ELECTROPHYSICAL PROPERTIES OF HIGHLY DISP ERSED POLYMER IN-SITU COMPOSITES BASED ON POLYVINYLALCOHOL AND CUS

A comparative study of electro-physical properties of two types of pol ymeric compositions based on PVA and CuS with significantly different degrees of dispersion of a semiconducting filler (CuS) was carried out . For in situ highly-dispersed compositions based on PVA and CuS, the mean size of filler particles was estimated to be 20 nm, whereas in me chanical blends this value was approximately 10 mum. Electro-physical properties of PVA-CuS systems were studied as a function of their comp osition, particle sizes of a conducting component, and relative humidi ty. Both a sharp rise in conductivity and maximal capacitance when app roaching a critical region of fractional content of conducting compone nt in the compositions studied suggest the existence of percolation th reshold. In a critical concentration range, the electro-physical prope rties of the PVA/CuS compositions are controlled by formation of well- developed chainlike conducting structures (clusters) composed of fille r particles. With decreasing the particle sizes of a conducting compon ent, the critical filler concentration tends to decrease, maximal capa citance increases, and electroconductive sensitivity of in situ compos itions to water vapors drastically increases (in the critical concentr ation range.) A high sensitivity of in situ compositions to water vapo rs is related to an important role of polymer matrix in formation of a conducting cluster.