Hydrophobic-lipophilic Balance Research Articles

Nanoscale Pluronic® micellar templates with varying %EO content for controlled drug release and cytotoxicity

This study investigates the self-assembly in ethylene oxide (EO)-propylene oxide (PO)-based block copolymers (BCPs) with various molecular features like molecular weight, EO/PO ratio, HLB (Hydrophobic lipophilic balance) in aqueous solution environment. Our BCP solution systems exhibit significant changes in solution behaviour that showed micellization, micelle growth/ transition, and progressively phase separation (2ϕ), all of which are well explained by clear solution, blue point (BP) and cloud Point (CP) respectively. The solubilization of the highly hydrophobic anticancer drug-Quercetin (QCT) in such BCPs is examined using UV–Visible spectroscopy. The spectral findings inferred the dissolution capability of QCT in the examined copolymeric micellar systems in terms of drug loading efficiency (DL%), encapsulation efficiency (EE%), partition coefficient (P), and standard free energy of solubilization (ΔGo). Amongst the varied tested BCPs, it was observed that Pluronics® P123 and F127 exhibited an enhanced QCT solubilization capability than others and is explained in terms of hydrophobicity and hydrophilicity. The micellar size distribution profile expressed as hydrodynamic diameter (Dh) was determined for QCT-loaded and QCT-unloaded BCP micelles employing dynamic light scattering (DLS). The drug release profile was fitted employing various kinetic models, allowing this study to serve as an excellent foundation for QCT delivery. Reversed-phase High-performance liquid chromatography (HPLC) system determined the retention period in the QCT-loaded micelle while the structural alterations involved in Pluronics®-QCT system is inferred using small-angle neutron scattering (SANS). Fourier transform infrared spectroscopy (FT-IR) depicted the compatibility between Pluronics® and QCT which was validated further from the evaluated optimum descriptors using Gaussian 09 computational simulation framework. It was discovered that the QCT-loaded micelles exhibited a greater anticancer effect than free drug when tested in vivo on cancer cells. The anticancer activity of QCT-loaded F127 micelles was determined to be the strongest. Thus, the current study on QCT solubilization in Pluronics® will benefit considerably from its investigated outcomes.

Impact of Surfactants on the Functionality of Prefilled Syringes

Previous studies revealed the impact of formulation factors (excipients and pH) on the functionality of prefilled syringes. Surfactant, a critical formulation component for therapeutic proteins and antibodies, aids in minimizing protein adsorption onto interfaces and reduces protein aggregation or particulate formation. This study evaluated the impact of different surfactants and protein concentration on the functionality of prefilled syringes. Syringes filled with solution formulations with different surfactants were stored at various temperatures and evaluated at selected time points. Upon thermal stress, polysorbate 80 and dodecyl-β-d-maltoside containing formulations showed significantly greater increase in glide force when compared with poloxamer 407 containing formulations. In contrast, syringes filled with poloxamer 188 containing formulations did not show any increase in glide force under the same conditions. Based on the results from this study, the increase in syringe glide force was inversely correlated with hydrophobic-lipophilic balance values and surface tension of different surfactants. The mechanism of increase in glide force was primarily the change of silicone oil coverage and lubricity in the barrel of syringes.

Morphological transformation of self-assemblies by tuning hydrophobic segment of small amphiphiles

HypothesisWith increasing surge in the development of supramolecular self-assemblies, it is crucial to predict the influence of amphiphilic segment in dictating the morphology of self-aggregates. This article reports the design and synthesis of low molecular weight amphiphiles with varying hydrophobicity both in the spacer unit and at the terminal moiety. ExperimentsHydrophobicity at the spacer moiety was modulated by altering alkyl chain length and by inclusion of aromatic ring and the same was changed at hydrophobic terminal using pyrene, naphthalene, n-hexadecane having 2-aminopyridine as polar head. Microscopy and spectroscopy were used to investigate the morphologies of self-aggregated amphiphiles. FindingsVariation of hydrophobicity of the spacer moiety either by changing the alkyl chain length (C0, C2, C6, C11 and phenyl ring) having pyrene as terminal hydrophobic unit led to the formation of only spherical vesicles in respective solvent system. Morphological transformation of self-aggregates from vesicle to fused-vesicle to gel was observed in DMSO-water upon alteration in the hydrophobic end of amphiphile from pyrene to naphthyl to C16 alkyl chain having C6 alkyl chain as spacer. Hence, the hydrophobicity at the terminal of the amphiphile has the predominant role in tuning the morphology of self-aggregates through modulation in the hydrophobic-lipophilic balance (HLB) of amphiphiles.

