A New Approach to Surface Functionalization of Fluoropolymers
A New Approach to Surface Functionalization of Fluoropolymers
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DOI：
10.1021/ma001685q
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发表时间：
2001-02
期刊：
影响因子：
5.5
通讯作者：
B. Coupe;Wei Chen
中科院分区：
文献类型：
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作者：
B. Coupe;Wei Chen
已有大量的表面化学研究旨在增加含氟聚合物的表面能，以改善润湿性和促进粘附性。1与大多数聚合物不同，没有直接的化学方法将全氟烷烃中的CF、CF2和CF3基团转化为任何官能团。含氟聚合物最成功的化学反应包括单电子还原。2等离子体化学3和表面接枝4，5也被用于氟聚合物表面的改性。已报道的化学方法都没有引入离散的官能团，而是引入了物种的混合物。然而，来自其他研究领域的许多报告表明，生物聚合物自发地吸附到含氟聚合物上。6-9报道了一种均聚物，聚(L-赖氨酸)，从水溶液中吸附到一种含氟聚合物上。10这些工作人员指出，正是界面自由能(高能水分子从氟聚合物/水界面置换)的减少推动了聚合物或生物聚合物的吸附(“疏水相互作用”)。本文报道了聚乙烯醇在水溶液中对聚(tetrafluoroethylene-co-hexafluoropropylene)(FEP)的独特吸附行为。我们的研究小组一直在使用功能聚合物在FEP/水界面上的吸附作为一种方法，将离散的极性官能团(-NH2，-OH，-CO2H)结合到氟聚合物表面。在不同条件下，将聚烯丙基胺盐酸盐、聚乙烯亚胺和聚丙烯酸从水溶液中吸附到FEP表面。11使用这些聚合物，表面官能化的程度最小。11 PVOH的吸附行为与观察到的其他功能聚合物的吸附行为非常不同。已有几个关于PVOH从水溶液中吸附到硅氧化物颗粒、12金属氧化物颗粒13和金表面的报道。14用石英晶体微天平分析，随着PVOH相对分子质量、PVOH浓度、NaC l浓度、溶液温度和吸附/干燥步骤数的增加，PVOH在金上的吸附增加。指出PVOH通过分子间和分子内氢键聚集，形成结晶区。在这项研究中，PVOH在FEP/水界面上的吸附被证明是氟聚合物表面改性的一种新方法。吸附导致润湿性的显著改善。PVOH的低溶解度以及PVOH在FEP/水界面的结晶很可能为吸附提供了额外的驱动力。进行了水溶液中PVOH15对FEP16的吸附实验。考察了PVOH浓度、吸附动力学、离子强度和分级沉积对吸附量和润湿性的影响。用水接触角18和X射线光电子能谱(XPS)对所有样品进行了分析。19最初的实验包括将FEP膜样品暴露在不同浓度(0.005、0.01、0.05、0.1和0.5M)的PVOH水溶液中89h。20这些FEP-PVOH样品的水接触角难以区分，θA/θR)65(3/18(3，与溶液浇注的PVOH膜，θA/θR)63/17。原始FEP的接触角为θA/θR)117/93。这表明PVOH的吸附厚度至少达到了几埃量级的接触角采样深度。从XPS获得的O/F比(在15个起飞角度下)分别为1.06、1.14、1.07、1.01和4.21，对于…
There have been numerous surface chemistry studies directed at increasing the surface energy of fluoropolymers to improve wettability and promote adhesion. 1 Unlike most polymers, there are not direct chemical methods for the conversion of CF, CF2, and CF3 groups in perfluoroalkanes to any functionality. The most successful chemical reactions of fluoropolymers involve single electron reduction. 2 Plasma chemistry3 and surface grafting4, 5 have also been used to modify fluoropolymer surfaces. None of the reported chemical methods introduce discrete functional groups, but rather a mixture of species. There are numerous reports from other research fields, however, of biopolymers spontaneously adsorbing to fluoropolymers. 6-9 There is one report of a homopolymer, poly (L-lysine), adsorbing to a fluoropolymer from aqueous solution. 10 These workers point out that it is the reduction of interfacial free energy (the displacement of high-energy water molecules from the fluoropolymer/water interface) that drives polymer or biopolymer adsorption (“hydrophobic interactions”). We report here the unique adsorption behavior of poly (vinyl alcohol)(PVOH) to poly (tetrafluoroethylene-co-hexafluoropropylene)(FEP) from aqueous solution. Our research group has been using the adsorption of functional polymers to the FEP/water interface as a method to incorporate discrete polar functionality (-NH2,-OH,-CO2H) to the fluoropolymer surface. Poly (allylamine hydrochloride), polyethylenimine, and poly-(acrylic acid) have been adsorbed to FEP surfaces from aqueous solutions under different conditions. 11 The extent of surface functionalization is minimal using these polymers. 11 The adsorption behavior of PVOH is very different than that observed for other functional polymers.There have been several reports of the adsorption of PVOH from aqueous solution onto silicon oxide particles, 12 metal oxide particles, 13 and a gold surface. 14 The adsorption of PVOH onto gold increases with increasing PVOH molecular weight, PVOH concentration, NaCl concentration, solution temperature, and the number of adsorption/drying steps, as analyzed using a quartz crystal microbalance. It was pointed out that PVOH aggregates by inter-and intramolecular hydrogen bonding and forms crystalline regions. 14 In the study reported here, the adsorption of PVOH to the FEP/water interface is demonstrated as a new approach to surface modification of fluoropolymers. The adsorption results in a dramatic improvement of wettability. The low solubility of PVOH and, most likely, the crystallization of PVOH at the FEP/water interface provide additional driving forces for adsorption. A series of adsorption experiments of PVOH15 to FEP16 from aqueous solution17 have been carried out. The effects of PVOH concentration, adsorption kinetics, ionic strength, and stepwise deposition on the adsorbed amount and wettability have been examined. All samples studied have been analyzed by water contact angle18 and X-ray photoelectron spectroscopy (XPS). 19 Initially experiments involved exposing FEP film samples to aqueous solutions of PVOH at different concentrations (0.005, 0.01, 0.05, 0.1, and 0.5 M) for 89 h. 20 These FEP-PVOH samples display indistinguishable water contact angles, θA/θR) 65 (3/18 (3, which are indistinguishable from those of solution-cast PVOH film, θA/θR) 63/17. Contact angles of virgin FEP are θA/θR) 117/93. This indicates that the thickness of the adsorbed PVOH reaches at least the sampling depth of contact angle, which is on the order of a few angstroms. O/F ratios obtained from XPS (at 15 takeoff angle) are 1.06, 1.14, 1.07, 1.01, and 4.21, respectively, for the …