Solubility, diffusion coefficient and ionic conductivity of alkyl viologens in poly(ethylene oxide) and its derivatives

A series of alkyl viologens RV (R denotes ethyl, butyl, hexyl, heptyl, and dodecyl) was dissolved in poly(ethylene oxide) (PEO) oligomers (average molar masses of 200, 300, 400, 600 and 1000 g mol⁻¹). The solubility of RV in PEO oligomers decreased with increasing alkyl chain length of RV and the molar mass of PEO. Cyclic voltammograms of RV in PEO containing 0.50 M LiClO₄ clearly show two redox waves. The ionic conductivity of PEO oligomers containing RV decreased with increasing alkyl chain length, suggesting the migration of RV itself in the PEO oligomers. Potential step chronoamperometry was used to obtain the apparent diffusion coefficient of RV in the PEO oligomers. The ionic conductivity has a linear relationship with the apparent diffusion coefficient regardless of the RV species, the PEO molar mass and the temperature. RV was shown to act as a redox mediator in PEO oligomers as long as the ionic conductivity of the PEO was high. Poly(oligo(oxyethylene) methacrylate) (PMEO) was used as a solid solvent for a series of alkyl viologens. Since PMEO is an excellent ion-conducting polymer, RV was confirmed to be an effective redox mediator in this PMEO. It was concluded in this study that ionic conductivity in the polymer matrix could be used as an effective parameter for prediction of the diffusion coefficient of charged organic molecules.     

Polymer solubility in mixed solvents

Modeling results indicate that polymer chains in mixtures of a good with a bad solvent exhibit preferential adsorption of the good solvent. That phenomenon is found to be strongly dependent on molecular weight and it increases with a decrease in chain length. These results have important consequences on polymer solubility. Thus, a low molecular weight chain in a solvent mixture behaves as if it were dissolved in the pure good solvent component, whereas the solubility of a longer chain is controlled by the average mixture composition. As a result, quenching a polydisperse system below the cloud point may induce molecular weight segregation between the two phases: the longer chains, which precipitate out first, tend to populate the polymer rich phase whereas the shorter chains, having greater solubility, remain in the solvent phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2782–2787, 1999     

Solubility of sodium soaps in aqueous salt solutions

The solubility of sodium soaps in dilute aqueous salt solutions has been systematically investigated by direct visual phase behavior observations. The added electrolytes, including simple inorganic salts and bulky organic salts, influence the solubility of sodium soaps in water, as represented by the varied soap Krafft point. Two inorganic salts, sodium chloride and sodium perchlorate, demonstrate a "salting-out" property. On the other hand, tetraalkylammonium bromides show an excellent ability to depress the soap Krafft point and enhance the soap solubility in water. With increasing the tetraalkylammonium ionic size, the degree of "salting-in" of soaps in water increases. However, solubility of pure tetraalkylammonium bromide in water decreases as the length of the alkyl chains increases. Furthermore, in the ternary water-tetrapentylammonium bromide (TPeAB)-sodium myristate (NaMy) system, we observed an upper cloud point phenomenon, which greatly shrinks the 1-phase micellar solution region in the phase diagram. This miscibility gap, together with the organic salt solubility limitation, restricts the use of tetraalkylammonium bromides with alkyl chains longer than 4 carbon atoms as effective soap solubility enhancement electrolytes. We also found that for sodium soap with a longer hydrocarbon chain, more tetrabutylammonium salt is required to reduce the soap Krafft point to room temperature.     

Phase behavior and local dynamics of concentrated triblock copolymer micelles

We report a neutron-scattering study to characterize the ordering and local dynamics of spherical micelles formed by the triblock copolymer polyethylene oxide (PEO)--polypropylene oxide (PPO)--polyethylene oxide (Pluronic) in aqueous solution. The study focuses on two Pluronic species, F68 and F108, that have the same weight fraction of PEO but that differ in chain length by approximately a factor of 2. At sufficiently high concentration, both species undergo a sequence of phase changes with increasing temperature from dissolved chains to micelles with liquid-like order to a cubic crystal phase and finally back to a micelle liquid phase. A comparison of the phase diagrams constructed from small-angle neutron scattering indicates that crystallization is suppressed for shorter chain micelles due to fluctuation effects. The intermediate scattering function I(Q,t)I(Q,0) determined by neutron spin echo displays a line shape with two distinct relaxations. Comparisons between I(Q,t)I(Q,0) for fully hydrogenated F68 chains in D2O and for F68 with deuterated PEO blocks reveal that the slower relaxation corresponds to Rouse modes of the PPO segments in the concentrated micelle cores. The faster relaxation is identified with longitudinal diffusive modes in the PEO corona characteristic of a polymer brush.     

