Iuliucci Robbie, Taylor Craig, Hollis W Kirk
Department of Chemistry, Washington and Jefferson College, Washington, PA 15301, USA.
Magn Reson Chem. 2006 Mar;44(3):375-84. doi: 10.1002/mrc.1763.
Polydimethylsiloxane (PDMS) elastomers reinforced with fumed silica exhibit unusual strength characteristics that are necessary for their designed applications. The microscopic details of the surface interaction between the polymer and silica are not well characterized. (1)H/(29)Si cross-polarization (cp) experiments are used to characterize cured and uncured samples of Dow Corning silastic 745. Changes to the cp dynamics upon curing are evident by the variation in peak intensities in the variable contact-time spectra of the two samples. Estimates of the cp relaxation parameters are reported for the cured sample. Additional information can be obtained by expanding the (1)H/(29)Si cp to a two-dimensional heteronuclear correlation experiment. Dramatic differences between the cured and uncured (1)H/(29)Si HetCor spectra are observed that are not visible in the 1D spectra. These changes can be rationalized as a dehydration of the silica surface and an increased hardening of the polymer after the curing process. Furthermore, isolation of the NMR signal corresponding to nuclei at or near the polymer-filler interface may be achieved in the 2D (1)H/(29)Si HetCor spectrum.
用气相法二氧化硅增强的聚二甲基硅氧烷（PDMS）弹性体表现出其设计应用所需的异常强度特性。聚合物与二氧化硅之间表面相互作用的微观细节尚未得到很好的表征。利用（1）H/（29）Si交叉极化（cp）实验对道康宁硅橡胶745的固化和未固化样品进行表征。通过两个样品的可变接触时间光谱中峰强度的变化，可以明显看出固化后cp动力学的变化。报告了固化样品的cp弛豫参数估计值。通过将（1）H/（29）Si cp扩展到二维异核相关实验，可以获得更多信息。观察到固化和未固化的（1）H/（29）Si异核相关光谱之间存在显著差异，这些差异在一维光谱中不可见。这些变化可以解释为固化过程后二氧化硅表面的脱水和聚合物硬度的增加。此外，在二维（1）H/（29）Si异核相关光谱中，可以实现与聚合物-填料界面处或附近原子核相对应的NMR信号的分离。
