Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3A, D-30167 Hannover, Germany ; Laboratory of Industrial Chemistry, Ruhr-University Bochum, Universitaetsstr. 150, D-44801 Bochum, Germany.
Beilstein J Nanotechnol. 2012;3:428-37. doi: 10.3762/bjnano.3.49. Epub 2012 May 30.
Periodic mesoporous materials of the type (R'O)(3)Si-R-Si(OR')(3) with benzene as an organic bridge and a crystal-like periodicity within the pore walls were functionalized with SO(3)H or SO(3) (-) groups and investigated by small-angle neutron scattering (SANS) with in situ nitrogen adsorption at 77 K. If N(2) is adsorbed in the pores the SANS measurements show a complete matching of all of the diffraction signals that are caused by the long-range ordering of the mesopores in the benzene-PMO, due to the fact that the benzene-PMO walls possess a neutron scattering length density (SLD) similar to that of nitrogen in the condensed state. However, signals at higher q-values (>1 1/Å) are not affected with respect to their SANS intensity, even after complete pore filling, confirming the assumption of a crystal-like periodicity within the PMO material walls due to π-π interactions between the organic bridges. The SLD of pristine benzene-PMO was altered by functionalizing the surface with different amounts of SO(3)H-groups, using the grafting method. For a low degree of functionalization (0.81 mmol SO(3)H·g(-1)) and/or an inhomogeneous distribution of the SO(3)H-groups, the SLD changes only negligibly, and thus, complete contrast matching is still found. However, for higher amounts of SO(3)H-groups (1.65 mmol SO(3)H·g(-1)) being present in the mesopores, complete matching of the neutron diffraction signals is no longer observed proving that homogeneously distributed SO(3)H-groups on the inner pore walls of the benzene-PMO alter the SLD in a way that it no longer fits to the SLD of the condensed N(2).
具有苯作为有机桥和孔壁内晶态周期性的（R'O）（3）Si-R-Si（OR'）（3）周期性介孔材料用 SO（3）H 或 SO（3）（-）基团功能化，并通过小角中子散射（SANS）原位在 77 K 下氮气吸附进行研究。如果氮气被吸附在孔中，则 SANS 测量显示所有衍射信号完全匹配，这是由于苯-PMO 中介孔的长程有序，由于苯-PMO 壁具有类似于凝聚态氮气的中子散射长度密度（SLD）。然而，对于较高的 q 值（>1 1/Å），即使在完全填充孔后，其 SANS 强度的信号也不受影响，这证实了 PMO 材料壁内存在晶态周期性的假设，这是由于有机桥之间的π-π相互作用。通过使用接枝法用不同量的 SO（3）H 基团对苯-PMO 的表面进行功能化，可以改变原始苯-PMO 的 SLD。对于低程度的功能化（0.81 mmol SO（3）H·g（-1））和/或 SO（3）H 基团的不均匀分布，SLD 仅发生微不足道的变化，因此仍然发现完全的对比度匹配。然而，对于存在于介孔中的更多量的 SO（3）H 基团（1.65 mmol SO（3）H·g（-1）），不再观察到完全匹配的中子衍射信号，这证明均匀分布在苯-PMO 内孔壁上的 SO（3）H 基团改变了 SLD，使其不再适合于凝聚态 N（2）的 SLD。
