In most lubrication systems, the oil is mixed with air, in contact with air, in contact with metals and at high temperature. This is mean cause of premature lubricant, deterioration which can result in oxidation produ...In most lubrication systems, the oil is mixed with air, in contact with air, in contact with metals and at high temperature. This is mean cause of premature lubricant, deterioration which can result in oxidation products, which are mainly acid. Hydrocarbon oxidation in the liquid phase proceeds by a radical chain reaction. In the present paper polyalkylphenol formaldehyde sulphonate and its ethoxylate were synthesized and evaluated as pour point depressant, viscosity improver and antioxidant. The efficiency of these additives depends on their chemical structure and degree of mixing (mole fraction). Values of surface tension of these additives were measured in oil phase and consequently CMC was determined for all additives and their mixtures. A novel method of inhibiting oxidation was proposed. The author suggests the mechanism of inhibiting oxidation according to surface activity of additive in oil phase. More confirmations for suggested mechanism were investigated by measuring the area occupied per molecule of additive at oil phase. The results indicate that the compatibility of sulphonate with ethoxylate group and forming stable micelle which acts as wax dispersant and improver viscosity.展开更多
Micelles have been studied as drug delivery carriers for decades. Their use can potentially result in high drug accumulation at the target site through the enhanced permeability and retention effect. Nevertheless, the...Micelles have been studied as drug delivery carriers for decades. Their use can potentially result in high drug accumulation at the target site through the enhanced permeability and retention effect. Nevertheless, the lack of stability of micelles in the physiological environment limits their efficacy as a drug carrier. In particular, micelles tend to disassociate and prematurely release the encapsulated drugs, lowering delivery efficacy and creating toxicity concerns. Many efforts to enhance the stability of micelles have focused mainly on decreasing the critical micelle forming concentration and improving blood circulation. Herein, we review different strategies including crosslinking and non-crosslinking approaches designed to stabilize micelles and offer perspectives on future research directions.展开更多
The fluorescence behavior of two near-infrared (NIR) chromophores with linear alkyl chains of different lengths, 2-[4'chloro-7'(3'ethyl-2'benzothiazolinylidene)-3',5'-(1''',3'&#...The fluorescence behavior of two near-infrared (NIR) chromophores with linear alkyl chains of different lengths, 2-[4'chloro-7'(3'ethyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)-1',3',5'-heptantriene-1'-yl]-3-ethylbenzo- thiazolium iodide (Probe I) and 2-[4'chloro-7'(3'hexadecyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)- 1',3',5'-heptantriene-1'-yl]-3-ethylbenzothiazolium iodide (Probe II), in aqueous solution containing different con-centrations of surfactants was studied. The fluorescence of the probe with a short chain (probe I) was completely quenched in water and aqueous solution containing a low concentration (below the critical micelle concentration, CMC) of surfactant Triton X-100. However, the fluorescence reappeared and reached maximum rapidly once the concentration of the surfactant approached the CMC. The probe with a long chain (probe II) displayed a similar fluorescence behavior but more dramatically fluorescent recovery in Triton X-100 system, which gave a direct in-dication for the micelle forming process and provided a simple method for the determination of the critical micelle concentration of the surfactant. The CMC values determined by this method were in good agreement with those ob-tained by other techniques. The fluorescence behavior of the two probes in other surfactant systems was also inves-tigated.展开更多
It induces the conception of micelle and gives the method for determining CMC thatvarious physical properties of surfactant solution, such as surface tension, molarconductivity, osmotic pressure, and so on, change sud...It induces the conception of micelle and gives the method for determining CMC thatvarious physical properties of surfactant solution, such as surface tension, molarconductivity, osmotic pressure, and so on, change suddenly at a very small range ofconcentration. Recently, Zana pointed out further that there are some sudden changesnear CMC in the effect of surfactant on some general non-oscillating reactions. From展开更多
The effects of electrolytes, alcohols, and urea on the aggregation of SDS, CTAB, and Triton X-100 at 25℃ have been investigated by fluorescence probing of pyrene. Both electrolytes and alcohols reduce the critical mi...The effects of electrolytes, alcohols, and urea on the aggregation of SDS, CTAB, and Triton X-100 at 25℃ have been investigated by fluorescence probing of pyrene. Both electrolytes and alcohols reduce the critical micelle concentration (CMC) of the ionic surfactants, while the effect of the former is more pronounced. It is shown that the effects of electrolytes mainly depend on the concentrations and especially the valence of the opposite charge ions, and only slightly depend on the same charge ions in respect of ion aggregate of micelle. The logarithm of CMC is not linearly correlated with the concentrations of the counter ion or the electrolytes. The results are rationalized in terms of Hartley's model. Propanol increases the CMC of TX-100, while electrolytes and urea do not. In all the three kinds of surfactant micelles the excitation spectrum of pyrene slightly red-shifts (ca. 4 nm) from that in water, but is not affected by the additives. The micropolarity of the environment in which pyrene molecule resides in SDS micelle decreases with the increase of the concentrations of electrolytes. This is not the case when alcohols and urea were added to SDS or to TX-100. It is suggested that the addition of electrolytes would result in more orderly orientation of SDS molecules. It is the binding strength of the counter ions that dominates the effects of additives on the aggregation of surfactants.展开更多
文摘In most lubrication systems, the oil is mixed with air, in contact with air, in contact with metals and at high temperature. This is mean cause of premature lubricant, deterioration which can result in oxidation products, which are mainly acid. Hydrocarbon oxidation in the liquid phase proceeds by a radical chain reaction. In the present paper polyalkylphenol formaldehyde sulphonate and its ethoxylate were synthesized and evaluated as pour point depressant, viscosity improver and antioxidant. The efficiency of these additives depends on their chemical structure and degree of mixing (mole fraction). Values of surface tension of these additives were measured in oil phase and consequently CMC was determined for all additives and their mixtures. A novel method of inhibiting oxidation was proposed. The author suggests the mechanism of inhibiting oxidation according to surface activity of additive in oil phase. More confirmations for suggested mechanism were investigated by measuring the area occupied per molecule of additive at oil phase. The results indicate that the compatibility of sulphonate with ethoxylate group and forming stable micelle which acts as wax dispersant and improver viscosity.
