Solution-cast Films Research Articles

Conduction and thermal properties of a proton conducting polymer electrolyte based on poly (ε-caprolactone)

A proton conducting polymer electrolyte based on poly(ε-caprolactone) (PCL) complexed with different concentrations of ammonium thiocyanate (NH 4SCN) salt has been investigated. The ionic conductivity of the solid polymer electrolyte (SPE) of pure PCL obtained at room temperature is 1.86 × 10 − 11 S cm − 1 . The maximum ionic conductivity achieved in the solution-cast films at room temperature is 1.01 × 10 − 4 S cm − 1 for PCL incorporated with 26 wt.% NH 4SCN. The calculated dielectric constant at selected frequencies follows the same trend as conductivity, concluding an increase in number density of ions with the salt content. DSC thermogram shows that the degree of crystallinity of PCL is reduced as more salt is accommodated in the PCL crystalline phase. The FTIR of asymmetric C≡N stretching mode is deconvoluted into three bands representing free ions, contact ion pairs and ion aggregates to obtain an insight on ion associations. The FTIR results show that the number of free ions become maximum at 26 wt.% NH 4SCN. The correlation between free ions, ion aggregates and conductivity is obvious. The increase in ion dissociation improves conductivity, while the formation of ion aggregates reduces conductivity.

Development of fish gelatin edible films using extrusion and compression molding

Fish gelatin was plasticized with 20% and 25% glycerol (w/w of gelatin) and used to develop edible films by twin-screw extrusion at 110 and 120°C followed by compression molding at 80°C. Tensile and moisture barrier properties and glass transition temperature were then measured and compared with solution-cast films. The films extruded at 110°C and with 25% glycerol had the highest percent elongation at break of 293±27%. The water vapor permeability values of extruded films (the highest value being 2.9±0.2gmmh−1cm−2Pa−1) were higher than those of solution-cast films while the glass transition temperatures (Tg) of the extruded films were generally lower than those of solution-cast films. Films with 25% glycerol that were extruded at 110°C had the lowest Tg (2.10±0.31°C). This investigation showed that extrusion processing followed by compression molding is a feasible method to produce fish gelatin films for commercial applications in a wide range of food products.

Channel orientation anisotropy in perfluorosulfonic acid/SiO 2 composite proton exchange membranes: Water self-diffusion study using NMR

A diffusion-exchange model with the assumption of two water pools was applied to describe the water transport in perfluorinated sulfonic acid (PFSA)/SiO 2 nanocomposites. The water diffusivity in-plane and through-plane in solution cast films was measured by NMR revealing higher in-plane mobility. Both diffusion coefficients reached maxima at ∼3%-wt. concentration in SiO 2. The anisotropy of the PFSA channels orientation reflected in the diffusivity anisotropy decreased with the increase in the nanofiller content. Water exchange rates reached a maximum at low concentration of silica. Gaussian displacement distribution for water diffusion was detected in PFSA membrane at 40 °C independent of the direction of gradient for small concentration in silica.

Investigation of the crystalline structure of PVDF in PVDF/PMMA/graphene polymer blend nanocomposites

AbstractIn this work, we report the preparation of poly(vinylidene fluoride)/poly methylmethacrylate (PVDF/PMMA)/graphene polymer blend nanocomposites via synthesis of PMMA/graphene as a masterbatch through in situ polymerization. The PMMA/graphene masterbatch compounded with PVDF by solution mixing in different ratios. The compounding was followed by solution casting to form polymer blend nanocomposites. Solution cast films were subjected to thermal treatments at three different temperatures. The crystalline structure of thermally treated samples was studied with X‐ray diffraction spectroscopy and Differential Scanning Calorimetric (DSC) analysis. Results indicated PMMA chains persuade the β crystalline form in PVDF but cannot stabilize them in elevated temperature; however, graphene sheets due to restricting effect on TT conformation chains are able to stabilize them. DSC data revealed the graphene sheets can increase the crystallinity of PVDF and also act as nucleating agents. Transmission Electron Microscopy demonstrated coexistence of the different stacking orders of graphene sheets in both masterbatch and polymer blend nanocomposite. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Uniformly Gold Nanoparticles Derived from P2VP-<I>b</I>-PCHMA Block Copolymer Templates with Different Reduction Methods

