Tacticity is the stereoregularity of polymers having chiral carbons.  For an explanation of tacticity, please refer to Wikipedia, and other sources on the internet. 

Polymers can be

• isotactic with substituents on the backbone oriented in the same direction,

• syndiotactic with substituents in alternating directions,

• or atactic with random orientation of sustituents. 

Tacticity - Wikipedia

How the polymer is made can govern its tacticity.  Polymers which have this property are generally vinyls such as polystyrene, poly(methyl methacrylate), and polypropylene. 

NMR can be used to determine a polymer's structure and tacticity.  Both isotactic and syndiotactic polymers have symmetry and lead to simple but different NMR patterns.  However atactic polymers have complex spectra.

In the example of isotactic polypropylene, the -CH₂- protons on the backbone are magnetically different and have different chemical shifts.  While the -CH₂- protons on the backbone of syndiotactic polypropylene are magnetically the same and exhibit a single chemical shift.  In the case of atactic polymers, these protons exhibit complicated patterns due to structures of diads, triads, etc.

Exova operates a 500 MHz Bruker Avance III NMR system under GMP compliance.

NMR at Exova

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