Tacticity refers to the orderliness of succession of configurational repeating units in the main chain of a polymer.This is an application of stereochemistry as it concerns the spatial arrangement of substituent groups. Dependent on the arrangement of the pendent groups, there will then be polymers of different tacticity ranging from isotactic, to syndiotactic and also atactic polymers.Tacticity will also affect the physical characteristics of the structure in terms of crystallinity. The tacticity will affect how well the atoms can pack together. Crystals have regular structures and polymers that are isotactic or syndiotactic will be able to solidify into crystalline or semicrystalline networks. In contrast, atactic polymers have a random arrangement of the repeating units so they will not be able to form crystals and will usually form amorphous glasses instead. When polymers have crystalline structure, the intermolecular forces of attraction are at a maximum, so the polymer created is denser and stronger. This can be seen in the case of polypropylene. Atactic polypropylene will be soft and sticky, making it suitable for making adhesives. On the other hand, isotactic polypropylene can form stronger crystals and can be made into structural components. Tacticity and crystallinity is important in the polymer synthesis industry. Different polymerisation conditions such as temperature and choice of solvent will affect the tacticity of the polymer formed. If a polymer of high strength is required, there is a need to first create isotactic or syndiotactic polymers [4]. If rubber is required, there is a need to use tactic polymers instead. Therefore, there is a need to match the polymerisation conditions to the type of polymer that is required.
8 сен 2024
