Solvents for casting films

Extensive data were obtained from the related compound 5,5 -bis(4-hexylphe-nyl)-2,2 -bithiophene, abbreviated 6PTTP6 [36]. Xylene was an ideal solvent for casting films of this compound, keeping the substrate 5-30° below the boiling point. 

The crystallization tendency of polycarbonate is enhanced by the action of solvents. For example, crystallization may be accomplished by slow evaporation of solvent from cast film (14, 17) or by treatment with swelling agents such as ethyl acetate or acetone. 

Three mixtures of CO-PNNA were blended together for analysis of lithographic performance. Compositions of 20, 33, and 50% CO by weight were blended by dissolution in THF to form a 13% (total solids) solution. Cyclohexanone was added to the blend to form a 7% solution to impart proper viscosity and volatility.for casting films. In the case of PNNA with N - 950 x 10, CO was dissolved in hot chlorobenzene and tnen mixed with PNNA (also in chlorobenzene). Solvent choice was a matter of convenience. 

Commercially available water soluble copolymers of maleic anhydride with ethylene and methyl vinyl ether (presumably partially hydrolyzed to vicinal carboxylic acids) and triphenylsulfonium triflate were dissolved in water as a casting solvent. Spin-cast films were baked at 130 °C for 10 s, exposed to 254 nm radiation, and postexposure-baked at 130 °C for 40 s. Development with pure water provided negative tone images, presumably due to acid-catalyzed dehydration between vicinal carboxylic acids to form less polar anhydride, as was demonstrated for polarity reversal (4.3.1). However, a copolymer of maleic acid with methyl vinyl ether failed to provide any negative images,... 

The results show that the temperature of the a-transition is significantly reduced for cast films compared to the bulk polymer, with a lower value for chloroform samples. The decrease of the a-transition temperature can be explained by the presence of residual solvent, inducing a plasticizing effect. On the contrary, an increase of the P-transition tempera-... 

Some spectra of oriented polypeptides obtained with polarized infrared radiation (Ambrose and Elliott, 1951a) are shown in Fig. 111. In the case of poly -benzyl-L-glutamate, the NH stretching mode at 3292 cm. and the C=0 stretching mode at 1653 cm. show parallel dichroism while the band associated with NH deformation at 1549 cm. shows perpendicular dichroism. The ester C=0 band at 1730 cm. does not show much dichroism. This is the behavior to be expected of the a form since the axes of the helices would be oriented preferentially in the direction of stretching, and the NH and CO bonds are essentially parallel to the axes of the helices. In some cases, the solvent used for casting films favors the extended /8 form, with the opposite dichroic behavior since the NH and CO bonds in the ]3 form are essentially normal to the backbone chain. Such is the case... 

Chlorinated hydrocarbons are convenient solvents for a variety of polymers and the same solvents are frequently used for casting films which are subjected to radiation failure to totally remove residual solvent could lead to erroneous conclusions about the mechanism of photoinduced oxidation. 

Solution processes are used mainly for coating, film casting and fibre spinning, i.e. in processes where the distance the solvent has to diffuse out of the solution once coated, cast or spun is short. Regulation of this diffusion process is important if products of even quality are to be obtained. 

The thermal imidization of a polyamic acid film (PMDA-ODA or BPDA-ODA) obtained by casting an NMP solution leads to an amorphous polyimide. Two different teams have shown that a polyamic acid solutions in NMP heated at 200°C for a short time (20 min) gives polyimide particles fully cyclized and highly crystalline, as shown by X-ray diffraction and solid 13C NMR spectroscopy.151152 The chemical imidization of the same solution gives only amorphous particles. The difference between the cyclization of a solution and a casted film in the same solvent is intriguing. In the case of the solution, the temperature and the heating time are lower than in the case of the casted film as a consequence, a less organized structure would be expected for the particle. 

In order to test the tissue compatibility of tyrosine-derived poly-(iminocarbonates), solvent cast films of poIy(CTTH) were subcutaneously implanted into the back of outbread mice. In this study, conventional poly(L-tyrosine) served as a control (42). With only small variations, the experimental protocol described for the biocompatibility testing of poly(N-palmitoylhydroxyproline ester) (Sec. III. 

Poly(CTTH) (Figs. 6 and 7) was also used as a model compound for the preliminary evaluation of the in vitro degradability of tyro-sine-derived poly(iminocarbonates) Solvent cast films of poly(CTTH)... 

The electrochemical behavior of the C70 solvent-cast films was similar to that of the C60 films, in that four reduction waves were observed, but some significant differences were also evident. The peak splitting for the first reduction/oxidation cycle was larger, and only abont 25% of the C70 was rednced on the first cycle. The prolate spheroidal shape of C70 is manifested in the II-A isotherm of C70 monolayers. Two transitions were observed that gave limiting radii consistent with a transition upon compression from a state with the long molecnlar axes parallel to the water snrface to a state with the long molecnlar axes per-pendicnlar to the water surface. 

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