PDMS Coatings Research Articles

Amphiphilic Marine Antifouling Coatings Based on Zwitterion-Modified Silicone Polymers.

Silicone coatings are widely employed in marine antifouling applications due to their low surface energy. However, in static marine environments, pure silicone coatings are ineffective in preventing the adhesion of marine biofilms, which consist of proteins, marine bacteria, and extracellular matrices, ultimately promoting the attachment of macrofouling organisms. To address the limitations in antifouling performance under static conditions, this study introduces a silicone-based antifouling coating modified with zwitterionic polymers. Sulfobetaine (SB) zwitterionic segments were grafted onto the side chains of poly(dimethylsiloxane) (PDMS) to synthesize the amphiphilic polymer P(DMS-SB), which was incorporated into the PDMS network to create an interpenetrating network-structured silicone coating. The zwitterionic segments effectively inhibited the adhesion of proteins, bacteria, and algae through hydration effects. Compared to pure PDMS coatings, the adhesion of proteins, bacteria, and algae was reduced by 88%, 98.9%, and 99.3%, respectively. Additionally, the coating demonstrated excellent fouling-release properties, achieving a 91.3% removal rate for settled algae under water flow conditions and reducing the simulated barnacle adhesion strength by 68.4%. This coating presents a promising antifouling solution for ships, offshore structures, and aquaculture facilities in static marine environments with significant potential for widespread application.

Single glass and polymer coated phosphate glass microwire photoactuators with instant response times and large actuating angles

Over the years significant scientific attention has been given towards the design of advanced photoactuating architectures as they are important elements for various optical tweezers, grippers, and soft robot applications. Most of the currently available photoactuators, rely on the existence of a free-space illumination pathway from the light sources to the device or on the employment of bendable optical fibers, while consisting of two or more elements, i.e. the photoactuating material and the substrate. Herein, we report on a facile method of preparing single-component pristine microwires (MWs) that exhibit photoactuating features upon utilizing a soft phosphate glass doped with silver nanoparticles (AgNPs), without the need of any additional photoactuating element. The developed photoactuators exhibited bending angles of around 110°, within a couple of seconds. In addition, we have fabricated double-component polymer-coated phosphate glass MWs photoactuators, upon employing PDMS coatings on the surface of the so-formed glass MWs. The introduction of the polymer component boosts the bending angle of the photoactuating device to over 200° within the a few seconds upon modest laser irradiation. The presence of AgNPs within the glass MWs, play a key role on the remarkable performance of the developed photoactuators, both in terms of actuating angles as well as of the respective response times, since they assist on the effective transmission of laser irradiation energy to thermal energy. The fabrication method reported here appears promising for the development of high-performance and low-cost free-space, as well as fiber-based photoactuators.

Marine biofouling mitigation of PDMS-based network coating with cross-linked contact- and release-active organoalkoxysilane

Poly (dimethylsiloxane) (PDMS) elastomer is one of key polymer resins for fouling release (FR) coatings, but it shows extremely poor antifouling (AF) activity in seawater since bacteria and diatoms could readily attach to surface. Modifying PDMS-based coatings via incorporating antifouling additives is effective for enhancing overall FR and AF activity. In this work, we prepared a well-defined organoalkoxysilane coating additive with quaternary ammonium and benzoisothiazolinone pendent groups, and the synthesized copolymers were covalently conjugated onto PDMS network in a one-pot reaction. AF and FR activities of the modified PDMS coatings were studied against soft fouling microorganisms. When microorganisms come into contact the coating surface, contact-active action mode works, quaternary ammonium groups could cause bacteria cell membrane disruption and microalgae photosynthesize inhibition via positive charge. Unexpectedly, a surprisingly lasting antimicrobial efficiency could be still observed in the neighboring coating, even the top-surface was completely covered with bacteria biofilm. Chemically conjugated benzoisothiazolinone could be sustainably released via side-group hydrolysis, thus, repelling and preventing the planktonic foulings from approaching the coating surface via release-active action mode. The modified PDMS coating with dual antifouling action modes could inhibit the biofilm formation at solid-liquid-air three-phase contact line, and could find valuable applications in marine transportation, water treatment and other antifouling fields.

