Polymers of acrylonitrile, Mtilon (Mt) cyanoethylated cellulose hydrate [(C6H7O2)(3-x)(OCH2CH2CN)(x)] and Nitron (Nt) - commercial acrylic fiber containing 10-60% carboxylic groups have been specially prepared and modified by various metals (Fe, Co, Ni). Subsequent special thermal treatment yielded polymers containing metal nanosize clusters (40-200 Angstrom) dispersed in the polymer matrix whose ferromagnetic properties has been thoroughly studied. The chief reasons hindering the creation of high-T-c molecular/polymer-based ferromagnets are determined and analyzed. The concept of fractal ferromagnetic exchange interaction between magnetic moments of neighboring nanosize metal clusters via polyconjugated system is proposed. A new effect of an increase in the specific saturation magnetization mu(s), of metal atoms in clusters is reported. The effect is explained by the spin polarization of the polyconjugated matrix coating the metal clusters, somewhat similar to the chemical polarization of spins of electrons in a fractal geometry of clusters.