Revisiting the crystallization of poly(2‐alkyl‐2‐oxazoline)s

Poly(2‐alkyl‐2‐oxazoline)s (PAOx) exhibit different crystallization behavior depending on the length of the alkyl side chain. PAOx having methyl, ethyl, or propyl side chains do not show any bulk crystallization. Crystallization in the heating cycle, that is, cold crystallization, is observed for PAOx with butyl and pentyl side chains. For PAOx with longer alkyl side chains crystallization occurs in the cooling cycle. The different crystallization behavior is attributed to the different polymer chain mobility in line with the glass transition temperature (T_g) dependency on alkyl side chain length. The decrease in chain mobility with decreasing alkyl side chain length hinders the relaxation of the polymer backbone to the thermodynamic equilibrium crystalline structure. Double melting behavior is observed for PButOx and PiPropOx which is explained by the melt‐recrystallization mechanism. Isothermal crystallization experiments of PButOx between 60 and 90 °C and PiPropOx between 90 and 150 °C show that PAOx can crystallize in bulk when enough time is given. The decrease of T_g and the corresponding increase in chain mobility at T > T_g with increasing alkyl side chain length can be attributed to an increasing distance between the polymer backbones and thus decreasing average strength of amide dipole interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 721–729     

Effects of several lanthanide trichloride hydrates on the melting behavior and spherulitic superstructure of poly(ethylene oxide)

Binary mixtures of poly(ethylene oxide) (PEO) with the trichloride hydrates of lanthanum, cerium, europium, terbium, and ytterbium have been studied with calorimetry, polarized optical microscopy, and infrared spectroscopy. Melting‐point depression of the PEO‐rich phase occurs in all cases. At sufficiently high concentrations of the low molecular weight lanthanide complex, crystallization of the polymer is absent. The lighter lanthanides with larger ionic radii, such as lanthanum and cerium, are more effective in suppressing PEO crystallization from solution or the molten state because they are more oxophilic. The spherulitic superstructure of PEO disappears at rather low concentrations of the lanthanide salts, between 2 and 8 mol % Ln³⁺. Lanthanum and terbium are most efficient at disrupting the formation of PEO spherulites, and europium is least efficient. Infrared spectroscopy identifies twisting and wagging vibrational absorptions of CH₂ groups in the polymer that are sensitive to the morphologies of these mixtures. Modifications of the PEO infrared absorbances in the presence of these five lanthanide salts correlate more closely with the presence or absence of major PEO melting, not the formation of a spherulitic superstructure. The phase behavior is rather simple, with no evidence of eutectic solidification upon cooling from the molten state. Multiple melting endotherms are observed in the differential scanning calorimetry heating traces of binary mixtures containing 8 mol % Yb³⁺ and between 10 and 20 mol % Eu³⁺, but the concentration dependence of these first‐order endothermic transitions is not characteristic of eutectic phase behavior. The presence of trivalent cations, such as Eu³⁺ or Yb³⁺, in these complexes perturbs the crystallization kinetics of PEO upon cooling from the molten state, as well as the melting behavior upon heating. Ion–dipole or electrostatic interactions between the lanthanide cation and the ether oxygen of PEO might alter the surface free energy at the periphery of the crystalline lamellae and perturb the chain‐folding characteristics of PEO. Consequently, coupling between the amorphous matrix and the PEO crystallites is strengthened, and this provides stability for the existence of multiple‐chain‐folded crystals composed of rather thin lamellae that could be responsible for multiple melting behavior. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2200–2213, 2003     