Enhanced adhesive and mechanically robust silicone-based coating with excellent marine anti-fouling and anti-corrosion performances.

Poly(dimethylsiloxane) (PDMS) is widely used in marine antifouling coatings due to its low surface energy property. However, certain drawbacks of PDMS coatings such as poor surface adhesion, weak mechanical properties, and inadequate static antifouling performance have hindered its practical applications. Herein, condensation polymerization is utilized to prepare PDMS-based polythiamine ester (PTUBAF) coatings that consist of PDMS, polytetrahydrofuran (PTMG), 2, 3, 5, 6-tetrafluoro-1, 4-benzenedimethanol (TBD) as the main chains and isobornyl acrylate(IBA) as the antifouling group. The surface adhesion to the substrate is enhanced due to the hydrogen bond between the coated carbamate group and the hydroxyl group on the surface of the substrate. Mechanical properties of PTUBAF are significantly improved due to the benzene ring and six-membered ring biphase hard structure. The strong synergistic effect of bactericidal groups and low surface energy surface endows the PTUBAF coating with outstanding antifouling performance. Due to the low surface energy surface, the PTUBAF coatings are also found to possess excellent anti-corrosion. Furthermore, since the PTUBAF coatings exhibit a visible light transmittance of 91 %, they can applied as protective films for smartphones. The proposed method has the potential to boost the production and practical applications of silicone-based coatings.

A PDMS coating with excellent durability for large-scale deicing

The icing of wind turbine blades leads to a decrease in output power, seriously jeopardizing the economic benefits and operational reliability of wind farms. Conventional deicing techniques require expensive equipment and consume a large amount of energy. Low-interfacial toughness coatings without energy dissipation are believed to be a highly potential passive deicing technology. However, the durability in service is facing challenges. Herein, low-interfacial toughness PDMS coatings were prepared by physical blending. Through the optimization of added plasticizers and SiO2, PDMS coatings with excellent large-scale deicing performance were obtained. The constant deicing force and ice adhesion strength were reduced to 14.69 N/cm and 12.63 kPa, respectively. Moreover, a systematic durability assessment of the PDMS coating was carried out to address the actual operating conditions of wind turbines. Fortunately, the results showed that the PDMS coating could withstand 200 icing/deicing cycles while maintaining constant deicing force and ice adhesion strength of less than 50 N/cm and 30 kPa, respectively. After long-term thermal aging (21 days), UV irradiation (42 days) and salt spray corrosion (20 days), the PDMS coating still retained superior icephobicity and outstanding large-scale deicing performance. This work contributes to the research and development of low-interfacial toughness materials for large-scale deicing applications on wind turbine blades.

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.

Geopolymer Antimicrobial and Hydrophobic Modifications: A Review

The article summarizes the state of the art in increasing antimicrobial activity and hydrophobic properties of geopolymer materials. Geopolymers are inorganic polymers formed by polycondensation of aluminosilicate precursors in an alkaline environment and are considered a viable alternative to ordinary Portland cement-based materials, due to their improved mechanical properties, resistance to chemicals, resistance to high temperature, and lower carbon footprint. Like concrete, they are susceptible to microbially induced deterioration (corrosion), especially in a humid environment, primarily due to surface colonization by sulphur-oxidizing bacteria. This paper reviews various methods for hydrophobic or antimicrobial protection by the method of critical analysis of the literature and the results are discussed, along with potential applications of geopolymers with improved antimicrobial properties. Metal nanoparticles, despite their risks, along with PDMS and epoxy coatings, are the most investigated and effective materials for geopolymer protection. Additionally, future prospects, risks, and challenges for geopolymer research and protection against degradation are presented and discussed.

