Polymerization of Formaldehyde

Abstract

A review is presented that covers the chemistry of various routes from formaldehyde to high-molecular-weight polyoxymethylenes, and emphasizes recent developments. The requirements of a feasible addition polymerization system are enumerated. The variety of possible polymerization mechanisms is illustrated by discussions of representative anionic, organometallic, and cationic initiator systems. The fundamental concepts of condensation polymerization of formaldehyde in aqueous or alcoholic media are considered in some detail, the analogy to crystallization is developed, and the effect of temperature, degree of supersaturation, and catalyst on the relative extent of growth versus nucleation is discussed. Techniques are described for preparing active seed polymer and for minimizing end-group occlusion during growth. Examples are given of the preparation of polymer of macromolecular properties from both water and methanol solutions. The recently discovered metastable orthorhombic form of polyoxymethylene and its preparation from aqueous solutions is described.