Preparation and characteristics of multiple emulsions containing liquid crystals

In this paper, multiple emulsions containing liquid crystals were prepared successfully and the influence of formulation parameters on the formation mechanism was studied. Moreover, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) spectra analysis and stability analysis were used to characterise the property of them. The results showed that the chemical structure of water-in-oil (W/O) emulsifiers directly impacted on the formation of multiple structure, but the effect on the formation of liquid crystal structure was negligible. With the gap of the polarity between inner and outer liquid oils decreased, both multiple structure and liquid crystal structure were harder to form. The content of sodium chloride in internal aqueous phase, which should be neither too high nor too low, has great impact on the formulation of multiple structure. It was easier to form two structures simultaneously when the carbon chain length of fatty alcohols was closer to that of emulsifier C₂₂ alkyl polyglucoside (202). DSC elucidated the phase transitions of water in the liquid crystal layer and the W/O emulsions. SAXS indicated that the liquid crystal orientation was lamellar. The stability analysis showed that the presence of liquid crystal structure had a significant contribution to the stability of the multiple emulsions.     

酰基苯肼的感染显影及反差促进剂的作用

研究了六种结构不同的酰基苯肼化合物(通式:R—PhNH—NH—COR′)对卤化银乳剂感光性能的影响。结果表明,感染显影作用程度与酰基苯肼的结构有密切的关系。另外本文还就反差促进剂(醇类化合物和胺类衍生物)的作用及其机理进行了较深入的研究。事实说明,显影液中加入反差促进剂,不但能消除单独使用酰基苯肼时出现的“自阻”效应,而且还大大促进了感染显影的进行,提高了乳剂的反差和感光度。同时,本实验在应用高压液相色谱、色-质联仪、顺磁共振等方法对酰基苯胼的还原反应产物及反应中间物进行分析的基础上,更加明确地解释了感染显影和反差促进的作用机理。     

Evaporation from an ionic liquid emulsion

The conditions during evaporation in a liquid crystal-in-ionic liquid microemulsion (LC/microEm) were estimated using the phase diagram of the system. The equations for selected tie lines were established and the coordinates calculated for the sites, at which the evaporation lines crossed the tie lines. These values combined with the coordinates for the phases connecting the tie lines were used to calculate the amounts and the composition of the fractions of the two phases present in the emulsion during the evaporation. One of the emulsion phases was a lamellar liquid crystal and high energy emulsification would lead to the liquid crystal being disrupted to form vesicles. Such a system tenders a unique opportunity to study the interaction between vesicles and normal micelles, which gradually change to inverse micelles over bi-continuous structures. The amount of vesicles in the liquid phase versus the fraction liquid crystal was calculated for two extreme cases of vesicle core size and shell thickness. The limit of evaporation while retaining the vesicle structure was calculated for emulsions of different original compositions assuming the minimum continuous liquid phase to be 50% of the emulsion.     

Hydrodynamic aspects of slurry packing processes in microcolumn liquid chromatography

A Stokesian dynamics computer simulation based method is presented for the estimation of the bed porosity of slurry-packed capillary liquid chromatography (LC) columns. A colloidally well-described reversed-phase stationary phase-slurry liquid suspension was used as a model system. The applied simulation method takes into account the velocity of the slurry and colloidal interaction forces, as well as inter-particle hydrodynamic interactions. The predicted bed porosities suggest that a lower slurry velocity leads to a denser packing structure due to the increased effect of colloidal repulsion effects. The results of the simulations were compared with the external porosity and chromatographic performance of capillary LC columns that were packed at different filtration and compaction pressures. However, the trends that were observed in the experimental results suggest that hydrodynamic packing parameters have no or little effect on the chromatographic performance of capillary LC columns. Within the experimental parameter window, the chromatographic performance and the column porosity were not influenced by the filtration and compaction pressure, nor by the duration of the compaction process.     

Effect of emulsification processes on the stability of Pickering emulsions stabilized by organomontmorillonites

In this paper, effect of emulsification processes on the properties of Pickering emulsions stabilized by organomontmorillonites (OMts) was studied. Results of micro-morphology and X-ray diffraction showed that the structure of OMt in emulsion depended on the emulsification processes and had an effect on the stability of emulsion. We propose a schematic diagram to reveal the relationship between emulsification processes-OMt laminates structure-stability of Pickering emulsion. In emulsion prepared by ultrasonic, OMt showed uniform dispersion, loose structure, and irregular crystalline. In emulsion prepared by vortex mixing method, OMt illustrated stacking and coagulation structure. In emulsion prepared by microwave method, OMt showed interacting structure and had a little interaction with oil/water interface, and thus the properties of emulsion prepared by microwave was weakly related to oil/water ratios. Emulsification processes had a profound effect on the structure of OMt and stability of Pickering emulsion, which can be used as a trigger to prepare emulsion for various applications.     

