Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kiev, Ukraine.
J Colloid Interface Sci. 2013 Mar 15;394:467-74. doi: 10.1016/j.jcis.2012.12.026. Epub 2012 Dec 22.
The interfacial behavior of silicone oils Oxane 1000 and Oxane 5700 (polydimethylsiloxanes, PDMS) interacting with dried or hydrated (hydration h=0.005 or 0.1g/g) silica gels Si-60 and Si-100 or nanosilica A-400 was studied using low-temperature (1)H NMR spectroscopy over the 210-310 K range. Broadening of the melting temperature range toward both sides from the freezing point is observed for silicone oils confined in mesopores (2-15 nm in radius) of silica gel particles (0.2-0.5 mm in size) or voids (1-100 nm) between silica nanoparticles (5-10 nm in size) in their aggregates. This effect is a consequence of the phase state heterogeneity, since both liquid and solid-like fractions of adsorbed PDMS are observed over a large temperature range. The adsorbed PDMS heterogeneity depends on the pore size distribution (confined space effect), and it is lower for silica gel Si-100 possessing broader pores than Si-60. An increase in the amounts of adsorbed polymer and water diminishes the effects of confined space on PDMS because a fraction of the polymers is located in broader pores or out of pores (voids). This leads to relative decrease in interactions of PDMS with the silica surface. (1)H NMR spectra of PDMS and n-decane bound to silica gels reveal much stronger heterogenization of adsorbed PDMS (depending on the polymer length) than that of the alkane.
使用低温 (1)H NMR 光谱在 210-310 K 范围内研究了硅油 Oxane 1000 和 Oxane 5700（聚二甲基硅氧烷，PDMS）与干燥或水合（水合 h=0.005 或 0.1g/g）硅胶 Si-60 和 Si-100 或纳米二氧化硅 A-400 的界面行为。在硅胶颗粒（0.2-0.5 毫米大小）的介孔（半径 2-15 纳米）或纳米二氧化硅（5-10 纳米大小）颗粒之间的空隙（1-100 纳米）中，硅油被限制在其中时，观察到熔融温度范围从冰点向两侧拓宽。这种效应是由于相态不均匀性所致，因为在很大的温度范围内观察到吸附 PDMS 的液体和类似固体的分数。吸附 PDMS 的不均匀性取决于孔径分布（受限空间效应），对于具有较宽孔的硅胶 Si-100 比 Si-60 吸附的聚合物更少。吸附聚合物和水的量增加会降低受限空间对 PDMS 的影响，因为一部分聚合物位于较宽的孔或孔外（空隙）。这导致 PDMS 与硅胶表面的相互作用相对减少。与硅胶结合的 PDMS 和正癸烷的 (1)H NMR 谱表明，吸附 PDMS 的异质性（取决于聚合物的长度）比烷烃强得多。
