THERMODYNAMICS OF INTERACTION BETWEEN WATER AND COPOLYMERS OF ACRYLATE AND ACRYLIC-ACID

The thermodynamics of swelling of acrylate-acrylic acid copolymers in water has been studied for acrylates of different chemical nature. Kinetic and equilibrium properties of water vapor sorption, as well as the values of factor of inaccessibility of copolymer polar groups for water molecules calculated by the method of group contributions, testify that the polymer structure becomes more close during the sorption. Because copolymers are hydrophobic, they absorb water in cluster form. For acrylic acid-methyl methacrylate and acrylic acid-methacrylate copolymers the thermodynamic stability of aqueous solutions rises with increasing acrylic acid content, which is accompanied by the increase in negative enthalpy DELTAh(M) values. For copolymers in a high-elasticity state DELTAS(m) > 0, while for glassy copolymers DELTAs(m) < 0. The dependences of DELTAh(m) and DELTAs(m) on the alkyl radical size have maximum, DELTAg(m) falls sharply with the increase in number of methylene groups, while all thermodynamic parameters tend zero.