Nanoporous membranes containing monodisperse pores of 24 nm diameter are fabricated using poly(styrene-b-lactide) block copolymers to template the pore structure. A 4 mum thin film of the block copolymer is cast onto a microporous membrane that provides mechanical reinforcement; by casting the copolymer film from the appropriate solvents and controlling the solvent evaporation rate, greater than 100 cm(2) of a thin film with polylactide cylinders oriented perpendicular to the thin dimension is produced. Exposing the composite membrane to a dilute aqueous base selectively etches the polylactide block, producing the porous structure. The ability of these pores to reject dissolved poly(ethylene oxide) molecules of varying molecular weight matches existing theories for transport through small pores.

Highly immiscible block copolymers are attractive materials for applications in nanolithography due to their ability to self-assemble on length scales that are difficult to access by conventional lithography. The incorporation of inorganic domains into such block copolymers provides etch contrast that can potentially reduce processing times and costs in nanolithographic applications. We explored thin films of polylactide-poly(dimethylsiloxane)-polylactide (PLA-PDMS-PLA) triblock copolymers as multifunctional nanolithographic templates. We demonstrate the formation of well-ordered arrays of hexagonally packed PDMS cylinders oriented normal to the substrate, the orthogonal etchability of these cylinders and the PLA matrix, and the formation of etch-resistant domains that can be used as pattern transfer masks.

Although nanolithographic techniques based on self-assembled block copolymer templates offer tremendous potential for fabrication of large-area nanostructure arrays, significant difficulties arise with both the lift-off and etch processes typically used for pattern transfer. These become progressively more important in the limit of extreme feature sizes. The few techniques that have been developed to avoid these issues are quite complex. Here, we demonstrate successful execution of a nanolithographic process based on solvent annealed, cylinder-forming, easily degradable, polystyrene-b-polylactide block copolymer films that completely avoids lift-off in addition to the most challenging aspects of etching. We report a "Damascene-type" process that overfills the polystyrene template with magnetic metal, employs ion beam milling to planarize the metal surface down to the underlying polystyrene template, then exploits the large etch rate contrast between polystyrene and typical metals to generate pattern reversal of the original template into the magnetic metal. The process is demonstrated via formation of a large-area array of 25 nm diameter ferromagnetic Ni(80)Fe(20) nanodots with hexagonally close-packed order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation. We argue that the approach is generalizable to a wide variety of materials, is scalable to smaller feature sizes, and critically, minimizes etch damage, thus preserving the essential functionality of the patterned material.

A general method for preparation of large-area inorganic nanostructure arrays based on the use of core-shell cylinder forming ABC triblock terpolymers is presented. The essential perpendicular cylinder alignment is achieved by the use of a low surface energy B block (polyisoprene), which drives spontaneous perpendicular alignment of cylindrical C domains (polylactide) in a matrix of A (polystyrene), eliminating the lengthy anneal steps, external field alignment procedures, or specialized surface preparations that could severely restrict potential applications.

Superabsorbent polymers have been around for nearly half a century. Presently, petroleum-based polyacrylic acid-type polymers are used in the majority of superabsorbent applications and markets. However, the rising costs of petroleum and the lack of a sustainable supply of fossil-based chemicals is driving a need for alternative, renewable based chemicals. Herein, we report the synthesis and superabsorbent properties of novel polymers derived from nature. Free-radical, emulsion polymerization methods were used to generate cross-linked polyacrylates containing lactone functionality, which were saponified into the corresponding cross-linked ionomers in a second step. The final cross-linked products displayed >50× absorption of water per weight of polymer and absorption under load of >15× the weight of saline solution per weight of polymer. The technology also offers the opportunity to perform additional chemistry and modification to the polymer backbone in order to improve its properties.