Synthesis and formulation of vinyl-containing polyacids for improved light-cured glass-ionomer cements

Vinyl-containing poly(acrylic acid-co-itaconic acid) copolymers were synthesized and used to formulate light-curable cements containing reactive glass fillers (Fuji II LC). The conditions for light curing were studied and optimized. Effects of molecular weight (MW), grafting ratio, comonomer, liquid composition, powder/liquid (P/L) ratio, glass powder and aging were evaluated. The results show that the vinyl-containing glass-ionomer cements (GICs) prepared in this study exhibit higher compressive strength (CS, 225.6 MPa), diametral tensile strength (DTS, 28.4 MPa) and much higher flexural strength (FS, 116.4 MPa), as compared to commercial Fuji II LC GIC (186.6 in CS, 19.1 in DTS and 57.1 in FS). The optimal light-exposure time was found to be around 10 min, and concentrations of CQ and DC were 0.5% (by weight) and 1.0%, respectively. Effects of MW, grafting ratio, P/L ratio and content of polymer in the liquid formulation were significant. The highest strengths were found for the optimal formulations where the MW was 15,000 (weight average), grafting ratio 25 mol%, P/L ratio 2.7 and liquid composition 50:20:30. During aging, the cement showed an increase of strength over the first week and then no change for a month. SEM analysis suggests that more integrated microstructures and smaller glass particles can lead to higher FS and higher polymer content in GICs leads to tough fracture surface and plastic deformation.     

卵磷脂类液晶乳液的性能

以卵磷脂为主乳化剂制备了一款液晶乳液。 该乳液在皮肤上具有良好的稳定性能,在皮肤表层停留6 h仍能保持完整的液晶结构,克服了一般液晶乳液中液晶织构无法在皮肤上长时间停留的问题。 液晶结构在皮肤温度范围内具有较高的稳定性,可为液晶乳液其他性能的发挥提供条件。 基于此,我们采用体外称重法研究了液晶乳液的锁水性,发现液晶乳液锁水性能明显优于传统乳液,实验7 h后仍能保持原有水分总质量的50%;体外透析实验证实,液晶乳液表现出显著的缓释性能且能释放完全,7 h后目标分子(水杨酸钠)释放率可达96%;耐温性能研究表明,液晶乳液耐高温性能及低温冻融性能优良,且温度对乳液中层状液晶的影响是可恢复的;采用离心法、高低温循环和高低温长时间(3个月)放置的方法探究了乳液储运稳定性,结果表明,液晶乳液产品储运稳定性极佳,便于实际的应用和储运。 该研究不仅可为开发多效的高端化妆品提供必要信息和参考数据,而且有望拓展卵磷脂类液晶乳化剂体系的应用范畴。     

Liquid-Crystal Based Formulations for Topical Drug Delivery

Monoolein, being a biocompatible and bioadhesive penetration enhancer that can form liquid crystalline (LC) phases, possesses remarkable characteristics for addressing drug delivery systems across the biological membrane. A range of formulations based on LC phases were investigated in this study, which includes lamellar, reverse hexagonal, and bicontinuous cubic phases along with an emulsion stabilized by LC phases. Caffeine was chosen as hydophilic model drug to evaluate in vitro release performance. The different monoolein based caffeine formulations were characterized by techniques such as polarized light microscopy, nuclear magnetic resonance (NMR) and small angle x-ray scattering (SAXS). The release experiments, performed through Franz diffusion cells, revealed that the presence of a liquid crystalline (LC) phase prevented burst release in all cases. In addition, taking into consideration that all ingredients are fully biocompatible, the creamy emulsion formulation stabilized by a hexagonal lipid LC phase can be proposed as a challenging preformulation for topical drug delivery.     

The significant effects of linear medium chain fatty alcohols on phase behavior of aqueous solution of mixed cationic–anionic surfactant

The effect of 1-hexanol on the phase behavior of aqueous solutions of sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) has been systematically studied. The phase ranges of vesicle and liquid crystal (LC) can be greatly extended with the addition of 1-hexanol. These specific structures distributed symmetrically on the two sides of the SDS/CTAB equimolar line in the pseudo ternary phase diagram. The aqueous two phase system (ATPS) contained vesicles that would transform into lamellar LC with the change of ratio of SDS/CTAB. The phase behaviors of SDS/CTAB system with addition of different alcohols (C₅OH–C₈OH) showed similar trends in structural transition except for phase span, demonstrating that the obstruction of electrostatic interaction between surfactant polar heads was affected by the insertion depth of the added alcohols.     

