Dynamics of Surface Bound Polymers and Coupling Agents

Blum, Frank D.; Funchess, Robert B.; Meesiri, Wiriya

doi:10.1007/978-1-4899-2474-2_16

Cited by 3 publications

(3 citation statements)

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“…The effect was consistent with a decreased mobility with increased surface coverage. That work 38 also suggested that saturation coverage from toluene was roughly the distance scale over which this motional alteration was active. However, the sensitivity of these experiments was not sufficient to address the mobility issue more quantitatively.…”

Section: Discussionmentioning

confidence: 89%

“…Extension of this technique to labeled PVAc 37 showed that some PVAc surface segments were solidlike well above temperatures where the bulk segments were liquidlike. For poly(isopropyl acrylate) (PIPA) on silica, CP-MAS NMR 2,5,38 techniques showed that at less than saturation coverages, the resolution of the polymer resonances increased (i.e., linewidths decreased) with increased amounts adsorbed. The effect was consistent with a decreased mobility with increased surface coverage.…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of Poly(vinyl acetate) in Bulk and on Silica

Blum

Liang

et al. 1996

Macromolecules

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Quadrupole echo deuterium NMR has been used to probe the dynamics of poly(vinyl acetate-d3) in bulk and at saturation coverage (from toluene) on silica at the solid-air interface. In bulk and at lower temperatures, the deuterium powder pattern of the labeled methyl group was found to be consistent with fast threefold jumps with a small asymmetry due to the interaction of the methyl deuteron with the carbonyl oxygen. This apparent asymmetry was a result either of a distortion in the C-C-D bond angle or a reduction of the axial symmetry of the electric field gradient along the C-D bond vector. At higher temperatures, the onset of backbone motion of the polymer caused the collapse of the powder pattern to a single broad resonance over a fairly small temperature range between 65 and 73 °C. The collapse was well above the glass transition temperature as measured by differential scanning calorimetry, Tg(DSC)) 32 °C, and can be considered the Tg(NMR). The differences in temperatures for these two experiments are due to their different time scales. For the PVAc-d3 adsorbed at monolayer coverage on a silica surface, a small fraction was found to result in a collapsed powder pattern below the Tg(NMR). This fraction with enhanced mobility was believed to be located near the air-polymer interface. The powder pattern for the majority of the surface-bound polymer was found to collapse gradually with temperature, with a rigid component observable well above the temperature where the splittings for all of the bulk material had collapsed. Thus, from the deuterium NMR spectra, it is possible to deduce that on a surface, different segments from a single molecule exhibit a range of mobilities.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Dynamics of Poly(vinyl acetate) in Bulk and on Silica

Blum

Liang

et al. 1996

Macromolecules

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“…To overcome the problems associated with overlapping resonances, selectively deuterated silanes have been used (7,101,128,145,147,168,171,(202)(203)(204)(205). The structure of these was similar to V with an R in place of the OR.…”

Section: H Studiesmentioning

confidence: 99%