Using a pseudophase model to determine AO distributions in emulsions: Why dynamic equilibrium matters

For decades, explorations with ground state, thermal reactions combined with pseudophase kinetic models and methods for interpreting the results have provided insights into the properties of the different regions of homogeneous association colloids. More recent successful determination of antioxidant (AO) distributions by this approach is providing new insights into AO efficiency in opaque, well‐mixed two‐phase intact emulsions and eliminating the need to separate the phases. The chemical probe reacts with AOs exclusively in the interfacial region of the emulsion, permitting simplification of the kinetic treatment, and determining its distribution between the oil, interfacial, and aqueous regions. AO distributions are obtained from the two partition constants, and , of the AOs between the oil‐interfacial and aqueous‐interfacial regions, respectively. and values are obtained by fitting the observed rate constant, kobs, versus surfactant concentration profiles with an overall kinetic approach or model we call the “pseudophase chemical kinetic method.” However, because emulsions break up and reform, and reactants and other components diffuse at various time scales within and between the oil, interfacial, and water regions, kobs could also depend on reactant diffusion coefficients. Here we demonstrate that reactant diffusion is generally orders of magnitude faster than most thermal reactions and reactant distributions between the multiple oil, aqueous, and interfacial droplets and regions of emulsions are in dynamic equilibrium throughout the multiphase systems during the time course of the reaction. Thus, kinetic probes are powerful tools for determining structure‐reactivity, for example, the HLB, relationships governing AO distributions and efficiencies in emulsions.Practical applications: The analysis presented here demonstrates that one of the basic assumptions of the pseudophase chemical kinetic model that we have developed has a solid foundation in the properties of emulsions. That is, we can determine the distributions of reactants between oil (O), interfacial (I), and aqueous (W) regions of the emulsions because the diffusivity coefficients of reactants within emulsions are orders of magnitude greater than the rate of the reaction between the antioxidant and the 4‐hexadecylbenzenediazonium probe. Consequently, we can use the same kinetic model in emulsions as we have used in homogeneous microemulsions. The method permits determination of the partition constants of many antioxidants between the O‐I and W‐I regions of the emulsions and from them their distributions. The method provides new insights into the relationships between antioxidant hydrophobic‐lipophilic balance (HLB) and its efficiency in emulsions and a natural explanation for the cut‐off effect observed with increasing antioxidant HLB.Interpreting chemical reactivity in emulsions requires that reactive components A and B be in dynamic equilibrium, that separate second order rate constants, k defined for the oil, interfacial, and aqueous regions, subscripts O, I, and W, and for simplicity, the volume of each region depends on the added volumes of oil, surfactant, and water.

Continuous low-level aquatic monitoring (CLAM) samplers for pesticide contaminant screening in urban runoff: Analytical approach and a field test case

Monitoring of surface waters for organic contaminants is costly. Grab water sampling often results in non-detects for organic contaminants due to missing a pulse event or analytical instrumentation limitations with a small sample size. Continuous Low-Level Aquatic Monitoring (CLAM) samplers (C.I.Agent® Solutions) continually extract and concentrate organic contaminants in surface water onto a solid phase extraction disk. Utilizing CLAM samplers, we developed a broad spectrum analytical screen for monitoring organic contaminants in urban runoff. An intermediate polarity solid phase, hydrophobic/lipophilic balance (HLB), was chosen as the sorbent for the CLAM to target a broad range of compounds. Eighteen urban-use pesticides and pesticide degradates were targeted for analysis by LC/MS/MS, with recoveries between 59 and 135% in laboratory studies. In field studies, CLAM samplers were deployed at discrete time points from February 2015 to March 2016. Half of the targeted chemicals were detected with reporting limits up to 90 times lower than routine 1-L grab samples with good precision between field replicates. In a final deployment, CLAM samplers were compared to 1-L water samples. In this side-by-side comparison, imidacloprid, fipronil, and three fipronil degradates were detected by the CLAM sampler but only imidacloprid and fipronil sulfone were detected in the water samples. However, concentrations of fipronil sulfone and imidacloprid were significantly lower with the CLAM and a transient spike of diuron was not detected. Although the CLAM sampler has limitations, it can be a powerful tool for development of more focused and informed monitoring efforts based on pre-identified targets in the field.

