Solid-state polymerization and polymer crystallization

Effects of the molecular and crystal structures of polymerizable substances on their radiation-induced solid-state polymerization are considered for two cases; the solid state polymerization of cyclic oligomers of formaldehyde and the canal polymerization of some monomers.

Cyclic oligomers of formaldehyde (–CH₂–O–)m from m = 3 to 6 are transformed into three-dimensionally oriented crystalline polyoxymethylene by irradiation. The polymer crystals are characteristically oriented, depending upon the parent oligomer crystal structures. A small amount of an oriented, unstable modification (orthorhombic) polyoxymethylene is also obtained in X-ray in-source polymerization of hexoxane.

Highly 1,4-trans tactic polymerization of 2,3-dichloro-1,3-butadiene and 2,3-dimethy1-1,3-butadiene in the thiourea canals is shown by structural evidence, based upon the crystal structure determinations of the monomerthiourea complexes, the polymer-thiourea complexes, and the resultant polymers for both dienes. The conversion of the monomer-thiourea complexes to the polymer-thiourea complexes by irradiation is performed, retaining the original single crystal habit, though in the canals the monomer-monomer distances are shortened by polymerization. The polymer samples obtained from the single crystals of polymer-thiourea complexes by removal of thiourea are uniaxially oriented and have unusual fine structures.