Amphiphilic Coatings Research Articles

Transparent, Flexible, Responsive Switching "Delayed" Amphiphilic Coatings Designed on the Basis of the Full-Cycle Antifouling Strategy.

Marine fouling on the surface of ships and equipment not only creates problems of enhanced resistance to navigation and increased energy consumption but also leads to unclear vision and inaccurate data collection. Antifouling coatings to resist fouling are effective, but it is difficult to achieve long-lasting fouling protection with a single interface state. Switching the status of the interface by intelligent response is a reasonable way to achieve full-cycle efficient antifouling. In this study, the hydrophobic and active antifouling interface in the initial state was achieved by adopting the fluorine-containing group and the natural extract (citronellol) as the antifouling active site. The switching of the interface relies on silanes, which respond to the generation of zwitterions in a seawater environment. Eventually, the interface switched from the hydrophobic state to the amphiphilic state with delayed formation, which achieved continued antifouling. Based on the full-cycle antifouling concept, the combination of low surface energy and antifouling active ingredients in the initial state sustainably switched surfaces in the midterm (free radicals generated during the hydrolysis process), and amphiphilic interfaces formed by "delays" produced an antifouling effect from the initial stage to the subsequent stage. The excellent antifouling activity (bacterial and diatom attachment inhibition by over 90% and significantly reduced mussel adhesion force), optical transparency, and flexibility of these coatings indicate the potential for the application of antifouling coatings prepared from hyperbranched silicone-based resins; they can also be used for data extraction sensors, underwater probes, marine photovoltaics, and other areas where transparency is required.

Marine Fouling Release Performance of Amphiphilic Carboxybetaine Perfluoropolyether Methacrylate Polymer Coatings

AbstractAmphiphilic polymer systems have been demonstrated to be an effective and environmentally friendly approach to combat the challenges of biofouling, especially in the real ocean environment. A variety of polymer compositions containing fluorophilic perfluoropolyether (PFPE) urethane dimethacrylate and zwitterionic carboxybetaine methacrylate (CBMA) are in situ copolymerized across a broad concentration range and anchored to chemically functionalized substrates by grafting‐through polymerization. Dynamic accumulation assays with the marine diatom Navicula perminuta and the marine bacterium Cobetia marina revealed an enhanced antifouling performance in most of the amphiphilic polymer mixtures when zwitterionic units are combined with hydrophobic PFPE compounds. It is noticed that the resulting polymer networks still possess enough orientational freedom to quickly rearrange in the presence of water. It is further observed that several of the very hydrophilic formulations and some of the moderately hydrophobic formulations exhibit low fouling against the marine fouling organisms Navicula perminuta and Cobetia marina. This correlated with increased surface roughness and the ability for underwater rearrangement. Furthermore, it is discussed whether the probability that highly hydrated hydrogels, which appear sponge‐like, may create a diffuse interphase which promotes the incorporation of silt. Latter is counteracted by the hydrophobic PFPE building blocks in the amphiphilic coatings.

In vitro biocompatibility analysis of protein-resistant amphiphilic polysulfobetaines as coatings for surgical implants in contact with complex body fluids.

The fouling resistance of zwitterionic coatings is conventionally explained by the strong hydrophilicity of such polymers. Here, the in vitro biocompatibility of a set of systematically varied amphiphilic, zwitterionic copolymers is investigated. Photocrosslinkable, amphiphilic copolymers containing hydrophilic sulfobetaine methacrylate (SPe) and butyl methacrylate (BMA) were systematically synthesized in different ratios (50:50, 70:30, and 90:10) with a fixed content of photo-crosslinker by free radical copolymerization. The copolymers were spin-coated onto substrates and subsequently photocured by UV irradiation. Pure pBMA and pSPe as well as the prepared amphiphilic copolymers showed BMA content-dependent wettability in the dry state, but overall hydrophilic properties a fortiori in aqueous conditions. All polysulfobetaine-containing copolymers showed high resistance against non-specific adsorption (NSA) of proteins, platelet adhesion, thrombocyte activation, and bacterial accumulation. In some cases, the amphiphilic coatings even outperformed the purely hydrophilic pSPe coatings.

Investigating the anti-bioadhesion properties of short, medium chain length, and amphiphilic polyhydroxyalkanoate films

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms.