Conformation and electrochemical reduction of myoglobin in PEO oligomers

Horse-heart myoglobin (Mb) was modified with poly(ethylene oxide) (PEO) to solubilize it in PEO oligomers. PEO-modified Mb (PEO–Mb) showed a quasi-reversible electrochemical redox reaction in PEO₂₀₀ (molar mass of 200 g). PEO–Mbs, modified with lower molecular weight of PEO chains, were soluble in PEO oligomers with wider range of molecular weight. A conformation of PEO–Mb was studied with circular dichroism spectroscopy in phosphate buffer solution (PBS) or PEO oligomers. The α-helix content of PEO–Mb, determined by the molar ellipticity at 222 nm, decreased from 71% to about 58% after PEO modification. However, the degree of PEO modification did not affect the α-helix content of PEO–Mbs. On the other hand, the α-helix content of PEO–Mbs was reduced by lowering the molecular weight of the modified PEO chains. Since the α-helix content of PEO–Mb in PBS and that in the PEO oligomers were almost identical, the conformation of PEO–Mb in PBS was considered to be maintained even in PEO oligomers. Although the reduction rate constant of PEO–Mb in PEO oligomers depended on the total molecular weight of the PEO–Mbs, their relation did not obey the Stokes–Einstein equation. The reduction of the PEO–Mb was probably affected by the interfacial electron transfer process at the electrode surface rather than by diffusion in the PEO oligomer.     

Retention mechanism of fatty alcohol ethoxylates in reversed-phase liquid chromatography

Fatty alcohol ethoxylates (FAEs) are widely used nonionic surfactants that have distributions in both alkyl and poly(ethylene oxide) (PEO) chain length. Generally, two-dimensional liquid chromatography technique is required for the complete characterization of both distributions. By selecting a proper stationary and mobile phase condition, however, we can obtain fully resolved chromatograms of a FAE sample (Brij 30) with respect to both alkyl and PEO chain length by using a single reversed-phase C18 column and aqueous acetonitrile mobile phase. FAEs show a peculiar reversed-phase liquid chromatography (RPLC) retention behavior with an aqueous-organic mobile phase, the retention mechanism of which has not been fully elucidated. For a fixed alkyl chain length, FAEs with higher-molecular-mass PEO block elutes first and the van't Hoff plot of the retention factor shows a curvature. The unique retention behavior can be understood from the opposite thermodynamic characteristics associated with RPLC retention of PEO block and alkyl chain: the sorption process of PEO to the non-polar stationary phase shows deltaH(o) > 0 and deltaS(o) > 0 while the alkyl chain shows deltaH(o) < 0 and deltaS(o) < 0 in contrast. The relative magnitude of the two contributions can change the elution order of the FAE. Therefore the often found, inverted elution order of FAEs (the early elution of FAEs with longer PEO block) is due to the positive enthalpic interaction of PEO blocks, which is a characteristic of the hydrophobic interaction. And the curvature of the van't Hoff plots was analyzed assuming the temperature dependent thermodynamic variables.     

Influence of Precursor Chemistry on the Formation of MTiO3 (M = Ba,Sr) Ceramic Thin Films

Thin films of BaTiO3 and SrTiO3 were prepared by a chemical solution deposition method. The impact of the precursor on the processing, on the microstructure, and on the dielectric properties has been studied by systematically varying the alkyl chain length of the used Ba- and Sr-carboxylates. In addition, the effect of stabilizing the Ti-alkoxide precursor by acetylacetone has been investigated. The decomposition process, the crystallization behavior, and the film morphology were analyzed by glancing incidence XRD, reflectance FT-IR and field emission SEM. Distinct precursor effects on the thin film morphology and properties were revealed. Part of this influence can be attributed to an intermediate complex carbonate phase which forms for selected carboxylates with short alkyl chains. The high transformation temperature of this intermediate phase to the perovskite obviously has a marked influence on the crystallization and densification process of the alkaline earth titanate thin films. We correlate the morphological differences of the films to their dielectric properties.     

Lamellar structure of poly(ethylene oxide) molecular complexes

The phase diagrams of some binary systems such as poly(ethy lene oxide)-p-dihalogenobenzene, poly(ethylene oxide)-resorcinol and poly(ethylene oxide)-p-nitrophenol show the existence of molecular complexes with a well definite stoichiometry. The crystal structure of these molecular complexes has been determined by wide-angle X-ray diffraction. The morphology of these molecular complexes crystallized from the melt is investigated by differential scanning calorimetry and small angle X-ray scattering. PEO-p-dichlorobenzene and PEO-resorcinol complexes crystallize from the melt as extended chains (EC) or integral folded chain (IFC) lamellar crystals. As observed for PEO oligomers, the fraction of EC crystals of PEO-resorcinol increases with the crystallization temperature. However EC crystals are present in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO-p-nitrophenol complex crystallizes over all the studied crystallization temperature range as stable non integral folded chain (NIFC) crystals. Explanations related to the crystal structure of these complexes and to their mode of growth are invoked to explain these two deeply different lamellar morphologies.     

