sequences include isotactic polystyrene (iPS), isotactic polypropylene (iPP), iso-
tactic poly(methyl methacrylate) (iPMMA), and syndiotactic polypropylene (sPP),
which all belong to the crystalline polymers. The examples of irregular sequences
include aPS, aPP, aPMMA, poly(vinyl acetate), which all belong to the non-
crystalline polymers. Some hetero-nuclei polymers may contain different backbone
atoms in each repeating unit with intrinsic optical isomerism, such as in poly
(propylene oxide) and poly(lactic acid). They have D or L types, while the optical
activity can be completely compensated in the racemate with half-half
compositions.
Question Sets
- Why are polymer chains still flexible although the angles between backbone
bonds are fixed? - Which factor is more important in polymer glass transition, the static flexibility
or the dynamic flexibility? - Try to analyze the usefulness of oriented polymers on account of the local
anisotropy of chain structures. - Why is the characterization of molecular weights important for polymers?
- How can we mix two incompatible polymers on the molecular level?
- Why do non-crystalline polymers often contain a high content of sequence
irregularities?
References
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32 2 Structure–Property Relationships