Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies

In this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies

Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies

In this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies

The National Center for Radioecology (NCoRE): A Network of Excellence for Environmental and Human Radiation Risk Reduction -13365

ABSTRACT Radioecology in the United States can be traced back to the early 1950s when small research programs were established to address the fate and effects of radionuclides released in the environment from activities at nuclear facilities. These programs focused primarily on local environmental effects, but global radioactive fallout from nuclear weapons testing and the potential for larger scale local releases of radioisotopes resulted in major concerns about the threat, not only to humans, but to other species and to ecosystems that support all life. These concerns were shared by other countries and it was quickly recognized that a multi-disciplinary approach would be required to address and understand the implications of anthropogenic radioactivity in the environment. The management, clean-up and long-term monitoring of legacy wastes at Department of Energy (DOE), Department of Defense (DOD), and Nuclear Regulatory Commission (NRC)-regulated facilities continues to be of concern as long as nuclear operations continue. Research conducted through radioecology programs provides the credible scientific data needed for decision-making purposes. The current status of radioecology programs in the United States are: fragmented with little coordination to identify national strategies and direct programs; suffering from a steadily decreasing funding base; soon to be hampered by closure of key infrastructure; hampered by aging and retiring workforce (loss of technical expertise); and in need of training of young scientists to ensure continuation of the science (no formal graduate education program in radioecology remaining in the U.S.). With these concerns in mind, the Savannah River National Laboratory (SRNL) took the lead to establish the National Center for Radioecology (NCoRE) as a network of excellence of the remaining radioecology expertise in the United States. As part of the NCoRE mission, scientists at SRNL are working with six key partner universities to re-establish a graduate education training program for radioecology. Recently, NCoRE hosted a workshop to identify the immediate needs for science-driven discoveries, tool development and the generation of scientific data to support the legislative decision-making process for remediation strategies, long-term monitoring of radiologicallycontaminated sites and protection of human health and the environment. Some of the immediate strategic research needs were identified in the fields of functional genomics for determining lowdose effects, improved low-level dosimetry, and mixed (radiological and chemical) contaminant studies. Longer term strategic research and tool development areas included development of radioecology case study sites, comprehensive decision-making tools, consequence response actions, and optimized scenario based ecosystem modeling. A summary of the NCoRE workshop findings related to waste management needs and priority areas will be presented in this paper

Laserstrukturen bei Sägewerkzeugen

Untersuchungen zum Potential von Laserstrukturen auf Sägewerkzeugen. Herausforderungen und Möglichkeiten für die Lasertechnik sowie erste Schnittergebnisse mit Kreis- und Bandsägen

Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV‐Mediated Cross‐Linking Strategies

In this work, a block copolymer (BCP) consisting of poly((butyl methacrylate‐co‐benzophenone methacrylate‐co‐methyl methacrylate)‐block‐(2‐hydroxyethyl methacrylate)) (P(BMA‐co‐BPMA‐co‐MMA)‐b‐P(HEMA)) is prepared by a two‐step atom‐transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self‐assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4‐dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV‐mediated cross‐linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross‐linked and cross‐linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross‐linking on the porous structures. Finally, the influence of the herein described cross‐linking protocols on water‐flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV‐mediated cross‐linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies