Simple freezing methods

There are some simple freezing methods that provide adequate preparation for some polymers. Cold stage microscopy of colloidal suspensions, microemulsions and liquids is possible by fast freezing and examination of the thin, frozen specimen in an EM. Talmon et al. [338] developed a rather interesting technique in which a thin sample is trapped between two polyimide 

Manual methods of freeze fracture are often useful in providing specimens for study in the SEM. An example of a freeze shattering method was described by Stoffer and Bon [340] for comparison with microtomy results. Polymers immersed in liquid nitrogen were mechanically shattered with a hammer, mounted, vacuum pumped and sputter coated for observation. This simple method is useful if the materials cannot be sectioned. However, fine structural details are not conclusive when specimens are prepared by such methods. 

Walter and Bryant [348] described a method for freeze drying latex specimens in a home made vacuum system rather than a commercially available device (as was typical of the state of the art at that time). Later, a freeze drying/image analysis method using commercially available equipment was described [347]. Important details of that 

Results of the experiment described above are shown in Fig. 4.37. A monodisperse latex of known particle size (Fig. 4.37A) was used both as a control and for calibration of the particle size distribution measurement [353]. A film forming latex is shown following both air drying (Fig. 4.37B) and freeze drying (Fig. 4.37C). Clearly, the flat, film forming, air dried particles are three dimensional following freeze drying. 

---

Mann and Mitchell [58] described a simple colorimetric method for estimation of (-D)-penicillamine in plasma. Blood containing 2-50 pg of penicillamine was mixed with 0.1 M EDTA solution in tromethamine buffer solution. 0.1 mL of this solution was adjusted to pH 7.4 and centrifuged. To a portion of the plasma was added 3 M HCL, the mixture was freeze-dried, and a suspension of the residue in ethanol was centrifuged. The supernatant liquid was mixed with tromethamine buffer solution (pH 8.2) and 10 mM 5,5 -dithiobis-(2-nitrobenzoic acid) in phosphate buffer solution (pH 7.0), the mixture was shaken with ethyl ether, and the absorbance of the separated aqueous layer was measured at 412 nm. The mean recovery was 60% (four determinations), and the calibration graph was linear for the cited range. 

Mechanical methods are fairly simple. The methods may be divided into two major groups. One involves the capture of a sample of droplets on a solid surface or in a cell containing a special liquid. The captured droplets are then observed or photographed by means of a microscope, generating information on droplet size. The other involves freeze-up of droplets into solid particles and subsequent sieving to generate droplet size distribution. The major problem is associated with the extraction and collection of representative spray samples. 

The practical applicability of such a system is quite clear nanospheres or nanoparticles may be produced by the emulsion-diffusion method and stored in the gel state of the particle framework. At any later point of time, an active ingredient may be added to the dispersion which easily diffuses into or through the porous gel matrix. By a simple freezing step, the particles are sealed and the active ingredient is trapped inside the spheres or capsules. The whole process is easily monitored by solid-state NMR which, in this case, could hardly be replaced by any other analytical approach. 

In all cases, unusually short 0-0 bond lengths were observed in the crystal structures, which led to closer examination of the complexes by other spectroscopic techniques as well as computational methods. It was then concluded that the complexes could be best described as singlet O2 adducts, where the metal had not been oxidized by O2. In the case of the Ru complex reported by Haller et al, the coordinated O2 could be removed by a simple freeze-pump-thaw technique to regenerate the starting complex. Moreover, these rhodium complexes did not undergo oxidation to rhodium(iii) when... 

A number of other thermodynamic properties of adamantane and diamantane in different phases are reported by Kabo et al. [5]. They include (1) standard molar thermodynamic functions for adamantane in the ideal gas state as calculated by statistical thermodynamics methods and (2) temperature dependence of the heat capacities of adamantane in the condensed state between 340 and 600 K as measured by a scanning calorimeter and reported here in Fig. 8. According to this figure, liquid adamantane converts to a solid plastic with simple cubic crystal structure upon freezing. After further cooling it moves into another solid state, an fee crystalline phase. 

---