Polymerization-crystallization of poly-4-oxybenzoate (P-4-OB) by various techniques on different solid substrates results in different crystal structures and orientation types. Confined thin film melt or solution polymerization of P-4-OB between glass slides or mica sheets resulted in various lamellar single crystal formations of phase I or II with crystal orientations of the hk0 or Ok1 type on the substrate surface. In some cases, different structures were formed in the polymerization-crystallization on the free surface of the solid substrate.