Isotactic polymers refer to those polymers formed by branched monomers that have the characteristic of having all the branch groups on the same side of the polymeric chain. The monomers are all oriented in the same way: If we represent a monomer by AB then an isotactic polymer is AB-AB-AB-AB-AB-etc.
Besides Isotactism, there are other two types of stereoregularity or tacticity frequently found in the scientific literature:
Syndiotactism- The monomers have alternating orientations within the polymer chain: AB-BA-AB-BA-AB-BA-etc.
and Atactism- The monomers have random orientations within the chain: e.g. AB-AB-BA-AB-BA-BA-BA-AB-etc.