COLLAPSE OF POROSITY DURING DRYING OF ALKYLENE-BRIDGED POLYSILSESQUIOXANE GELS. INFLUENCE OF THE BRIDGING GROUP LENGTH

2004 ◽  
Vol 847 ◽  
Author(s):  
Douglas A. Loy ◽  
James H. Small ◽  
Kimberly A. DeFriend ◽  
Kennard V. Wilson ◽  
McKenzie Minke ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Nmr ◽  
Sol Gel ◽  
Network Polymer ◽  
Porous Coatings ◽  
Acidic Conditions ◽  
Bridged Polysilsesquioxane ◽  
Hybrid Xerogels ◽  
Bridging Groups

ABSTRACTThe introduction of organic substituents into sol-gel materials can often result in networks that collapse during drying to afford non-porous xerogels. This can prove useful if non-porous coatings or membranes are the ultimate objectives. Collapse of porosity is also manifested in bridged polysilsesquioxanes with flexible bridging groups. Alkylene-bridged polysilsesquioxanes are hybrid xerogels whose organic bridging group is an integral constituent of the network polymer that can be systematically varied to probe the influence of its length on the xerogels' porosity and morphology. Our previous studies have shown that hexylene-bridged polysilsesquioxane xerogels prepared from 1, 6-bis(triethoxysilyl)hexane under acidic conditions are nonporous while the pentylene-bridged polysilsesquioxanes prepared under the same conditions are porous. We also discovered that the more reactive 1, 6-bis(trimethoxysilyl)hexane monomer could polymerize under acidic conditions to afford porous xerogels. Here, we have extended our study of bis(trimethoxysilyl)alkanes to include the heptylene (C7), octylene (C8), nonylene(C9) and decylene (C10) bridges so as to ascertain at what bridging group length the porosity collapses. The morphology of the resulting xerogels was characterized by nitrogen sorption porosimetry and electron microscopy. Solid state NMR was used to structurally characterize the materials.

scholarly journals Proteorhodopsin: Characterisation of 2D crystals by electron microscopy and solid state NMR

2007 ◽  
Vol 1768 (12) ◽  
pp. 3012-3019 ◽  
Author(s):  
Sarika Shastri ◽  
Janet Vonck ◽  
Nicole Pfleger ◽  
Winfried Haase ◽  
Werner Kuehlbrandt ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Nmr ◽  
2D Crystals

Solid State NMR as A Probe of Inorganic Materials:Examples From Glasses and Sol-Gels

2006 ◽  
Vol 984 ◽  
Author(s):  
Paul Guerry ◽  
Donna L Carroll ◽  
Phillips N Gunawidjaja ◽  
Prodipta Bhattacharya ◽  
Daniela Carta ◽  
...  
Keyword(s):  
Solid State ◽  
Phosphate Glass ◽  
Solid State Nmr ◽  
Short Range ◽  
Sol Gel ◽  
The Other ◽  
Disordered Materials ◽  
Structural Sensitivity ◽  
Nmr Data ◽  
Wide Range

AbstractTo understand amorphous and structurally disordered materials requires the application of a wide-range of advanced physical probe techniques and herein a combined methodology is outlined. The relatively short-range structural sensitivity of solid state NMR means that it is a core probe technique for characterizing such materials. The aspects of the solid state NMR contribution are emphasized here with examples given from a number of systems, with especial emphasis on the information available from 17O NMR in oxygen-containing materials. 17O NMR data for crystallization of pure sol-gel prepared oxides is compared, with new data presented from In2O3 and Sc2O3. Sol-gel formed oxide mixtures containing silica have been widely studied, but again the role and effect of the other added oxide varies widely. In a ternary ZrO2-TiO2-SiO2 silicate sol-gel the level of Q4 formation is dependent not only on the composition, as expected, but also the nature of the second added oxide. Sol-gel formed phosphates have been much less widely studied than silicates and some 31P NMR data from xerogel, sonogel and melt-quench glasses of the same composition are compared. The effect of small amounts of added antibacterial copper on phosphate glass networks is also explored.