The micellization of poly(2-vinylpyridine)-block-poly(cyclohexyl methacrylate) (P2VP-b-PCHMA) in THF can be induced by the complexation between the P2VP blocks and HAuCl4, forming composite polymeric micelles with PCHMA being the shell and P2VP/HAuCl4 complex being the core. In order to obtain regular arrays of gold nanoparticles (Au NPs), monolayer of HAuCl4-loaded surface micelles have been produced by spin-coating the micellar solution, and Au NPs in different size have been obtained by oxygen plasma with different reduction processes. In addition, pyrole (PY) has been used as an efficient reducing agent to fabricate dispersed Au NPs within micellar structure in a short reducing time, resulting in a raspberry-like morphology of the Au-polymer composites. With the addition of annealing processes or longer reducing time (one month), different shapes of Au NPs have been observed in the cast films. Furthermore, core-shell nanostructures of gold-polypyrole (Au-PPY) have also been observed by employing vapor phase polymerization of PY onto HAuCl4-loaded polymeric solution-cast films.

Polymer chain organization in tensile-stretched poly(ethylene oxide)-based polymer electrolytes

Polymer chain orientation in tensile-stretched poly(ethylene oxide)–lithium trifluoromethanesulfonate polymer electrolytes are investigated with polarized infrared spectroscopy as a function of the degree of strain and salt composition (ether oxygen atom to lithium ion ratios of 20:1, 15:1, and 10:1). The 1359 and 1352 cm −1 bands are used to probe the crystalline PEO and P(EO) 3LiCF 3SO 3 domains, respectively, allowing a direct comparison of chain orientation for the two phases. Two-dimensional correlation FT-IR spectroscopy indicates that the two crystalline domains align at the same rate as the polymer electrolytes are stretched. Quantitative measurements of polymer chain orientation obtained through dichroic infrared spectroscopy show that chain orientation predominantly occurs between strain values of 150% and 250%, regardless of salt composition investigated. There are few changes in chain orientation for either phase when the films are further elongated to a strain of 300%; however, the PEO domains are slightly more oriented at the high strain values. The spectroscopic data are consistent with stretching-induced melt-recrystallization of the unoriented crystalline domains in the solution-cast polymer films. Stretching the films pulls polymer chains from the crystalline domains, which subsequently recrystallize with the polymer helices parallel to the stretch direction. If lithium ion conduction in crystalline polymer electrolytes is viewed as consisting of two major components (facile intra-chain lithium ion conduction and slow helix-to-helix inter-grain hopping), then alignment of the polymer helices will affect the ion conduction pathways for these materials by reducing the number of inter-grain hops required to migrate through the polymer electrolyte.

Grafting of N-isopropyl Acrylamide onto Bacterial Polyhydroxybutrate/Hydroxyvalerate Copolymers

This work deals with the grafting of N-isopropyl acrylamide (IPA) onto poly (3-hydroxybutyrate-3-hydroxyvalerate), (PHBV) (5.4 mole % 3-hydroxyvalerate), using benzoyl peroxide as free radical initiators. The effect of N-isopropyl acrylamide and initiator concentrations and reaction time on the degree of grafting has been investigated. The maximum degree of grafting was 82%. The grafted products were characterized by FTIR, 1HNMR, DSC, wide-angle X-ray diffraction and TGA analysis. The DSC results showed that the cold crystallization temperature from the glassy state increased with increasing the extent of grafting, while the Tg and Tm are not affected significantly. TGA analysis revealed that grafting of the host PHBV polymer did not affect much its onset decomposition temperature. The Grafted products swell in aqueous solution and the swelling is controlled by the extent of grafting, temperature, and pH. The biodegradability of PHBV and its graft copolymers solution-cast films was investigated in active soil. The results indicated that the introduction of the hydrophilic PVP and PIPA graft chains enhanced the biodegradability of PHBV.

Morphology and Structure of Rod/Coil Nanocomposite Thin Film

A rod/coil nanocomposite was prepared by a reactive mixing process of Poly(p-phenylenebenzobisthiazole) (PBZT) and Nylon66 in polyphosphoric acid (PPA). PBZT-Nylon66 block copolymers were synthesized during the reactive mixing process to act as compatibilizers of PBZT and Nylon66. The morphology and structure of the solution-cast thin film of PBZT/Nylon66 nanocomposites were investigated by using Optical Microscopy(OM), Differential Thermal Analysis(DTA), and Transmitted Electron Microscopy(TEM). PBZT were dispersed in Nylon66 matrix as fibrils which had diameters ranging from 100nm to 400nm and lengths ranging from 500nm to 2μm. The crystal behavior of Nylon66 was considerably disturbed by PBZT in the nanocomposite. Even after heating above the melting point of Nylon66, the nanocomposite exhibited no macrophase separation.

In situ FTIR and generalized 2D IR correlation spectroscopic studies on the crystallization behavior of solution-cast PHB film

The crystallization behavior of biosynthesized poly(3-hydroxybutyrate) film cast from 1,1,2,2-tetrachloromethane was studied by in situ FTIR spectroscopy and two-dimensional (2D) correlation analysis. Time-dependent in situ FTIR spectral variations in the C=O stretching region (1,780-1,700 cm(-1)) were monitored and analyzed by a series of data processing methods, including calculation of difference spectrum and second derivative spectrum, Fourier self-deconvolution, curve-fitting and 2D correlation analysis. Four bands have been resolved from the 2D correlation analysis, and the following overall sequential order among the intensity changes of the four bands has been obtained at 1,750 > 1,739 > 1,722 > 1,715 cm(-1). Combining with the other data processing methods, a curve-fitting approach has been employed to reveal that there are probably five component bands under the C=O band profile, centered at 1,746; 1,737; 1,728; 1,722; and 1,712 cm(-1). Detailed analysis on the in situ component band intensity variations in the C=O stretching region indicates that the crystalline and amorphous band intensities change simultaneously during the crystallization process, with no local sequential order. Further analysis on the relative area percentage changes of the five component bands suggests that the crystalline component only changes in a fully cooperative manner with part of the amorphous component at the initial crystallization period.

Molecular orientation and optical anisotropy in drawn films of cellulose diacetate-graft-PLLA: comparative investigation with poly(vinyl acetate-co-vinyl alcohol)-graft-PLLA

Cellulose diacetate-graft-poly(L-lactide) (CDA-g-PLLA) and poly(vinyl acetate-co-vinyl alcohol)-graft-PLLA (P(VAc-co-VOH)-g-PLLA) were synthesized over a range of compositions, by ring-opening copolymerization of L-lactide at the original hydroxyl positions of the respective trunk polymers, CDA (acetyl DS = 2.15) and P(VAc-co-VOH)-g-PLLA (VAc = 64.2 mol%). All the products of both graft copolymer series were non-crystallizable and their solution-cast films showed no domain segregation of the two components that constituted the trunk and side-chains. A comparative study on the molecular orientation and optical anisotropy induced by uniaxial stretching of film samples was undertaken for the two copolymer series with various side-chain lengths. Overall behaviour of the orientation was estimated from the statistical second (<cos2 ω>) and fourth (<cos4 ω>) moments obtained by a fluorescence polarization method using a rod-like probe of ~2.5 nm. Upon stretching, any film of both series imparted a positive orientation function, i.e., f = (3 <cos2 ω> − 1)/2 > 0, which increased with the extent of deformation. The degree of molecular orientation was higher in the CDA-graft series with a semi-rigid trunk, and, in both series, it declined monotonically with increasing content of the PLLA side-chain. With regard to the optical anisotropy, CDA-g-PLLA films always exhibited a positive birefringence (Δn > 0) upon stretching, while drawn films of P(VAc-co-VOH)-g-PLLA displayed a negative one. This contrast in polarity reflects a difference in the intrinsic birefringence between the two trunk polymers. Of interest was the finding of a discontinuous change in Δn value with copolymer composition (PLLA content) for the respective graft series, when compared at a given stage of elongation of the films. Discussion took into consideration the locally different orientation manners of the attached PLLA chain segments.

Solution casting, characterization, and performance evaluation of perfluorosulfonic sodium type membranes for chlor‐alkali application

AbstractThis investigation describes solution casting, characterization and performance evaluation of perfluorosulfonic sodium (PFSS) type membranes prepared by three different methods from Nafion solution and Nafion‐117 for Chlor‐Alkali (CA) application. A Chlor‐Alkali experimental set‐up was designed and constructed for performance evaluation of the recast membranes. The chemical structure of solution cast films was studied and confirmed by FTIR (Fourier Transform infrared spectroscopy) and ATR (Attenuated total reflection) techniques. The physical properties of solution cast films including mechanical strength, thermal behavior, water sorption, ion‐exchange capacity (IEC), morphology, and crystallinity were also evaluated. All the recast polymeric films behave like elastomers with low modulus but high elongation at break. Differential scanning calorimetric (DSC) thermograms of solution cast films showed two endothermic peaks at 180°C and 250°C attributed to matrix glass transition (Tgm) and ionic cluster glass transition (Tgc) of the Nafion polymer, respectively. The water uptake of polymeric films was reasonable in comparison with Nafion‐117. Solution casting has no significant effect on ion exchange capacity of the recast films. The scanning electron microscope (SEM) micrograph showed that the morphology of recast films is reasonably similar with Nafion‐117. However, the as‐cast films have some micro pores, which are produced during solution casting. The crystallinity of annealed film, because of the heat treatment was slightly high due to local ordering. According to the experimental results, which obtained from performance evaluation in CA cell, the properties of recycled films are similar to commercial membranes such as Nafion‐117 and can be used in CA process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Spatially resolved drying kinetics of multi-component solution cast films for organic electronics

