Addition with termination by combination only
(1) In class we showed that for an addition (chain growth) polymerization with
termination by combination only, the mol fraction or number distribution of the”dead”
polymer is given by:
x(Pj) = (j – 1)(1-p)2(pj-2) where p is the probability of propagation and x(Pj) is mol
fraction of polymer containing j units.
(a) What is the number average degree of polymerization (DOP)?
distribution of weight fractions (Pj)? What is the weight average DOP?
Hint:
See “Chapter 3, Part 1” file, at the CHEM 4010
http://macro.lsu.edu/CoreCourses/MSweb4/VirtualMacroBook.htm .
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(2) (a) For the same example, since p at any time t must be: (rp)/(rp + rt) where rp is
chain propagation rate, and rt is chain termination rate, what is p as a function of
observable (no radical) concentrations and rate constants? What is the number average
DOP in terms of these same quantities?
(b) Is it possible for p to remain constant in a batch reactor? Give two possible ways in
which p could remain constant. A constant p would lead to a constant distribution with
respect to time.