Determination of quinolonones in food of animal origin by liquid chromatography coupled with fluorescence and mass spectrometric detection

High-performance liquid chromatography coupled with fluorescence (HPLC-FD) and tandem mass spectrometric detection (LC-MS/MS) was studied as a versatile tool for fast and reliable determination of nine regulated quinolones in food of animal origin (Council Regulation 2377/90/ECC). The sample pre-treatment protocol includes double step extraction with acetonitrile followed by solid phase extraction (SPE) cleanup on hydrophobic-lipophilic balance (HLB) cartridge. The separation of quinolones in HPLC-FD determination was performed on C18 Zorbax column with a gradient mixture of aqueous formic acid, methanol, and acetonitrile. A multi-wavelength excitation/emission program was used for sensitive quinolones detection. The separation efficiency of newly available chromatographic columns: Gemini C18 and Synergi Polar RP (fully porous particles), as well as Kinetex PFP and Poroshell 120 EC-C18 (core-shell particles), was studied in liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/...

Novel strategy involving surfactant-polymer combinations for enhanced stability of aqueous teflon dispersions.

Among various polymers, the Teflon surface possesses extreme hydrophobicity (low surface energy), which is of great interest to both industry and academia. In this report, we discuss the stability of aqueous Teflon dispersions (particle size range of 100-3000 nm) formulated by a novel strategy that involves distinct combinations of surfactant and polymer mixtures for dispersion stabilization. As a first step, the hydrophobic Teflon particles were wetted using a range of surfactants (ionic, Triton, Brij, Tween, and Pluronic series) bearing different hydrophobic-lipophilic balance (HLB) and further characterized by contact angle and liquid penetration in packed powder measurements. The interaction between hydrophobic chains of surfactants and the Teflon particle surface is the driving force resulting in wetting of the Teflon particle surface. Further, these wetted particles in aqueous solutions were mixed with various polymers, for example, poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), hydroxyethyl cellulose (HEC), and hydroxypropyl methyl cellulose (HPMC). The rate of sedimentation for the final dispersions was measured using a pan suspended into the dispersion from a transducer recording the increase in weight with time. A significant stability was noticed for Teflon particles suspended in surfactant + polymer mixtures, which was linearly proportional to the concentration of added polymer. The observed phenomenon can be possibly explained by molecular interactions between the hydrophobic chains of surfactant molecules and polar groups in the polymer architecture. Brij-O10 + HEC mixture was found to be the best surfactant-polymer combination for decreasing the sedimentation of the Teflon particles in the final dispersion. As measured by dynamic light scattering (DLS), the hydrodynamic volume of the Teflon particles increases up to ∼55% in the final formulation. These dispersions could be further explored for various technological applications such as paints, inks, protective coatings, and so forth.

Poly(alkylene oxide) copolymers for nucleic acid delivery.

The advancement of gene-based therapeutics to the clinic is limited by the ability to deliver physiologically relevant doses of nucleic acids to target tissues safely and effectively. Over the last couple of decades, researchers have successfully employed polymer and lipid based nanoassemblies to deliver nucleic acids for the treatment of a variety of diseases. Results of phase I/II clinical studies to evaluate the efficacy and biosafety of these gene delivery vehicles have been encouraging, which has promoted the design of more efficient and biocompatible systems. Research has focused on designing carriers to achieve biocompatibility, stability in the circulatory system, biodistribution to target the disease site, and intracellular delivery, all of which enhance the resulting therapeutic effect. The family of poly(alkylene oxide) (PAO) polymers includes random, block, and branched structures, among which the ABA type triblocks copolymers of ethylene oxide (EO) and propylene oxide (PO) (commercially known as Pluronic) have received the greatest consideration. In this Account, we highlight examples of polycation-PAO conjugates, liposome-PAO formulations, and PAO micelles for nucleic acid delivery. Among the various polymer design considerations, which include molecular weight of polymer, molecular weight of blocks, and length of blocks, the overall hydrophobic-lipophilic balance (HLB) is a critical parameter in defining the behavior of the polymer conjugates for gene delivery. We discuss the effects of varying this parameter in the context of improving gene delivery processes, such as serum stability and association with cell membranes. Other innovative macromolecular modifications discussed in this category include our work to enhance the serum stability and efficiency of lipoplexes using PAO graft copolymers, the development of a PAO gel-based carrier for sustained and stimuli responsive delivery, and the development of biodegradable PAO-based amphiphilic block copolymers.

