Hydrophobin as a Nanolayer Primer That Enables the Fluorinated Coating of Poorly Reactive Polymer Surfaces

Abstract

thick fi lm to achieve signifi cant durability and, therefore, requires a relatively large amount of fl uoropolymer. Alternative approaches, such as chemical grafting of fl uoropolymers by radical methods through irradiation, [ 6−8 ] plasma, [ 9−12 ] or direct fl uorination with fl uorine gas, [ 1,2,13 ] require only moderate amounts of fl uorinated surface modifi ers but are much more aggressive and, in some cases, potentially hazardous.Other possibilities involve functionalization with fl uorinated molecules/ polymers consisting of specifi c chemical moieties that are able to bind either covalently or noncovalently to the polymer surface. [ 4,5,14,15 ] However, to achieve sufficiently stable bonding, this general strategy requires the presence of reactive hydrophilic sites, typically OH groups, which are not typically observed on the surfaces of apolar, hydrophobic polymers, such as polyolefi ns, and need to be introduced via oxidizing pretreatments that are usually either energy-intensive or not environmentally friendly. [ 16−19 ] Expanding on this strategy, we present an effi cient, rapid, and more environmentally friendly method to perform the fl uorocarbon coating of hydrophobic polymer surfaces. The method is based on the use of hydrophobins, i.e., amphiphilic surface-active proteins, as a nanosized primer layer that adheres to the hydrophobic polymer surface, making the surface hydrophilic and preparing it for the subsequent binding of a fl uoropolymer containing ionic moieties.Hydrophobins are a class of nontoxic, surface-active, and fi lm-forming proteins that are produced by fi lamentous A new and simple method is presented to fl uorinate the surfaces of poorly reactive hydrophobic polymers in a more environmentally friendly way using the protein hydrophobin (HFBII) as a nanosized primer layer. In particular, HFBII, via electrostatic interactions, enables the otherwise ineffi cient binding of a phosphate-terminated perfl uoropolyether onto polystyrene, polypropylene, and low-density polyethylene surfaces. The binding between HFBII and the perfl uoropolyether depends signifi cantly on the environmental pH, reaching the maximum stability at pH 4. Upon treatment, the polymeric surfaces mostly retain their hydrophobic character but also acquire remarkable oil repellency, which is not observed in the absence of the protein primer. The functionalization proceeds rapidly and spontaneously at room temperature in aqueous solutions without requiring energy-intensive procedures, such as plasma or irradiation treatments.

Natural surfactants towards a more sustainable fluorine chemistry

“…polystyrene, polypropylene, low-density polyethylene) could be rapidly and spontaneously functionalized with the phosphate-terminated perfluoropolyether Fluorolink® F10, in aqueous solutions and at room temperature. 97 The presence of an HFBII monolayer on a polystyrene surface increased the binding of Fluorolink® F10 almost twenty-fold, by exploiting electrostatic interactions between the phosphate groups of the fluorocarbon and the positively charged amino acid residues of the protein (Fig. 5).…”

Evaluating the potential of natural surfactants in the petroleum industry: the case of hydrophobins

“…The good surface activity and exceptionally high surface elasticity of HFBs makes them the most surface-active proteins currently known, which promoted their successful Brought to you by | MIT Libraries Authenticated Download Date | 5/12/18 9:00 AM exploitation in several different fields. Some of the uses proposed for HFBs include stabilization of foams and emulsions in the food industry [16], biotechnological applications such as drug delivery [17,18], biomedical imaging [19] and coatings for biomedical devices [20], but also use as dispersing agents [21,22] and intermediates for surface immobilization of proteins [23,24] and polymers [25]. The ability of HFBs to self-assemble at oil-water interfaces and stabilize oil droplets makes them potential candidates for a more efficient and greener EOR strategy, also in consideration of the fact that the potential for large scale production of these proteins has been shown in industrial operations for both classes of HFBs [14,16].…”

Bioreducible Hydrophobin-Stabilized Supraparticles for Selective Intracellular Release

“…This behavior is due to HFBII that at its pI (isoelectric point), at pH = 5.2, is in its zwitterionic form with a net charge close to 0. 36 Overall, these data highlight the high colloidal stability of the prepared SPs as well as their good compatibility with physiologic pH, which is important for biomedical purposes.…”