To quantify the swelling response of polyelectrolyte dendrimers in aqueous solutions as affected by changes in solution conditions, we have studied eighth generation, G8, poly(amidoamine) (PAMAM) dendrimers in D 2O using small-angle neutron scattering. The charge density is manipulated by varying the pH of the solution in order to protonate and deprotonate the primary and tertiary amines. The coherent scattered intensity at high q values yields size information from the form factor of individual dendrimers. The distance distribution functions of the dendrimers in a variety of experimental situations were determined by indirect Fourier transform. For all the conditions studied, we find that the size of G8 dendrimers is essentially insensitive to variations of the pH (4.7 < pH < 10.1) and of ionic strength (up to 3 M of NaCl). In all cases, the scattering curves yield density profiles that correspond well to a uniform sphere with a radius of gyration R G ) 4.0 ( 0.15 nm. We conclude that the dendrimer size is essentially independent of the charge density or ionic strength of the solvent, contrary to the predictions of current models and simulations.

Data visualization plays a crucial role in our society, as illustrated by the many displays that surround us. In the future, displays may become even more pervasive, ranging from individually addressable image-rendering wall hangings to data displays integrated in clothes. Liquid-crystal displays (LCDs) provide most of the flat-panel displays currently used. To keep pace with the ever-increasing possibilities afforded by developments in information technology, we need to develop manufacturing processes that will make LCDs cheaper and larger, with more freedom in design. Existing batch processes for making and filling LCD cells are relatively expensive, with size and shape limitations. Here we report a cost-effective, single-substrate technique in which a coated film is transformed into a polymer-covered liquid-crystal layer. This approach is based on photo-enforced stratification: a two-step photopolymerization-induced phase separation of a liquid-crystal blend and a polymer precursor. The process leads to the formation of micrometre-sized containers filled with a switchable liquid-crystal phase. In this way, displays can be produced on a variety of substrates using current coating technology. The developed process may be an important step towards new technologies such as 'display-on-anything' and 'paintable displays'.

The phase separation kinetics of ultrathin deuterated poly(styrene)/poly(butadiene) polymer blend films spun cast onto striped self-assembled monolayer (SAM) substrates is studied by atomic force microscopy (AFM). Fourier transform analysis of the AFM topographic data at various stages of the film pattern development reveals the presence of quantized surface deformation modes. These modes are excited by the phase separation process when the scale of phase separation becomes commensurate with the period of the striped surface pattern. Thus, higher frequency modes become excited at early stages of phase separation, and these excitations decay with time as the phase separation pattern further coarsens. The film ultimately self-organizes into a periodic structure in which the fundamental mode has the largest amplitude. The influence of film thickness on the film morphology in this late stage is also investigated. A decrease in the film thickness leads to surface patterns that match those of the SAM substrates with increasing resolution. However, these film patterns break up into droplet arrays along the SAM stripes if the films are made too thin. This phenomenon is attributed to a capillary wave instability.

We studied the swelling and elastic behavior of chemically cross-linked [2-(methacryloyloxy)ethyltrimethylammonium chloride−2-(acrylamido)-2-ethylpropanesulfonate] polyampholyte gels in equilibrium with saline solutions. The net charge of the polymer network and the ionic strength of the swelling solvent are crucial parameters governing the properties of the gels. The swelling equilibrium behavior of gels with a strong charge imbalance was analogous to polyelectrolyte systems (monotonic decrease of swelling ratio with rising salt concentration). Globally neutral gels showed an antipolyelectrolyte behavior (collapse at low ionic strength and monotonic increase of swelling ratio with rising salt concentration). Weakly unbalanced polyampholyte gels showed a characteristic minimum in their swelling curves, the same gel reaching the same equilibrium volume in two different ionic conditions. The internal structure was imaged using differential interference contrast microscopy and revealed that morphological modifications of the gel structure accompany volume variations. The evolution of the elastic modulus of polyampholyte gels at equilibrium is quite complex, because the same sample can behave like a polyelectrolyte in low ionic strength conditions and as a balanced polyampholyte at high ionic strength. Thus a polyampholyte gel can reach the same swelling ratio at equilibrium for two different ionic strengths, but is then characterized by two different values of the shear modulus.