In the formation of a polymer from monomers such as propylene, styrene and chlorethylene there are basically three possibilities, "head-tail", "head-head" and "tail-tail" bindings. Head tail isomerism
In most cases, head-tail polymers are produced. Thus, in such polymers, the two carbon atoms represent an R group.
On each carbon atom (which is in the sp3 hybridization state) there is such an R group, there are two more options, depending on the spatial position of the R group: the R group can either be forward, either facing backwards.
The relative position of the R groups determines the tactics of the polymer. There can be three cases for tactics.
At radical polymerization predominantly occur atactic polymers, while using Ziegler-Natta catalysts, especially isotactic polymers are formed. And this difference is very important! The tactics appear to exert a great influence on the properties of polymers. For example, polypropylene produced radically is a viscous paste, which is totally unsuitable for further processing into objects. All polypropylene that is converted to objects is therefore isotactic, and is obtained through solid catalyst production. Atactisch
A first kind of tacticity is the atactic polymers. An atactic polymer has irregularly divided X groups. Polymer chains are generally built up regularly, but some variations are possible. One of these variations is the placement of the side groups in the polymer chain. The placement of the X groups at the -CH2 -CHX- chain may be regular or irregular. If the X groups are irregularly placed, they are called atactic. Isotactisch
A second kind of tacticity is the isotactic polymers. Here, all R groups are on the same side of the chain in the spatial structure of the polymer. This structure is much more ordered than atactic polymers. Syndiotactisch
A third type of tacticity is the syndiotactic polymers. Here, all X groups are alternating to and fro in the spatial structure of the polymer. This structure is much more ordered than atactic polymers.
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