Interpolymer complex between hydroxypropyl cellulose and maleic acid-styrene copolymer: phase behavior of semi-dilute solutions.

The phase behavior of a water/hydroxypropyl cellulose/maleic acid-styrene copolymer (H2O/HPC/MAc-S) system was investigated in the semi-dilute range by turbidimetry, rheology, and optical microscopy. The two polymers under investigation form interpolymer complexes via hydrogen bonding. In the case of a total polymer concentration of cpol = 5 mg . mL(-1) a second phase segregates upon heating the homogeneous ternary system. By applying a constant shear rate (gamma = 50 s(-1)) the phase separation temperature of the system is 10-15 degrees C lower than for an unsheared one. For cpol = 10 mg . mL(-1) phase separation has already occurred at room temperature when the two binary polymer solutions are mixed. The distribution of the partners among the coexisting phases was examined by FT-IR spectroscopy. The stoichiometry of the interpolymeric complex (IPC) was estimated to be HPC/MAc-S = 40:60 (w/w) independent of cpol.