Phase behaviour of binary and ternary mixtures for the poly(methyl methacrylate-co-hexafluorobutyl methacrylate) [P(MMA-co-HFBMA)] in supercritical fluorine solvents

Abstract

In this study, the poly(methyl methacrylate-co-2,2,3,4,4,4-hexafluorobutyl methacrylate) [P(MMA-co-HFBMA)] as a fluoric copolymer was prepared using dispersion polymerization in supercritical carbon dioxide. The characterization for the prepared P(MMA-co-HFBMA) was investigated with varied ratios of MMA vs HFBMA (30:1, 25:1, 22:1 and 20:1), 2,2′-azobisisobutyronitrile (AIBN) amounts (1.0, 2.0, 3.0, and 4.0)wt% and the weight average molar mass (Mw).Experimental cloud-point data at temperatures to 454K and pressures up to 184MPa are reported for binary and ternary mixtures of P(MMA-co-HFBMA) in supercritical CH2F2, CHF3 and CHClF2. Experiments are performed in order to determine phase behaviour of binary system for the P(MMA-co-HFBMA) (mole ratio: 25:1, AIBN: (1.0, 2.0, 3.0 and 4.0)wt%)+supercritical solvents (CH2F2, CHF3 and CHClF2) mixtures at temperature range from (333 to 454)K and pressure up to 184MPa. It appears that the {P(MMA-co-HFBMA)+CH2F2} mixtures show the upper critical solution temperature (UCST) type behaviour with negative slope, while the {P(MMA-co-HFBMA)+CHF3} and {P(MMA-co-HFBMA)+CHClF2} mixtures show lower critical solution temperature (LCST) type curve with positive slope. Cloud-point curves for the P(MMA-co-HFBMA) [mole ratio: 30:1 (Mw=186,000g·mol−1), 25:1 (Mw=176,000g·mol−1), 22:1 (Mw=158,000g·mol−1) and 20:1 (Mw=126,000g·mol−1); AIBN: 1.0wt%)+supercritical (CH2F2, CHF3 and CHClF2) mixtures show a negative slope for the {P(MMA-co-HFBMA)+CH2F2}, and a positive slope for the {P(MMA-co-HFBMA)+CHF3} and {P(MMA-co-HFBMA)+CHClF2} mixtures at temperatures to 454K and pressure up to 184MPa. Also, the impact of MMA on phase behaviour for the {P(MMA-co-HFBMA) (mole ratio: 25:1; AIBN: (1.0 and 2.0)wt%)+CH2F2} mixtures are measured in changes of the (pressure+temperature) slope from UCST behaviour to LCST behaviour, and with MMA co-solvent concentrations of (0.0 to 40.1)wt%.