Thermo- and pH-Sensitive Copolymers of N-(3-(Diethylamino)Propyl)-N-methylacrylamide and N,N-Dipropylacrylamide

Buffer solutions of random (co)polymers of N-(3-(diethylamino)propyl)-N-methylacrylamide and N,N-dipropylacrylamide, which contain from 0 to 95 mol % of N-(3-(diethylamino)propyl)-N-methyl-acrylamide units and have close molecular weights and the same degrees of polymerization (170 ± 10) are studied by the methods of potentiometric titration, light scattering, turbidimetry, refractometry, and viscometry. The samples are synthesized by the interaction of poly(acryloyl chloride) with N,N-diethyl-N ′-methyl-1,3-propanediamine and dipropylamine. The aqueous solutions are investigated in the concentration range from 0.0001 to 0.0350 g/cm³ and in pH range from 7.0 to 13.0. Temperature dependences of optical transmission I*, scattered light intensity I, and hydrodynamic sizes of scattering objects are obtained. Phase separation temperatures are determined. The results obtained are comparable with the data available for the previously studied copolymers but containing N-(3-(diethylamino)propyl)-N-methylacrylamide and N,N–diethyl-acrylamide units. It is shown that the structural phase transition and the characteristics of aqueous solutions for the compared copolymers depend on the structure of the (co)polymers and their composition.