prov:value
| - hydrogen or methyl and p is an integer from 1-50, R.sub.2, R.sub.a, R.sub.b, R.sub.c, R.sub.d, R.sub.e, R.sub.f, R.sub.g, R.sub.h, R.sub.i, R.sub.j and R.sub.k are independently methyl or phenyl, x.sub.1, x.sub.2 are integers from 1 to 500 with the
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