Molecular association complexes of polymers. Urea and thiourea complexes of high molecular weight poly(ethylene oxide)

Abstract

AbstractComplexes have been formed by mixing urea or thiourea with high molecular weight yoly(ethylene oxide) on a hot roll mill and by precipitation of the complex from benzene solution. The most dramatic method of complex formation, however, is observed when finely divided urea or thiourea is suspended in a benzene solution of poly(ethylene oxide). The complex forms quantitatively, abstracting all the polymer from solution. The rate of complex formation from solid urea or thiourea and poly(ethylene oxide) in solution has been observed, the thiourea complex forming more rapidly than that of urea. This process of formation can be followed by microscopic examination of the suspended urea particles. The crystalline complex appears to form in a ratio of 2 moles of urea or thiourea to 1 mole of oxyethylene monomer unit. The urea complex melts at 143°C. in comparison with the melting point of urea, 132°C., and of poly(ethylene oxide), 65°C. The complex with either urea or thiourea shows distinct x‐ray diffraction patterns, and the presence of complex in a poly(ethylene oxide) matrix can be detected both by x‐ray diffraction and by stiffness–temperature measurements. Both complexes are water‐soluble.