Poly diethylsiloxane

Figure 9 Illustrative stress-strain isotherms for poly(diethylsiloxane), as a function of the amount of mesophase present. 

Pochan, J. M., Hinman, D. F. and Froix, M. F. Morphological studies on the viscous crystalline phase of poly(diethylsiloxane) including the dynamics of phase formation and the relationship of viscous crystalline structure and crystalline structure. Macromolecules 9, 611 (1976)... 

FIGURE 40. Polymorphism and melting of poly(diethylsiloxane). Reprinted with permission from Reference 145. Copyright 1989 American Chemical Society... 

FIGURE 41. Temperature variation of the MAS 29Si NMR spectrum of poly(diethylsiloxane) (a) spectra of the pure /6-modification (b) spectra of a mixture of a and /6-modification. Spectra were recorded by stepwise heating of the samples. Reprinted with permission from Reference 145. Copyright 1989 American Chemical Society... 

It is intriguing that even some flexible siloxane polymers form mesomorphic (liquid-crystalline) phases.34 139-166 Some illustrative data are given in Table 4.2. Both poly(diethylsiloxane) and pol y(di-n-propylsiloxane) show two crystalline modifications as well as a mesomorphic phase. (The other major class of semi-inorganic polymers, the polyphosphazenes, are also relatively flexible, and show similarly interesting behavior.)10167... 

Galin, M., "Gas-Chromatographic Investigation of the Thermodynamic Interactions of Poly(dimethylsiloxane) or Poly(diethylsiloxane) with Some Solvents between 60 and 180 C," Macromolecules, 10, 1239 (1977). 

Wyzgol has found such relations for poly(dimethylsiloxane)/poly(diethylsiloxane) (PDS) and low density polyethylene (PE, g = 0.92 g cm ) ... 

C 2Hg-Si Bond Torsion in Poly(diethyhiloxane), Poly(diethylsiloxane)... 

Figure 10. Torsional potential of CzHs-Si bond in poly(diethylsiloxane) (PDES) in solid and liquid states. PDES exists in two crystalline forms, each of which has two isomorphic forms because of ethyl group reorientation, which has an activation energy of 9.3 kcal/mol (theoretical value, 9.4 kcal/mol). Experimental values were obtained from reference 16.

Contact-Angle Studies. Siloxanes with higher alkyl substituents have thermal properties that are also much more like those of paraffins than of PDMS, as shown by an early study by Hunter and co-workers (8). Figure 2 shows some of their data comparing the water contact angles of soda-lime glass surfaces treated with PDMS, poly(diethylsiloxane), and poly(octadecyl-methylsiloxane). Compared with PDMS, poly(diethylsiloxane) and poly(octa-... 

At higher treatment temperatures, differences between the water contact angles of the polymers are small, but at even higher temperatures, the hydrophobicity of poly(octadecylmethylsiloxane) declines more rapidly than that of poly(diethylsiloxane) and PDMS because of the poorer thermal stability of siloxanes with higher alkyl substituents. Despite this defect, some-... 

Of the many other ways of detecting phase transitions, including cloud points for systems with mixed phases, particular mention should be made of the use of dynamic-mechanical methods, and specifically measurement of the shear compliance to 1 kbar. When applied to columnar crystals of poly-diethylsiloxane) such a method was able to detect the melting point in conditions where the volume change was close to zero. 

Tsvankin DYa, Papkov VS, Zhukov VP, Godovsky YuK, Svistunov VS, Zhdanov AA (1985) Structure and phase transitions in poly(diethylsiloxane). J. Polymer Sci., Polymer Phys. Ed., 23 1043... 

Brillouin spectroscopy can also be used to study the change of sound velocity with deformation. Anders et al. reported the longitudinal sound velocity in stretched poly (urethane) and poly (diethylsiloxane) (PDFS, Figure 60.8) networks [15]. They used the lattice-model to determine the force constants [11]. The samples showed different deformation-dependent behavior of the force constants. For the... 

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