Surface-immobilized PAMAM-dendrimers modified with cationic or anionic terminal functions: Physicochemical surface properties and conformational changes after application of liquid interface stress
Surface-immobilized PAMAM-dendrimers modified with cationic or anionic terminal functions: Physicochemical surface properties and conformational changes after application of liquid interface stress
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DOI：
10.1016/j.jcis.2011.09.029
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发表时间：
2012-01-15
影响因子：
9.9
通讯作者：
Mueller, Rainer
中科院分区：
文献类型：
--
作者：
Katzur, Verena;Eichler, Mirjam;Mueller, Rainer
用高度支化的树枝状聚合物分子官能化表面已经获得了对于各种应用的吸引力，因为官能团的数量超过了用自组装单层官能化的表面。到目前为止，人们对树枝状聚合物功能化表面的物理化学性质知之甚少，特别是在共价固定后树枝状聚合物结构的灵活性是否仍然存在。因此，本研究的目的是共价连接聚酰胺-胺（PAMAM）树枝状分子显示终端胺和羧基硅模型表面，并探讨其在固-气和固-液界面的性能和结构。我们的研究结果表明，PAMAM涂层的表面自由能高于类似终止自组装膜，也高于羧基比胺官能化涂层。此外，一些研究结果表明，构象自由的树枝状聚合物表面固定后被保存。与干燥的PAMAM-NH 2表面相比，湿的PAMAM-NH 2表面显示出降低的亲水性和增加的接触角滞后，而PAMAM-COOH表面变得更加亲水并显示出降低的滞后。流动电流测量显示出PAMAM-COOH表面的意想不到的行为，因为它们在宽的pH范围内显示出净正表面电荷，尽管羧基化的外围。所有这些结果都表明，在环境变化时，功能基团会发生一定程度的掩蔽、挖洞、回折和展开。(C)2011 Elsevier Inc. All rights reserved.
Functionalization of surfaces with highly branched dendrimer molecules has gained attractiveness for various applications because the number of functional groups exceeds those of surfaces functionalized with self-assembled monolayers. So far, little is known about the physicochemical properties of dendrimer functionalized surfaces, especially if the flexibility of dendrimer structure remains after covalent immobilization. Therefore, the purpose of this study was to covalently immobilize polyamidoamine (PAMAM) dendrimer molecules exhibiting terminal amine and carboxyl groups to silicon model surfaces and to explore their properties and structure at the solid-air and solid-liquid interface. Our results show that the surface free energy is higher for PAMAM coatings than for analogously terminated SAMs and also higher for carboxyl than amine functionalized coatings. Furthermore, several findings suggest that conformational freedom of the dendrimers was preserved after surface immobilization. Wet compared to dry PAMAM-NH2 surfaces show reduced hydrophilicity and increased contact angle hysteresis, whereas PAMAM-COOH surfaces become more hydrophilic and showed decreased hysteresis. Streaming current measurements showed an unexpected behavior for PAMAM-COOH surfaces in that they reveal a net positive surface charge over a wide pH range in spite of the carboxylated periphery. All of these results indicate a certain degree of masking, burrowing, back-folding and unfolding of functional groups upon environmental changes. (C) 2011 Elsevier Inc. All rights reserved.