For each of the following pairs of polymers, do the following: 1. State whether it is possible to determine whether one polymer is more likely to crystallize than the other.
2. If it is possible, note which is the more likely and then cite reason(s) for your choice; and (3) if it is not possible to decide, then state why.

a. Linear and atactic poly(vinyl chloride); linear and isotactic polypropylene
b. Linear and syndiotactic polypropylene; crosslinked cis-polyisoprene
c. Network phenol-formaldehyde; linear and isotactic polystyrene
d. Block poly(acrylonitrile-isoprene) copolymer; graft poly(chloroprene-isobutylene) copolymer