Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500°C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35° to 80°C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140°C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

One of the most pervasive problems afflicting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally, even in regions currently considered water-rich. Addressing these problems calls out for a tremendous amount of research to be conducted to identify robust new methods of purifying water at lower cost and with less energy, while at the same time minimizing the use of chemicals and impact on the environment. Here we highlight some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water.

Science and technology for water purification in the coming decades

A family of highly ordered mesoporous (20−300 A) silica structures have been synthesized by the use of commercially available nonionic alkyl poly(ethylene oxide) (PEO) oligomeric surfactants and poly(alkylene oxide) block copolymers in acid media. Periodic arrangements of mescoscopically ordered pores with cubic Im3m, cubic Pm3m (or others), 3-d hexagonal (P63/mmc), 2-d hexagonal (p6mm), and lamellar (Lα) symmetries have been prepared. Under acidic conditions at room temperature, the nonionic oligomeric surfactants frequently form cubic or 3-d hexagonal mesoporous silica structures, while the nonionic triblock copolymers tend to form hexagonal (p6mm) mesoporous silica structures. A cubic mesoporous silica structure (SBA-11) with Pm3m diffraction symmetry has been synthesized in the presence of C16H33(OCH2CH2)10OH (C16EO10) surfactant species, while a 3-d hexagonal (P63/mmc) mesoporous silica structure (SBA-12) results when C18EO10 is used. Surfactants with short EO segments tend to form lamellar mesost...

Nonionic Triblock and Star Diblock Copolymer and Oligomeric Surfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures

https://www.researchgate.net/file.PostFileLoader.html?id=526892a1d4c118a61d4360bd&assetKey=AS%3A272155479085058%401441898330516

Porosity of 3D biomaterial scaffolds and osteogenesis.

3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

Low-molecular-weight poly(ethylene oxide)-polyalkane (PEO-PA) diblock copolymers have been examined between the order-disorder transition and PEO melting temperature using small-angle neutron scattering (SANS), differential scanning calorimetry (DSC), and dynamic mechanical spectroscopy (DMS). Crystallization imposes layered ordering with polymer stems oriented perpendicular, or tilted, relative to the microdomain interface, thereby disrupting conventional amorphous microdomain morphologies. This effect can be used to switch the high symmetry bicontinuous ordered G phase to lower symmetry cylinders or lamellae.

Influence of crystallinity on the morphology of poly(ethylene oxide) containing diblock copolymers

The successful design of new biodegradable, renewable resource plastics as replacements to commodity barrier plastics would benefit from an accurate measurement of sorption and diffusion of liquids. In this study, the diffusion of liquid water in amorphous polylactide [PLA] and a PLA graft copolymer, poly(1,5-cyclooctadiene-co-5-norbornene-2-methanol-graft-dl-lactide) [PCNL], was examined with time-resolved Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior was observed for all experiments, indicated by a slow approach to steady state due to diffusion and polymer relaxation occurring on similar time scales. This non-Fickian behavior highlights the variability of the sorption isotherms reported in the literature, where others have collected nonequilibrium sorption behavior (instead of true steady-state equilibrium sorption) at different time points and film thicknesses. The dynamic infrared data provided direct evidence for both water diffusion and water-i...

Liquid water transport in polylactide homo and graft copolymers.

Aliphatic polyesters are a versatile class of materials that can be sourced from bioderived feedstocks. Poly(γ-methyl-e-caprolactone) (PγMCL) in particular can be used to make degradable thermoplas...

Efficient Polymerization of Methyl-ε-Caprolactone Mixtures To Access Sustainable Aliphatic Polyesters

Symmetric poly(ethylene oxide-b-styrene-b-isoprene-b-styrene-b-ethylene oxide) (OSISO) pentablock terpolymers with narrow molecular weight distributions in all blocks were synthesized by anionic polymerization. These OSISO pentablock terpolymers have a common poly(styrene-b-isoprene-b-styrene) (SIS) core containing equal volume fractions of polyisoprene and polystyrene but having different lengths of terminal poly(ethylene oxide) (PEO) chains. Small-angle X-ray scattering, transmission electron microscopy, dynamic mechanical spectroscopy, and differential scanning calorimetry were used to identify two-domain lamellae, O70 (the orthorhombic Fddd network), and three-domain lamellae (LAM3) in the OSISO materials; these morphologies were previously identified in poly(isoprene-b-styrene-b-ethylene oxide) (ISO) triblock terpolymers with comparable compositions. Mechanical tensile testing was employed to probe the consequences of adding different lengths of semicrystalline PEO to the ends of intrinsically tough ...

Marc A. Hillmyer

Papers

Influence of crystallinity on the morphology of poly(ethylene oxide) containing diblock copolymers

Liquid water transport in polylactide homo and graft copolymers.

Efficient Polymerization of Methyl-ε-Caprolactone Mixtures To Access Sustainable Aliphatic Polyesters

Structure and Mechanical Properties of an O70(Fddd) Network-Forming Pentablock Terpolymer

Direct observation of stereodefect sites in semicrystalline poly(lactide) using 13c solid-state nmr