The use of multi-component solvent/additive systems can be beneficial in the manufacturing process of organic and printed electronics because they can provide an extended degree of freedom, in terms of optimized wetting properties or their influence on the molecular ordering during solvent evaporation. For a systematic investigation of the drying process of such systems a technique for the measurement of the evaporation kinetics for micrometer to nanometer thin films is required. Since large area films are drying faster at the edges, we determine the drying kinetics spatially resolved in a linear array of 5 reflectometers simultaneously for single and binary solvent systems for polymer–fullerene (P3HT:PCBM) solutions as used in organic photovoltaic. In order to design a specific drying process, e.g. combined fast and slow evaporation of high or less solving solvents, a spatial resolved numerical investigation of solvent mass transfer is addressed. A numerical approach including the effect of a moving drying front shows reasonable agreement for single and binary solvent systems with spatially resolved experimental data. The effect of the moving drying front accelerates the drying kinetics at a distinct position as the front approaches and must also be considered for integral measurements (e.g. gravimetric experiments).

Electronic interactions within composites of polyanilines formed under acidic and alkaline conditions. Conductivity, ESR, Raman, UV-vis and fluorescence studies

The properties of two forms of polyaniline (PAni) synthesised under acidic and basic conditions have been investigated both individually and as combined complexes. The PAni polymerised within alkaline media was redox inactive and non-conducting while the PAni emeraldine salt (ES) was electroactive and conducting. Raman, electron spin resonance, UV-Vis and fluorescence spectroscopies were used to monitor the changes in electronic properties of these conducting polymer composites. Solution cast films of alkaline synthesised (A-PAni) with the PAni ES resulted in an increase in the high spin polaron population suggesting that it acts as a pseudodopant. The ability of the A-PAni to increase and maintain the population of the polaron charge carrier was confirmed by UV-vis and Raman spectroscopy. Significantly, the presence of the A-PAni in PAni ES helped to sustain higher electrical conductivities at loading levels that were well below the percolation threshold of an insulating polystyrene sulfonate polymeric oligomer model. Fluorescence studies indicated that the A-PAni was fluorescent. However, mixtures of A-PAni with the PAni ES resulted in quenching of the A-PAni emission. The quenching process was observed to involve both static and dynamic processes, with the static quenching being dominant. These results suggest that the two polymers are strongly associated with each other when in the solid state. In stark contrast, the alkaline synthesized PAni did not influence the electrochemical properties of the emeraldine salt. These results deviate significantly from the expected outcome of the addition of an insulating A-PAni additive and highlight the unusual interactions occurring between PAni and its alkaline analogue.

Self-assembled aggregates of dendritic-linear copolymers: vesicles and microspheres

Owing to the peculiarity of its molecular architecture, dendritic-linear copolymer consisting of Percec type dendron molecules and a relatively stiff poly{2,5-bis[(4′-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) chain could self-assemble into hollow spherical particles in common solvent. This type of self-assembly offers a new convenient route for obtaining hollow vesicles in copolymer systems without secondary bonding. And vesicular structures and micro-spherical compound micelles can be obtained in selective solvents. Additionally, under moisture-rich conditions, solution-cast films of dendron-b-PMPCS can form well-defined honey-comb patterns.

Effect of Processing Conditions on the Dielectric and Raman Response of Electroactive Polymers

The relationship between the molecular and crystalline structure and the dielectric response of hot-pressed PVDF film and the films cast from N,N-dimethylacetamide solution was studied by means of wide angle X-ray scattering, Raman and dielectric spectroscopy. We have found that the degree of crystallinity of hot-pressed PVDF is by about 10% higher than that of solution-cast films, which results in a decrease in the activation energy of segmental motions and a rise in the freezing temperature. We have also observed that the solution-cast samples are more reach in sequences containing trans conformation (T)nG with n ≥ 3 which leads to an increase in their permittivity value.

