Tacticity

related topics
{acid, form, water}
{math, energy, light}
{math, number, function}
{@card@, make, design}
{rate, high, increase}
{war, force, army}

Tacticity (from Greek 'taktikos': of or relating to arrangement or order) is the relative stereochemistry of adjacent chiral centers within a macromolecule [1]. The practical significance of tacticity rests in the link between tacticity and the physical properties of the polymer. The regularity of the macromolecular structure influences the degree to which it has rigid, crystalline long range order or flexible, amorphous long range disorder. Precise knowledge of tacticity of a polymer also helps understanding at what temperature a polymer melts, how soluble it is in a solvent and its mechanical properties.

A tactic macromolecule in the IUPAC definition is a macromolecule in which essentially all the configurational (repeating) units are identical. Tacticity is particularly significant in vinyl polymers of the type -H2C-CH(R)- where each repeating unit with a substituent R on one side of the polymer backbone is followed by the next repeating unit with the substituent on the same side as the previous one, the other side as the previous one or positioned randomly with respect to the previous one. In a hydrocarbon macromolecule with all carbon atoms making up the backbone in a tetrahedral molecular geometry, the zigzag backbone is in the paper plane with the substituents either sticking out of the paper or retreating into the paper. This projection is called the Natta projection after Giulio Natta. Monotactic macromolecules have one stereoisomeric atom per repeat unit, ditactic to n-tactic macromolecules have more than one stereoisomeric atom per unit.

Contents

Full article ▸

related documents
Buffer solution
Ionic bond
Holmium
Dysprosium
Aromatic hydrocarbon
Rhenium
Sulfur mustard
Anaerobic organism
Francium
Peroxisome
Spray drying
Essential amino acid
Carbide
Racemic mixture
Curium
Ascorbic acid
Guanine
NADH dehydrogenase
Geiger-Müller tube
Bitumen
Hydrate
Titration
Resin
Solution
Nitrate
Peroxide
Barium
Evaporation
Proline
Rubidium-strontium dating