Björn Lindman

Micelles. Physical chemistry of surfactant association

Abstract Molecules or ions which are amphiphilic, i.e. contain at the same time a hydrophilic and a hydrophobic (normally an alkyl chain) part frequently display in aqueous solutions a characteristic strongly cooperative association into colloidal aggregates termed micelles. A general treatment of micellization and related phenomena is given in order to provide an understanding on a molecular level. Hydrophobic interactions are the driving force in micellization but the inclusion of hydrophilic group interactions is required in the thermodynamic description. Intra- and intermicellar electrostatic repulsions are discussed in connection with the changes in micelle shape occuring at higher concentrations or at addition of electrolyte etc. The kinetics of micelle formation is characterized by two greatly different time constants, the rapid one referring to the micelle-monomer exchange and the other to the dissolution and formation of micelles. A large number of physico-chemical methods applicable to the study of micelle formation are surveyed with special emphasis on recent spectroscopic approaches which give a detailed insight into structure, dynamics and interactions. For example, the hydrocarbon chains are characterized by a rapid but slightly hindered motion. The polar head-groups are hydrated while otherwise no appreciable water-amphiphile contact occurs in the micelles. The binding of small counter-ions to micelles of ionic amphiphiles is characterized by a marked specificity affecting both spectroscopic and macroscopic properties. The phenomena of solubilization, mixed micelle formation and micellar catalysis are discussion on a molecular basis as well as the formation of reversed micelles and amphiphile aggregation in non-aqueous media. The biological implications of micelle formation are briefly indicated.

Association and segregation in aqueous polymer/polymer, polymer/surfactant, and surfactant/surfactant mixtures: similarities and differences

Abstract Recent experimental findings on the phase behaviour of aqueous polymer/surfactant mixtures are reviewed and compared with the phase behaviour of “analogous” polymer/polymer or surfactant/surfactant mixtures, which is also reviewed. Polyelectrolyte effects are given special consideration. Attention is drawn to the polymer aspect of a surfactant aggregate, and, also, to the surfactant aspect of an hydrophobe-modified polymer. It is proposed that a consideration of these aspects should be helpful in predicting the phase behaviour of polymer/surfactant mixtures.

Rationalizing cellulose (in)solubility: reviewing basic physicochemical aspects and role of hydrophobic interactions

Despite being the world’s most abundant natural polymer and one of the most studied, cellulose is still challenging researchers. Cellulose is known to be insoluble in water and in many organic solvents, but can be dissolved in a number of solvents of intermediate properties, like N-methylmorpholine N-oxide and ionic liquids which, apparently, are not related. It can also be dissolved in water at extreme pHs, in particular if a cosolute of intermediate polarity is added. The insolubility in water is often referred to strong intermolecular hydrogen bonding between cellulose molecules. Revisiting some fundamental polymer physicochemical aspects (i.e. intermolecular interactions) a different picture is now revealed: cellulose is significantly amphiphilic and hydrophobic interactions are important to understand its solubility pattern. In this paper we try to provide a basis for developing novel solvents for cellulose based on a critical analysis of the intermolecular interactions involved and mechanisms of dissolution.

Vesicle Formation and General Phase Behavior in the Catanionic Mixture SDS−DDAB−Water. The Anionic-Rich Side

Catanionic mixtures are aqueous mixtures of oppositely charged surfactants which display novel phase behavior and interfacial properties in comparison with those of the individual surfactants. One phase behavior property is the ability of these systems to spontaneously form stable vesicles at high dilution. The phase behavior of the mixture sodium dodecyl sulfate (SDS) didodecyldimethylammonium bromide (DDAB) in water has been studied in detail, and two regions of isotropic vesicular phases (anionic-rich and cationic-rich) were identified. Cryo-transmission electron microscopy allowed direct visualization of relatively small and polydisperse unilamellar vesicles on the SDS-rich side. Monitoring of the microstructure evolution from mixed micelles to vesicles as the surfactant mixing ratio is varied toward equimolarity was also obtained. Further information was provided by water self-diffusion measurements by pulsed field gradient spin-echo NMR. Water molecules can be in fast or slow exchange between the inside and outside of the vesicle with respect to the experimental time scale, depending on membrane permeability and vesicle size. For the SDSrich vesicles, a slow-diffusing component of very low molar fraction observed for the echo decays was traced down to very large vesicles in solution. Light microscopy confirmed the presence of vesicles of several microns in diameter. Thus, polydispersity seems to be an inherent feature of the system.

