STEREOCHEMISTRY OF POLYMERIZATION The polymer properties are strongly affected by the molecular microstructure and not only the R. U. from which it is formed, but also how the atoms are arranged in the R.U. This differences are areas from the possibility of different modes of propagation (head to tail and head to head).

TACTICITY For polymer with general structure of the R.U. CH 2 -CXY then are three configuration.

ISOTACTIC X Y X Y CCC C H 2 H 2

SYNDIOTACTIC X Y Y X CCC C H 2 H 2

ATACTIC This is irregular configuration.

Examples 1.Polypropylene X = H and Y = CH 3 The commercial material is Isotactic due to its regular structures (65% crystalline). But atactic polypropylene is unable to crystalline and have poor mechanical properties because it is soft and waxy like.

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