Amphiphilic Balance: Effect of the Hydrophilic-Hydrophobic Ratio on Fouling-Release Surfaces.

This study demonstrated the importance of identifying the optimal balance of hydrophilic and hydrophobic moieties in amphiphilic coatings to achieve fouling-release (FR) performance that surpasses that of traditional hydrophobic marine coatings. While there have been many reports on fouling-release properties of amphiphilic surfaces, the offered understanding is often limited. Hence, this work is focused on further understanding of the amphiphilic surfaces. Poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) were used to create a series of noncross-linked amphiphilic additives that were then added to a hydrophobic-designed siloxane-polyurethane (SiPU) FR system. After being characterized by ATR-FTIR, XPS, contact angle analysis, and AFM, the FR performance was evaluated by using different marine organisms. The assessments showed that the closer the hydrophilic and hydrophobic moieties in a system reached a relatively equalized level, the more desirable the FR performance of the coating system became. A balanced ratio of hydrophilicity-hydrophobicity in the system at around 10-15 wt % of each component had the best FR performance and was comparable to or better than commercial FR coatings.

Transparent amphiphilic silicone-based fouling-release coatings: Analyzing the effect on coating-fouling interfacial behavior

The amphiphilic antifouling coatings are effective for inhibiting fouling adhesion. Herein, the amphiphilic coatings were prepared by introducing polyether-modified polydimethylsiloxane (PE-PDMS). Uniform morphology, high transmittance, low surface roughness and amphiphilic property were obtained. PE-PDMS appearing as interspersed chains endowed the coating with amphiphilic characteristic. The artificial seawater promoted the migration of polyether to the surface. The protein adhesion force and quality were significantly reduced according to AFM-based colloidal probe technique and Quartz Crystal Microbalance with Dissipation, respectively. The coating exhibited antibacterial activity against Pseudoalteromonas xiamenensis (84.0%), Escherichia coli (69.2%) and Staphylococcus aureus (63.0%), respectively. 63.1% Halamphora. sp and 75.8% Nitzschia closterium f. had been inhibited, while the coatings possessed outstanding fouling release property with above 76.1% diatom detached after water exposure, proving that the amphiphilic parts weakened the adhesion of fouling. The mussel settlement assay confirmed that less adhesive plaques existed over the amphiphilic coatings. In addition, the expression for mussel adhesion proteins (mfp-5 and mfp-6) were significantly increased, demonstrating that amphiphilic polymers interfered with the adhesion response of the mussels. The effect on the interfacial behavior between fouling and coating is explored, providing a meaningful issue for the development of environmentally friendly antifouling coatings.

Investigation of Icephobic Coatings for Supercooling Heat Exchangers under Submerged Conditions Using Ice Detection Equipment

By using ice slurry generated through a supercooler as storage, it is possible to reduce energy consumption due to high energy density and heat transfer rate along with the phase change. The supercooled water will then be disturbed to create ice crystals in a crystallizer. The main challenge is to prevent the formation of ice in the supercooler since this leads to its blockage. One aim of the European H2020 TRI-HP project is to develop icephobic coatings for supercoolers, that promote high-water supercooling and avoid the formation of ice. In this study, three coatings to prevent or depress freezing in supercoolers are investigated. Specialized equipment for testing freezing on submerged surfaces has been developed, and the results have been correlated to standard surface properties like roughness and contact angle. It was found that the submerged surfaces do not necessarily follow normal icing theory, where freeze depression is related to contact angle. Instead, it is believed that the mobility of surface additives in amphiphilic coatings has an important role.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions.

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe3O4 nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Reduced Ice Adhesion Using Amphiphilic Poly(Ionic Liquid)-Based Surfaces.