Improved Mechanical and Ablative Properties of PDMS Coatings Incorporating Epoxy as a Suspended Chain

Flexible thermal protection materials with excellent mechanical and ablative properties were one of the key components in promoting the development of a new generation of aircraft. In the present work, a robust, strongly adhesive, and ablation-resistant PDMS coating was prepared through the covalent connection between PDMS and vinyl-functionalized epoxy resin (EAP) by hydrosilylation. The EAP synthesized by molecular design was uniformly dispersed in the PDMS matrix as an island phase-separation structure. The tensile strength, elongation at break, and shear strength of EAP-modified PDMS (EAP@PDMS) were significantly increased by 575%, 155%, and 183%, respectively, when compared with pure PDMS. Besides, the linear ablation rate (LAR) of EAP@PDMS was greatly declined, which was 80.1% lower than that of pure PDMS, exhibiting excellent ablation resistance. This work opened an avenue toward developing flexible thermal protection coatings with excellent mechanical and ablative properties for aerospace applications.

Exploring the water capture efficiency of covalently attached liquid-like surfaces.

The capture of moisture from the atmosphere through condensation has the potential to provide a sustainable source of water. Here, we investigate the condensation of humid air at low subcooling condition (11 °C), similar to conditions for natural dew capture, and explore how water contact angle and contact angle hysteresis affect the rates of water capture. We compare water collection on three families of surfaces: (i) hydrophilic (polyethylene oxide, MPEO) and hydrophobic (polydimethylsiloxane, PDMS) molecularly thin coatings grafted on smooth silicon wafers, which produce slippery covalently attached liquid surfaces (SCALSs), with low contact angle hysteresis (CAH = 6°); (ii) the same coatings grafted on rougher glass, with high CAH (20°-25°); (iii) hydrophilic polymer surfaces [poly(N-vinylpyrrolidone), PNVP] with high CAH (30°). Upon exposure to water, the MPEO SCALS swell, which likely further increases their droplet shedding ability. MPEO and PDMS coatings collect similar volume of water (around 5 l m-2day-1), both when they are SCALS and non-slippery. Both MPEO and PDMS layers collect about 20% more water than PNVP surfaces. We present a basic model showing that, under low heat flux conditions, on all MPEO and PDMS layers, the droplets are so small (600-2000 µm) that there is no/low heat conduction resistance across the droplets, irrespective of the exact value of contact angle and CAH. As the time to first droplet departure is much faster on MPEO SCALS (28min) than on PDMS SCALS (90min), slippery hydrophilic surfaces are preferable in dew collection applications where the collection time frame is limited.

Effective large-scale deicing based on the interfacial toughness tuning of a UV-curable PDMS coating

In this study, the effective large-scale deicing based on the interfacial toughness-tuning strategy of an ultraviolet-curable PDMS coating was developed. Methacrylate groups were grafted on the hydroxyl-terminated PDMS molecular chains to endow PDMS the response to UV irradiation. Then the precursor was doped with different proportions of silicon dioxide nanoparticle (SiO2 NP) to tune the interfacial toughness between the coating and the ice layer. The PDMS coating was fabricated through manual spraying and the polymerization under UV irradiation. The effects of the amounts of the methacrylate groups and SiO2 NP on the deicing properties of UV-curable PDMS coatings were investigated systematically. In addition, it was found that the large-scale deicing performance of the PDMS coating with 10% SiO2 NP improved when lowering the ambient temperature, which was mainly related to the increase of the shear modulus and thermal residual stress on the interface and might indicate attractive advantage on the extremely cold environment. Meanwhile, the durability and the adaptability to different substrates of the PDMS coating were also examined for the verification of the possible practical application. In summary, the effective large-scale deicing based on the interfacial toughness tuning of a UV-curable PDMS coating was achieved and the coating showed great potential for practice.

