Adsorption of water and 18O exchange of surface hydroxyl groups on silica

1970 ◽  
Vol 48 (15) ◽  
pp. 2454-2456 ◽  
Author(s):  
B. A. Morrow ◽  
A. Devi
Keyword(s):  
Infrared Spectroscopy ◽  
Infrared Spectra ◽  
Sample Temperature ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Silanol Groups ◽  
Surface Hydroxyl Groups ◽  
Adsorption Of Water ◽  
Exchange Technique

Infrared spectroscopy has been used to show that the surface hydroxyl groups on highly dehydrated silica will exchange with 18O-labeled water. The degree of exchange depends on the sample temperature and is a maximum at about 400 °C, where approximately 65% of the silanol groups contain 18O. The use of the 18O exchange technique for assigning surface-adsorbate stretching modes is illustrated by considering the infrared spectra of BF3 chemisorbed on silica.

Infrared spectra in the Ag2O-CO2-Ag2CO3 system

1966 ◽  
Vol 19 (5) ◽  
pp. 715 ◽  
Author(s):  
JA Allen ◽  
PH Scaife
Keyword(s):  
Infrared Spectrum ◽  
Infrared Spectra ◽  
Silver Oxide ◽  
Broad Band ◽  
Hydroxyl Groups ◽  
Silver Carbonate ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups

The infrared spectrum of silver oxide, Ag2O, has been clarified by comparison with that of silver carbonate. In the region 4000-400 cm-l the spectrum consists of one broad band centred around 530 cm-l, other bands being accounted for in terms of normal, basic, and complex carbonates and surface hydroxyl groups, which are frequently present as contaminants. Conditions for the preparation, storage, and purification of silver oxide to minimize carbonate contamination are defined.

Reinforcement of Silicone Rubber by Particulate Silica

1975 ◽  
Vol 48 (4) ◽  
pp. 558-576 ◽  
Author(s):  
B. B. Boonstra ◽  
H. Cochrane ◽  
E. M. Dánnenberg
Keyword(s):  
Silicone Rubber ◽  
Silica Surface ◽  
Specific Interaction ◽  
Interaction Coefficient ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Silanol Groups ◽  
Compression Set ◽  
Surface Hydroxyl Groups ◽  
Bound Rubber

Abstract The interaction between fumed silica and silicone elastomer after various treatments of the silica surface has been investigated. The effect of the treatments was determined by measuring bound rubber, an interaction coefficient by means of the oscillating disk rheometer, the mechanical properties of the vulcanizates, the morphology of the silica aggregates, and the use of an hydroxyl-terminated silicone rubber. The results indicated that the interaction is much more intensive than in carbon black-hydrocarbon rubber systems. This is demonstrated by much higher bound rubber values (by a factor of 2–3) and a higher interaction coefficient. It is shown that the major effect on this interaction coefficient is the specific interaction by hydrogen bonding, between silica surface silanol groups and the polydimethylsiloxane chain. In this bonding the isolated hydroxyl groups should play the major part. Partial inactivation of these isolated silanol groups leads to improved strength but lower modulus. Maximum inactivation of the surface hydroxyl groups leads to soft compounds with lower tensile strengths and moduli, as well as very low bound rubber. Replacement of surface hydroxyl groups by vinyldimethylsilyl groups did not have the expected activating effect. Apparently the attached vinyldimethylsilyl groups do not form crosslinks with the elastomer chains, so that the overall result of the presence of these groups on the silica surface is a weakening of the interaction with the silicone rubber chains, although to a lesser degree than in the case of trimethylsilyl groups. The interaction between filler surface and polysiloxane can be maximizedby the use of a hydroxyl-terminated elastomer. The terminal groups will react with the silica surface so strongly that the particles act as crosslinks after proper heat treatment and a crosslinked polymer is obtained with a tensile strength of the same level as a peroxide-crosslinked vulcanizate but with higher compression set. At the temperature of the compression set test (175°C) the bonds apparently rearrange so that the permanent deformation is practically 100%. Quantitative data have been presented which prove that breakdown of silica aggregates does occur during mixing in silicone rubber on a two-roll mill.

The synthesis and structure of silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complexes

1986 ◽  
Vol 51 (7) ◽  
pp. 1430-1438 ◽  
Author(s):  
Alena Reissová ◽  
Zdeněk Bastl ◽  
Martin Čapka
Keyword(s):  
Free Surface ◽  
Hydroxyl Groups ◽  
Titanium Complex ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Cyclopentadienyl Anion

The title complexes have been obtained by functionalization of silica with cyclopentadienylsilanes of the type Rx(CH3)3 - xSi(CH2)nC5H5 (x = 1-3, n = 0, 1, 3), trimethylsilylation of free surface hydroxyl groups, transformation of the bonded cyclopentadienyl group to the cyclopentadienyl anion, followed by coordination of (h5-cyclopentadienyl)trichlorotitanium. The effects of single steps of the above immobilization on texture of the support, the number of free hydroxyl groups, the coverage of the surface by cyclopentadienyl groups and the degree of their utilization in anchoring the titanium complex have been investigated. ESCA study has shown that the above anchoring leads to formation of the silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complex.

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