基金This work was supported by the National Science Foundation （DMR-1410853） and National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health （DP2DK111910）.
文摘Micelles have been studied as drug delivery carriers for decades. Their use can potentially result in high drug accumulation at the target site through the enhanced permeability and retention effect. Nevertheless, the lack of stability of micelles in the physiological environment limits their efficacy as a drug carrier. In particular, micelles tend to disassociate and prematurely release the encapsulated drugs, lowering delivery efficacy and creating toxicity concerns. Many efforts to enhance the stability of micelles have focused mainly on decreasing the critical micelle forming concentration and improving blood circulation. Herein, we review different strategies including crosslinking and non-crosslinking approaches designed to stabilize micelles and offer perspectives on future research directions.
基金Project supported by the National Natural Science Foundation of China (No. 29775021).
文摘The fluorescence behavior of two near-infrared (NIR) chromophores with linear alkyl chains of different lengths, 2-[4'chloro-7'(3'ethyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)-1',3',5'-heptantriene-1'-yl]-3-ethylbenzo- thiazolium iodide (Probe I) and 2-[4'chloro-7'(3'hexadecyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)- 1',3',5'-heptantriene-1'-yl]-3-ethylbenzothiazolium iodide (Probe II), in aqueous solution containing different con-centrations of surfactants was studied. The fluorescence of the probe with a short chain (probe I) was completely quenched in water and aqueous solution containing a low concentration (below the critical micelle concentration, CMC) of surfactant Triton X-100. However, the fluorescence reappeared and reached maximum rapidly once the concentration of the surfactant approached the CMC. The probe with a long chain (probe II) displayed a similar fluorescence behavior but more dramatically fluorescent recovery in Triton X-100 system, which gave a direct in-dication for the micelle forming process and provided a simple method for the determination of the critical micelle concentration of the surfactant. The CMC values determined by this method were in good agreement with those ob-tained by other techniques. The fluorescence behavior of the two probes in other surfactant systems was also inves-tigated.
文摘It induces the conception of micelle and gives the method for determining CMC thatvarious physical properties of surfactant solution, such as surface tension, molarconductivity, osmotic pressure, and so on, change suddenly at a very small range ofconcentration. Recently, Zana pointed out further that there are some sudden changesnear CMC in the effect of surfactant on some general non-oscillating reactions. From
基金Project supported by the National Naural Science Foundation of China the State Education Commission Foundation of China.
文摘The effects of electrolytes, alcohols, and urea on the aggregation of SDS, CTAB, and Triton X-100 at 25℃ have been investigated by fluorescence probing of pyrene. Both electrolytes and alcohols reduce the critical micelle concentration (CMC) of the ionic surfactants, while the effect of the former is more pronounced. It is shown that the effects of electrolytes mainly depend on the concentrations and especially the valence of the opposite charge ions, and only slightly depend on the same charge ions in respect of ion aggregate of micelle. The logarithm of CMC is not linearly correlated with the concentrations of the counter ion or the electrolytes. The results are rationalized in terms of Hartley's model. Propanol increases the CMC of TX-100, while electrolytes and urea do not. In all the three kinds of surfactant micelles the excitation spectrum of pyrene slightly red-shifts (ca. 4 nm) from that in water, but is not affected by the additives. The micropolarity of the environment in which pyrene molecule resides in SDS micelle decreases with the increase of the concentrations of electrolytes. This is not the case when alcohols and urea were added to SDS or to TX-100. It is suggested that the addition of electrolytes would result in more orderly orientation of SDS molecules. It is the binding strength of the counter ions that dominates the effects of additives on the aggregation of surfactants.
