Molecular weight and degree of polymerization

The next step in the development of a model is to postulate a perfect network. By definition, a perfect network has no free chain ends. An actual network will contain dangling ends, but it is easier to begin with the perfect case and subsequently correct it to a more realistic picture. We define v as the number of subchains contained in this perfect network, a subchain being the portion of chain between the crosslink points. The molecular weight and degree of polymerization of the chain between crosslinks are defined to be Mj, and n, respectively. Note that these same symbols were used in the last chapter with different definitions. 

After the initial reaction of a radical with the first monomer unit, a series of propagation steps follows, rapidly building up the molecular weight and degree of polymerization. The important part of this mechanism is therefore the (3), (3), etc. noted. This is what makes the polymer With unsymmetrical monomers the head-to-tail addition is preferred because whatever it is in the R group that stabilized the radical once will do so each time a propagation step happens. 

This exponential decrease in molecular weight and degree of polymerization with time can be expressed by an empirical relationship of the form... 

The structure, molecular weights, and degrees of polymerization, m, of these compounds are unknown. Some may be 6-heteropolymolybdates — for example, the P+3 and As+3 complexes. 

A 1% aqueous solution of gum arabic (simplest formula CigHo-jOu) was found to have an osmotic pressure of 7.2 mm Hg.. What are tlie average molecular weight and degree of polymerization of the solute ... 

Table 6.5. The dependence of elastic constant ratios of nematic PBG solution on the average molecular weight and degree of polymerization (4> 0.16).

In use of abbreviations, we have attempted to use accepted and common forms. When molecular weight and degree of polymerization have been cited, the abbreviations for the text and equations have been respectively MW and DP and M and P. This designation in equations avoids complications particularly where subscripts are used. 

Calculate number average and weight-average molecular weights and degree of polymerization for a specified polymer. 

Computations of Average Molecular Weights and Degree of Polymerization... 

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