tacticity

Catalyst 2 (Cat2) generates another chain of a different tacticity.

Living polymerization, however, produces only one type of tacticity per catalyst.

An important concept in understanding the link between the structure of polypropylene and its properties is tacticity.

The Natta projection is useful for representing the tacticity of a polymer.

Catalyst 1 (Cat1) propagates a polyolefin of a desired tacticity.

These alterations include the chain length, or branching, or the tacticity.

It is interesting to note that when no α-methyl group is present in a polymer, tacticity has little influence on T g.

Tacticity may be measured directly using proton or carbon-13 NMR.

A reduced tacticity of a synthetic layer or covering can protect surfaces and release small molecules that could have remained attached.

The practical significance of tacticity rests on the effects on the physical properties of the polymer.

The mass fraction of isotactic (mm) triads is a common quantitative measure of tacticity.

This tacticity introduces crystallinity in otherwise amorphous polymers.

An alternative expression for tacticity is the average length of meso and racemo sequences within the polymer molecule.

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

Stereoblock copolymers A special structure can be formed from one monomer where now the distinguishing feature is the tacticity of each block.

These can be dealt with under the general headings, symmetry, intermolecular bonding, tacticity, branching and molar mass.

The primary convention for expressing tacticity is in terms of the relative weight fraction of triad or higher-order components, as described above.

With the new catalysts, the tacticity of the polypropene chain, the alignment of alkyl groups, was also able to be controlled.

To alternate the tacticity, a CSA will transfer the polymer chain from its respective catalyst.

Aside from this qualitative control, they allow better quantitative control, with a much greater ratio of the desired tacticity than previous Ziegler-Natta techniques.

Chain shuttling polymerization is a dual-catalyst method for producing block copolymers with alternating or variable tacticity.

This is particularly true in the case of polyolefins where tacticity and regiochemistry can have dramatic influence on the thermal, rheological, and crystallization properties.

Interpretation of chain tacticity, based on the work of Bovey and Tiers, can be illustrated using poly (methyl methacrylate).

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

In addition to identification, the technique has been used to elucidate certain aspects of polymer microstructure, such as branching, crystallinity, tacticity, and cis-trans isomerism.