MODIFICATION OF SURFACE REACTIVITIES ON SILICA (1000) AS MODELS OF BIOADHESION

对有机硫化合物在二氧化硅表面的附着进行了研究。这项工作定义了一种以前未知的将碳氢化合物结合到二氧化硅表面的模式。嫁接在表面的分子的化学反应在表面科学中日益引起人们的兴趣；这些系统的红外透射率和固体核磁共振的特征与生物黏附--细菌附着在膜上或白细胞附着在生物植入物上的物理和化学作用--有直接的关系。主要有四个目标：1.二氧化硅(100012)上的新表面反应。我们将在高真空下将有机硫化合物与加热到1000摄氏度的二氧化硅表面反应。例如，硫醇生成含有S-硅键的硫代硅氧烷薄膜。2.双功能分子在二氧化硅(1000)上的表面接枝。含有与二氧化硅(1000)反应的有机硫头基团和暴露在表面的末端官能团的双功能分子将被接枝。第二个官能团不能与二氧化硅(1000)反应，也不能被化学保护而不发生这种反应。例如，在一个双功能分子，如卤代烷硫醇，氯-(CH2)nsh，S和氯都可能与表面硅氧烷相互作用。通过酯化保护羧酸，通过烷基化保护胺，三官能半胱氨酸可以通过其SH基团被独占吸附。3.原位反应。其目标是制备不能直接通过吸附双功能分子制备的表面官能团。以上2中提到的保护基团的脱烷基化和水解将是第一次实验。另一项研究是制备端醛的硫代硅氧烷薄膜；吸附的前体C=O(CH2)nsh在合成上是不可接近的。这家公司可能会对金属进行弱配位/粘合。4.吸附-与改性表面的相互作用。对界面分子环境的研究揭示了影响表面-吸附相互作用的基本因素。我们将系统地改变烷基链长和链端，以影响表面的吸附性质的空间和化学控制。这些影响将通过对受控大气环境的光谱研究来探讨，例如可逆的吡啶配位。

A study of the adhesion of organosulfur compounds at the surface of silica is proposed. This work defines a previously unknown mode of binding hydrocarbon to the surface of silica. Chemical reactions of molecules grafted on surfaces are of growing interest in surface science; these systems, characterized by IR transmission and solid state NMR, have direct relevance to bioadhesion--the physical and chemical interactions of bacteria adhering to membrane, or white blood cells adhering to bioimplants. There are four major targets: 1. New surface reactions on Silica (100012). We will react organosulfur compounds with the surface of silica heated to 1000C in high vacuum. For example, a thiol gives a thiosiloxane film containing the S-Si bond. 2.Surface Grafting of Bifunctional Molecules on Silica (1000). Bifunctional molecules, containing the organosulfur head group to react with the silica (1000) and a terminal functional group exposed at the surface will be grafted. The second functionality must either not react with the silica (1000) or be chemically protected from such reaction. For example, in a bifunctional molecule such as a halogenated alkanethiol, Cl-(CH2)nSH, both the S and the Cl could potentially interact with surface siloxanes. Trifunctional cysteine could be absorbed exclusive through its SH group by protecting the carboxylate through esterification and the amine through alkylation. 3. In-situ reactions. The goal is to prepare surface functionalities which could not be prepared directly from absorption of bifunctional molecules. Dealkylation and hydrolysis of protected groups referred to in 2 above will be the first experiments. Another examine would be preparation of an aldehyde terminated thiosiloxane film; the adsorbate precursor C=O (CH2)nSH is synthetically inaccessible. This firm may weakly coordinate /adhere metals. 4. Adsorbate-Interactions with the Modified Surfaces. Studies of the molecular environment at the interface reveal the fundamental factors affecting surface-adsorbate interactions. We will vary systematically the alkyl chain length and the chain terminus to effect steric and chemical control of the surface's absorption properties. These effects will be probed with spectroscopic studies of controlled atmosphere environments such as e.g. reversible pyridine coordination.