Isolated number average sequence lengths

The number of styrene units in an average sequence is a little larger than the length of the average hemin sequence. It is not unreasonable to describe the hemin clusters as isolated, on the average, in this molecule. The product rir2 = 11.7 in this system, which also indicates a tendency toward block formation. Use Eq. (7.37) with [Mi]/[M2] = 0.046 and the rj and r2 values to evaluate... 

Thus the fraction of Mi sequences that consists of an isolated Mi unit is Pu, the fraction that consists of isolated Mi Mi diads is P11P12, the fraction of triads is PiiPi2> etc. The number-average length of Mi sequences (Ni) is given by ... 

The near-lR spectrum of C2-C3 copolymers has been studied (76) in order to ascertain the possibility of obtaining information about the average length of the methylenic sequences from the frequency of the band near 1.7 p the existence of such a correlation could be foreseen from the fact that in polyethylene, where methylenic sequences have infinite length, the frequency of the band is 1.730 p, while in polypropylene, where all methylenic units are isolated between tertiary carbon atoms, the frequency is 1.724 p. It has been found that the frequency increases steadily with the C3 content, but the correlation cannot be used to yield information on the sequence distribution since the average number n of methylenes in each methylenic sequence depends only on the copolymer composition and is independent of the product... 

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