High-molecular-weight poly

Ghdants are needed to faciUtate the flow of granulation from the hopper. Lubricants ensure the release of the compressed mass from the punch surfaces and the release/ejection of the tablet from the die. Combinations of siUcas, com starch, talc (qv), magnesium stearate, and high molecular weight poly(ethylene glycols) are used. Most lubricants are hydrophobic and may slow down disintegration and dmg dissolution. 

The constants K and a for high molecular weight poly(ethylene oxide) in several solvents at various temperatures are summarized in Table 2. 

Thermoplasticity. High molecular weight poly(ethylene oxide) can be molded, extmded, or calendered by means of conventional thermoplastic processing equipment (13). Films of poly(ethylene oxide) can be produced by the blown-film extmsion process and, in addition to complete water solubiUty, have the typical physical properties shown in Table 3. Films of poly(ethylene oxide) tend to orient under stress, resulting in high strength in the draw direction. The physical properties, melting behavior, and crystallinity of drawn films have been studied by several researchers (14—17). 

Ring-opening polymerization of strained metallocenophanes, mainly ferroceno-phanes with Si atom at the bridge, to give high-molecular-weight poly-(metallocenes) 99PAC1471. 

Table 7.2-4 Polymerization of isobutene to high molecular weight poly(isobutene)s in the ionic liquid [EMIM]CI/AICl3 under biphasic conditions [35].

Thus, measuring rheological properties of dispersions of low-molecular-weight (with viscosity about 60 Pa s) and high-molecular-weight poly(isobutilene) (with viscosity about 10s Pa s) with the same content of filler we see that the values of creep viscosity r c of these systems are practically equal, in spite of the difference of the viscosity of the dispersion medium more than 1000 times [3],... 

Synthesis of High Molecular Weight Poly (p-Pinene)... 

Expts. 18-20 carried out with the TMPCl/EtAlCl2 system showed more promising results. For example, Exp. 20 yielded relatively high molecular weight poly(P-PIN), M = 8200, and Ieff = 105%, which is close to the theoretical value. 

We have found that high molecular weight poly (p-PIN)s readily yields fibers by manual drawing from the melt. X-ray analysis of melt-drawn fibers showed a characteristic amorphous halo with a d spacing at 6.2 A. 

The SnAt reactions were first successfully used in the synthesis of high-molecular-weight poly(arylene etherjs by Johnson et al.4,5 This reaction represents a good example for poly(ether sulfonejs in general, either in laboratory -or industrial-scale preparations. In this procedure, the bisphenol A and sodium hydroxide with an exact mole ratio of 1 2 were dissolved into dimethyl sulfoxide (DMSO)-chlorobenzene. The bisphenol A was converted into disodium bisphenolate A, and water was removed by azeotropic distillation. After the formation of the anhydrous disodium bisphenolate A, an equal molar amount of 4,4,-dichlorodiphenyl sulfone (DCDPS) was added in chlorobenzene under anhydrous conditions and the temperature was increased to 160°C for over 1 h... 

Some of these bi-metallic oxyalkoxides are able to polymerize oxiranes to high-molecular weight poly-ethers8 b) (M.W. of the order of 106 ). The resulting polymers reveal a quasi-living character, their DPn increases with conversion and is further... 

Allcock HR, Kugel RL, and Valan KJ. Phosphonitrilic compounds. Vll. High molecular weight poly (diaminophosphazenes). Inorg Chem, 1966, 5, 1716-1718. 

Allcock, H. R., Kugel, R. L., and Valan, K. J., High molecular weight poly (alkoxy- and aryloxyphosphazenes), Inorg. 

Another limitation is related to the fact that synthetic poly(amino acids) have rather unfavorable material properties. For instance, most synthetic poly (amino acids) derived from a single amino acid are insoluble, high-melting materials that cannot be processed into shaped objects by conventional fabrication techniques. The often undesirable tendency to absorb a significant amount of water when exposed to an aqueous environment is another common property of many poly (amino acids) (7). Finally, high molecular weight poly-(amino acids) are best prepared via N-carboxyanhydrides which are expensive to make. Hence poly(amino acids) are comparatively costly polymers, even if they are derived from inexpensive amino acids (8). 

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