Nanoscale segregation in room temperature ionic liquids

Room-temperature ionic liquids (RTILs) are organic salts that are characterized by low melting points. They are considered to possess a homogeneous microscopic structure. We provide the first experimental evidence of the existence of nanoscale heterogeneities in neat liquid and supercooled RTILs, such as 1-alkyl-3-methyl imidazolium-based salts, using X-ray diffraction. These heterogeneities are of the order of a few nanometers and their size is proportional to the alkyl chain length. These results provide strong support to the findings from recent molecular dynamics simulations, which proposed the occurrence of nanostructures in RTILs, as a consequence of alkyl chains segregation. Moreover, our study addresses the issue of the temperature dependence of the heterogeneities size, showing a behavior that resembles the density one only below the glass transition, thus suggesting a complex behavior above this temperature. These results will provide a novel interpretation approach for the unique chemical physical properties of RTILs.     

Langmuir monolayers of the long-chain alkyl derivatives of a nucleoside analogue and the formation of self-assembled nanoparticles

The long-chain alkyl derivatives of a nucleoside analogue-acyclovir were prepared in the paper. One is stearyl-glycero-succinyl-acyclovir (SGSA) with a single 18-carbon length (C18) alkyl chain. Another is dioctadecyl-aspartate-succinyl-acyclovir (DASA) with double C18 alkyl chains. They were prepared by the esterification of succinyl-acyclovir with the lipids, and sodium salts of them were also prepared. Guanine moieties and alkyl moieties bring the derivatives intermolecular hydrogen bonding and hydrophobic interaction in water separately. The forces are influenced by the number of alkyl chains and the charged state, and determine the solubility and the self-assembly behavior of the derivatives. The double alkyl-chain derivatives (DASA and DASA-Na) formed rigid Langmuir monolayers on air/water surface, while the single alkyl chain derivatives (SGSA and SGSA-Na) did not. However, cholesterol (Chol) could assist SGSA to form rigid monolayers through inserting into the alkyl chains of SGSA to mimic the second alkyl chain. SGSA self-aggregates in water were prepared by the injection method with tetrahydrofuran as solvent. Cuboid-like shape and nanoscale size demonstrated that SGSA self-aggregates were self-assembled nanoparticles. Shape, particle size, zeta potential and phase transition of the nanoparticles were characterized. And they showed an average size of 83.2 nm, a negative surface charge of -31.3-mV zeta potential and a gel-liquid crystalline phase transition of 50.38 degrees C. The formation mechanism of self-assembled nanoparticles was analyzed. Hydrophobic interaction of alkyl chains improves SGSA molecules to form bilayers, and then cuboid-like nanoparticles were obtained by layer-by-layer aggregation based on inter-bilayers hydrogen bonding. However, the charged guanine moieties make SGSA-Na lose the function of hydrogen bonding so that SGSA-Na only forms vesicles in water based on hydrophobic interaction. Strong hydrophobicity and wide-open rigid double alkyl chains of DASA and DASA-Na restrict self-assembly in water media, and no homogeneous suspensions were obtained. Therefore, the molecular self-assembly behavior of the long-chain alkyl derivatives of nucleoside analogues on water surface or in water media is determined by the number of alkyl chains and the charged state.     

Construction of higher-ordered monolayer membranes derived from archaeal membrane lipid-inspired cyclic lipids with longer alkyl chains

