Predicting and Measuring the Sequence Distribution of Condensation Polymers - Mathematical Approaches to Polymer Sequence Analysis and Related Problems - page 231

Fig. 11.2 Theoretical mass spectra for a copolymer ( a ), a terpolymer ( b ), and a tetrapolymer
( c ) respectively. Reprinted from [ 6 ] with permission from the copyright holder ACS 1998

11.4 Condensation Copolymerization Using

Asymmetric Monomers

Figure 11.3 reports the chemical structure of an asymmetric monomer and, more
specifically, an asymmetric diol. When it is splitted in the middle, it does not leave
two identical parts. Lactones and lactams are other two examples of asymmet-
ric monomers. In this case, the monomer is a ring. Lactones are used to produce
poly(epslon-caprolactone) and other poly(lactone)s. Lactams are even more im-
portant, since they are used to produce Nylon6 and other nylons. Industrially,
some chemicals are used more than others. Important diisocyanates are methy-
lene bis(para phenyl isocyanate) (MDI for brief ) and 2,4-toluene diisocyanate
(TDI for brief ). An important chain extender is PTMO1000, which is made of
poly(tetramethylene oxide) chains of 1,000 g mol 1 . Speckhard et al. [ 8 , 9 ]de-
veloped a Monte Carlo algorithm which predicts the sequence of condensation
copolymers obtained from symmetric and asymmetric monomers and applied it to
copolyurethanes obtained reacting three monomers, namely a diisocyanate (MDI or
TDI), a long glycol (such as hydroxy-terminated polybutadiene), and a chain ex-
tender (PTMO1000). The method developed by Zetterlund et al. [ 10 , 11 ] also relies
on a Monte Carlo algorithm. Ray and Jacobsen applied the method of moments to
solve the differential equations [ 12 ]. These numerical methods are certainly useful,
but our interest is in exactly soluble models. Vasnev and Kuchanov [ 13 ] proposed