Effect of Ethoxlate Chain Length on the Pour Point Depressant of Middle Distillate Fuel Oil

A series of ethoxylated laurates, C12En (n = 7, 9, and 14) surfactants were prepared by reacting lauric acid with polyethylene glycol of different molecular weights 300, 400, and 600. The chemical structures of these prepared surfactants were confirmed by high performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (NMR) analysis. The surface tension of the synthesized surfactants was measured at 25°C, critical micelle concentration (CMC) and hydrophobic lipophilic balance (HLB) were calculated. The additives prepared were added to improve oils properties as pour point depressant and improve viscosity or storage stability. They were added at different concentration to meet the performance requirements. It was found that the ethoxylate laurate, C12En, n = 14 (C) is more effective as pour point depressant and improve viscosity than ethoxylated laurate, C12En, n = 7 (A) as pour point depressant and viscosity improver were determined. Storage stability of the treated middle distillate fuel was tested in terms of pour point depression for 28 days. The obtained data were used to explain the discrepancy of these ethoxylate laurate as pour point depressants.

Benzoxazine Miniemulsions Stabilized with Polymerizable Nonionic Benzoxazine Surfactants

For the first time, the concept of polymerizable nonionic benzoxazine surfactants is described. Different target structures with varying hydrophobic−lipophilic balance (HLB) values were synthesized and successfully tested for the miniemulsification of two N-aliphatic and N-aromatic benzoxazine resins. As a model system, the difunctional benzoxazine surfactant bis(3,4-dihydro-2H-3-(polypropyleneoxide-block-polyethyleneoxide-1,3-benzoxazinyl)isopropane (B2000) was analyzed in detail via FT-IR, 1H NMR, surface tension measurements, and thermal analysis such as DSC and TGA. Additional to the colloidal stability of the benzoxazine miniemulsions, investigations focused on the surfactant copolymerization behavior and compatibility with other resins. It was found that despite the observed slow homopolymerization the described surfactants easily undergo copolymerization with the model benzoxazine resins.

Trastuzumab-Functionalized Nanoparticles of Biodegradable Copolymers for Targeted Delivery of Docetaxel

We synthesized a novel system of docetaxel-loaded, trastuzumab-functionalized nanoparticles (NPs) of biodegradable copolymers for targeted and synergistic chemotherapy. NPs of two component biodegradable copolymers were prepared by a modified solvent extraction/evaporation method with D-alpha-tocopheryl polyethylene glycol succinate (TPGS) as emulsifier. One component copolymer is poly(lactide)-TPGS, which is of desired hydrophobic-lipophilic balance for cellular adhesion, and another is carboxyl group-terminated TPGS, which facilitates the conjugation of trastuzumab on the NP surface for targeting. In vitro investigation with SK-BR-3 breast cancer cells of HER2 overexpression showed that the trastuzumab-functionalized NPs have great advantages over nude NPs in cellular uptake and cytotoxicity. Trastuzumab conjugated onto the NP surface has two functions: one is to target HER2-overexpressing cancer cells and the other is to enhance the cytotoxicity of docetaxel through synergistic effects. The trastuzumab-functionalized, docetaxel-loaded NPs have great potential for targeted chemotherapy to treat HER2-overexpressing cancer.

Comparison of solid‐phase sorbents for the determination of fluoroquinolone antibiotics in wastewater

Three different SPE sorbents (weak cation exchange, mixed cation exchange, and hydrophobic-lipophilic balance polymers) were compared in terms of recovery, precision, and the effect of matrix components on analyte response for the determination of fluoroquinolones antibiotics. The influence of ethylenediaminetetraacetic acid disodium salt (Na2-EDTA) was as well tested. Two of the sorbents, hydrophilic-lipophilic balance (HLB) and weak cation exchange (WCX), turned out to be suitable for ultratrace analysis. HLB sorbent showed higher capacity for analyte trapping and better precision while weak cation exchange sorbent had a superior performance in terms of selectivity. In complex samples, the higher capacity of HLB was outweighed by the higher selectivity of WCX when considering the LODs of the methods.

