hybrid poss lecture 12 class 2b: inorganic and organic polymeric phases are mixed and form covalent...
TRANSCRIPT
Hybrid POSS Lecture 12
Class 2B: Inorganic and organic polymeric phases are mixed and
form covalent interactions
Cross-linking through fullerenes
Used to purify C60.Did not look at mechanical propertiesRequires solvent to prepare
Grafted triethoxysilyl groups on polyethylene for moisture crosslinking
May also be applied with vinyltriethoxysilane and RF plasma
Excellent for moisture curing polyethylene
Macromolecules, 2004, 37 (10), pp 3532–3535
Anisotropic Micellar Nanoobjects from Reactive Liquid Crystalline Rod−Coil Diblock Copolymers
Triethoxysilyl terminated polysulfone
Macromolecules 1991;24:3449–50.
Anneal > 200 °CTiO2 sol in THF
Tailorable refractive index1.6 < n < 1.8
Chem. Mater., 2009, 21 (3), pp 463–467
Drug delivery hybrid gel
Polyethylene glycolTreithoxysilyl group on each endUrea linkage
PEO Bridged polysilsesquioxane hybrids
• Bacteriocide Ag-silsesquioxane coatings Biomacromolecules, 2007, 8 (4), pp 1246–1254
• Polymer electrolytes Solid State Ionics, 1999, 116, 197–209
• Coatings for steel. Adv. Technology 2008, 27, 117-126
• Electrochemically deposited coatings for stints New J. Chem., 2009, 33, 1596-1604
• Luminescent materials J. Non-Crystal Solids 2006, 352, 2292–2295 & Chem. Mater., 2004, 16 (13), pp 2530–2543
• Contolled druge release Chem. Mater., 2009, 21 (3), pp 463–467
Templating of structures and pores in hybrids, inorganics and organics
In templating, you build a material around some molecule, macromolecules or liquid crystal
Opals were used as templates for inverse opals and photonic solids (described in an earlier lecture).First we will see polymers phase segregation during sol-gel polymerization generating bone linke structures in hybrids.
Then we will look at liquid crystalline surfactant or block copolymer templates
Using other phase separations to control how particles aggregate
Surfactants
Polymers
Block copolymers
Hydrophilic Phase
Hydrophobic PhaseMonomers are often dissolve in this phase
Hydrolyzed monomers and polymers are often dissolve in this phase
Polymers are not very soluble in each other and will phase separate like oil and water
Larger structures
Smallerstructures
The Mobil patent was duplicating something already in the literatureSomebody did not do a careful literature search!!!!!!
Pore models of mesostructures with symmetries of (A) p6mm, (B) Ia3Cd, (C) Pm3Cn, (D) Im3Cm, (E) Fd3Cm, and (F) Fm3Cm.
MCM-41
FDU-12SBA-16
SBA-1
FDU-2
MCM-48
First model for surfactant templating: assumes liquid crystal occupies entire solution
A few nanometers in diameter
1) n-Hexadecyltrimethylammonium bromide (2.5 g, 0.007 mol) was dissolved in deionized water (50 g)2) To this surfactant solution, 13.2 g of aqueous ammonia (32 wt.%, 0.25 mol) and 60.0 g of absolute ethanol (EtOH, 1.3 mol) were added and the solution was stirred for 15 min (250 rpm).3) TEOS (4.7 g, 0.022 mol, freshly distilled) was added at one time resulting in a gel. 4) After stirring for 2 h the white precipitate was filtered and washed with 100 ml of deionized water and 100 ml of methanol. 5) After drying overnight at 363 K, the sample was heated to 823 K (rate:1 K min−1) in air and kept at that temperature for 5 h.
Synthesis of MCM-41 spheres
Microporous and Mesoporous Materials, 1999, 27, 207–216
Synthesis of MCM-41 silica spheres
Microporous and Mesoporous Materials, 1999, 27, 207–216
X-ray diffraction pattern of an MCM-41 sample prepared in heterogeneous medium with n-hexadecylpyridinium chloride as template.
TEM image of the honeycomb structure of MCM-41 and a schematic representation of the hexagonal shaped one-dimensional pores.
A close look at the structure shows that it is made of small amorphous silica particles
Just like the silica in living sponges> 1 nm in size
X-Ray Diffraction (XRD)
These materials show peaks at very small angles = larger structures than are typical in crystalline materials
formation mechanism of the templated nanoporous silicas
New mechanism has individual surfactant molecules and micelles playing a role in developing architecture
Structure of SBA-1 or SBA-6 observed as an electron density and described either in terms of a clathrate structure or as a surface enveloping the micellar templating agents Nature, 2000, 408, 449
Electron micrographs of SBA-1 and SBA-6 along [100]
What are some of these materials and what do they look like (SBA-Santa Barbara.
HREM images of CMK-4 along the three zone axes [100], [110] and [111] together with a representation of the carbonaceous surface.
J. Phys. Chem. B, 2002, 106, 1256
Liquid crystal forms then monomer enters and reacts
Monomer starts reacting and interacting with surfactant as the liquid crystal forms
Tools for hierarchical materials structures
Phil. Trans. R. Soc. A 28 April 2009 vol. 367 no. 1893 1587-1605
Other challenges
• Ladder polysilsesquioxanes = super strong materials
• Pure polyhedral analogs the size of C60
• Fundamentals of particle formation and connectivity at nm length scale
• Mechanochemical direction of materials-like exercising developing muscles