THERMAL ANALYSES OF GRAFT-COPOLYMERS OF POLY(METHYL METHACRYLATE) MAIN-CHAIN WITH POLY(PROPYLENE OXIDE-B-ETHYLENE OXIDE) GRAFT CHAIN

Poly (methyl methacrylate-g- (propylene oxide-b-ethylene oxide)) and p oly (methyl methacrylate-g-(ethylene oxide-b-propylene oxide)), compri sing chemically dissimilar sequences, exhibit intramolecular phase sep aration. These compositions have applications in coatings and as surfa ce-tension modifiers. This paper presents the thermal behavior of thes e graft copolymers: separate samples of the homopolymer and of the gra fts were also analyzed to provide comparisons. The phase behavior has been analyzed by differential scanning calorimetry and by dynamic-mech anical thermal measurements. Two glass transitions (T(g)) are observed , caused by the partial incompatibility within the copolymers. The act ivation energy of the T(g) relaxation process of the main chain is dec reased by the graft chain. The influence of poly(propylene oxide-b-eth ylene oxide) grafts on the thermal degradation of the poly(methyl meth acrylate) (PMMA) main chain was studied by using thermogravimetric ana lysis. Prolysis of the graft copolymers occurs in three stages and beg ins on the graft chain and at a lower temperature than the pyrolysis o f pure PMMA. Both the phase behavior and the thermal stability are fou nd to depend sensitively on the composition of the copolymer. (C) 1993 John Wiley & Sons, Inc.