Storage Polydispersity, effect

Chen, R. H., Chang, J. R., and Shyru, J. S. 1997. Effects of ultrasonic condition and storage in acidic solutions on changes in molecular weight and polydispersity of treated chitosan. Carbohydrate Research, 299 287. 

In this section, we present the molecular theory for the linear dynamic viscoelasticity of miscible polymer blends by Han and Kim (1989a, 1989b), which is based on the concept of the tube model presented in Chapter 4. Specifically, the reptation of two primitive chains of dissimilar chemical structures under an external potential will be considered, and the expressions for the linear viscoelastic properties of miscible polymer blends will be presented. We will first present the expressions for zero-shear viscosity ob. dynamic storage and loss moduli G co) and G " co), and steady-state compliance J° for binary miscible blends of monodisperse, entangled flexible homopolymers and then consider the effect of polydispersity. There are a few other molecular theories reported... 

Wu [49] proposed estimating G° as the storage modulus at the frequency where tan 5= minimum, but often there is no minimum in the data. Using this method, Fuchs et al. [38] reported a modest effect of the tacticity of PMMA on the plateau modulus. They also found that Eq. 5.4 fitted their viscosity data with a = 3.4 but that the constant K depended on tacticity. Plazek et al. [50] studied the effect of tacticity on the creep behavior of PMMA and noted that absorbed water is always a problem in making measurements on polar polymers. Wu [51] later proposed an empirical equation between the ratio (G Gq) of the plateau modulus to the crossover modulus, G, (where G = G") and the polydispersity index. 

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