Low surface energy polymeric films from partially fluorinated photocurable solventless liquid oligoesters

Abstract

We have recently shown that low surface energy polymeric films can be readily obtained from partially fluorinated hydroxyl-end-capped solventless liquid oligoesters by thermal curing [1]. Photocurable liquid oligoesters can be prepared by further substituting the remaining hydroxyl end groups with acrylic double bonds. A conventional photoinitiator containing 2-hydroxy-2-methylpropiophenone was used to cure the liquid oligoesters. As the fluorine content increases from 0 to about 1.57 wt %, the surface energy decreases by about 14 mN/m. The fluorine level in the outer few nanometers is significantly greater than that in the bulk, as revealed by XPS studies. The driving force for the surface segregation of fluorinated species comes from the large difference in surface energy between the oligoesters and their fluorinated counterparts.

A fluorinated compound used as migrated photoinitiator in the presence of air

“…And when the hydroxyl is substituted by alkyl chain, the addition efficiency of hydroxyalkyl radical would decrease dramatically [33]. Similar thing would happen when fluoroalkyl groups were grafted to benzoyl radicals [33]. However, even the reactivity of benzoyl radicals was lowered, the highly reactive hydroxyalkyl could still initiate the polymerization efficiently.…”

“…It was reported that the addition reactivity of hydroxyalkyl radicals towards acrylate double bond is almost 100 times higher than benzoyl radicals [40]. And when the hydroxyl is substituted by alkyl chain, the addition efficiency of hydroxyalkyl radical would decrease dramatically [33]. Similar thing would happen when fluoroalkyl groups were grafted to benzoyl radicals [33].…”

“…The fluorinated species would migrate toward the liquideair interface to minimize the interfacial energy [31]. It had been reported that the addition of 1e1.5 wt% of fluorinated compounds could reduce the surface energy from 45 to 20e30 mN/m [32,33]. The surface stratification of fluorine was also demonstrated by photocopolymerizing fluorinated monomers and typical difunctional oligomers [34e36].…”

Chemical and Morphological Surface Modification of Epoxy Based Thermosets

“…In Table 1, the average and surface F/C atomic ratios are presented together with the FSE calculations and the CA measurements, for the different fluorinated polymers synthesized. The FSE follows a known tendency [24][25][26][27] with the average fluorine concentration, i.e. the lower the average fluorine content, the higher the FSE.…”

Superhydrophobic Fluorinated Polyurethane Films

“…Surface segregation provides an excellent strategy to create a coating with a fluorine-rich surface. In such an approach, due to its low surface energy, the fluorinated species would migrate toward the air/film interface to minimize the interfacial energy [18][19][20][21][22][23][24][25][26][27]. Thus, only a small quantity of fluorinated species is needed to provide a surface with low surface energy.…”