Crystallization in polyethylene oxide containing high concentrations of Cu(II) chloride has been studied as a function of temperature. As concentrations above 1:4 mole/monomer ratio, highly crystalline acicular morphology is observed which can be attributed to precipitation of the inorganic component. The crystalline structure and morphology of these deposites is strongly influenced by the polymer matrix. The crystallites are seen to grow along the radical direction of the spherulitic domains of the polymer. A new hexagonal type structure with unit cell dimensions of a = 6.52 Å and c = 19 Å is seen to occur for high concentrations of the copper chloride, while an orthorhombic phase is observed at high temperatures. These various findings have been explained on the basis of complex formation at low concentrations with Cu2+ ions being bound within the polymer matrix which acts as the template for subsequent crystallization of the excess salt. © 1992.