Cloud-point measurement of the biodegradable poly(d,l-lactide-co-glycolide) solution in supercritical fluid solvents

摘要

Experimental data of high pressure phase behavior between 35℃ and 105℃ and pressures up to 2,200 bar is presented for poly(d,l-lactic acid)(d,l-PLA) and poly(lactide-co-glycolide)_(15) (PLGA_(15)), PLGA_(25), and PLGA_(50) in supercritical carbon dioxide, trifluoromethane (CHF_3), chlorodifluoromethane (CHClF_2), dichloromethane (CH_2Cl_2), and chloroform (CHCl_3). d,l-PLA dissolves in carbon dioxide at pressures of 1,250 bar, in CHF_3 at pressures of 500 to 750 bar, and in CHClF_2 at pressures of 30-145 bar. As glycolic acid (glycolide) is added to the backbone of PLGA, the cloud point pressure increases by 36 bar/(mol GA) in carbon dioxide, 27 bar/(mol GA) in CHF_3, and by only 3.9 bar/(mol GA) in CHClF_2. PLGA_(50) does not dissolve in carbon dioxide at pressures of 2,800 bar, whereas it is readily soluble in CHClF_2 at pressures as low as 95 bar at 40℃. Cloud point behavior of d,l-PLA, PLGA_(15), and PLGA_(25) in supercritical carbon dioxide shows the effect of glycolide content between 35℃ and 108℃. Also, the phase behavior for poly(lactic acid) - carbon dioxide-CHClF_2 mixture shows the changes of pressure-temperature slope, and with CHClF_2 concentration of 6 wt%, 19 wt%, 36 wt% and 65 wt%. The cloud-point behavior shows the impact of glycolide content on the phase behavior of PLA, PLGA_(15), PLGA_(25) and PLGA_(50) in supercritical CHClF_2. A comparison was made between the phase behaviors of d,l-PLA and poly(l-lactide)(l-PLA) in supercritical CHF_3. The phase behavior of CHF_3 as a cosolvent for 5 wt% d,l-PLA-supercritical carbon dioxide system is presented for the effect being added 10 wt% and 29 wt% to CHF_3 content.