Poly grown from dilute solution

X-ray diffraction techniques can be used to establish the structure of crystalline polymers. Measurements are typically made on crystalline lamellar platelets grown from dilute solution, fibres or stretched films. Such methods have been applied to several different inorganic polymers. For example, based on measurements on stretched samples of silicone rubber, poly(dimethylsiloxane) (Me2SiO) has been shown to possess a helical conformation (Figure 8.4). ... 

Dynamic mechanical and NMR investigations of crystals grown from dilute solutions for polymers other than linear polyethylene have been much less extensive. Studies have been reported for the linear polymers polyoxy methylene (3, 40, 94), poly (ethylene oxide) (3, 78), and nylon 6 (42), and the branched polymers polypropylene (40), poly-l-butene (19, 95), poly(4-methyl-l-pentene) (33), poly (vinyl alcohol) (78), and branched polyethylene (78). In addition, dielectric loss measurements have been made on crystal aggregates of poly (ethylene oxide) (23), poly (vinyl alcohol) (68), and polyoxymethylene (3) and mechanical loss measurements have been carried out on polyoxymethylene formed by solid state polymerization (94). 

Poly(ethylene oxide) has been investigated in both a single-crystal form and in normal or commercial, partially crystalline form. Single crystals have been examined by X-ray analysis and have been shown to be flat platelets with the c-axis of the unit cell oriented normal to the basal plane (34). Electron microscopy has shown bulk crystallized polymer to have a lamellar structure (35, 36), and single-crystal lamellae have been grown from dilute solution (37, 38). 

To obtain isometric crystals as described in Fig. 5.41, one must restrict the width of the thin lamellae. This is illustrated in Fig. 5.74 with single-molecule single crystals grown from droplets of a very dilute solution of poly(oxyethylene) in benzene. Each of the crystals contains only one molecule [27]. The poly(oxyethylene) was of a broad... 

Figure 10 (a) Complex entities of poly(a-isobutyl-j0,L-aspartate)s grown upon slow evaporation of a dilute solution in chloroform, (b) Fingerprint pattern displayed by a 23% (v/v) dichloromethane solution. (Taken from J.M. Montserrat, S. Munoz-Guerra, and J.A. Subirana. Makromol. Chem. Macromol. Symp. 20/21 319, 1988. With permission.)... 

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