Diblock copolymers (BCPs) show phase separation on mesoscopic length scales and form ordered morphologies in both bulk and thin films, the latter resulting in nanostructured surfaces. Morphologies in thin films are strongly influenced by film parameters, the ratio of film thickness and bulk domain spacing. Laterally structured polymer surfaces may serve as templates for controlled assembly of nanoparticles (NPs). We investigated the BCP of poly(n-pentyl methacrylate) and poly(methyl methacrylate) which show bulk morphologies of stacked lamellae or hexagonally packed cylinders. Thin films were investigated by atomic force microscopy and grazing-incidence small-angle X-ray scattering. For film thicknesses f well below d bulk, standing cylinder morphologies were observed in appropriate molar ratios, while film thicknesses around and larger than d bulk resulted in cylinders arranged parallel to surface. To alter and/or improve the morphology also in presence of different NPs (e.g., silica, gold), solvent vapour annealing (SVA) was applied. The BCP morphology usually remains unchanged but periodicities change depending on type and amount of incorporated NPs. It was found that silica clusters enlarge lateral distances of cylinders, whereas Au NPs reduce it. The effect of SVA is weak. The quality of morphology is slightly improved by SVA and lateral distances remain constant or are slightly reduced.

The synthesis of materials via self-assembly typically involves the spontaneous and reversible organization of small building blocks for the purpose of creating conglomerate structures over larger length scales. This introductory article describes self-assembly processes on several length scales, from subnanometer up to millimeter scales, and briefly summarizes some of the incredible diversity of materials that exhibit selfassembly. Articles in this issue cover self-assembly using zeolitic structures, organic molecular crystals, block copolymers, surfactants, mesoscale templates, and soluble crystallization additives. Keywords: block copolymers, materials synthesis, self-assembly, surfactants, templates, zeolites.

Self-assembled block copolymer systems with an appropriate molecular weight to produce a length scale that will interact with visible light are an alternative platform material for the fabrication of large-area, well-ordered photonic-bandgap structures at visible and near-IR frequencies.Over the past years, one-, two-, and three-dimensional photonic crystals have been demonstrated with various microdomain structures created through microphase separation of block copolymers. The size and shape of periodic microstructures of block copolymers can be readily tuned by molecular weight, relative composition of the copolymer, and blending with homopolymers or plasticizers.The versatility of photonic crystals based on block copolymers is further increased by incorporating inorganic nanoparticles or liquid-crystalline guest molecules (or using a liquid-crystalline block), or by selective etching of one of the microdomains and backfilling with high-refractive-index materials. This article presents an overview of photonic-bandgap materials enabled by self-assembled block copolymers and discusses the morphology and photonic properties of block-copolymer-based photonic crystals containing nanocomposite additives.We also provide a view of the direction of future research, especially toward novel photonic devices.

The following article is an edited transcript based on the David Turnbull Lecture given by Frank S. Bates of the University of Minnesota on December 1, 2004, at the Materials Research Society Fall Meeting in Boston. Bates received the award for “pioneering contributions to the fundamental understanding of structure and properties of complex polymeric materials, particularly block copolymers and polymeric vesicles, coupled with outstanding lecturing, writing, teaching, and educational leadership.” This article outlines the research accomplishments of a group of Bates' students that provide fresh insights into the molecular factors governing complex self-assembly in block copolymers. Three triply periodic and multicontinuous network phases were discovered in poly(isoprene-bstyrene-b-ethylene oxide) (ISO) triblock copolymers.Two cubic phases (Q230 and Q214) and an orthorhombic phase (O70) were identified using small-angle x-ray scattering (SAXS), transmission electron microscopy (TEM), birefringence measurements, and dynamic mechanical spectroscopy, along with level-set modeling. These findings establish a concrete strategy for locating potentially valuable network morphologies in ABC triblock copolymer melts.

Hot-melt adhesives facilitate fast production processes because the adhesives set simply by cooling. Formulations contain polymers to provide strength and hot tack (resistance to separation while adhesive is hot), and tackifiers and/or oils to dilute the polymer entanglement network, adjust the glass-transition temperature, lower the viscosity, and improve wet-out (molecular contact of the adhesive with the substrate over the entire bonding area). Some adhesives also contain waxes to speed setting, lower viscosity, and improve heat resistance. Obtaining adequate strength and heat resistance from nonreactive hot melts requires that some component of the hot melt separate out into a dispersed but interconnected hard-phase network upon cooling. The hard phases are commonly either glassy styrene domains (for adhesives based on styrenic block copolymers) or organic crystallites (for adhesives based on waxes, olefinic copolymers, or ethylene copolymers). This article will describe first the material properties relevant to the processing and performance of hot-melt adhesives, then the chemistry and function of the specific raw materials used in hot melts, and will conclude with illustrative application examples and corresponding formulations.

Self-adhesive materials are called, in the adhesives trade, “pressure-sensitive adhesives” (PSAs). PSAs are designed to stick on almost any surface by simple contact under light pressure. This special class of adhesives does not undergo any physical transformation or chemical reaction during the bonding process. Because of this, the rheological properties of the adhesive must be finely tuned for the application, combining a carefully chosen polymer architecture and monomer composition with the proper addition of small molecules called tackifying resins. PSAs are soft, deformable solids and, depending on the formulation, easily form bridging fibrils between two surfaces upon debonding. They are safe to use and easy to handle and thus are increasingly replacing more conventional types of adhesives. In this article, we review both the primary material characteristics of PSAs and the main physical principles that make them work effectively.