Accession Number : ADA258118


Title :   Effects of Water on the Interface in a Model Composite System: An NMR study


Descriptive Note : Interim rept. Nov 1991-Nov 1992


Corporate Author : MISSOURI UNIV-ROLLA DEPT OF CHEMISTRY


Personal Author(s) : Gambogi, Joan E ; Blum, Frank D


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a258118.pdf


Report Date : 01 Nov 1992


Pagination or Media Count : 25


Abstract : The molecular motion of the interfacial material in a model polymer composite has been probed and quantitatively described based on deuterium NMR studies. The system consisted of a silica surface (Cab-O-Sil), an aminobutylsilane coupling agent (aminobutylsilane-d2, DABS) which was labelled with deuterium in the beta position, and a polymer matrix (bismaleimide). the addition of water to the system increased the molecular mobility of the surface- bound coupling agent. The motions of the coupling agent adsorbed on amorphous silica were simulated using a two-site jump model with tetrahedral jumps. For the coupling agent at the air interface, jump rates increased from 1.0 x 10 to the 6th power s-1 for the dry sample, to 4.0 x 10 to the 6th power s-1 for the sample in contact with water. For the sample with BMI reacted over it, the jump rate increased from 1.7 x 10 to the 5th power s-1 for the dry system to 5.0 x 10 to the 5th power s-1 for the wet system. The motional rate increase for both systems was a factor on the order of 3-4 with the addition of water. Deuterium exchange experiments were conducted between adsorbed aminobutylsilane and D20. This resulted in the deuteration of the amino-group. The motions of the amino group were only slightly faster than those of the labelled methylene segment. Silicon-29 NMR was used to probe the effects of water. The results were consistent with the breaking of Si-O-Si bonds and increased mobility at the Si end of the coupling agent AH systems appeared to returned to their original state when the sample was dried.


Descriptors :   *INTERFACES , *WATER , *COMPOSITE MATERIALS , PROBES , MOBILITY , ADSORPTION , SITES , RATES , SILICON , COUPLINGS , LABELED SUBSTANCES , MOLECULAR PROPERTIES , EXCHANGE , METHYLENES , DEUTERIUM , BUTYL RADICALS , SILANES , SURFACES , MOTION , POLYMERS , MATERIALS , NUCLEAR MAGNETIC RESONANCE , MODELS , AIR


Subject Categories : Inorganic Chemistry
      Polymer Chemistry
      Laminates and Composite Materials
      Atomic and Molecular Physics and Spectroscopy


Distribution Statement : APPROVED FOR PUBLIC RELEASE