Surfactant-polymer interactions

Whereas mixed solutions of a homopolymer and a surfactant show interesting analogies with mixed polymer solutions, it has been demonstrated recently that mixtures of hydrophobically modified water-soluble polymers and surfactants show analogies with mixed surfactant systems. Other recent progress has concerned the micellization of an ionic surfactant on a polyelectrolyte chain, the behavior of polymers in the presence of connected surfactant self-assemblies, and surfactant micellization in covalent polymer gels.

Relationship between the physical shape and the efficiency of oligomeric chitosan as a gene delivery system in vitro and in vivo

Chitosans of high molecular weights have emerged as efficient nonviral gene delivery systems, but the properties and efficiency of well‐defined low molecular weight chitosans (<5 kDa) have not been studied. We therefore characterized DNA complexes of such low molecular weight chitosans and related their physical shape and stability to their efficiency as gene delivery systems in vitro and in vivo.

Fourier transform NMR self-diffusion and microemulsion structure

A novel Fourier transform pulsed-gradient spin-echo 1H and 13C NMR method was employed to obtain multicomponent self-diffusion data for seven microemulsion systems. These included ionic surfactant-cosurfactant (short- or long-chain alcohol)-hydrocarbon-water, nonionic surfactant-hydrocarbon-water, and ionic surfactant (of the swelling type)-hydrocarbon-water systems. For the short-chain alcohol (butanol or pentanol) systems both water, hydrocarbon, and alcohol self-diffusion are very rapid over wide concentration regions. In contrast to micellar solutions and certain liquid crystalline phases there is apparently no marked separation into hydrophobic and hydrophilic domains; this is considered to be due to the alcohol having a compatibility with both aqueous and hydrocarbon environments as well as internal interfaces. There appear to be no extended well-defined structures in these systems. Instead the microemulsions are argued to have very flexible and low-order internal interfaces which open up and reform at a short time scale. It seems reasonable to assume a polydispersity in aggregate size and shape and it appears to be a clear possibility that there are mainly quite small aggregates. The nonionic surfactant system shows strong resemblances to the short-chain alcohol system while the remaining systems (long-chain alcohol or absence of alcohol) show a more pronounced separation into hydrophobic and hydrophilic regions.

Self-organization of double-chained and pseudodouble-chained surfactants: counterion and geometry effects

Self-organization in aqueous systems based on ionic surfactants, and their mixtures, can be broadly understood by a balance between the packing properties of the surfactants and double-layer electrostatic interactions. While the equilibrium properties of micellar systems have been extensively studied and are understood, those of bilayer systems are less well characterized. Double-chained and pseudodouble-chained (or catanionic) surfactants are among the amphiphiles which typically form bilayer structures, such as lamellar liquid-crystalline phases and vesicles. In the past 10-15 years, an experimental effort has been made to get deeper insight into their aggregation patterns. With the double-chai ed amphiphiles, by changing counterion, adding salt or adding anionic surfactant, there are possibilities to depart from the bilayer aggregate in a controlled manner. This is demonstrated by several studies on the didodecyldimethylammonium bromide surfactant. Mixtures of cationic and anionic surfactants yield the catanionics, surfactants of the swelling type, and also show a rich phase behavior per se. A variety of liquid-crystalline phases and, in dilute regimes, equilibrium vesicles and different micellar shapes are often encountered. Phase diagrams and detailed structural studies, based on several techniques (NMR, microscopy and scattering methods), have been reported, as well as theoretical studies. The main features and conclusions emerging from such investigations are presented