scholarly journals Sol–Gel Treatments to Flame Retard PA11/Flax Composites

Fibers ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 86 ◽  
Author(s):  
Samyn ◽  
Vandewalle ◽  
Bellayer ◽  
Duquesne
Keyword(s):  
Solid State ◽  
Flame Retardant ◽  
Solid State Nmr ◽  
Flame Retardants ◽  
Sol Gel ◽  
Deposition Method ◽  
One Pot ◽  
Successive Layer ◽  
Coating Methods ◽  
Flame Retardant Properties

This work investigates the efficiency of sol–gel treatments to flame retard flax fabric/PA11 composites. Different sol–gel treatments applied to the flax fabrics were prepared using TEOS in combination with phosphorus and/or nitrogen containing co-precursors (DEPTES, APTES) or additives (OP1230, OP1311). When the nitrogen and the phosphorus co-precursors were used, two coating methods were studied: a ‘one-pot’ route and a successive layer deposition method. For the “one-pot” method, the three precursors (TEOS, DEPTES, and APTES) were mixed together in the same solutions whereas for the different layers deposition method, the three different treatments were deposited on the fibers successively, first the TEOS, then a mix of TEOS/DEPTES, and finally a mix of TEOS/APTES. After deposition, the sol–gel coatings were characterized using scanning electron microscope, electron probe microanalyzer, and 29Si and 31P solid-state NMR. When only TEOS or a mix of TEOS and DEPTES is used, homogeneous coatings are obtained presenting well-condensed Si units (mainly Q units). When APTES is added, the coatings are less homogenous and agglomerates are present. A lower condensation rate of the Si network is also noticed by solid-state NMR. When additives are used in combination with TEOS, the TEOS forms a homogenous and continuous film at the surface of the fibers, but the flame retardants are not well distributed and form aggregates. The flame retardant (FR) efficiency of the different treatments on flax fabrics was evaluated using horizontal flame spread test. The following ranking of the different systems is obtained: TEOS + Additives > TEOS > TEOS + DEPTES ~ TEOS + DEPTES + APTES > multilayers. All the sol–gel coatings improve the flame retardant properties of the flax fabric, except the multilayer treatment. Based on these results, the three most efficient sol–gels were selected to prepare sol–gel-modified flax/PA11 composites. The composite modified with only TEOS showed the best FR properties. Surprisingly, the composite modified with the phosphorus-based flame retardant (AlPi) did not exhibit improved FR properties. This effect was attributed to the fact that the amount of the FR additive deposited on the fabrics was too low.

Sol–gel synthesis of alumina modified by phosphorus: a solid state NMR characterization study

1999 ◽  
Vol 9 (10) ◽  
pp. 2637-2646 ◽  
Author(s):  
Juliette Quartararo ◽  
Michel Guelton ◽  
Monique Rigole ◽  
Jean‐Paul Amoureux ◽  
Christian Fernandez ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Sol Gel ◽  
Characterization Study ◽  
Nmr Characterization ◽  
Sol Gel Synthesis

Interfaces Involving Biomolecules and Inorganic Materials: a Solid State NMR Approach

2007 ◽  
Vol 1008 ◽  
Author(s):  
Christian Bonhomme ◽  
Geoffrey Hartmeyer ◽  
Florence Babonneau ◽  
Michel Wong Chi Man ◽  
Guilhem Arrachart ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Chemical Nature ◽  
Sol Gel ◽  
Magic Angle Spinning ◽  
Inorganic Materials ◽  
Double Quantum ◽  
Magic Angle ◽  
Angle Spinning ◽  
Very High

AbstractMaterials based on ureidopyrimidinone (UPY) dimers and Adenine (A) / Thymine (T) derivatives were synthesized and characterized by advanced solid state NMR (Nuclear Magnetic Resonance) techniques. Silylated UPY molecules were used as model compounds, leading to structured organic-inorganic materials after hydrolysis and condensation processes (sol-gel reactions). High resolution 1H solid state NMR has been extensively used for the in-depth description of the H-bond networks, including very fast MAS (Magic Angle Spinning) experiments at very high field and DQ (double quantum) recoupling experiments. The chemical nature of the organic-inorganic interface has been illuminated by such techniques. In, particular, it has been demonstrated that H-bond networks were preserved during sol-gel reactions and were comparable to those observed in the UPY crystalline precursors.

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