Amplification of Surface-Initiated Ring-Opening Metathesis Polymerization of 5-(Perfluoro-n-alkyl)norbornenes by Macroinitiation

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• 作者：Carlos A. Escobar ; Robert R. Harl ; Kathryn E. Maxwell ; Nur N. Mahfuz ; Bridget R. Rogers ; G. Kane Jennings
• 刊名：Langmuir
• 出版年：2013
• 出版时间：October 8, 2013
• 年：2013
• 卷：29
• 期：40
• 页码：12560-12571
• 全文大小：572K
• 年卷期：v.29,no.40(October 8, 2013)
• ISSN：1520-5827

文摘

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鈥?2 渭m. 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 渭m 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 脳 10¹⁰ 惟路cm².