Low Surface Energy Polymeric Films from Novel Fluorinated Blocked Isocyanates

Abstract

Polymeric films with surface energies as low as 10 mN/m were prepared from a mixture of a hydroxyl-end-capped solventless liquid oligoester (SLO), a blocked polyisocyanate, and a novel fluorinated blocked isocyanate (FnB-NCO; the ratio of the fluorinated tail and the caprolactam blocking group: 1:1), with less than 4 wt % of fluorine in the films. The curing temperature demonstrated a significant effect on the reaction rate and the film wettability: a higher curing temperature led to a less significant surface enrichment of fluorine, especially at a low F content (<2 wt %), due to the fast immobilization of the cross-linked networks. The mixtures had excellent stability below the deblocking temperature (∼ 140 °C) of the blocked isocyanates, which allowed the determination of the diffusion coefficients of fluorinated species in the reaction mixtures by pulsed field gradient (PFG) NMR. The well-defined FnB-NCOs enabled an easy and accurate adjustment of the fluorine concentration, making this approach practically attractive and efficient to prepare low surface energy films by using small amounts of fluorinated species.