases with increasing molecular weight of the polymer. The intercalation of the polymer is driven by its attractive interaction at the low molecular weight, but reduces considerably at high molecular weight because of both entanglement and larger radius of gyration. Variations of the gyration radius of the diffusing polymer chains with molecular weight and interaction with the clay are consistent with the results of their corresponding density profiles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2487–2500, 2009     

Thickness, Morphology and Structure of Sol-Gel Hybrid Films: II—The Role of the Solvent

The influence of the solvent on the thickness, morphology and structure of silica-polytetrahydrofuran hybrid films, prepared by spin coating, has been analysed. The inorganic precursor, tetraethylorthosilicate, was hydrolysed under acid catalysis, the hydrolysis molar ratio being 4. Polymers of average molecular weight (M _n) 650 and 2900 were incorporated in the initial colloidal solutions, in a low concentration (organic/inorganic molar ratio 0.01). Two solvents were compared: ethanol, protic, and tetrahydrofuran, aprotic and a little less polar. The thickness and surface texture parameters of the films were determined by profilometry, their morphology characterized by SEM and their structure studied by FTIR. It is shown that the solvent has no effect on the molecular structure of the films, but strongly influences the surface texture and the morphology of both pure silica and hybrid films. The solutions prepared in tetrahydrofuran present shorter gelation times (t _G) and allow the deposition of good quality films almost up to the gelation point (to a reduced time, t/t _G, of 0.9). The films are thinner than those prepared from corresponding ethanolic solutions at the same reduced ageing times. For pure silica films, tetrahydrofuran is the best choice, since it reduces the fractured region on the edge of the substrate. For hybrid films, this effect is achieved by the polymer and tetrahydrofuran is responsible for a higher arithmetical mean roughness. Therefore, ethanol becomes the preferable solvent.