EFFECT OF DRYING CONDITIONS ON THE GLASS-TRANSITION OF POLY(ACRYLIC ACID)

Systematic changes of drying conditions of poly(acrylic acid) were tested to study their effect on the glass transition of the material. The materials were synthesized in two different mediums of water and benzene, respectively. The glass transition temperatures of the samples were determined by thermal analysis using DSC. The samples were also characterized by IR spectra. The glass transition of poly(acrylic acid) was found to be significantly dependent on the drying conditions and also dependent on the medium in which poly(acrylic acid) was prepared. The anhydride formation in poly(acrylic acid) was increased as the drying temperature was raised, resulting in the increase of the glass transition temperature. The "bound" water involved in the preparation of poly(acrylic acid) in water medium could affect significantly the glass transition of the sample. A significant discrepancy in the previously reported values of the glass transition temperature of poly(acrylic acid) seems to be due to the differences in the drying conditions of the materials.