Polymer films solution casting

Polymer Processing. Polymer films were cast in trimethylsilyl coated glass molds from membrane filtered 15% (w/v) methylene chloride or chloroform solutions. Transparent films were obtained which were dried to constant weight in high vacuum. Rectangular strips or round disks were cut from the films. For compression molding a Carver laboratory press equipped with thermostated, heated platens was used. Polymers were placed in a stainless steel mold and heated to 40 °C above their glass transition temperature. Then a load of 1-2 tons was applied for 5 min. 

Each solvent used was observed to contain no impurities which fluoresce in the spectral region of interest. All solution concentrations used were in the range 10-5 to 10 4 M. Polymer films were cast onto quartz plates from either chloroform or dichloromethane solutions containing 4% (wt/wt) of polymer. The films were air dried at room temperature and had an average thickness of 65 10 )lm. The absorption spectra of the polymer films were measured using an appropriate PMMA or PS film as the reference. 

For higher molecular weight polymers, films were cast from solution for soluble polymers and melt pressed ca. 300 for insoluble polymers. 

In addition to the criticisms from Anderman, a further challenge to the application of SPEs comes from their interfacial contact with the electrode materials, which presents a far more severe problem to the ion transport than the bulk ion conduction does. In liquid electrolytes, the electrodes are well wetted and soaked, so that the electrode/electrolyte interface is well extended into the porosity structure of the electrode hence, the ion path is little affected by the tortuosity of the electrode materials. However, the solid nature of the polymer would make it impossible to fill these voids with SPEs that would have been accessible to the liquid electrolytes, even if the polymer film is cast on the electrode surface from a solution. Hence, the actual area of the interface could be close to the geometric area of the electrode, that is, only a fraction of the actual surface area. The high interfacial impedance frequently encountered in the electrochemical characterization of SPEs should originate at least partially from this reduced surface contact between electrode and electrolyte. Since the porous structure is present in both electrodes in a lithium ion cell, the effect of interfacial impedances associated with SPEs would become more pronounced as compared with the case of lithium cells in which only the cathode material is porous. 

The polymer film was cast on glass plates from a 20% (by weight) solution of polymer in dimethylformamide. After the film was dried at 50°C for 40 min it was removed from the glass plate by immersion in water. No difference was found in the properties of sulphonated products based on the P-1700 resin or P-3500 resin. 

The finding of a best method for introducing photoinitiators and photosensitizers into polymers is a very important practical problem. Two main methods are in this case applied a polymer film is cast from a solution with the respective photosensitizer added,or the photosensitizer is pressed into the film at an elevated temperature. In the first method it is sometimes very difficult to remove all traces of solvent,which may influence the photoreactions observed. In the second method conditions of pressing (temperature of 100-200°C and pressure of 100-200 atm) may alter the polymer and compound added. 

Torikai et al. [1994] compared the effects of gamma irradiation of films of PS/PMMA blends and PS-PMMA copolymer (co-PS-PMMA) (Table 11.9). Polymer films were cast from methylene chloride solutions and were dried under vacuum. Based on the UV and FTIR spectroscopy, and viscosity measurements, Torikai et al. [1994] concluded that whereas the presence of PS in the copolymer provided protection against radiation-induced degradation to the PMMA units, similar... 

PDA-Containing polymer films. The DA-containing polymer films were cast fi om solutions (chloroform for 1 and N-methylpyrrolidone for 2). In the case of 2 the solvent was evaporated at 60°C under reduced pressure. When a heated spin coater was used for 2, highly transparent films could be obtained, but due to their amorphous nature, no crosspolymerization took place on irradiation. In the case of 1, the transparency (crystallinity) of the films depended on the number of meth>iene units (x andy). For exanq)le, when x is 2 and is 5, the film is always conq>letefy opaque, and in other cases reasonably transparent films can be obtained, although the transparency depends on the casting conditions. 

The primary photoexcitation dynamics in PDPA solutions and films in the fs to ps time domain using transient PM spectroscopy were extensively studied [182]. The PDPA polymer used was a disubstituted biphenyl derivative of frans-polyacetylene, where one of the hydrogen-substituted phenyl groups was attached to a butyl group, which is referred to as PDPA-mBu (Figure 22.25 inset) [181]. The polymer films were cast on sapphire substrates from a toluene solution the same solution was used for measuring the photoexcitation dynamics in a PDPA-mBu solution. 

The elastomers were purified by precipitation of DMA solutions with excess methanol. Polymer films were cast from DMA solution and dried in vacuum at 50 C for 8 days and stored in a dessicator at room temperature. 

Vadimsky [23] described a useful method for preparation of thin films from the melt or solution. The method involves the evaporation of carbon onto freshly cleaved mica or fractured NaCl crystal substrates. The thin polymer film is cast onto the carbon coated substrate or the substrate is dipped into a polymer solution. After solvent evaporation, the film is scored and removed from the glass by floating it onto a water surface. The specimen can also be deposited directly onto the substrate followed by carbon coating. Geil [24,25], in a variation of this method, deformed PE single crystals by deposition on a Mylar substrate and drawing it before carbon coating and TEM examination. 

