Abstract: According to our invention, thermoplastic poly(vinyl chloride) block copolymer resins of the (AB).sub.n type are formed which are flexible without the addition of an external plasticizer for poly(vinyl chloride). These novel block copolymer resins have average molecular weights (Mn) in the range of from about 15,000 to 60,000 and contain alternating rigid poly(vinyl chloride) segments and flexible linear aliphatic polyether or polyester segments, each having an average molecular weight in the range of from about 1,000 to 5,000. The resins of our invention have excellent physical properties which make them suitable substitutes for externally plasticized poly(vinyl chloride) homopolymers, particularly in automotive applications.

Abstract: Macroazonitrile molecules formed of flexible poly(ethylene oxide) segments connected by azo linkages are heated in the presence of vinyl chloride to initiate the addition polymerization of the monomer onto the ends of the poly(ethylene oxide) segments. An ABA type block copolymer is formed wherein the A parts are poly(vinyl chloride) segments and B is a poly(ethylene oxide) block which was originally part of the macroazonitrile. The flexible poly(ethylene oxide) segments of this block serve as an internal (intramolecular) plasticizer such that the copolymer may be used in applications typically filled by externally plasticized poly(vinyl chloride). External plasticizers are still required but their concentrations may be reduced to a level where plasticizer migration problems are eliminated.