Low-melting polymers containing at least one Z-configured stilbene group are produced by reaction of Z-configured bifunctional stilbene compounds with bifunctional monomers, oligomers or relatively high molecular weight components at temperatures in the range from -30.degree. to 250.degree. C., optionally in the presence of organic solvents and/or diluents and/or catalysts, the Z-configuration of the stilbene units remaining intact. The low-melting polymers may be processed by standard methods to moldings of various kinds which may be converted by treatment of temperatures of 250.degree. to 500.degree. C. and/or by irradiation at wavelengths of 200 to 800 nm into high-melting plastics articles of high heat resistance.