Department of Chemical and Biomolecular Engineering, Vanderbilt University , Nashville, Tennessee 37325-1604, United States.
Langmuir. 2013 Oct 8;29(40):12560-71. doi: 10.1021/la402173z. Epub 2013 Sep 25.
This article reports the enhanced rate of the surface-initiated polymerization (SIP) of 5-(perfluoro-n-alkyl)norbornenes (NBFn) by combining two SIP techniques, namely surface-initiated atom-transfer polymerization (SI-ATRP) to grow a macroinitiator and surface-initiated ring-opening metathesis polymerization (SI-ROMP) to produce the final coating. This polymerization approach promotes the rapid growth of dense partially fluorinated coatings that are highly hydrophobic and oleophobic and yield thicknesses from 4-12 μm. Specifically, the growth rate and the limiting thickness of pNBFn with different side chain lengths (n = 4, 6, 8, and 10) at various monomer concentrations and temperatures are evaluated through two approaches: growing the polymer from an initiator-terminated monolayer (control) or from a modified poly(2-hydroxyethyl methacrylate) (PHEMA) macroinitiator. X-ray photoelectron spectroscopy (XPS) analysis shows that 38% of the hydroxyl termini in the macroinitiator react with a norbornenyl diacid chloride (NBDAC) molecule, and 7% of such anchored norbornenyl groups react with a catalyst molecule. The kinetic data have been modeled to determine the propagation velocity and the termination rate constant. The PHEMA macroinitiator provides thicker films and faster growth as compared to the monolayer, achieving a 12 μm thick coating of pNBF8 in 15 min. Increasing the monomer side chain length, n, from 4 to 10 improves the growth rate and the limiting polymer thickness. Performing the polymerization process at higher temperature increases the growth rate and the limiting thickness as evidenced by an increase in the film growth rate constant. Arrhenius plots show that the reactions involved in the macroinitiation process exhibit lower activation energies than those formed from a monolayer. Electrochemical impedance spectroscopy reveals that the films exhibit resistance against ion transport in excess of 1 × 10(10) Ω·cm(2).
本文报道了通过结合两种表面引发聚合技术（表面引发原子转移聚合（SI-ATRP）来生长大分子引发剂和表面引发开环易位聚合（SI-ROMP）来制备最终涂层），提高了 5-（全氟-n-烷基）降冰片烯（NBFn）的表面引发聚合（SIP）速率。这种聚合方法促进了高密度部分氟化涂层的快速生长，这些涂层具有高度的疏水性和疏油性，厚度为 4-12μm。具体而言，通过两种方法评估了不同侧链长度（n=4、6、8 和 10）的 pNBFn 的生长速率和极限厚度，即在不同单体浓度和温度下从引发剂端单层（对照）或改性聚（2-羟乙基甲基丙烯酸酯）（PHEMA）大分子引发剂生长聚合物。X 射线光电子能谱（XPS）分析表明，大分子引发剂中 38%的羟基末端与降冰片烯二酰氯（NBDAC）分子反应，并且 7%的这种锚定的降冰片烯基团与催化剂分子反应。动力学数据已被建模以确定增长速度和终止速率常数。与单层相比，PHEMA 大分子引发剂提供了更厚的膜和更快的生长，在 15 分钟内实现了 pNBF8 的 12μm 厚涂层。增加单体侧链长度 n 从 4 增加到 10 提高了生长速度和极限聚合物厚度。在较高温度下进行聚合反应会增加生长速度和极限厚度，这可以通过增加膜生长速度常数来证明。阿仑尼乌斯图表明，涉及大分子引发过程的反应的活化能低于从单层形成的反应的活化能。电化学阻抗谱表明，该膜对超过 1×10(10)Ω·cm(2)的离子传输具有电阻。