Comprehensive Measurement of the Adhesion between Ice or Glass and Model PDMS Coatings

Ice accretion is an unavoidable phenomenon that endangers the performance of outdoor infrastructure and vehicles at low temperatures. To combat ice accretion, the use of anti‐icing coatings has been one of the most appealing approaches because of their simplicity. Silicone elastomers have been increasingly employed due to their natural hydrophobicity, simple preparation, and low price. However, most of the characterization of silicone‐based polymers and other anti‐icing coatings has been done using unproven techniques that often do not directly relate to materials’ properties. In this work, the adhesion between glass and ice and four PDMS‐based elastomers has been studied by a combination of a macroscale shear test, a microscale technique (the Johnson–Kendall–Roberts (JKR) approach), and a commonly used push‐off test. Results are obtained at different temperatures and, importantly, different test velocities. The shear tests yield an energy release rate (the material's property related to adhesion) in the range of 1–10 J m−2, whereas the quasistatic JKR test yields values in the 0.1–0.5 J m−2 range for glass/PDMS interfaces. Ice/PDMS interfaces are found to have larger energy release rates in shear tests and lower values in quasistatic JKR tests. Both differences can be attributed to differences in interfacial crack dynamics.

Oligo(2-alkyl-2-oxazoline)-based graft copolymers for marine antifouling coatings

Poly(ethylene glycol) (PEG)-based graft copolymers have been widely applied for the modification of poly(dimethyl siloxane) (PDMS)-based coatings that resist marine biofouling. In this research, we synthesized oligo(2-alkyl-2-oxazoline) (OAOXA)-based graft copolymer analogues, and subsequently tested their applicability in the formulation of structurally similar coatings, aiming to highlight the influence of polymer composition on biopassive properties. In particular, poly(dimethyl siloxane methacrylate)-co-oligo(2-alkyl-2-oxazoline)methacrylate copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization, starting from oligo(2-ethyl-2-oxazoline)- and oligo(2-methyl-2-oxazoline)-methacrylate macromonomers (OEOXMA and OMOXMA, respectively). Amphiphilic copolymer films with OAOXA grafts were found to be more hydrophilic with respect to those obtained using PEG analogues. PDMS coatings containing the graft copolymers as surface additives were tested towards the settlement of the macrofouler Ficopomatus enigmaticus and the diatom Navicula salinicola. The biofouling experiments indicated that OAOXA-containing films showed a comparable and in some cases improved performance with respect to their PEG-based counterparts, thus highlighting how OAOXA-based graft copolymers represent a valid alternative to PEG derivatives as surface-active additives to design antibiofouling coatings.

Enhanced mechanical and adhesive properties of PDMS coatings via in-situ formation of uniformly dispersed epoxy reinforcing phase

A uniformly dispersed epoxy/polydimethylsiloxane (PDMS) hybrid system was prepared through hydrosilylation and in-situ polymerization reaction. The obtained epoxy/PDMS coating possessed enhanced mechanical and adhesive properties. The hybrid structure of epoxy/PDMS was confirmed by FTIR, 1H NMR, GPC and SEM, respectively. Results indicated that the tensile strength, elongation at break and shear strength of the epoxy-containing polydimethylsiloxane (EPS) modified PDMS (EPS-PDMS) were increased by 187 %, 185 % and 137 %, respectively, when compared to the pure PDMS. Besides, TGA analysis indicated that the initial degradation temperature of EPS-PDMS was well maintained when compared to that of pure PDMS. Therefore, the convenient strategy of in-situ formation of epoxy reinforcing phase with flexible long-chain siloxane into PDMS effectively integrated the advantages of two incompatible polymers. The prepared EPS-PDMS coatings with enhanced mechanical and adhesive properties show great potential applications in the aerospace and industrial fields as flexible thermal protection coatings.

Effect of Doping SiO2 Nanoparticles and Phenylmethyl Silicone Oil on the Large-Scale Deicing Property of PDMS Coatings.