DNA interactions with polymers and surfactants

Preface. Contributors. 1 Polyelectrolytes. Physicochemical Aspects and Biological Significance (Magnus Ullner). 1.1 Introduction. 1.2 Polyelectrolytes and Biological Function. 1.3 Electrostatic Interactions. 1.4 Solution Properties. 1.5 Flexibility. References. 2 Solution Behavior of Nucleic Acids (Rita S. Dias). 2.1 Biological Function of Nucleic Acids. 2.2 Discovery of DNA. 2.3 Structure of Nucleic Acids. 2.4 Nuclei Acids Nanostructures. 2.5 Behavior of DNA in Solution. 2.6 Melting of Double-Stranded DNA. Acknowledgments. References. 3 Single DNA Molecules: Compaction and Decompaction (Anatoly A. Zinchenko, Olga A. Pyshkina, Andrey V. Lezov, Vladimir G. Sergeyev, and Kenichi Yoshikawa). 3.1 Introduction. 3.2 Condensation and Compaction of DNA by Surfactants. 3.3 DNA Condensation by Cationic Liposomes. 3.4 DNA Compaction and Decompaction by Multivalent Cations. 3.5 DNA Compaction by Polycations. 3.6 Compaction of DNA in a Crowded Environment of Neutral Polymer. 3.7 Conclusion. References. 4 Interaction of DNA with Surfactants in Solution (Rita S. Dias, Kenneth Dawson, and Maria G. Miguel). 4.1 Introduction. 4.2 DNA-Cationic Surfactant Interactions. 4.3 DNA Covalent Gels and Their Interaction with Surfactants. 4.4 Applications. Acknowledgments. References. 5 Interaction of DNA with Cationic Polymers (Eric Raspaud, Adriana C. Toma, Francoise Livolant, and Joachim Radler). 5.1 Introduction. 5.2 Theory of DNA Interacting with Polycations. 5.3 Condensation of DNA, Phase Diagram, and Structure. 5.4 Formation of Polycation-DNA Complexes: Polyplexes. 5.5 DNA-Nanoparticles for Gene Delivery. 5.6 Cellular Uptake and Intracellular Interactions of Polyplexes. 5.7 Conclusion. Acknowledgment. References. 6 Interactions of Histones with DNA: Nucleosome Assembly, Stability, Dynamics, and Higher Order Structure (Karsten Rippe, Jacek Mazurkiewicz, and Nick Kepper). 6.1 Introduction. 6.2 Histones. 6.3 Structure of Histone-DNA Complexes. 6.4 Assembly of Nucleosomes and Chromatosomes. 6.5 Stability and Dynamics of Nucleosomes. 6.6 Higher Order Chromatin Structures. Acknowledgments. References. 7 Opening and Closing DNA: Theories on the Nucleosome (Igor M. Kulic and Helmut Schiessel). 7.1 Introduction. 7.2 Unwrapping Nucleosomes. 7.3 Nucleosome Sliding. 7.4 Transcription Through Nucleosomes. 7.5 Tail Bridging. 7.6 Discussion and Conclusion. Acknowledgment. References. 8 DNA-DNA Interactions (Lars Nordenskiold, Nikolay Korolev, and Alexander P. Lyubartsev). 8.1 Introduction. 8.2 The Statistical Polymer Solution Model Predicts DNA Collapse/Aggregation Phase Behavior. 8.3 DNA in Solution is Condensed to a Compact State by Multivalent Cationic Ligands. 8.4 Ion Correlation Effects Included in Theory and in Computer Modeling Explain DNA-DNA Attraction. 8.5 Conclusions and Future Prospects. References. 9 Hydration of DNA-Amphiphile Complexes (Cecilia Leal and Hakan Wennerstrom). 9.1 Introduction. 9.2 General Properties of DNA Double Helices and Cationic Aggregates. 9.3 Thermodynamics of DNA-Amphiphile Complexes. 9.4 Molecular Properties of DNA-Amphiphile Complexes. 9.5 Concluding Remarks. References. 10 DNA-Surfactant/Lipid Complexes at Liquid Interfaces (Dominique Langevin). 10.1 Introduction. 10.2 Soluble Surfactants. 10.3 Insoluble Surfactants. 10.4 Lipids. 10.5 Mixtures of Surfactants and Lipids. 10.6 Conclusion. References 286 11 DNA and DNA-Surfactant Complexes at Solid Surfaces (Marite Cardenas and Tommy Nylander). 11.1 Introduction. 11.2 Adsorption of DNA at Surfaces. 11.3 Attachment of DNA Surfaces-Strategies and Challenges. 11.4 DNA Structure on Surfaces-Comparison with Highly Charged Polyelectrolytes. 11.5 Some Applications-Arrays and Nanostamping. Acknowledgments. References. 12 Role of Correlation Forces for DNA-Cosolute Interactions (Malek O. Khan). 12.1 Introduction. 12.2 Experimental Evidence of DNA Condensation Induced by Electrostatic Agents. 12.3 Simulations Used to Characterize the DNA Compaction Mechanism. 12.4 Ion Correlations Limiting the Validity of DLVO Theory. 12.5 Ion Correlations Driving the Compaction of DNA. 12.6 Conformation of Compact DNA-The Coil to Toroid Transition. 12.7 Conclusions. References. 13 Simulations of Polyions: Compaction, Adsorption onto Surfaces, and Confinement (A.A.C.C. Pais and P. Linse). 13.1 Introduction. 13.2 Models. 13.3 Solutions of Polyions with Multivalent Counterions. 13.4 Polyion Adsorption onto Charged Surfaces. 13.5 Polyions in Confined Geometries. 13.6 Concluding Remarks. References. 14 Cross-linked DNA Gels and Gel Particles (Diana Costa, M. Carmen Moran, Maria G. Miguel, and Bjorn Lindman) 14.1 Introduction. 14.2 Covalently Cross-Linked DNA Gels. 14.3 ds-DNA versus ss-DNA: Skin Formation. 14.4 DNA Gel Particles. 14.5 Physical DNA Gels. References. 15 DNA as an Amphiphilic Polymer (Rita S. Dias, Maria G. Miguel, and Bjorn Lindman). 15.1 Some General Aspects of Self-Assembly. 15.2 Illustrations. References. 16 Lipid-DNA Interactions: Structure-Function Studies of Nanomaterials for Gene Delivery (Kai K. Ewert, Charles E. Samuel, and Cyrus R. Safinya). 16.1 Introduction. 16.2 Formation and Structures of CL-DNA Complexes. 16.3 Effect of the Lipid-DNA Charge Ratio ( r chg) on CL-DNA Complex Properties. 16.4 Effect of the Membrane Charge Density (sM) on CL-DNA Complex Properties. 16.5 Effect of Nonlamellar CL-DNA Complex Structure on the Transfection Mechanism. 16.6 Model of Transfection with Lamellar CL-DNA Complexes. 16.7 Model of Transfection with Inverted Hexagonal CL-DNA Complexes. 16.8 PEGylated CL-DNA Complexes: Surface Functionalization and Distinct DNA-DNA Interaction Regimes. 16.9 Conclusion and Summary. Acknowledgments. References. Index.

