For each of the following pairs of polymers, do the following: (1) state whether or not it is possible to determine whether one poly- mer 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-isoprene.
(c) Network phenol-formaldehyde; linear and isotactic polystyrene.
(d) Block poly(acrylonitrile-isoprene) copoly- mer; graft poly(chloroprene-isobutylene) copolymer.