A series of artificial cyclic lipids that mimic archaeal membrane ones has been synthesized. The structural features of these molecules include a longer cyclic framework, in which the alkyl chain length ranges from 24 to 32 in carbon number, which is longer than our first analogous molecule with 20-carbon long alkyl chains [K. Miyawaki, T. Takagi, M. Shibakami, Synlett 8 (2002) 1326]. Microscopic observation reveals that these molecules have a self-assembling ability: hydration of the lipids yields multilamellar vesicles in aqueous solution and monolayer sheets on solid supports. High-sensitivity differential scanning calorimetry (24- and 28-carbon alkyl chain lipids) indicates that (i) the alkyl chain length affects their phase behavior and (ii) the enthalpies of endothermic peaks accompanied by phase transition were considerably lower than those of their monomeric phospholipid analogs. Fluorescence polarization measurements suggest that the membranes made from the 24-carbon alkyl chain lipid have a higher polarization factor than membranes composed of DMPC and DMPC plus cholesterol. These findings imply that the cyclic lipids containing 24- and 28-carbon alkyl chain construct well-organized monolayer membranes and, in particular, that the molecular order of the 24-carbon alkyl chain lipid is higher than that of bilayer membranes in the liquid-ordered phase.     

Crystallization of silver carboxylates from sodium carboxylate mixtures

Silver carboxylates can be made by the reaction of silver nitrate and the corresponding sodium carboxylates. The length of the alkyl chain has a significant impact on the product behavior. In this study, 18, 20, and 22 carbon chains (stearate, arachidate, and behenate, respectively) have been selected. All three sodium carboxylates are very insoluble in water at room temperature. Solutions are obtained above the Krafft temperature, which precipitates lamellar crystals if cooled at the proper cooling rate. Depending on the chain length, metastable morphologies, such as vesicles and tiny fibers, can be seen consecutively before hexagonal plates form. The carboxylate with the shorter chain length reaches equilibrium more quickly. All three silver carboxylates also take on a lamellar structure. Small-angle X-ray scattering (SAXS) shows that the d spacing of the crystals increases as the chain length increases. Cryo-TEM illustrates that the crystallites are the result of micelle nucleation and micelle aggregation. In addition, the crystallization process in the presence of silver bromide nanocrystals has been investigated. In the initial stage, an epitaxial interface is formed between the silver carboxylate crystallites and the cubic silver bromide grains. Budlike and strandlike structures grow because of it. The consequent strand enclosure restrains the crystal growth, which reduces the size and changes the morphology of the crystals.     

Novel hydrogels from diepoxy‐terminated poly(ethylene glycol)s and aliphatic primary diamines: synthesis and equilibrium swelling studies

New hydrogels were prepared from diepoxy‐terminated poly(ethylene glycol)s of approximate molecular weights 600, 1000, 2000, and 4000 Da and aliphatic primary diamines with different numbers of carbon atoms (ethylenediamine, 1,4‐diaminobutane, hexamethylenediamine, 1,8‐octanediamine, 1,10‐decanediamine, 1,12‐dodecanediamine), in water or ethanol–water mixture, depending on the amine solubility. The swelling behavior of these gels was tested in distilled water/aqueous solution at constant temperature and the equilibrium swelling degree (ESD) was determined for structurally different hydrogels and under various environmental conditions. It was shown that ESD was influenced by the molecular weight of PEG oligomers, amine/epoxy groups mole ratio, amine chain length, temperature, pH, and concentration of salts present in the swelling medium. Higher ESDs were obtained for either longer‐chain PEGs, non‐stoichiometric amine/epoxy groups ratio, shorter amines, acidic pH, lower temperatures, or in the absence of salts. Copyright © 2009 John Wiley & Sons, Ltd.     

Study on liquid crystallinity in 2,9-dialkylpentacenes

A series of semiconducting and symmetrical 2,9-dialkylpentacenes was successfully synthesized via a five-step process and their structures confirmed by ¹H NMR, IR and elemental analyses. Their liquid crystallinity was investigated by differential scanning calorimetry and polarizing optical microscopy. The introduction of alkyl chains also improved their solubility. For alkyl chains longer than butyl, focal conic or baton texture was observed, indicating the existence of an ordered smectic phase. Thermal analyses revealed that the both melting and smectic-isotropic transition temperatures show an odd-even effect when the alkyl chain is larger than heptyl or octyl. The synthesized compounds are promising candidates for semiconductors in organic field-effect transistors because their liquid crystallinity allows easy molecular alignment in the device fabrication process.     

