Thermal analyses of graft copolymers of poly (methyl methacrylate) main chain with poly (propylene oxide‐b‐ethylene oxide) graft chain

摘要

AbstractPoly(methyl methacrylate‐g‐(propylene oxide‐b‐ethylene oxide)) and poly (methyl methacrylate‐g‐(ethylene oxide‐b‐propylene oxide)), comprising chemically dissimilar sequences, exhibit intramolecular phase separation. These compositions have applications in coatings and as surface‐tension modifiers. This paper presents the thermal behavior of these graft copolymers: separate samples of the homopolymer and of the grafts were also analyzed to provide comparisons. The phase behavior has been analyzed by differential scanning calorimetry and by dynamic‐mechanical thermal measurements. Two glass transitions (Tg) are observed, caused by the partial incompatibility within the copolymers. The activation energy of theTgrelaxation process of the main chain is decreased by the graft chain. The influence of poly(propylene oxide‐b‐ethylene oxide) grafts on the thermal degradation of the poly(methyl methacrylate) (PMMA) main chain was studied by using thermogravimetric analysis. Prolysis of the graft copolymers occurs in three stages and begins on the graft chain and at a lower temperature than the pyrolysis of pure PMMA. Both the phase behavior and the thermal stability are found to depend sensitively on the composition of the copolymer. © 1