- When these associations are stacks of alternating ( " R " ) and ( " S " ) molecules ( as in syndiotactic polymers ) this can be accomplished very efficiently.
- Isotactic and syndiotactic polymers are instances of the more general class of eutactic polymers, which also includes heterogeneous macromolecules in which the sequence consists of substituents of different kinds ( for example, the side-chains in proteins and the bases in nucleic acids ).
- If free rotation does not occur before the next monomer adds, the mirror approach will always lead to an isotactic polymer and the non-mirror approach will always lead to a syndiotactic polymer ( Figure 25 ) . " Figure 26 " : Penultimate unit interactions cause monomer to add in a way that minimizes steric hindrance between substituent groups . ( P represents polymer chain .)