Chap._900006 - groups of polymer molecules can react with...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
In actual Practice, p may approach but never becomes equal to unity 1 - r 1 + r Xn = When polymerization is 100% complete (p = 1) 1 - p 1 Xn = When the two bifunctional monomers are present in stoichiometric amounts (r = 1) The effect of an error in r is progressively greater at higher degree of polymerization. Progressively greater control is required to synthesize the higher molecular weight polymer. In the polymerization of A-B type monomers containing two different functional groups, such as amino acid or hydroxy acid, n - H 2 O x O R-C-O COOH HO R The polymerization takes place with internally supplied stoichiometry (r = 1). This leads to a polymer product that is subsequently unstable toward molecular weight changes because the end
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: groups of polymer molecules can react with each other. Molecular weight stabilization is usually accomplished by using a small amount of monofunctional B reactant. In this case the same equation apply with r redefined as N B' is the number of B monofunctional molecules and N A = N B = the number of A-B molecules The coefficient 2 is required, since one B molecule has the same quantitative effect as one excess B-B molecules on limitting the growth of a polymer chani. N B + 2 N B' N A r = The plots in Figure 2-10 apply equally well to polymerization of A-B monomers, although the scale of the x-axis may be different....
View Full Document

This note was uploaded on 10/16/2010 for the course MATSE 441 at Penn State.

Ask a homework question - tutors are online