Halochromism of N-phenoxide betaine dye in salt-containing poly(ethylene oxide) oligomers

The polarity of poly(ethylene oxide) (PEO) oligomers and PEO/salt mixed system was analyzed as the negative solvatochromism and halochromism of betaine dye, 2,6-diphenyl-4-(2,4,6-triphenylpyridinio) phenolate ( 1 ). The polarity of PEO oligomers, detected as the shift of the absorption maximum of the dye ( 1 ), decreased with increasing PEO chain length, reflecting the terminal hydroxyl group fraction. The polarity of the PEO matrix was the function of both lattice energy and cation radius of the added salt under the same salt concentration. There is a clear relation between the absorption maximum and the lattice energy of a series of salts having the same cation. The lattice energy of most salts was suggested to be estimated empirically by this relation.     

Protein-resistant poly(ethylene oxide)-grafted surfaces: chain density-dependent multiple mechanisms of action

A clear understanding of the mechanisms responsible for the protein-resistant nature of end-tethered poly(ethylene oxide) (PEO) surfaces remains elusive. A barrier to improved understanding is the fact that many of the factors involved (chain length, chain density, hydration, conformation, and distal chemistry) are inherently correlated. We hypothesize that, by comparing systems of variable but precisely known chain density, it should be possible to gain additional insight into the effects of the other factors. To evaluate this hypothesis, chain-end-thiolated PEOs were chemisorbed to gold-coated silicon wafers such that a range of chain densities was obtained. Three different PEOs were investigated: hydroxy-terminated chains of molecular weight 600 (600-OH), methoxy-terminated chains of molecular weight 750 (750-OCH3), and methoxy-terminated chains of molecular weight 2000 (2000-OCH3). In situ null ellipsometry was used to determine PEO chemisorption kinetics, ultimate PEO chain densities, protein adsorption kinetics, and ultimate protein adsorbed quantities. With this approach, it was possible to ascertain the effects of PEO distal chemistry (-OH, -OCH3), chain length, and layer hydration on protein adsorption. The data obtained suggested that properties related to chain density (conformational freedom, hydration) were the main determinants of protein resistance at chain densities up to a critical value of approximately 0.5 chain/nm2; at this value, protein adsorption was a minimum for the methoxy-terminated PEOs. For the hydroxyl-terminated PEO, adsorption leveled off at the critical value. Thus distal chemistry appears to be a major determinant of protein resistance at chain densities greater than the critical value.     

Imidazolium camphorsulfonamides: chiral catanionic liquid crystals with tunable thermal properties

We report the synthesis of novel chiral catanionic liquid crystals bearing camphorsulfonamide substructures. The phase behaviour of these long-chain substituted imidazolium sulphates and sulfonates was investigated using X-ray diffraction (XRD), polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). We observed that the phase behaviour clearly depends on the substitution of both cation and anion. The chiral camphorsulfonamide substructures have an unfavourable influence on the formation of liquid crystalline (LC-) phases. Contrary to N,N'-di-alkyl-imidazolium salts, the formation of LC phases was only observed when both cation and anion are substituted with long alkyl chains (C(12) or C(16)). Furthermore, the phase transition temperatures depend on the chain length of the alkyl groups, as higher phase transition temperatures were observed for compounds bearing longer alkyl chains. However, no macroscopic evidence for the formation of chiral mesophases was obtained.     

Relation between packing density and thermal transitions of alkyl chains on layered silicate and metal surfaces

Self-assembled layers of alkyl chains grafted onto the surfaces of layered silicates, metal, and oxidic nanoparticles are utilized to control interactions with external media by tuning the packing density of the chains on the surface, head group functionality, and chain length. Characterization through experiment and simulation shows that the orientation of the alkyl layers and reversible phase transitions on heating are a function of the cross-sectional area of the alkyl chains in relation to the available surface area per alkyl chain. On even surfaces, a packing density less than 0.2 leads to nearly parallel orientation of the alkyl chains on the surface, a high degree of conformational disorder, and no reversible melting transitions. A packing density between 0.2 and 0.75 leads to intermediate inclination angles, semicrystalline order, and reversible melting transitions on heating. A packing density above 0.75 results in nearly vertical alignment of the surfactants on the surface, a high degree of crystalline character, and absence of reversible melting transitions. Curved surfaces can be understood by the same principle, taking into account a local radius of curvature and a distance-dependent packing density on the surface. In good approximation, this simple model is independent from the length of the alkyl chains (a minimum length of C10 is required to form sufficiently distinctive patterns), the chemical nature of the surface, and of the surfactant head group. These structural details primarily determine the functionality of alkyl modified surfaces and the temperature of thermal transitions.