Institut National de la Santé et de la Recherche Médicale, UMR 977, 11 rue Humann, 67085 Strasbourg Cedex, France.
Langmuir. 2010 Jul 20;26(14):12351-7. doi: 10.1021/la101670g.
The step-by-step buildup of organic films through physical or covalent bonds is usually performed by the alternating adsorption of two types of polymeric chains. Overcompensation of the interacting groups after each deposition step (e.g., charge overcompensation in the case of polyelectrolyte multilayers) allows the buildup process to proceed. This overcompensation is intimately linked to the polymeric nature of the interacting species. We report here another type of film architecture also based on step-by-step construction but involving the covalent bonding, through the Sharpless click reaction, between polyelectrolytes (i.e., polyanions) and neutral bifunctional molecules. The films are built by the Cu(I)-catalyzed click reaction of poly(acrylic acid) (PAA) functionalized with ethylene glycol (EG) arms, each ending with either an alkyne or an azide group, and bifunctionalized EG spacers ended with either alkyne or azide functions. We prove that these systems lead to the regular buildup of films that cover the whole substrate surface and whose roughness varies as the thickness of the film core. The effects of various parameters on film buildup are investigated. The grafting density of reactive moieties along the PAA chains has no influence on the thickness increment per bilayer. EG spacers bifunctionalized with alkyne groups reacting with PAA chains functionalized with azide arms give films that grow more rapidly than those obtained with azide-functionalized EG spacers and alkyne-functionalized PAA chains. The influence of the length of the EG arm (grafted on PAA) and of the EG spacer on the film buildup is also investigated: longer arms or longer spacers lead to larger thickness increments per bilayer, except for very large spacers of 50 EG units for which the thickness is the smallest probably because of size exclusion effects during the deposition.
通过物理或共价键逐步构建有机膜通常是通过两种类型的聚合链的交替吸附来完成的。在每个沉积步骤后，相互作用基团的过补偿（例如，在聚电解质多层的情况下，电荷过补偿）允许构建过程进行。这种过补偿与相互作用物质的聚合性质密切相关。我们在这里报告另一种基于逐步构建的膜结构，但涉及共价键，通过Sharpless 点击反应，将聚电解质（即聚阴离子）与中性双官能分子结合。通过 Cu(I) 催化的带有乙二醇（EG）臂的聚丙烯酸（PAA）的点击反应构建了这些膜，每个臂的末端都带有炔基或叠氮基团，以及带有炔基或叠氮基团的双官能化 EG 间隔物。我们证明这些系统导致了覆盖整个基底表面的规则膜的构建，并且其粗糙度随膜芯的厚度而变化。研究了各种参数对膜构建的影响。沿着 PAA 链的反应性基团的接枝密度对每双层的厚度增量没有影响。与带有叠氮基团的 PAA 链反应的带有炔基的双官能化 EG 间隔物形成的膜比带有叠氮基团的 EG 间隔物和带有炔基的 PAA 链形成的膜生长得更快。还研究了 EG 臂（接枝在 PAA 上）的长度和 EG 间隔物对膜构建的影响：更长的臂或更长的间隔物导致每双层的厚度增量更大，但对于长度为 50 EG 个单位的非常长的间隔物除外，其厚度可能最小，因为在沉积过程中存在尺寸排除效应。
