A new class of epoxy nanocomposites with completely defined organic/inorganic phases was prepared by reacting octakis(glycidyldimethylsiloxy)octasilsesquioxane [(glydicylMe(2)SiOSiO(1.5))(8)] (OG) with diaminodiphenylmethane (DDM) at various compositional ratios. The effects of reaction curing conditions on nanostructural organization and mechanical properties were explored. A commercial epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) was used as a reference material throughout these studies. FTIR was used to follow the curing process and to demonstrate that the silsesquioxane structure is preserved during processing. OG/DDM composites possess comparable tensile moduli (E) and fracture toughness (K(IC)) to, and better thermal stabilities than, DGEBA/DDM cured under similar conditions. Dynamic mechanical analysis and model reaction studies suggest that the maximum cross-link density is obtained at N = 0.5 (NH(2):epoxy groups = 0.5) whereas the mechanical properties are maximized at N = 1.0. Digestion of the inorganic core with HF followed by GPC analysis of the resulting organic tether fragments when combined with the model reaction studies confirms that, at N = 0.5, each organic tether connects four cubes, while, at N = 1.0, linear tethers connecting two cubes dominate the network structure. Thus, well-defined nanocomposites with controlled variation of the organic tether architecture can be made and their properties assessed.

Barrier function of hair follicles (HFs) is of great interest because they might be an entry port for allergens/pathogens, but could on the other hand be used for drug delivery or vaccination. Therefore we investigated tight junction (TJ) barrier function in human HFs. We show that there is a TJ barrier in the outermost living layer bordering to the environment from the infundibulum to the lower central part and between Henle’s and Huxles layer of anagen HFs. In club hair typical for catagen and telogen HFs a TJ barrier is found surrounding the club. This demonstrates that there is a continuous TJ barrier along interfollicular epidermis and HFs in different phases of HF cycle. However, interestingly, in cell culture experiments we can show that barrier is less tight in HF keratinocytes compared to interfollicular keratinocytes. Knock-down of the TJ protein claudin-1, which we demonstrate here to be less expressed in HFs of lesional atopic dermatitis skin, results in impaired barrier function, decreased proliferation and increased apoptosis of hair keratinocytes. This is in line with a hair growth phenotype in claudin-1 deficient patients (NISCH syndrome) and corresponding knock-out mice and indicates an important role of claudin-1 in HF barrier function and growth.

Octafunctionalized silsesquioxanes [(RSiO!.5)8, cubes] offer potential as rigid, hard nanoplatforms to which a variety of organofunctional groups can be appended. Crosslinking these groups leads to novel organic/inorganic nanocomposites that consist primarily of interfacial interactions. These materials can be 100% interphase. We present efforts to develop nanocomposite materials that consist of both continuous and discontinuous organic/inorganic phases. We then discuss methods of probing the properties of these materials. INTRODUCTIONTwo general principles are often used to describe the origin of macroscopic properties in materials. The first is, "Intrinsic materials properties and processing taken together define microstructure." The second is,"Intrinsic materials properties and microstructure together define global properties."With the advent of chemical processing of materials, one can often replace the term microstructure with nanostructure.A less encompassing general principle is that "Control at the finest scales gives the highest homogeneity, thereby providing the highest reproducibility, predictability and ability to tailor properties." This principle is less encompassing because we often would like to prepare materials with "controlled heterogeneity," ie. composite materials. We may generally describe composites as materials that combine two (or more) materials and microstructures. In composite manufacture, the goal is usually to achieve properties that are more than the sum of the properties of the individual components; however, it is often possible to estimate the properties of typical composites using the rule of mixtures. The utility of the rule of mixtures in predicting properties is greatly diminished when applied to nanocomposites.