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

A one-pot, one-catalyst, sequential ring-opening transesterification polymerization (ROTEP) was used to prepare fully renewable amorphous poly(d,l-lactide)–poly(e-decalactone)–poly(d,l-lactide) (LDL) triblock polymers. These α,ω hydroxy-telechelic polymers were subsequently coupled to prepare linear alternating (LDL)n multiblock polymers. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) indicated microphase separation into two domains in both the triblock and multiblock architectures. The temperature dependent Flory–Huggins interaction parameter for this system, χ(T) = 69.1/T – 0.072, was estimated from the experimentally determined order–disorder transition temperature (TODT) values of four symmetric LDL triblock polymers. Uniaxial extension tests revealed a dramatic dependence of the room-temperature mechanical properties on overall molar mass. Additionally, coupling low molar mass LDL triblocks to prepare (LDL)n multiblocks led to substantial increases in the ultimate elo...

Synthesis and Melt Processing of Sustainable Poly(ε-decalactone)-block-Poly(lactide) Multiblock Thermoplastic Elastomers

We report gas and liquid transport measurements through membranes that have 40% voids made of 14 nm pores. A reactive polylactide−polynorbornenylethylstyrene block polymer is used as a structural template in the polymerization of dicyclopentadiene during the membrane formation process. After the membrane is cast, the pore structure is formed by etching the polylactide component using dilute aqueous base. The pore structure is isotropic; therefore, there is no need for special alignment techniques. Knudsen diffusion experiments and water flow experiments show pores with a tortuosity of 1.81 and a size of 14 nm, a diameter consistent with nitrogen adsorption and small-angle X-ray scattering measurements. These membranes are effective for ultrafiltration, with molecular weight cutoffs (MWCO) consistent with theoretical predictions with no adjustable parameters. These MWCO’s can be tuned by changing the size of the constituent blocks in the templating copolymer.

Diffusion and flow across nanoporous polydicyclopentadiene-based membranes.

Block copolymers containing a chemically degradable block are versatile precursors to nanoporous organic materials. Most work in this area has been accomplished in thin films. However, high surface area catalysis, separations, and nanotemplating can require monolithic samples with macroscopic pore volumes. Only a few examples of monolithic nanoporous materials from ordered block copolymers have been reported. In nearly all of these cases, the materials contain parallel cylindrical pores templated from the commonly observed hexagonally packed cylindrical (C) morphology adopted by AB diblock copolymers. To significantly expand the potential utility of this class of materials, we have targeted the bicontinuous gyroid (G) morphology in polystyrene block copolymers containing a degradable component. In this communication we describe the preparation of macroscopic samples of polystyrene with ordered three-dimensional nanochannels using either a polystyrene–polylactide (PS–PLA) block copolymer or a polystyrene–poly(ethylene oxide) (PS–PEO) block copolymer that adopts the G morphology. In addition, we show that a blend of these two materials also adopts the G morphology and that selective removal of the polylactide phase leaves a nanoporous material with poly(ethylene oxide)-lined pore walls that render the material water wettable.

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Macroscopic samples of polystyrene with ordered three-dimensional nanochannels

The ring-opening metathesis polymerization (ROMP) of exo-N-methyl-7-oxabicyclo[2.2.1]-hept-5-ene-2,3-dicarboximide (1) was accomplished in aqueous solution under mild conditions using the simple ruthenium(II) coordination complex Ru^(II)(H_2O)_6(tos)_2 (tos = p-toluenesulfonate) (2). The polymerization yield was nearly quantitative. The resultant high molecular weight polymer (poly-1) exhibited a glass transition temperature (T_g) of 225 °C and was thermally stable up to 402 °C. The thermal and radiative stabilities of poly-1 were further investigated. Poly-1 was hydrogenated to yield its saturated analogue, which had a lower T_g (170 °C) but a higher temperature of decomposition (430 °C). Complex 2 was deactivated by coordination of free maleimides formed during the polymerization of carboximide-functionalized monomers capable of undergoing retro Diels-Alder chemistry. The scope of this polymerization was therefore limited to carboximide-functionalized monomers that are stable toward retro Diels-Alder reactions at the polymerization temperature. Both ruthenium (II)-1 and ruthenium(II)-N-methylmaleimide olefin complexes were identified.

Marc A. Hillmyer

Papers

Synthesis and Melt Processing of Sustainable Poly(ε-decalactone)-block-Poly(lactide) Multiblock Thermoplastic Elastomers

Diffusion and flow across nanoporous polydicyclopentadiene-based membranes.

Macroscopic samples of polystyrene with ordered three-dimensional nanochannels

Aqueous ring-opening metathesis polymerization of carboximide-functionalized 7-oxanorbornenes

Aqueous Dispersions of Poly(ethylene oxide)-b-poly(γ-methyl-ε-caprolactone) Block Copolymers