Molecular weight, changes

Polymer-Fluid Equilibria and the Glass Transition Most polymer systems fall in the Class HI or Class V phase diagrams, and the same system can often change from one class into the other as the polymer s molecular weight changes. Most polymers are insoluble in CO9 below 100°C, yet CO9 can be quite sohible in the polymer. For example, the sorption of CO9 into silicone rubber is highly dependent upon temperature and pressure, since these properties have a large influence on the density and activity of CO9. 

Gready reduced sensitivity to molecular weight change. 

C. Poly( olefin sulfonejs Molecular Weight Changes.920... 

C. Poly(olefin sulfone)s Molecular Weight Changes... 

Example 13.9 Illustrate temperature and molecular weight changes in a tubular reactor by constructing a simple model of styrene polymerization in a tube. 

A mathematical model has been developed which allows the calculation of the degradation of polymeric drug delivery systems. The model has been shown to accurately simulate both the drug release and molecular weight changes in such systems. The concentration of anhydride levels affect the erosion characteristics of... 

Table L Molecular Weight Change in PLA as a Function of Thermal Processing1...

THERMAL DECOMPOSITION TEMPERATURES BY THERMAL GRAVIMETRIC ANALYSIS. MOLECULAR WEIGHT CHANGES HAVE BEEN REPORTED BELOW 200°C. 

Using the molecular weight change and the number of photons required for the change, the absolute quantum yield at 2537 A of PMMA was obtained where the value of 0.9 was used as the density of PMMA film. Once the absolute quantum yield at 2537 A was obtained, the absolute quantum yields over all the spectral range can be calculated from the relative data of the spectral sensiti-... 

Simple molecular weight changes relative to the parent molecule may indicate the gain or loss of the equivalent of a methylene group (i.e. the loss of a methyl group replaced by a proton), oxidation, and hydration/dehydration or hydrolysis to list only a few possibihties. The formation of adduct ions, for example, sodium, potassium, or acetonitrile at +23, +39, and +43 Da, respectively, can provide the means for the preliminary identification of the molecular ion of a molecule. Isotope patterns, for example, from Cl, and even can also be diagnosti-... 

The radiation G values, G(s) and G(x), of a polymer can be determined by measuring molecular weight changes which occur during irradiation and applying equations 1 and 2 (5.61. 

Preparation pH-Dependent Molecular Weight Changes of GMP and Its Application to Large Scale Preparation. 

The surface tension of aqueous solutions of PVA varies with concentration, temperature, degree of hydrolysis, and acetate distribution on the PVA backbone. Surface lension decreases slightly as the molecular weight is reduced. The relationship between the intrinsic viscosity and molecular weight changes with degree of hydrolysis of the polymer. 

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