Tacticity

Head/tail configurations are not part of polymer tacticity but should be taken into account when considering polymer defects.

Short segments of polypropylene, showing examples of isotactic (above) and syndiotactic (below) tacticity The concept of stereoregularity in polymer chains is illustrated in the picture on the left with polypropylene.

Tacticity measurements obtained by Carbon-13 NMR are typically expressed in terms of the relative abundance of various pentads within the polymer molecule, e.g. mmmm, mrrm.

Tetrads, Pentads, etc. The definition of tetrads and pentads introduce further sophistication and precision to defining tacticity, especially when information on long-range ordering is desirable.

This technique enables quantification of the tacticity distribution by comparison of peak areas or integral ranges corresponding to known diads (r, m), triads (mm, rm+mr, rr) and/or higher order n-ads depending on spectral resolution.