PMMA solution drying

Blends of PMMA with various additives and copolymers of methyl methacrylate with 2-sulfoethyl methacrylate (2-SEM) are discussed in this paper. Blends of transition metal salts and PMMA were prepared by dissolving the salt in a suitable solvent and combining this with a PMMA solution in chloroform. Homogeneous blends were obtained after evaporation of the solvents. The blend of Nafion-H and PMMA was obtained by pouring a chloroform solution of PMMA onto Nafion-H film and drying at room temperature. The copolymers were obtained by standard techniques. 

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. 

Fig. 25 Dry poly(methyl methacrylate) (PMMA) thickness as a function of the position on the silica substrate. The inset shows the dry PMMA thickness as a function of the polymerization time. The arrows mark instances where the drain speed of the polymerization solution from the chamber was decreased relative to the previous drain speed. The lines are meant to guide the eye. (Reproduced with permission from [94])...

The PP was supplied by Shell Research Ltd., completely free from additives (M 222,300). The PMMA (M 516,000) was prepared from monomer (HDH Ltd.) idilch was purified by washing with sodium hydroxide solution and distilled water, followed by drying and vacuum degassing and distillation. It was polymerized at 60°C under vacuum with azo-di-isobutyronltrile (0.1% w/v) as initiator and purified by precipitation three times by methanol from toluene solution followed by vacuum drying at 60 C. 

Figure 5.5 illustrates an example of PL spectra, where 2.8 and 5.6nm diameter nanocrystals were incorporated into a PMMA film. The 2.8 nm nanocrystals had an initial emission maximum in toluene at 541 nm, which was slightly red-shifted to 543 nm upon an addition of a polymer solution. A strong blue shift to 519nm was observed in a dry film containing 2.8 nm nanocrystals and PMMA, with an additional blue shift to 504nm upon an extended photoactivation. As shown in Fig. 5.6, the peak shift of 5.6-nm nanocrystals in PMMA was less dramatic upon photoactivation, but mirrored the behavior of the 2.8-nm nanocrystals. The peak positions for... 

In order to avoid the infiltration of seeds in the support and to develop ultra-thin membranes (typically 500 nm thick) with a high permeability, a masking techniques has been recently developed in Lulea University [111]. A solution of poly methyl methacrylate (PMMA) in acetone was applied and dried on the support top surface. The interior of the support was subsequently filled with wax and the protective PMMA layer was dissolved in acetone. The masked support was then seeded with a monolayer of silicalite-1 crystals before being submitted to the classical hydrothermal and calcination steps. 

The freeze drying of co-solutions of thermodynamically immiscible polymer pairs is a method of capturing kinetically the unlike molecules in molecular or segmental mixtures. PMMA/PVAc blends freeze-dried from co-solutions in benzene were reported homogeneous by dynamic mechanical and dilatometric observations. They showed a single T intermediate between those of the pure polymers [Miyata and Hata, 1970]. Further dilatometric and differential calorimetric data corroborated the findings of homogeneity [Ichihara et al., 1971]. 

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... 

Polystyrene was prepared from freshly distilled and degassed styrene by bulk polymerization at 50° C.imder nitrogen with benzoyl peroxide as the initiator Conversion was about 50%. After precipitation with methanol, the polymer was purified by two reprecipitations from tetrahydrofuran solution with methanol, exhaustively extracted with metha- 1, and finally vacuum-dried at room temperature. The polymer had Mv = 1.8 X 105. Films of this material were prepared from methylene chloride solution in the same way as the PMMA films. 

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