Poly viscosity -molecular weight relationship

The original poly(vinyl alcohol) was studied in both aqueous and DMSO solutions. Viscosity-molecular weight relationships have been reported for each of these solutions at 30°C as shown in Equations 19 and 20 (3). 

Intrinsic Viscosity - Molecular Weight Relationship. A rod-like polymer has a large a value in the Mark-Houwink equation (Eq. 25). Such an example is poly(y-benzyl L-glutamate)... 

The exponent a in the intrinsic viscosity-molecular weight relationship ([rj] = K.M ) of a polymer is associated with the expansion of the polymer in solution, and hence with the conformation and stiffness of the polymer (Table 24). The a values of tobacco mosaic virus, Kevlar and helical poly(a-amino acids) are close to 2, which means that they take rigid-rod structures. The a values of vinyl polymers are usually 0.5-0.8, indicating randomly coiled structures. In contrast, the a values of substituted polyacetylenes are all about unity. This result indicates that these polymers are taking more expanded conformations than do vinyl polymers. This is atrributed to their polymer-chain stiffness stemming from both the alternating double bonds and the presence of bulky substituents. 

Fig. 3. Intrinsic viscosity-molecular weight relationship of poly-7-benzyl-L-glutamates. The open circles represent the randomly coiled form and other symbols the a-helical form. The line of steeper slope is a plot of Simha s equation. Abbreviations dichloroacetic acid, DCA chloroform saturated with formamide, C-F dimethyl formamide, DMF light scattering, L.S. weight-average molecular weight, A/m. Reproduced from Doty et al. (1956).

S. Berkowitz, Viscosity-molecular weight relationships for poly(ethylene terephthalate) in hexafluoroiso-propanol-pentafluorophenol using SEC-LALLS, /. Appl. Polym. Sci. 29 4353-4361 (1984). 

Poly(thioglycolide) is readily degraded by aqueous alkali and amines. It is soluble without degradation only in dichloroacetic acid (DCA) and hexafluoroacetone sesquihydrate (4). The viscosity-molecular weight relationship is... 

Cellulose and its derivatives have g values of about 2, i.e., thermodynamically they are about as flexible as poly(isobutylene). Thus, cellulose chains are not extraordinarily stiff, although they are often assumed to be so on the basis of their high exponents in the intrinsic viscosity-molecular weight relationship (see Section 9.9.7). These high exponents are interpreted as arising from the particular (high) draining properties of the cellulose molecule. 

The dye interaction technique was used to follow polymer degradations in in vivo and in vitro studies as well as to establish a viscosity-molecular weight relationship for racemic poly(lactide). In order to assure the presence of one carboxyl group per chain partially hydrolized polymers of high initial molecular weights were used in the latter case. The polymers were hydrolyzed with deionized water either in form of solid powder or in tetrahydrofuran or acetone solution with complete agreement of data obtained in both ways. 

Viscosity Molecular Weight Relationships of Cellulose and Derivatives, Polysaccharides vn j 43 TABLE 4. CELLULOSE AND DERIVATIVES, POLY(SACCHARIDES) (See also table Properties of Cellulose Materials )... 

Gupta, P., C. Elkins, T.E. Long, and G.L. Wilkes. Electrospinning of linear homopolymers of poly (methyl methacrylate) exploring relationships between fiber formation, viscosity, molecular weight and concentration in a good solvent. Polymer 46(13) (2005) 4799 810. 

Dodgson, K. Semiyen, J. A., Studies of Cydic and Linear Poly(dimethylsiloxanes) 1. Limiting Viscosity Number-Molecular Weight Relationships. Polymer 1977,18, 1265-1268. 

Dodgson, K. and Semiyen, J.A. (1977) Studies of cycUc and Unear poly(dimethylsiloxanes) 1. Limiting viscosity number-molecular weight relationships. Polymer, 18,1265-1268. 

Effect of Shear. Concentrated aqueous solutions of poly(ethylene oxide) are pseudoplastic. The degree of pseudoplasticity increases as the molecular weight increases. Therefore, the viscosity of a given aqueous solution is a function of the shear rate used for the measurement. This relationship between viscosity and shear rate for solutions of various molecular weight poly(ethylene oxide) resins is presented in Figure 8. 

Nakayasc, H., and T. G Fox Molecular weight-temperature-concentration relationship for the viscosity of poly(vinyl acetate) and its dieth5rl phthalate solutions. Abstr. 137 th ACS, p. ll-I, Cleveland, Ohio (Apr. 1960). 

Staudinger, H. and Heuer, W. (1930) High polymeric compounds, 33. Announcement relationship between viscosity and molecular weight in poly sterols. Ber. Dtsch. Chem. Ges., 63, 222-234. 

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