Targeted delivery of paclitaxel using folate-decorated poly(lactide)–vitamin E TPGS nanoparticles

We synthesized nanoparticles (NPs) of the blend of two-component copolymers for targeted chemotherapy with paclitaxel used as model drug. One component is poly(lactide)– d-α-tocopheryl polyethylene glycol succinate (PLA–TPGS), which is of desired hydrophobic–lipophilic balance, and another is TPGS–COOH, which facilitates the folate conjugation for targeting. The nanoparticles of the two-copolymer blend at various component ratio were prepared by the solvent extraction/evaporation single emulsion method and then decorated by folate, which were characterized by laser light scattering (LLS) for particles' size and size distribution, zeta potential analyzer for surface charge, and X-ray photoelectron spectroscopy (XPS) for surface chemistry. The drug encapsulation efficiency (EE) and in vitro drug release were measured by high performance liquid chromatography (HPLC). The targeting effect was investigated in vitro by cancer cell uptake of coumarin-6-loaded NPs and further confirmed by cytotoxicity of cancer cells treated with the drug formulated in the NPs. We showed that the NP formulation has great advantages vs the pristine drug in achieving better therapeutic effect, which increased 8.68% for MCF-7 breast cancer cells, and that the folate-decoration can significantly promote targeted delivery of the drug into the corresponding cancer cells and thus enhance its therapeutic effect, which increased 24.4% for the NP formulation of 16.7% TPGS–COOH component and 31.1% for the NP formulation of 33.3% TPGS–COOH component after 24 h treatment at the same 25 μg/ml paclitaxel concentration. The experiments on C6 glioma cells further confirmed these advantages.

Determination of carbofuran, carbaryl and their main metabolites in plasma samples of agricultural populations using gas chromatography–tandem mass spectrometry

A gas chromatography-tandem mass spectrometric (GC-MS/MS) method has been developed for the determination of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), carbaryl (1-naphthyl-N-methylcarbamate) and their main metabolites in human blood plasma. Optimization of the isolation of the compounds from plasma matrix included the precipitation, denaturation and digestion of plasma proteins. Derivatization was achieved by the use of trifluoroacetic acid anhydride and was optimized for temperature, time and volume of derivatization agent. In the proposed method, a mild precipitation technique was applied using beta-mercaptoethanol and ascorbic acid in combination with solid-phase extraction technique using Oasis HLB (Hydrophobic Lipophilic Balance) cartridges for further clean up of samples. Carbamate linkage was not hydrolyzed to its phenol product, but both carbamate phenol and ketones were transformed into trifluoroacetyl derivatives in order to become volatile compounds and were determined using tandem mass spectrometry. The linearity of the method was shown for nine concentrations in the range of 0.50-250 ng mL(-1) in fortified plasma aliquots. Limits of detection (LODs) for all compounds ranged from 0.015-0.151 ng mL(-1). Inter-day and intra-day assays (RSD) for all compounds, at three concentration levels of 2.5, 25 and 100 ng mL(-1) (n=3) in fortified plasma samples were less than 18%. Accuracy (%E (r)) was calculated at three concentration levels, 8, 80 and 160 ng mL(-1) (n=3), and ranged from -12.0 to 15.0%. Matrix effect was evaluated so mean recoveries were calculated for all compounds and ranged from 81-107%. Specificity for the use of this method to biological monitoring studies was achieved including four main metabolites of CF, 1-naphthol and 2-naphthol from the naphthalene metabolism pathways, and both the parent compound of carbofuran and carbaryl. The proposed method was applied to plasma samples of pesticide users.

Effect of maltodextrins on the surface activity of small-molecule surfactants

We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na +), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed.

Dissolution and partitioning behavior of hydrophobic ion-paired compounds.

This study was conducted to determine the effects of counterion hydrophobicity on organic/aqueous partition coefficients for hydrophobic ion paired (HIP) complexes. Furthermore, the coupled dissolution and reverse ion-exchange kinetics for dissolution of HIP complexes into aqueous electrolyte solutions were measured and mathematically modeled. HIP complexes of model drugs tacrine and l-phenylephrine were formed using linear sodium alkylsulfates and bis (2-ethylhexyl sodium sulfosuccinate). Equilibrium partition coefficients between chloroform and aqueous solutions for the complexes and the kinetics of dissolution of the complexes in buffered aqueous solutions were measured. The chloroform/aqueous partition coefficients for l-phenylephrine/bis (2-ethylhexyl sodium sulfosuccinate) complexes decrease with increasing molar surface tension increment of salts added to the aqueous solution. The logarithm of the partition coefficient for a homologous series of alkyl sulfate complexes decreases as the hydrophilic-lipophilic balance number increases. Dissolution of HIP complexes in deionized water shows first order kinetics, whereas dissolution in aqueous electrolyte solutions shows biphasic kinetics. A kinetic model explains these dissolution rates. Solubility and dissolution rates for HIP complexes depend on the hydrophobic-lipophilic balance number of the organic counter ion as well as on the electrolyte composition of aqueous solutions. Reverse ion-exchange kinetics are sufficiently slow to allow HIP complexes to be considered simple prodrugs.