Surface characterization and liquid crystal alignment behavior of comb-like poly(oxyethylene)/poly(3-hexylthiophene) blend films

The blend surfaces of poly[oxy(n-decylsulfonylmethyl)ethylene] (CH(3)-10SE) and poly (3-hexylthiophene) (P3HT) with different weight ratios were prepared by spin coating the polymer solution mixtures. In this study, their surface properties such as surface morphology, chemical composition, molecular structure, and wettability were systematically studied and correlated with liquid crystal (LC) alignment behaviors on the blend films. Therefore, we found that CH(3)-10SE part with a well-ordered side chain structure predominantly affects the both of wettability and LC alignment behavior of the blend films while there was no clear association between the wettability and the LC alignment behavior.     

Morphologies and electro-optic properties of polystyrene/liquid crystal composite films

Morphology and electro-optic properties of composite films composed of polystyrene (PS) and nematic liquid crystal (LC) have been studied for a wide range (30-70 wt% of liquid crystal) of film composition. At two specific levels of LC loadings (50 and 60 wt%), effects of temperature, frequency and voltage of applied ac electric field on the transmittance of the films were intensively measured, and the results were interpreted in terms of aggregation structure of the film, the geometry of LC domains, LC loading, dielectric constant, conductivity, birefringence, and the solubility of LC in polymer. © 1994 John Wiley & Sons, Inc.     

Combined use of liquid chromatography with mass spectrometry and nuclear magnetic resonance for the identification of degradation compounds in an erythromycin formulation

A commercial erythromycin formulation containing erythromycin A (EA) as the major compound showed the presence of an unknown degradation compound that was co-eluted with erythromycin E (EE) in the European Pharmacopoeia (Ph. Eur.) liquid chromatographic (LC) method. The amount of the degradation compound increased with respect to time. To separate this unknown (UNK1), investigation was performed with different LC methods coupled to ultraviolet detection (LC-UV). With the present Ph. Eur. method, the degradation compound could not be well separated. However, with the most selective LC-UV method (XTerra method), two more degradation products (UNK2 and UNK3) were found in the formulation which could not be observed using other methods because of their poor separation. By combining the results obtained with LC-UV, LC/MS and LC/NMR, the degradation products were identified as pseudoerythromycin A hemiketal (PsEAHK), erythromycin A enol ether carboxylic acid and erythromycin C enol ether carboxylic acid. PsEAHK is known to be a base-catalysed degradation product of EA, whereas the other two degradation products were newly identified.     

The effect of glycolic acid monomer ratio on the emulsifying activity of PLGA in preparation of protein-loaded SLN

Our previous work demonstrated that lactic/glycolic acid copolymer (PLGA) was an efficient emulsifier for the primary w/o emulsion in the formulation of protein-loaded solid lipid nanoparticles (SLN) by w/o/w double emulsion-solvent evaporation technique. In this work, the effect of PLGA composition on the emulsifying activity was studied with PLGA of different lactic/glycolic acid ratios (90/10, 75/25, 50/50). The results demonstrated that the glycolic acid monomer ratio significantly affected the emulsifying activity of PLGA. Increasing the glycolic acid monomer ratio from 10% to 50% decreased the minimum PLGA content needed to produce stable w/o emulsions. With same PLGA contents, increase of the glycolic acid monomer ratio increased the stable time of the w/o emulsion, yielded smaller and narrower-distributed SLN, and enhanced the encapsulation efficiency and loading capacity.     

Novel resin modified glass-ionomer cements with improved flexural strength and ease of handling

Poly(acrylic acid-co-itaconic acid) copolymers containing pendent methacrylates were synthesized and used to formulate redox-initiated in situ cured glass-ionomer cements (GICs) by mixing with reactive glass fillers (Fuji II LC). Various formulations for the redox initiator were studied, and flexural strength (FS) was used as a screening tool for optimization. Effects of molecular weight (MW), grafting ratio, comonomer, polymer content in the liquid composition, powder/liquid (P/L) ratio, and aging on FS were investigated. The results show that the in situ cured GICs demonstrated higher FS (89.6-123.2 MPa), as compared to commercial Fuji II LC GIC (57.1 MPa). The optimal concentrations for redox initiators were found to be 0.15% (by weight) for K₂S₂O₈ and 0.2% for ascorbic acid (or 0.6% for microencapsulated ascorbic acid), respectively. Effects of MW, grafting ratio, P/L ratio and polymer content in the liquid formulation were significant. During aging, the cement showed an increase in strength over 24 h and then no change for time periods up to six months. SEM analysis supports the strength data associated with the formulations. The exotherm and setting time suggest that novel redox-initiated resin-modified GICs hold promise as biocompatible and workable cement for orthopedic applications.     

