Would it be easier to crystallize polytetrafluoroethylene (teflon) (c2f4) or polystyrene (cshs)? why?

Crystallization of tetrafloroethane C₂F₄ is easier than styrene C₈H₈ .

Explanation:  

Crystallization -

crystallization is a process in which atoms are restructured in the form of crystals , some of the ways by which crystals form are melting , precipitating from a solution.

we need to consider the melting point of the given compounds ,  

the melting point of styrene C₈H₈ is -30 °C

whereas the melting point of tetrafloroethane C₂F₄ is -140 °C ( 130.7 K ) since the melting point of C₂F₄ is less than C₈H₈ so it is easy to melt C₂F₄.  

Hence it is easier to crystallize C₂F₄ .