Properties of polystyrene/poly(dimethyl siloxane) blends partially compatibilized with star polymers containing a γ-cyclodextrin core and polystyrene arms

A star polymer with a γ-CD core and PS arms (CD-star) is used to partially compatibilize blends of the immiscible polymers polystyrene (PS) and poly(dimethylsiloxane) (PDMS). The mechanism of compatibilization is threading of the CD core by PDMS and subsequent solubilization in the PS matrix facilitated by the star arms. Films cast from clear solutions in chloroform exhibit large wispy PDMS domains, indicating that some dethreading of CD-star and agglomeration of PDMS takes place during the slow process of solvent evaporation. However, DSC and DMA data show that partial compatibilization takes place, as evidenced by a shift in the PS and PDMS Tgs toward each other. The shift in PS Tg is greater when CD-star is present compared to samples without CD-star. PDMS also tends to leach out of the solution-cast films during solvent evaporation and post-processing of the films. The amount of retained PDMS is significantly increased when CD-star is present. The DMA data also show that PDMS has a lower molecular mobility when CD-star is present.

Ultraviolet Photoelectron Spectroscopy Study of the Polydiacetylene of the Bis-p-Chlorocinnamate of 10,12-Docosadiyn-1,22-diol and Related Subjects

The bis-p-chlorocinnamate of 10,12-docosadiyn-1,22-diol (Cl-Cin-22) interacts with 60Co γ radiation to give a polydiacetylene (PDA) soluble in organic solvents. This PDA has been previously studied with respect to its optical spectroscopy and exciton binding energy. In this work, solution cast films of PDA-Cl-Cin-22 have been studied by ultraviolet photoelectron spectroscopy (UPS). The threshold solid state ionization energy of 5.9 eV is consistent with earlier UPS studies of PDA. Exposure of a Cl-Cin-22 monomer film to He I (21.2 eV radiation) initially gives a blue colored film that converts to a red film on heating, consistent with an irreversible thermochromic transition. In situ polymerization in ultrahigh vacuum of spin coated films of Cl-Cin-22 using He I (21.2 eV radiation) has been explored by recording UPS spectra as a function of exposure time, and for comparison UPS data of p-chlorocinnamic acid and bis-p-chlorotruxinic acid are also reported.

Preparation and comparative evaluation of well-defined fluorinated acrylic copolymer latex and solution for ancient stone protection

In this work the well-defined fluorinated acrylic copolymer latex and solution were prepared by the radical initiated seed emulsion polymerization and solution polymerization, respectively, using the same monomers of dodecafluoroheptyl methacrylate (DFHM), butyl acrylate (BA) and methyl methylacrylate (MMA). The copolymer latex BA/MMA/DFHM was designed as core–shell structure and the copolymer solution poly(BA–MMA–DFHM) was structured with low molecular weight. The chemical and morphology structures as well as the film properties obtained from latex and solution were analyzed and compared by spectroscopic techniques (FT-IR and NMR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscopy coupled with energy-dispersive X-ray detector (SEM–EDX) and static contact angles (CAs) instrument. Moreover, the BA/MMA/DFHM latex and poly(BA–MMA–DFHM) solution (with 29wt% of DFHM) were applied onto two kinds of sandstone samples by capillary absorption, and their preliminary protecting efficiency was evaluated. It is demonstrated that the comprehensive performances of BA/MMA/DFHM latex films were quite comparable to those of poly(BA–MMA–DFHM) solution cast films, the latter exhibited a better protective performance.

Mechanical, Thermal, and Surface Properties of Ultrahigh Molecular Weight Polyethylene/Polypropylene Blends

Various compositions of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were prepared in decalin, with the rheological, mechanical, thermal, and surface properties of the blends being determined using the solution cast film. Viscosity and mechanical properties of the blends decreased below the additivity value with increasing PP content implying that PP molecules disturb the entanglement of UHMWPE. Contact angle of the blend films with a water drop increased with increasing content of PP. The atomic force microscope (AFM) images showed that the surface of cast UHMWPE was very smooth whereas that of cast PP was very uneven. For blends, the surface became rough and uneven with increasing content of PP. The melting temperature of PP (T mP) decreased in the blends with increasing UHMWPE content while that of UHMWPE (T mU) remained almost constant in blends.

New analytical approach to the insulator–metal transition in conductive polyaniline

A new empirical formula describing the temperature dependence of the conductivity of polyaniline films in the metallic regime close to the insulator–metal transition at temperature below 30 K is deduced from the analysis of the temperature dependence of the reduced activation energy. Its elaboration is based on a careful study of electrical transport properties of camphorsulfonic acid-doped polyaniline (PANI(CSA) 0.5) films, containing increasing amounts of triphenyl phosphate (TPP) plasticizer. The use of this three component system (polymer, protonating agent, plasticizer) and control of the amount of adsorbed water enable precise tuning of the electrical transport properties in the solution cast films, in this manner providing the set of experimental data, covering the insulating, critical and metallic regimes, necessary for the elaboration of the proposed new empirical formula.