Ice build-up on solid surfaces causes significant economic losses for a range of industries. One solution to this problem is the development of coatings with low ice adhesion strength. Amphiphilic poly(ionic liquid) (PIL)-based surfaces have been recently reported for antifogging/antifrosting applications. However, they have possible anti-icing properties through lowering the ice adhesion strength that have yet to be reported. Herein, we designed well-defined triblock copolymers composed of a polydimethylsiloxane component coupled with PIL segments of poly([2 (methacryloyloxy)ethyl] trimethylammonium chloride) (PMETAC), which were subsequently UV-cured with an oligo(ethylene glycol) dimethacrylate (OEGDMA) cross-linker. The structure-property relationships of the resultant semi-interpenetrating polymer networks (SIPNs) were investigated by varying the counterion (i.e., trimethylammonium bis(trifluoromethanesulfonyl)imide (TFSI-)) and the content of the PIL segments and cross-linker. An ice adhesion strength as low as 13.3 ± 8.6 kPa was observed for the coating containing 12.5 wt % of PMETAC segment and 5 wt % of OEGDMA, which is one of the lowest values reported so far for the amphiphilic coatings. Characterization of the coatings in terms of surface features, wettability, and hydration states have enabled the elucidation of different deicing mechanisms. Self-lubrication due to the existence of nonfreezable bound water led to the obtained low ice adhesion strength. This work offers a new approach for the exploration of PIL-based icephobic coatings for practical applications.

Seawater-triggered self-renewable amphiphilic coatings with low water swelling and excellent biofilm prevention properties

Amphiphilic antifouling coatings have the potential to revolutionize the field of eco-friendly antifouling coatings, which are still beset by the drawbacks of instability, complex procedures and water swelling. Herein, we construct seawater-triggered amphiphilic coatings with self-renewable capabilities in seawater via the facile casting of a physical mixture of a hydrolyzable polymer (PTMH), hydroxyl-terminated polydimethoxysilane and an isocyanate crosslinker. The hydrophilic chain is generated in situ from PTMH at the coating/seawater interface and thus ultimately mitigates its seawater swelling. The hydrolyzability of PTMH and the degradation of the urethane crosslinking bond endow the coating with self-renewable properties. Owing to the appropriate hydrolysis rate of PTMH, its water absorption is lower than 3 wt% for 30 days of seawater submersion. Notably, the biofilm prevention capability of the coatings is excellent, outperforming that of polydimethoxysilane-based polyurethane and self-polishing polymers in real sea conditions. We envision that this work will provide a new avenue to design microphase separation-based antifouling coatings for practical applications.

Investigation of N-Substituted Morpholine Structures in an Amphiphilic PDMS-Based Antifouling and Fouling-Release Coating.

Biofouling is a major disruptive process affecting the fuel efficiency and durability of maritime vessel coatings. Previous research has shown that amphiphilic coatings consisting of a siloxane backbone functionalized with hydrophilic moieties are effective marine antifouling and fouling-release materials. Poly(ethylene glycol) (PEG) has been the primary hydrophilic component used in such systems. Recently, the morpholine group has emerged as a promising compact alternative in antifouling membranes but is yet to be studied against marine foulants. In this work, the use of morpholine moieties to generate amphiphilicity in a poly(dimethylsiloxane) (PDMS)-based antifouling and fouling-release coating was explored. Two separate coating sets were investigated. The first set examined the incorporation of an N-substituted morpholine amine, and while these coatings showed promising fouling-release properties for Ulva linza, they had unusually high settlement of spores compared to controls. Based on those results, a second set of materials was synthesized using an N-substituted morpholine amide to probe the source of the high settlement and was found to significantly improve antifouling performance. Both coating sets included PEG controls with varying lengths to compare the viability of the morpholine structures as alternative hydrophilic groups. Surfaces were evaluated through a combination of bubble contact angle goniometry, profilometry, X-ray photoelectron spectroscopy (XPS), and marine bioassays against two soft fouling species, U. linza and Navicula incerta, known to have different adhesion characteristics.

Amphiphilic Alginate-Based Layer-by-Layer Coatings Exhibiting Resistance against Nonspecific Protein Adsorption and Marine Biofouling.

Amphiphilic coatings are promising materials for fouling-release applications, especially when their building blocks are inexpensive, biodegradable, and readily accessible polysaccharides. Here, amphiphilic polysaccharides were fabricated by coupling hydrophobic pentafluoropropylamine (PFPA) to carboxylate groups of hydrophilic alginic acid, a natural biopolymer with high water-binding capacity. Layer-by-layer (LbL) coatings comprising unmodified or amphiphilic alginic acid (AA*) and polyethylenimine (PEI) were assembled to explore how different PFPA contents affect their physicochemical properties, resistance against nonspecific adsorption (NSA) of proteins, and antifouling activity against marine bacteria (Cobetia marina) and diatoms (Navicula perminuta). The amphiphilic multilayers, characterized through spectroscopic ellipsometry, water contact angle goniometry, elemental analysis, AFM, XPS, and SPR spectroscopy, showed similar or even higher swelling in water and exhibited higher resistance toward NSA of proteins and microfouling marine organisms than multilayers without fluoroalkyl groups.