Recently, low interfacial toughness (LIT) materials have been developed to solve large-scale deicing problems. According to the theory of interfacial fracture, ice detachment is dominated by strength-controlled or toughness-controlled regimes, which are characterized by adhesive strength or constant shear force. Here, a new strategy is introduced to regulate the interfacial toughness of poly(dimethylsiloxane) (PDMS) coatings using silicon dioxide nanoparticles (SiO2 NPs) and phenylmethyl silicone oil (PMSO). By systematically adjusting the doping proportion of SiO2 NPs and PMSO, it is found that a lower interfacial toughness can be achieved with a lower constant shear force. The synergistic effect of the two dopants on the adhesive strength and interfacial toughness is analyzed. Meanwhile, finite element method (FEM) analysis of ice detachment is conducted to show the cracking process intuitively and explicate the mechanism of lowering the interfacial toughness of PDMS by doping SiO2 NPs and PMSO. It can be concluded that the cohesive zone material (CZM) model is effective for simulating the deicing process of PDMS coatings and provides a comprehensive understanding of the modulation of interfacial toughness.

Breathable fabric-based triboelectric nanogenerators with open-porous architected polydimethylsiloxane coating for wearable applications

Triboelectric nanogenerators (TENGs), which can harvest low-frequency mechanical energy from human activities, are potential for wearable electronics, especially textile-based TENGs. Besides triboelectric performance, wearable comfort, like air permeability, is crucial for wearable electronics. However, the textile-based TENGs integrated with high performance and wearable comfort still remain challenging. Here, we construct the open porous architected PDMS coatings on fabric for breathable fabric-based TENG (oPF-TENG) based on the synergistic effect of insoluble NaCl, DBP and soluble silicone oil. The open porous structure constitutes the airflow channel with the air permeability of ∼73 mm/s. Meanwhile, the porous structure and the PVDF filler enhance the triboelectric output. The open circuit voltage, short circuit current and power density of oPF-TENG reach ∼600 V, ∼15 μA and 5.67 W/m2, respectively. The as-made oPF-TENG with good air permeability and triboelectric output can not only contribute to the human body energy harvesting but also show potential for wearable self-powered sensing.

Effect of the properties of long afterglow phosphors on the antifouling performance of silicone fouling-release coating

To improve the static antifouling performance of the fouling-release silicone antifouling coating, blue-green (BG), yellow-green (YG), and sky blue (SB) long afterglow phosphors (LAP) with two kinds of luminescence intensities are added into the silicone coating, respectively, and the LAP/polydimethylsiloxane (PDMS) composite antifouling coating with different colors and luminance was prepared. Using a scanning electron microscope (SEM), X-ray diffractometer (XRD), laser particle size analyzer, and fluorescence spectrometer, the crystal structure, particle size, fluorescence properties, and emission wavelength of LAP were studied. Through laser confocal scanning microscope (CLSM), tensile test, contact angle measurement, photometer, marine bacteria, and boat-shaped benthic diatom attachment test, the surface morphology and roughness, tensile properties, wettability, and surface of the coating were studied energy, fluorescence illuminance, and anti-fouling performance. The results showed that the addition of LAP increased the fracture strength, elastic modulus, and surface free energy of the coatings. Each kind of LAP can improve the performance of PDMS coatings to inhibit the adhesion of marine bacterial biofilm and benthic marine algae. The higher the luminous illuminance, the better the antifouling performance of the coating. The SB coating has the most excellent antifouling performance and in particular, the relative adhesion rate (RAR) of fouling organisms of the SB highlight LAP/PDMS composite antifouling coating is only 37.8 %. This research provides new ideas for the development of new fluorescent antifouling coatings and has a certain enlightening significance for improving the static antifouling performance of fouling-release antifouling coatings (FRC).