1H, 13C, 35Cl, and 81Br NMR of aqueous hexadecyltrimethylammonium salt solutions: Solubilization, viscoelasticity, and counterion specificity

Abstract A combination of 1H, 13C, 35Cl, and 81Br NMR is used to investigate counterion specificity and solubilization behavior of hexaldecyltrimethylammonium micelles. The concentration dependence of the quadrupole relaxation of 81Br− and 35Cl− counterions in aqueous solutions of hexadecyltrimethylammonium bromide (CTAB) and chloride (CTAC), respectively, is found to be quite different and this can be referred to the formation of large elongated micelles in the former case but not in the latter. This striking difference is maintained in solutions containing both CTAB and CTAC. This is attributed to the coexistence of two types of micelles and a considerable specificity in the counterion binding, the Br− ions having a preference for the cylindrical and the Cl− ions for the globular micelles. For mixtures of CTAB with tetradecyltrimethylammonium chloride (TTAC), the same type of counterion specificity in 35Cl and 81Br NMR was observed as for mixtures of CTAB and CTAC. The 13C chemical shifts are closely the same for solutions of either CTAB, CTAC, or TTAC, but in mixtures of CTAB + TTAC or CTAC + TTAC there is a marked splitting of the ω-CH3 resonance into two peaks. This is referred to alkyl chain packing disturbances in mixed micelles of two amphiphiles with different alkyl chain lengths. 1H and 13C NMR were employed to study the solubilization site for viscoelastic solutions of CTAB and 1-methylnaphthalene. A highly variable effect along the amphiphile chain was observed for both 1H and 13C relaxation and shielding. It could be established that solubilization of 1-methylnaphthalene occurs toward the polar part of CTAB micelles, about seven methylenes being affected appreciably. Chain flexibility is found to be influenced in a complex way by solubilization.