In situ generation of amphiphilic coatings based on a self-catalytic zwitterionic precursor and their antifouling performance

Amphiphilic coatings, especially those containing zwitterionic groups, are promising as antifouling coatings. Nevertheless, zwitterion based amphiphilic coatings suffer from poor miscibility between hydrophobic and hydrophilic ingredients. Zwitterionic precursors are good candidates to circumvent this issue, but acid or alkaline water must be used in-situ for the zwitterionic group to be self-generated. The in-situ feature restricts its applicability. The objective of this work focuses on developing a new zwitterionic precursor for easy fabrication of zwitterionic groups containing amphiphilic antifouling coatings. This precursor, i.e., triisopropylsilyl 2-methyl-3-((3-(triethoxysilyl)propyl) amino) propanoate (TMAP), was facile synthesized by one step of aza-Michael addition of (3-aminopropyl) triethoxysilane (APS) and triisopropylsilyl methacrylate. Then further blended with hydroxyl-terminated PDMS (HO-PDMS). The curing behavior, morphology, wetting behavior and the antifouling performance both in lab and field were thoroughly examined for coatings with various amounts of TMAP. It was interesting to find that TMAP could not only be hydrolyzed in-situ into a zwitterionic group via a self-catalytic effect during the curing process, but it also efficiently crosslinked the HO-PDMS under ambient conditions. In contrast to APS, TMAP was also more compatible with HO-PDMS and endowed the coating with relatively homogeneous and a smooth surface after prolonged submersion in artificial seawater. The TMAP-based amphiphilic coatings efficiently mitigated the microfouling in both the laboratory assay and the natural field condition in contrast with common silicone elastomer. Notably, excellent resistance for the macrofouler of the mussel was observed for these coatings, especially for 50 wt% TMAP containing coating with zero settlement.

Antifogging and antibacterial properties of amphiphilic coatings based on zwitterionic copolymers

Tackling fogging and microbial infection problems related to the endoscope lens remain challenges due to visual disturbances and bacterial threats to human health. Herein, highly transparent antifogging and antibacterial coatings were developed in a facile way by thermal curing of zwitterionic copolymers poly(n-butyl methacrylate-co-2-aminoethyl methacrylate-co-sulfobetaine methacrylate)s with 1,3,5-triformylbenzene. Characterizations of surface chemical composition and wettability suggested that the copolymer coatings exhibited amphiphilicity with a hydrophobic surface and internal hydrophilicity. The prepared amphiphilic coating exhibited excellent antifogging properties both in vivo and in vitro. The introduction of hydrophobic n-butyl methacrylate and cationic aminoethylmethacrylate could improve the stability and antibacterial capability of the coating. The growth inhibition rates of the coatings against Staphylococcus aureus and Escherichia coli were up to 99% and the copolymer coatings with the zwitterionic groups had low hemolytic rates less than 3%. The amphiphilic copolymer coatings combined antifogging and antibacterial properties may have a promising potential for applications in biomedical devices.

Amphiphilically modified self-stratified siloxane-glycidyl carbamate coatings for anti-icing applications

Icephobic coatings have applications in many industries to protect surfaces from deterioration and avoid catastrophic incidents. In this work, we report a new strategy to prepare amphiphilic siloxane-glycidyl carbamate coatings (AmpSiGC) coatings with anti-icing property. Polydimethyl siloxane (PDMS) and poly(ethylene glycol) (PEG) provided amphiphilicity for the AmpSiGC coatings. The designed experiment considered several factors: molecular weight of the surface-modifying polymers and their amount in the coating system. Although amphiphilic coatings have demonstrated promising results as marine coatings, investigations on their icephobic applications have been limited. This work discusses three aspects of the developed AmpSiGC systems: (1) preparation of the incorporated ingredients and their characterization by Fourier transform infrared spectroscopy (FTIR); (2) surface characterization of coatings via ATR (attenuated total reflectance)-FTIR, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM); and (3) ice-adhesion, electrochemical impedance spectroscopy (EIS), and mechanical property evaluations. Overall, the surface analysis indicated the presence of both hydrophobic and hydrophilic domains and most of the coatings demonstrated promising performance for anti-icing applications with desirable barrier and mechanical properties in comparison to controls.

