title: The ascorbyl palmitate-polyethyleneglycol 400-water system phase behavior.
abstract: Ascorbyl palmitate (Asc16) in polyethyleneglycol 400 (PEG 400)-water mixtures at weight fractions (w/w) between 0.05 and 1.0 were studied by differential scanning calorimetry (DSC) and polarizing microscopy (PM) at different temperatures. The employed PEG 400-water proportions were: 0-25-50% and 75% of polymer. A complete phase diagram was determined for each PEG 400-water mixture. A cubic mesophase and two (probably three) lamellar mesophases were detected in different regions of the phase diagrams. The addition of PEG 400 to the Asc16-water system shifts the limits of the liquid crystalline domains to lower temperature and surfactant concentration. At weight fraction of PEG 400≥50%, the limits of the domain of existence of cubic mesophase shift to low surfactant concentration compared with water-rich systems. The hydrated crystals are Asc16.2·6H(2)O. If the proportion of water is lower than that value, a mixture of hydrated and anhydrous crystals appears. Heating these crystals produce waxy crystals having melted hydrocarbon bilayers retaining their crystalline structure because the polar bilayers are still rigid.
authors: Departamento de Química e INQUISUR, Universidad Nacional del Sur, CONICET, Bahía Blanca, Argentina.
authors: Luciano
authors: L
authors: Benedini
authors: Paula V
authors: PV
authors: Messina
authors: Santiago D
authors: SD
authors: Palma
authors: Daniel A
authors: DA
authors: Allemandi
authors: Pablo C
authors: PC
authors: Schulz
mesh_terms: D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D011092:Polyethylene Glycols / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature
chemical_list: D013501:Surface-Active Agents; D011092:Polyethylene Glycols; D001205:Ascorbic Acid; C031226:6-O-palmitoylascorbic acid