A bit of historyThe key role of surfaces for many material properties as well as for many biological processes has been recognized now. Therefore, new strategies aim at the tailoring of the material's surface only -or of a thin surface layer, respectively -, while preserving the bulk properties of the underlying support. Particular emphasis has been given to the surface modification by polymers, in an attempt to extend the known versatility of polymer bulk materials to ultrathin films and coatings, and to prepare bulk-surface composite materials. The self-organization of polymers has been increasingly explored for the preparation of well-defined surfaces and interfaces in recent years, extending the use of the established methods of low molar mass compounds (for comparative reviews, see ref. 1-3)). With such techniques, polymer films are formed spontaneously on substrates, due to balanced interactions between substrate, polymer (or its precursor) and medium. Typically, very thin, often monomolecular layers are produced. Repetitive deposition steps provide a precise control over the total thickness of the coatings, in the range from a few angstroms up to the micrometer range. Moreover, the step-by-step procedures allow for a fine structuring in the third dimension. In addition to the preparation of uniform and homogeneous coatings, gratings, gradients or steps of defined height in molecular dimensions can be easily constructed.The most recent of the self-organization techniques is the alternating physisorption of oppositely charged polyelectrolytes, the so-called "layer-by-layer" method or "electrostatic self-assembly" (ESA) [3][4][5][6][7][8][9][10] . Although some early, singular studies of self-assembly by alternating adsorption of oppositely charged polyions are reported [11][12][13] , a practical method for ESA was developed Feature Article: The article presents the state-of-the-art of alternating physisorption of oppositely charged polyelectrolytes, the so-called "layer-by-layer" method or "electrostatic self-assembly" (ESA), for the preparation of thin polymer coatings. In comparison to other, more established self-organization techniques, this recent method is distinguished by its simplicity, versatility, and speed. In particular, the tendency for self-healing is unique. Emphasis is given to the role of the molecular structure of the polyelectrolytes, and to the nature of the support. Also, various parameters for the preparation of multilayer films are highlighted, which are very important due to the kinetic control of the build-up process. The structure of the resulting coatings, their quality and stability, chemical reactions in the films, and potential applications are discussed.Macromol. Rapid Commun. 21, No. 7

Water-soluble block copolymers were prepared from the nonionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermoresponsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0 and 100 degrees C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates which switch reversibly can be prepared in water, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus.

Abstract:The structures and synthesis of polyzwitterions ("polybetaines") are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of "click" chemical reactions is presented. Furthermore, the emerging topic of responsive ("smart") polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples.

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Like a doughnut with a raspberry filling: ABC triblock copolymers, composed of a hydrophilic block with morpholinium units (blue in the picture), a hydrophobic hydrocarbon block (red), and a hydrophobic fluorocarbon‐rich block (black), self‐assemble in water to form multicompartment micelles with a hydrophilic corona and a hydrophobic core with nanometer‐scale subdomains.

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Thermal properties of the novel, double thermosensitive block copolymer, poly(N-isopropyl acrylamide)block-poly (3-[N-(3-methacrylamido-propyl)-N,N-dimethyl]-ammonio propane sulfonate) (PNIPA-b-PSPP) have been studied in pure and saline (NaCl) aqueous solutions by dynamic laser light scattering. The block copolymer [Mn(PNIPA) ) 10 800 g/mol and Mn(PSPP) ) 9700 g/mol] exhibits both upper (UCST about 9 °C) and lower (LCST about 32 °C) critical solution temperatures in pure water. The addition of NaCl enhances the solubility of the zwitterionic block, PSPP, leading to the disappearance of the UCST. On the other hand, the solubility of PNIPA in water decreases as NaCl is added. At 20 °C, the copolymer shows a bimodal size distribution through the NaCl concentration range of 0-0.93 M above a certain limiting polymer concentration. The slow and fast components of the diffusion coefficients of the polymer have been calculated. A gradual addition of salt turns the mutual interactions from zwitterionic attractions between PSPP blocks to hydrophobic attractions between PNIPA blocks. The formation of the aggregates and the aggregate sizes at T < UCST and T > LCST are influenced by polymer and salt concentrations. Below the UCST, the aggregates in saline polymer solutions are somewhat larger than those in pure polymer solutions. Above LCST, the aggregate size is determined by the salt concentration.