Amphiphilic zwitterionic-PDMS-based surface-modifying additives to tune fouling-release of siloxane-polyurethane marine coatings

Amphiphilic coatings have shown promising performance for marine applications to deter and limit biofouling. Hydrophobic marine coatings are unable to deter marine organisms that prefer hydrophobic surfaces for settlements, thus a series of amphiphilic additives were prepared and introduced to a hydrophobic system to attain surface amphiphilicity and improved performance without changing the base matrix. In this work, we report the successful synthesis of amphiphilic additives where highly incompatible blocks of hydrophobic polydimethylsiloxane (PDMS) and hydrophilic poly(sulfobetaine methacrylate) (poly(SBMA)) were connected, using ARGET ATRP (activators regenerated by electron transfer atom transfer radical polymerization) controlled radical polymerization technique. The surface characterization confirmed the presence of self-migrated amphiphilic additives to the surface of hydrophobic coating systems, and biological assessments indicated that the additives desirably improved fouling-release performance of the base hydrophobic system against macroalgal spores (Ulva linza) and barnacles (Amphibalanus amphitrite) while these additives had no detrimental effect on ability of the base matrix to release bacteria (Cellulophaga lytica), diatoms (Navicula incerta), and mussels (Geukensia demissa). Furthermore, this study not only reported the outstanding contribution of poly(SBMA)-PDMS additives towards contending with marine biofouling as well as the facile preparation of amphiphilic additives, but also concluded that several factors should be considered in the design of these additives for tailoring hydrophobic coatings: 1) PDMS block with a molecular weight of 1000 M¯n is preferred over higher molecular weights of PDMS; 2) hydrophilic portion between a range of 50% to 80% provides the desired amphiphilicity on a surface; and 3) poly(SBMA) block size does not necessarily impact the effectiveness of an additive.

Amphiphilic Dicyclopentenyl/Carboxybetaine-Containing Copolymers for Marine Fouling-Release Applications.

Zwitterionic materials received great attention in recent studies due to their high antifouling potential, though their application in practical coatings is still challenging. Amphiphilic polymers have been proven to be an effective method to combat fouling in the marine environment. This study reports the incorporation of small amounts of zwitterionic carboxybetaine methacrylate (CBMA) into hydrophobic ethylene glycol dicyclopentenyl ether acrylate (DCPEA). A new set of copolymers with varying amphiphilicities was synthesized and coated on chemically modified glass substrates. The antifouling capabilities were assessed against the diatom Navicula perminuta and multiple species in the field. Unsurprisingly, high diatom densities were observed on the hydrophobic control coatings. The integration of small zwitterionic contents of only ∼5 wt % was already sufficient to rapidly form a hydrophilic interface that led to a strong reduction of fouling. Ultralow fouling was also observed for the pure zwitterionic coatings in laboratory experiments, but it failed when tested in the real ocean environment. We noticed that the ability to absorb large amounts of water and the diffuse nature of the interphase correlate with the adsorption of silt, which can mask the hydrophilic chemistries and facilitate the settlement of organisms. The amphiphilic coatings showed low fouling in dynamic short-term field exposures, which could be explained by the reduced tendency of the coatings for sediment adsorption.

Preparation and evaluation of fouling-release properties of amphiphilic perfluoropolyether-zwitterion cross-linked polymer films

