291612 Kinetics of the Surface-Initiated Polymerization of 5-(Perfluoro-n-alkyl)Norbornene
Kinetics of the Surface-Initiated Polymerization of 5-(Perfluoro-n-alkyl)norbornene
Nur Nabilah Mahfuz, Carlos Escobar, Dr. Kane G. Jennings
Chemical and Biomolecular Department, Vanderbilt University, Nashville TN
Micromolding surface-initiated polymerization is a new method to replicate the complex topography of natural and artificial surfaces as a low-surface-energy polymer coating with thicknesses between 10-50 µm. The essential aspect of this strategy is to have rapid surface-initiated growth. Surface-initiated ring opening metathesis (SI-ROMP) provides a rapid growth of 5-(perfluoro-n-alkyl)norbornenes (NBFn), to create a dense coating that is highly hydrophobic and oleophobic, providing a suitable candidate process for micromolding surface-initiated polymerization. Here, we investigate the growth rate and the limiting thickness of pNBFn with different side chain lengths (n = 4, 6, 8, and 10) at different monomer concentrations and temperatures with two different approaches: growing the polymer from an initiator-terminated monolayer or from a polyhydroxyethylmethacrylate (pHEMA) macroinitiator. The kinetic data are modeled using a first-order termination equation to determine the propagation velocity and the termination rate constant. The pHEMA macroinitiotor 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 from n = 4 to n = 10 improves the growth rate and limiting polymer thickness. Performing the reaction at higher temperature also increases the growth rate and the limiting thickness because the propagation velocity and termination rate constant are temperature dependent as described by the Arrhenius equation.
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