Influencing factors on liquid crystalline properties of cholesterol side-chain liquid crystalline polymers without spacer: molecular weight and copolymerisation

ABSTRACT

It is a challenge to tailor the phase behavior and phase structure of side-chain liquid crystalline polymers carrying targeted ordered structures and functional properties. In this work, liquid crystalline (LC) properties of cholesterol side-chain polymers without spacer were controlled by molecular weight (M_n) and copolymerization. On the one hand, two series of homopolymers without the spacer, poly (methacrylic acid) cholesterol esters (PCholMC_n) and poly (acrylic acid) cholesterol esters (PCholAC_n) with different M_n and low polydispersity, were achieved by reversible addition-fragmentation chain transfer polymerization. The experiment results indicated that the M_n had little effect on the LC properties of PCholMC_n and all homopolymers formed the smectic A phase. However, the phase structures of PCholAC were found to be strongly M_n dependent. The polymers PCholAC_n were amorphous when the M_n was lower than a critical value of approximately 1210₃ g/mol. But when the M_n exceeded the critical value, the polymers exhibited smectic A phase. On the other hand, two kinds of random copolymers, poly(cholest-5-en-3-methacrylate)-co-polymethyl acrylate (PCholMC-co-MA) and poly(cholest-5-en-3-acrylate)-co-polymethyl acrylate (PCholAC-co-MA) were synthesized with various composition. The findings suggested that the steric effect of main-chain and the interaction of mesogens would promote the formation of LC phase.     

Concentration of amino acids by a liquid emulsion membrane with a cationic extractant

The concentration of -phenylalanine in a liquid emulsion membrane system was studied using a cation complexing agent, di-2-ethylhexyl phosphoric acid (D2EHPA), as a carrier. The membrane formulation, the pH in the internal phase of the acid concentration in the external phase were optimized with respect to concentration performance and membrane stability. It was found that a liquid emulsion membrane obtained by demulsification of the emulsion by an electrostatic coalescer could be reused. Based on the laboratory tests, a continuous multistage process for the concentration of amino acids was proposed (with the development of a commercial process in mind) and its technical feasibility was discussed.     

胶原液晶膜的制备及对细胞生长的影响

从仿生角度出发, 制备了一系列液晶态胶原薄膜. 采用偏光显微镜、扫描电镜和原子力显微镜分别研究了各种膜的液晶织构和拓扑结构, 并通过3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)法及细胞骨架荧光染色观察研究了各种膜对鼠成纤维细胞3T3的黏附、增殖以及形貌的影响. 结果表明, 胶原液晶薄膜呈现典型的胆甾型液晶织构, 与非液晶薄膜相比, 它不仅能更好地促进细胞的黏附、生长及增殖, 而且其拓扑结构对细胞生长具有接触引导效应.     

Thermotropic liquid crystals embedded in a high water gel system

An emulsion was formed when the thermotropic liquid crystal (LC) mixture E5 was added to an aqueous polyvinylalcohol (pva) solution and shaken. This emulsion was gelled by addition of an aqueous borax solution. The pva polymer functioned not only as the gelling agent but also appeared to act as a polymeric surfactant which stabilised the LC droplets. This high water gel-liquid crystal (HWG-LC) system contained nearly 80 wt % water and more LC wt % than polymer. The system was thermally reversible, undergoing a gel to sol transition upon heating to 70°C and reforming a gel upon cooling. The HWG-LC showed electrooptical behaviour dependent upon a switched electric field when constrained between transparent electrodes. The pressure required to form a thin film between these electrodes induced a structural emulsion in the dispersion causing LC droplet disruption and the formation of an LC network in the gel.     

Physicochemical parameters influencing the emulsion drop size

The stirring-mixing energy is the most obvious factor in the drop size reduction process, but it is not necessarily the most important one. Both the physicochemical formulation and the composition variables are shown to play a determinant role, at constant stirring condition.The generalized formulation versus water/oil ratio diagram allows to map emulsion properties such as emulsion type, stability and viscosity. It is used to discuss the combined effect of the formulation and composition upon the emulsion drop size, through their influences on the interfacial tension, and the emulsion viscosity and stability.     

碱助剂对完全液相-热解法CuZnAl催化合成低碳醇性能的影响

采用完全液相技术结合热解方法制备了固定床用CuZnAl催化剂,研究表明,该方法能保留完全液相技术赋予催化剂的特殊性能,可以发展成为将完全液相技术拓展于固定床催化剂的通用方法.在所制催化剂中引入碱助剂同样可以增加C₂₊醇的选择性,但主要不是异丁醇,与现行常规方法制备的催化剂不同.通过对催化剂进行XRD、H₂-TPR、NH₃-TPD-MS、BET等表征,结果表明,不同碱助剂对催化剂的作用方式和影响程度不同,使得催化剂中Cu物种的存在形式和数量、催化剂表面的酸碱性和量以及孔道结构存在差异,进而对催化剂性能产生影响.