Interference 103,482
in analyses of polymers with long average sequence
lengths can be high. . . . Despite this handicap, this
method
could provide an accurate determination of the average
sequence lengths in amorphous polypropylenes and others
where the average sequence length is less than ten units.
In the paragraph bridging pages 2093-2094, Randall concludes:
Average sequence lengths in the 1-5 range can probably
be determined with a high degree of accuracy. With the
present method for area determinations, the accuracy is
estimated at +15 per cent for sequences of like additions
5-10 units long and +25 per cent for a range of 10-15
units.
As assignments are confirmed, the accuracy will depend
totally upon the methods used to measure relative areas.
Some assignment difficulties can be resolved if the
observed
resonances can be combined to produce either diad or
triad
distributions. This approach will depend, of course,
upon
an identification of resonances that arise from sequences
with common diad or triad centers.
We note that Buschermohle, citing Randall, used data from a
triad analysis of C-13 NMR spectrum and Winter’s formulas
(III) and (IV), which correspond to Winter’s formulas (I) and
(II)(RD 2-3), to calculate the average sequence length for
isotactic and syndiotactic sequences of her polypropylenes (DE
9, pp. 38-39). We repeat our finding, based on the
uncontested declaration of Winter (RD 2), Buschermohle’s
corroborative citation of Randall (DE 9, pp, 38-39), and Dr.
Gauthier’s declarations (RE 27-28
78
Page: Previous 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Next
Last modified: November 3, 2007