From melt to room temperature

Figure 7 UV-Vis spectra of a film of polymer, 21b, at different temperatures, (a) Room temperature, (b) Heated to 130°C. (c) Heated to 145°C. (d) Cooled from / melt to room temperature. (Adapted from data of Kawatsuki and co-workers [51]).

Figure 3.15 Specific voiume-temperature reiations for linear polyethylene (Marlex 50). Specimen slowly cooled from melt to room temperature prior to experiments (0) and specimen crystallized at 130°C for 40 days and then cooled to room temperature prior to experiment (0). (From Mardelkem, L, Rubber Chem. Techno ., 32, 1392, 1959. With permission.)...

Due to the fact that the extrapolation of surface tensions of melts to room temperature leads to reliable values for the solid polymer, the surface tension of solid polymers may be calculated from the parachor per structural unit by applying Eq. (8.5). The molar volume of the amorphous state has to be used, since semi-crystalline polymers usually have amorphous surfaces when prepared by cooling from the melt. We have found that the original group contributions given by Sugden show the best correspondence with experimental values for polymers. 

If isotactic polypropylene is quenched from the melt to room temperature a so-called smectic modification is formed which shows only two crystal reflexions. Cabarcos, Bbsecke, and Zachmann investigated the kinetics of the transition from this modification into the a-modification. Fig. 54 shows the change of wide angle scattering during isothermal annealing at 90 °C. One sees that the 040-reflexion of the a-modification appears after about 200 sec and continues to increase in intensity afterwards. The time until the constant temperature is reached is about 150 sec. Therefore we can say that most of the process occurs at constant temperature. If the same is done at 130 °C the process occurs so rapidly that it is almost finished as constant temperature is reached. 

This is not a method commonly used for coordination compounds, which do not often melt without decomposition. Where applicable, it can be used by cooling from a high-temperature melt to room temperature, or by cooling a room-temperature liquid to a lower temperature. The latter is a specialized technique, usually carried out in situ on a diffractometer, with monitoring of the crystal growth by optical and X-ray methods the sample is contained in a sealed capillary tube, and selective heating may be applied by an infra-red laser to develop a single crystal. Twins and multiple crystals often result from these methods. 

The iPP sample of lowest stereoregularity (sample iamPP) does not crystallize by cooling the melt to room temperature, but slowly crystallizes in disordered modifications intermediate between a and 7 forms (Fig. 17.3B), if the sample, cooled from the melt, is kept at room temperature for several days [32]. In fact, the X-ray diffraction profile of sample iamPP of Fig. 17.2g... 

Fig. 17.4. Relative amount of 7 form f-y (0)j nd degree of crystallinity Xc ( ), in the iPP samples of Table 17.1 crystallized from the melt by compression molding and cooling the melt to room temperature at cooling rate of 1 C/min, as a function the concentration of rr defects [18]...

Figure 7.14 Melting DSC curves of isofactic polyfbut-ene-1) (iPB-1) having various crystalline forms 12,13]. 1, Sample cast from xylene 2, melt crystallized sample 3, sample held for 24 h after cooling from the melt to room temperature...

Y-Phenylbutyric acid. Prepare amalgamated zinc from 120 g. of zinc wool contained in a 1-litre rovmd-bottomed flask (Section 111,50, IS), decant the liquid as completely as possible, and add in the following order 75 ml. of water, 180 ml. of concentrated hydrochloric acid, 100 ml. of pure toluene (1) and 50 g. of p benzoylpropionic acid. Fit the flask with a reflux condenser connected to a gas absorption device (Fig. II, 8, l,c), and boil the reaction mixture vigorously for 30 hours add three or four 50 ml. portions of concentrated hydrochloric acid at approximately six hour intervals during the refluxing period in order to maintain the concentration of the acid. Allow to cool to room temperature and separate the two layers. Dilute the aqueous portion with about 200 ml. of water and extract with three 75 ml. portions of ether. Combine the toluene layer with the ether extracts, wash with water, and dry over anhydrous magnesium or calcium sulphate. Remove the solvents by distillation under diminished pressure on a water bath (compare Fig. II, 37, 1), transfer the residue to a Claisen flask, and distil imder reduced pressure (Fig. II, 19, 1). Collect the y-phenylbutyric acid at 178-181°/19 mm. this solidifies on coohng to a colourless sohd (40 g.) and melts at 47-48°. 

Hydrolysis of methyl m-nitrobenzoate to m-nitrobenzoic acid. Place 90 -5 g. of methyl m-nitrobenzoate and a solution of 40 g. of sodium hydroxide in 160 ml. of water in a 1-htre round-bottomed flask equipped with a reflux condenser. Heat the mixture to boiling during 5-10 minutes or until the ester has disappeared. Dilute the reaction mixture with an equal volume of water. When cold pour the diluted reaction product, with vigorous stirring, into 125 ml. of concentrated hydrochloric acid. Allow to cool to room temperature, filter the crude acid at the pump and wash it with a httle water. Upon drying at 100°, the crude m-nitrobenzoic acid, which has a pale brownish colour, weighs 80 g. and melts at 140°, Recrystalhsation from 1 per cent, hydrochloric acid afibrds the pure acid, m.p. 141°, as a pale cream sohd the loss of material is about 5 per cent. 

The flask is placed in an ice-salt mixture and the contents decomposed by the gradual addition of 300 cc. of saturated ammonium chloride solution and 100 cc. of water (Note 4). The aqueous layer is removed by means of a 1500-cc. separatory funnel and sufficient ether is added to dissolve the yellow precipitate. The total volume of ether solution is about one liter. This is washed with two 200-cc. portions of water, and the three aqueous layers are extracted consecutively with a loo-cc. portion of ether. The combined ether solution is dried over 30 g. of anhydrous sodium sulfate, coricentrated on the steam bath to a volume of about 200 cc., and cooled to room temperature. The product which crystallizes is collected with suction and washed with two 25-cc. portions of ether. The yield is 35-38 g. of light yellow product, m.p. 122-123°. The ether is completely removed from the combined filtrates by heating on the steam bath, and the black oil is allowed to stand overnight. The semi-solid mass is filtered with suction and washed with a minimum amount of cold ether. In this way an additional 6-7 g. of yellow material is obtained which melts at 119-121°. 

---