The biofouling of marine structures presents a problem for maritime industries, including increasing fuel and operational costs. There has been much work developing and evaluating chemically ‘ambiguous’ amphiphilic coatings based upon hydrophobic fluoropolymer and hydrophilic poly(ethylene glycol) (PEG). Many of these coatings have shown good fouling-release performance against diatoms, which present a fouling challenge to commercially-available state-of-the-art silicone-based fouling-release coatings. However, PEG is prone to oxidation, which limits its practical use in the marine environment, and thus an alternative hydrophilic material would be desirable in the future development of amphiphilic coatings. In this regard, zwitterionic materials are emerging as a promising class of hydrophilic antifouling material, which we hypothesized would be a suitable alternative to PEG within amphiphilic coatings. To test this hypothesis, cross-linked amphiphilic films consisting of commercially available perfluoropolyethers and the zwitterionic monomer sulfobetaine methacrylate were developed and studied. The difficulty in formulating these chemically incompatible species was overcome by careful choice of solvents and a series of prototype cross-linked films were prepared in which increasing quantities of zwitterion were systematically incorporated. The fouling-release performance of these films was tested against the diatom Navicula incerta, a common microfouling organism responsible for the formation of so-called ‘slime’ layers, and antifouling performance with cypris larvae of two barnacle species, Balanus amphitrite, and Balanus improvisus. To expand the scope of the study, the clinically-relevant biofilm-forming pathogen Staphylococcus aureus, which is a major culprit in the infection and failure of millions of indwelling medical devices, was also evaluated. Results indicate that the incorporation of zwitterion into perfluoropolyethers leads to significant improvements in fouling-release performance and these amphiphilic coatings display potential in fouling-release applications.

Slime-resistant marine anti-biofouling coating with PVP-based copolymer in PDMS matrix

Poly(dimethylsiloxane) (PDMS) has been widely used as the fouling-release coatings due to its low surface energy. However, for marine anti-biofouling applications, current PDMS-based materials with hydrophobic property still suffer from marine slime attachment. Therefore, the design of novel amphiphilic coatings by modifying PDMS with hydrophilic polymers has been widely explored. In this work, based on poly(N-vinylpyrrolidone) (PVP), a novel hydrophilicity-active poly(N-vinyl-2-pyrrolidone-co-methyl methacrylate-co-butyl acrylate-co- 2-hydroxyethyl methacrylate) (PNMBH) was synthesized using a robust free radical polymerization method. Next, amphiphilic coatings were prepared by crosslinking different amounts of PNMBH with PDMS at room temperature. The resultant PNMBH-PDMS coatings were characterized with water contact angle tests, presenting their increased hydrophilicity and the optimal PNMBH content (10%). Moreover, the anti-biofouling performance of these coatings was evaluated using proteins (bovine serum albumin and fibrinogen), bacteria (Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus), and marine diatom (Navicula parva). Compared with pristine PDMS coating, PNMBH-PDMS coatings could reduce ∼82% adhesion of fibrinogen, ∼97% adhesion of Staphylococcus aureus, and ∼97% adhesion of diatom, the major composition of marine slime. More importantly, PNMBH-PDMS coatings were also tested in the marine field, and results showed their excellent anti-biofouling performance for at least 4 months in the ocean. This work developed a novel amphiphilic coating with appealing marine anti-biofouling performance and might provide new opportunities for marine coating applications.

Advances in design and manufacturing of environmentally friendly and biocide-free antifouling/foul-release coatings: replacement of fluorinate species

Amphiphilic coatings are nowadays described as the most promising strategy for the achievement of an effective and eco-friendly antifouling marine paint, based on a physical principle. Nevertheless, most of the preparations imply the introduction of fluorinate chemicals for the formation of the hydrophobic moieties, which are potentially toxic for the marine environment in the case of an accidental release. The present work evaluates the possibility of removing fluorinate species for the implementation of such coatings and their replacement with analogous long-alkyls. In particular, this work presents an easily implementable procedure for the manufacturing of an amphiphilic system that exploits the reactivity of a commercially available –OH-rich hybrid polysiloxane resin. The resin was first modified through sol–gel chemistry that was used in the grafting of a silane-bearing hydrophobic long-alkyl chain, while the introduction of the hydrophilic moieties was conducted contextually to the curing process, through the reaction with a commercially available PEG-ilate isocyanate hardener. The effective persistence of the amphiphilic character with respect to the replacement of the fluorinate silane by the alkylsilane was ensured by the measurement of the hysteresis contact angle. The effectiveness of the persistence of the antifouling/foul-release properties was assessed through testing against the adhesion and deposition of egg white, as a proteinaceous probe, Mytilus edulis (mussel) and Ulva intestinalis (algae). All the tests indicated that the amphiphilic coating prepared from long-alkyl silane performed even better than fluorinate silane-containing samples in this hybrid coating system resulting from the fusion of a xerogel and a resin. The results suggested that the use of a long alkyl silane was an effective alternative to the use of potentially noxious fluorinate silanes, with advantages that boost the ecological benefits and also include the performance of the coating.