Thermal and rheological behavior of acrylonitrile-carboxylic acid copolymers and their metal salt complexes

The influence of acrylic, methacrylic, and itaconic acid comonomers in the nitrile oligomerization of acrylonitrile copolymers has been studied by DSC and DSC-FTIR in air and nitrogen atmospheres. Addition of metal salts in p oly(acrylonitrile-acrylic acid) copolymer, PA on thermal and rheological be havior has also been reported. Incorporation of CuSO4, FeSO4, ZnSO4, and Al -2(SO4)(3) (1 to 5 wt %) salt in the polymer solution affects its solubilit y in DMF. The complexes of PA with zinc sulphate, took a longer time to dis solve in DMF, whereas the complexes with Fe(SO4) and Al-2(SO4)(3) are almos t insoluble in DMF, perhaps due to intermolecular crosslinking. Addition of these metal salts to the PA solution also affects its Brookfield viscosity . The viscosity of 19 wt % polymer solution increases from 400 centipoise ( Cps) to 1090 Cps for complex with 5% FeSO4 (on the weight of dope solids) a nd 690 Cps for Al-2(SO4)(3) and 906 cps for ZnSO4 complex. However, for CuS O4 salt complex this value is 770 Cps. FTIR spectra shows the participation of COOH and CN group in the complex formation, which is responsible for en hanced Brookfield viscosity. Thermal behavior of the polymer-metal salt com plex showed that these salts also affect the exothermic reaction. The initi ation of cyclization reaction takes place at a lower temperature compared t o neat acrylonitrile-acrylic acid copolymer. However, the heat liberated pe r unit time in N-2 atmosphere in case of neat polymer is 6.3 Jg(-1) min(-1) which reduces to 5.5 Jg(-1) min(-1) in the case of the PA/Al complex, conf irming the role of Al-2(SO4)(3) in retarding the rate of cyclization reacti on. (C) 1999 John Wiley & Sons, Inc.