Although both polymers are prepared by free radical processes, poly (vinyl chloride) is amorphous and poly (vinylidene chloride) (saran) is highly crystalline. How do you account for the different? (vinylidene chloride is 1,1-dichloroethene).

Explanation

As poly (vinyl chloride) is able to show stereoisomerism and further it is formed by a free radical process, it is atactic (chlorine atoms distributed randomly), the molecules fit together poorly.
Poly (vinylidene chloride) has two identical substituents on each and the chains fit together well.