Buck Maren E, Schwartz Sarina C, Lynn David M
Department of Chemistry, 1101 University Avenue, Madison, WI 53706.
Chem Mater. 2010 Sep 11;22(23):6319-6327. doi: 10.1021/cm102115e.
We report an approach to the fabrication of superhydrophobic thin films that is based on the 'reactive' layer-by-layer assembly of azlactone-containing polymer multilayers. We demonstrate that films fabricated from alternating layers of the azlactone functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and poly(ethyleneimine) (PEI) exhibit micro- and nanoscale surface features that result in water contact angles in excess of 150º. Our results reveal that the formation of these surface features is (i) dependent upon film thickness (i.e., the number of layers of PEI and PVDMA deposited) and (ii) that it is influenced strongly by the presence (or absence) of cyclic azlactone-functionalized oligomers that can form upon storage of the 2-vinyl-4,4-dimethylazlactone (VDMA) used to synthesize PVDMA. For example, films fabricated using polymers synthesized in the presence of these oligomers exhibited rough, textured surfaces and superhydrophobic behavior (i.e., advancing contact angles in excess of 150º). In contrast, films fabricated from PVDMA polymerized in the absence of this oligomer (e.g., using freshly distilled monomer) were smooth and only moderately hydrophobic (i.e., advancing contact angles of ~75º). The addition of authentic, independently synthesized oligomer to samples of distilled VDMA at specified and controlled concentrations permitted reproducible fabrication of superhydrophobic thin films on the surfaces of a variety of different substrates. The surfaces of these films were demonstrated to be superhydrophobic immediately after fabrication, but they became hydrophilic after exposure to water for six days. Additional experiments demonstrated that it was possible to stabilize and prolong the superhydrophobic properties of these films (e.g., advancing contact angles in excess of 150° even after complete submersion in water for at least six weeks) by exploiting the reactivity of residual azlactones to functionalize the surfaces of the films using hydrophobic amines (e.g., aliphatic or semi-fluorinated aliphatic amines). Our results demonstrate a straightforward and substrate-independent approach to the design of superhydrophobic and reactive polymer-based coatings of potential use in a broad range of fundamental and applied contexts.
我们报道了一种基于含氮杂环丙烷聚合物多层膜的“反应性”逐层组装来制备超疏水薄膜的方法。我们证明，由氮杂环丙烷官能化聚合物聚（2-乙烯基-4,4-二甲基氮杂环丙烷）（PVDMA）和聚（乙烯亚胺）（PEI）的交替层制成的薄膜呈现出微米和纳米级的表面特征，这导致水接触角超过150°。我们的结果表明，这些表面特征的形成（i）取决于薄膜厚度（即沉积的PEI和PVDMA层数），并且（ii）受到环状氮杂环丙烷官能化低聚物存在（或不存在）的强烈影响，这些低聚物可在用于合成PVDMA的2-乙烯基-4,4-二甲基氮杂环丙烷（VDMA）储存时形成。例如，使用在这些低聚物存在下合成的聚合物制成的薄膜呈现出粗糙、有纹理的表面和超疏水行为（即前进接触角超过150°）。相比之下，在没有这种低聚物的情况下聚合的PVDMA制成的薄膜（例如使用新鲜蒸馏的单体）是光滑的，并且只是中等疏水性（即前进接触角约为75°）。以指定和受控的浓度向蒸馏的VDMA样品中添加纯正的、独立合成的低聚物，可以在各种不同基材的表面上可重复地制备超疏水薄膜。这些薄膜的表面在制备后立即被证明是超疏水的，但在暴露于水六天后变成亲水性。额外的实验表明，通过利用残留氮杂环丙烷的反应性，使用疏水性胺（例如脂肪族或半氟化脂肪族胺）对薄膜表面进行功能化，可以稳定并延长这些薄膜的超疏水性能（例如，即使在完全浸入水中至少六周后，前进接触角仍超过150°）。我们的结果展示了一种直接且与基材无关的方法，用于设计在广泛的基础和应用背景中具有潜在用途的超疏水和反应性聚合物基涂层。