Acetoxyquinoline-2-carboxylic acid (1.2 g, 5.2 mmol), benzotri-azole (0.62 g, 5.2 mmol), and DCC (1.07 g, 5.2 mmol) in dry THF (8 mL) were stirred at 0 C (2h), then 25 C (Ih). After filtration and concentration, the residual solid (1.79 g), PVA (MW = 25000 88% hydrolyzed 1.02 g, 20.8 mmol) and triethylamine (0.61 g) in DMSO (17 mL) were heated at 60 C for 48 hr. under nitrogen. The product was precipitated by pouring onto ice water, filtered, and washed with acetonitrile. Yield 1.35 g. Unchanged QA and other low molecular weight species were removed by precipitation from DMF with acetonitrile, then dialysis in 50% aq. ethanol using an Amicon YMIO membrane (10,000 cutoff). The QA incorporation was determined to be 5 mole-% by comparison of the UV absorbance at 258 nm with a calibration curve derived from standard solutions of QA in 50% aq. ethanol this result was verified qualitatively by H-NMR spectroscopy. A satisfactory elemental analysis was not obtained. Analysis calculated for 5 mole-% QA in PVA C, 61.4 H, 6.39 N, 3.58. Found C, 55.27 H, 6.87 N, 1.63. Films of the polymer were solution cast from DMF. 

Thianthrene-2,7- and -2,8-dicarboxylic adds plus a synthetic intermediate, 4,4 -thiobis[3-chlorobenzoic acid], were converted to new aromatic polyamides having inherent viscosities of 1.29 to 2.39 dL/g by direct polycondensation with 4,4-oxydianiline and 1,4-phenylenediamine in N-methyl-2-pynolidinone using triphenyl phosphite and pyridine. Thianthrene-based polyamides were more soluble than analogous poly(tluoether amide)s. Polymer films were cast from either DMF or DMAc/LiCl solutions and analyzed by FTIR and NMR. All prepared aramids displayed good thermal stability by DSC and TGA. 

However, membranes were not prepared from solution casting due to the crystalline form of the sulfonated polymer. In another report by Fei et al., a hybrid polymer with a polynorbomene backbone and pendent sulfonated cyclic phosphazene side groups was synthesized [93]. Co gamma radiation cross-linking was applied after the polymer film was cast, in order to restrict water swelling. The prepared membranes had relatively low lEC ranging from 0.267 to 0.49 mmol g. It was also found that there... 

Solvent evaporation A mixture of solvents, with one of them being volatile, is nsed to form the casting solution. After casting, the volatile solvent evaporates, thns changing the polymer-film-solution composition, which canses precipitation. In the simplest form, a polymer is dissolved in a two-component solvent mixture consisting of a volatile solvent, in which the polymer is readily soluble, and a less volatile nonsolvent, typically water or an alcohol. 

According to the above results, PS-DMF-MC-SW was chosen as the best substrate membrane. This was a membrane prepared from a casting solution containing polysulfone (12.5 wt.%), dimethylformamide (75 wt.%) and cellosolve (12.5 wt.%). The polymer film was cast on a glass plate to a thickness of 0.3 mm and then coagulated in an aqueous solution containing 15 wt. % NaCl. All remaining SPPO TFC membranes were prepared based on this substrate membrane. 

Solution Casting. The production of unsupported film and sheet by solution casting has generally passed from favor and is used only for special polymers not amenable to melt processes. The use of solvents was generally very hazardous because of their flammabiUty or toxic nature. The cost of recovery and disposal of solvents became prohibitive for many lower price film appHcations. The nature of the drying operations leads to problems with solvent migration and retention that are not problems with melt-processed polymers. 

Most solution-cast composite membranes are prepared by a technique pioneered at UOP (35). In this technique, a polymer solution is cast directly onto the microporous support film. The support film must be clean, defect-free, and very finely microporous, to prevent penetration of the coating solution into the pores. If these conditions are met, the support can be coated with a Hquid layer 50—100 p.m thick, which after evaporation leaves a thin permselective film, 0.5—2 pm thick. This technique was used to form the Monsanto Prism gas separation membranes (6) and at Membrane Technology and Research to form pervaporation and organic vapor—air separation membranes (36,37) (Fig. 16). 

The first five of these techniques involve deformation and this has to be followed by some setting operation which stabilises the new shape. In the case of polymer melt deformation this can be affected by cooling of thermoplastics and cross-linking of thermosetting plastics and similtir comments can apply to deformation in the rubbery state. Solution-cast film and fibre requires solvent evaporation (with also perhaps some chemical coagulation process). Latex suspensions can simply be dried as with emulsion paints or subjected to some... 

Phenoxaphosphine ring-containing poly (1,3,4-oxa-diazoles) were synthesized by cyclodehydration of poly-hydrazides obtained from (BCPO) and aliphatic and aromatic dihydrazines [152]. All these polymers are soluble in formic acid, w-cresol and concentrated H2SO4. The polyhydrazides yield transparent and flexible films when cast from DMSO solution under reduced pressure at 80-100°C. The polyhydrazides exhibit reduced viscosities of 0.24-0.40 dl/g in DMAC. Phenoxaphosphine ring-containing oxadiazole polymers showed little degradation below 400°C. 

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