Film cast from solution

To produce resins for paints and for electrical insulation, film cast from solution copolymers based on bis-phenol A and bis-phenol Z (l,l-bis-(4-hydroxyphenyl)cyclohexane) have been used. 

Quite often, NBR adhesives are used to bond various kinds of gasketing (cork, fibre, foam, rubber, metal) to rigid superstructures, such as aircraft. Films cast from solution are often used to fabricate honeycomb structures for aircraft. 

Cakmak M. and Wang M.D., Structure development in the tubular blown film of PP/EPDM thermoplastic elastomer, Antec 89, 47th Annual Tech. Conference of SPE, New York, May 1, 1989, 1756. Hashimoto T., Todo A., Itoi H., and Kawai H. Domain boundary structure of styrene-isoprene block copolymer films cast from solution. 2. Quantitative estimation of the interfacial thickness of lamellar microphase systems. Macromolecules, 10, 377, 1977. 

To what extent are the ordered structures observable in the electron microscopic photographs of the polymer films cast from solution influenced by the substrate Any significant influence can be excluded for the following reasons ... 

As shown in Figures 5 and 7 the nature of the solvent does not appear to have any effect on T0 within experimental error. However, the solvent can have a profound influence on the morphology of cast block copolymer specimens. Thus, instead of the continuous polybutadiene phase normally observed, a continuous polystyrene phase appears to exist in Kraton 101 films cast from solution in MEK/THF mixtures (2). Methyl ethyl ketone has a solubility parameter of 9.3, only slightly higher than that of the solvents used in our work. It is clear from the data presented here that our films must have had continuous polybutadiene phases. 

Figure 16.20. Micro-SERS spectra of FA films cast from solutions at (a) pH 5, (b) pH 8, and (c) pH 11 on 9-nm gold island films. Laser excitation at 785 nm and spectra were collected from different spots as marked on the optical image. Reprinted from Alvarez-Puebla et al. (2004).

Cellulose nitrate film cast from solution is highly brittle and is made flexible for surface coating applications bv the addition of plasticizers like dibutylphthalate, dioctylphthalate,... 

Fig. 1. The loss of solvent vs polyamic acid weight percent in DGEBA/PAA films cast from solution and dried in the atmosphere for 48 h...

Figure 13 Optical absorption of the PDA poly-4BCMU in three differently ordered states (a) solution in chloroform (b) gel from toluene (dense homogeneous films cast from solution have similar, though slightly less structured, spectra) (c) single crystal.

Hashimoto T., Fujimura M. and Kawai H., Domain-boundary structure of styrene-isoprene block copolymer films cast from solutions 5. molecular-weight dependence of spherical microdomains. Macromolecules 13 (1980) pp. 1660-1669. 

In conjugated polymers, however, both band-based models and exciton-based models have been used to explain aspects of the optical properties. Moreover, conjugated polymers are typically highly disordered materials for example, thin films cast from solution show clear evidence of spectral broadening and bandtailing with characteristic energies of a few tenths of an eV. 

Indeed, the fact that the onset of photoconductivity occurs at a higher energy than the absorption edge in the polydiacetylenes, both in single crystal samples and in thin films cast from solution is a clear indication that the photoexcitations generated below 2.3 eV are neutral bound excitons [200]. 

Figure 2. Ratio of anthracene and carbazole emission intensities from freeze-dried mixtures of monodisperse polystyrene (M - 410,000) carrying 0.0092 moles/kg of the labels, relative to this ratio in films cast from solutions of a mixture of these polymers. Excitation at the carbazole absorption peak at 294 nm. Original solution in benzene dioxane (D) and cyclohexane (0). Arrows indicate l/iq] in the various solvents.

Some studies have examined the effect of solvent on the structure of EB films cast from solutions. For example, Ou and Samuels193 found that EB films cast from NMP solution were partially crystalline, as evidenced by shoulders appearing above the amorphous band in x-ray diffraction (XRD) studies. However, when the EB was cast from a solution in A, A-dimethyl propylene urea (DMPU), no evidence of crystallinity was observed. Whereas the NMP solutions were unstable (undergoing gelation owing to the formation of H-bonded networks between the PAn chains), the... 

Figure 3. TCNQ concentration in films cast from solutions of 23.5 mg polymer per mL DMF as a function of added TCNQ. (Reproduced with permission from Ref. 8. Copyright 1982,...

Concentration quenching is not a major problem in semiconducting polymers. Typically, the quantum efficiency for photoluminescence from thin films is comparable to that from dilute solutions. The absence of strong concentration quenching is the result of the spatial delocalization of the excited states. Because the weakly bound excitons are spread over many repeat units, the Davidov splitting that results from interchain interactions is small. As a result, the disorder that is present in films cast from solution is sufficiently large to mix the dark and emissive Davidov-split states. Thus, quantum efficiencies in excess of 60-70% can be obtained from thin solid films of luminescent semiconducting polymers. 

Polymers are sometimes studied in solution. This has the advantage that the systems are free from kinetic and mechanistic complexities typical of solid state reactions. However, the conditions are far from natural. When solid polymers are to be studied, reliable results are most easily obtained by irradiating thin films cast from solutions. The use of thin films ensures homogeneous dissipation of energy into the sample, and the solvent casting technique does not require high temperatures which are sometimes responsible for partial oxidation or degradation of the polymer prior to the photolysis. 

As shown in Table 4.7, several methods have been used to characterize the morphology of polymer blends containing a block copolymer. In the pioneering works, transparency of films cast from solutions was used as a measure of the emulsifying agent efficiency [Riess et al, 1967 Banderet et al, 1967]. Other studies have focused on the observation of phase size reduction in the scanning... 

Recently, formation of transparent blend films cast from solutions of PVC and (PC-PDMS) multiblock copolymer has created concern [Gorelova et al, 1992]. The finding is interesting because the refractive indices of PVC, PC and PDMS are different and consequently, transparency of the blend films may suggest miscibility of their constituents, despite the fact that PVC is immiscible with PC and PDMS [Krause, 1978]. In other words, these blends are pseudo-miscible and their transparency is caused by the very small size of the dispersed block copolymer phase. 

Figure I. VUCD spectra of amylose (A) solution (10 mg/mL) autoclaved at 120°C, 30 min (B) gel (20 mg/mL), aged 2 d (C) film cast from aged solution (10 mg/mL) (D) film cast from Solution A.

Film cast from solutions in a tetrachloroethane phenol (3 1) mixture had a tensile strength of the order of 60-80 N/m and retained up to 50% of their initial strength upon heating to 200 C. 

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