Spacer arm influence on glucidoamphiphile compound properties

We prepared glucidoamphiphile derivatives from d-glucose, d-galactose and xylitol, in which the glucidic moiety and the hydrophobic alkyl chain are separated by spacer arm E (E=glyceryl, (OEt) 2-α-polypropyleneglycyl and butyloxy). Their amphiphile characteristics are compared to those of the corresponding analogs 3- O-alkyl- d-glucopyranoses, 6- O-alkyl- d-galactopyranoses and 1- O-alkyl- d, l-xylitols. We discussed the spacer arm influence on hydrophobic lipophilic balance (HLB), critical micellar concentration (CMC), water solubility ( S w) and phase transition temperatures of thermotropic and lyotropic mesophases.

Phase behaviour of polymer emulsions during the phase inversion process in the presence of non-ionic surfactants

A phase inversion map for polyisobutene–water–nonionic surfactant system showing the behaviour of the emulsion system as a function of the hydrophobic–lipophilic balance (HLB) and water volume fraction is developed. The apparatus and the different experimental techniques used to characterise the emulsion system is described. It was found that, using information from the phase inversion map, it is possible to produce stable polymer emulsions with sub-micron polymer drops via the transitional inversion route. The drop size distribution before transitional inversion was wide, while after transitional inversion it was much narrower. An average drop size of ∼200 nm was obtained for a mixture of polyoxyethylene nonylphenyl ether (NPE) surfactants (5% overall concentration by weight). It is, also, possible to produce small polymer drops via stable catastrophic inversion as the emulsion becomes more concentrated. The unstable multiple emulsion drops were found to decrease in size as we get closer to the transitional inversion line.

Control of mesostructure and morphology of surfactant-templated silica in a mixed surfactant system

Mixed cationic surfactants were used in the synthesis of MCM-41 materials. Synthetic conditions for controlling the nanometer-scale channels size and micrometer-scale morphology in mixed alkyltrimethylammonium halides (CnTMAX) systems (n=8–18; X=Cl or Br) were studied. The d100 spacing of MCM-41 synthesized using the C18TMABr–C14TMABr system decreases linearly with increase in the C14TMABr molar fraction. Such linearity was also reproduced in other systems with some deviation at high molar fractions of short chain length surfactants (n<14). The morphology in mixed CnTMABr system can be changed from particle form to a tubules-within-tubule (TWT) structure by adjusting the average surfactant chain length. It was found that the optimum average chain length for preparing a TWT structure is 15–16 for the mixed CnTMABr system and 16–17 for the mixed CnTMACl system. A high yield TWT morphology also can be prepared by adding the cosolvent acetone to a suitable value of the hydrophobic–lipophilic balance (HLB). The change in morphology of the products with respect to average chain length, counter ions and cosolvents are explained by the principle of hydrophilic–hydrophobic (lipophilic) balance (HLB).

Process‐Induced Changes in Molecular Structure that Alter Adsorbed Layer Properties in Oil‐in‐Water Emulsions Stabilised by β‐Casein/Tween20 Mixtures

Competitive adsorption of purified β-casein and the non-ionic surfactant Tween20 has been investigated in model oil-in-water emulsions. The emulsions were characterised by measurement of droplet size distribution and specific surface area as a function of surfactant content. The distributions of β-casein and Tween20 between the subnatant and the adsorbed layer were measured. The results revealed subtle but important differences that are dependent upon the processing history of the components. Further studies examining the effect of Tween20 on the extent of interactions formed between β-casein molecules adsorbed at the interfaces of oil water thin films using the fluorescence recovery after photobleaching technique have provided evidence of a homogenisation-induced structural change in Tween20 resulting in a major reduction in its hydrophobic-lipophilic balance (HLB) value. Analytical evidence supporting these observations was provided by thin layer chromatography. The process-induced change in emulsifier structure has important implications for the formulation of food and non-food emulsions. In particular, emulsion formulations based on the HLB method may fail due to homogenisation-induced changes in the emulsifier's HLB during homogenisation. In addition, our findings resolve apparent contradictions arising from a number of competitive adsorption studies reported in the literature.