Conductive and superhydrophobic Ag/PDMS films with high stability for passive de-icing and electromagnetic shielding

In this work, silver nanoparticles (AgNPs) are synthesized and sprayed onto the surface of cotton fabric to produce a conductive film. Then a layer of poly(dimethyl siloxane) (PDMS) was deposited onto the film to prepare Ag/PDMS composite film. The Ag film is with FCC crystalline and particle-like morphology, while layers of organic PDMS are cladding the Ag micro-nano structures. With increasing spraying time, nano‑silver particles changed from round spherical to worm-like, resulting rougher and higher electrical conductivity. By optimizing the PDMS coatings, the contact angle of surface winkled-like microstructure reached 163° and volume resistivity was 9.2 × 10−3 Ω·cm. In addition to the improvement of interfacial adhesion, the introduction of PDMS made the loose particles closely connected, which enhanced the stability of the structure. Meanwhile, the films exhibited great electron-thermal effects, which could be applied in high-speed deicing. Combined with superhydrophobicity, the electromagnetic shielding efficiency can reach 75 dB. The Ag/PDMS films maintained high electromagnetic shielding effectiveness even for servicing in harsh environments, showing that this conductive superhydrophobic fabric composite can be applied as a new electromagnetic shielding material for flexible electronic devices.

Rationally Regulating the Mechanical Performance of Porous PDMS Coatings for the Enhanced Icephobicity toward Large-Scale Ice.

Ice accumulation on various surfaces in low-temperature and high-humidity environments is still a major challenge for several engineering applications. Herein, we fabricated a kind of PDMS coating with the introduction of porous structures under the surface by a two-step curing and phase separation method. The coatings with no further surface modification showed good hydrophobicity and icephobicity, and the typical ice adhesion strength was down to 40 kPa with a water contact angle of 116.5°. More than that, the porous PDMS coatings showed extraordinary icephobicity, especially toward large-scale ice (>10 cm2). In this case, the large-scale ice layer can be rapidly removed under a small external deicing force in a form of interface crack propagation rather than whole direct fracture. It was confirmed that by regulating the pore size and porosity of PDMS coatings properly, the stiffness mismatch between coatings and ice can be controlled to induce the initiation of interfacial cracks. On this basis, under the condition of a large-scale icing area, a small external deicing force can cause an increased surface stress concentration, and the formed interface cracks can propagate quickly, resulting in the ice layer falling off easily. In addition, under the influence of the size effect, ice can be removed without an additional force, and the minimum external force (per unit width) can be only 60 N/cm. This paper proposes that prefabricating a large number of microcracks at the interface can significantly weaken the bonding between ice and coatings, that is, reduce the fracture toughness. The new coatings have a remarkable effect toward large-scale icing.

Antifouling properties of amphiphilic poly(3-hydroxyalkanoate): an environmentally-friendly coating

The development of biofouling is a major problem for marine industries. The conception of antifouling and fouling release coatings, with controlled physical-chemical properties is a promising strategy. Among them, amphiphilic systems, such as those composed of a hydrophobic polydimethylsiloxane matrix and a hydrophilic polyethyleneglycol additive are the most efficient and up to date. Despite their effectiveness, these systems are questioned due to the petrochemical origin of PDMS. The aim of this project was to substitute the PDMS matrix with a biopolymer, poly(3-hydroxybuyrate-co-3-hydroxyvalerate) and to improve its anti-adhesion properties through the elaboration of an amphiphilic system, via the addition of PEG or PHBHHx-b-PEG copolymer. The results, including the physico-chemical properties of PHBHV based coatings and static adhesion tests on a marine bacterium, Bacillus 4J6 and a diatom, Phaeodactylum tricornutum are compared with those of PDMS and PEG-modified PDMS coatings. Real antiadhesion activity was obtained for the PHBHV/PHBHHx-b-PEG system for a promising eco-friendly strategy.

Amphiphilic hydrolyzable polydimethylsiloxane-b-poly(ethyleneglycol methacrylate-co-trialkylsilyl methacrylate) block copolymers for marine coatings. II. Antifouling laboratory tests and field trials

Poly(dimethylsiloxane) (PDMS) elastomer coatings containing an amphiphilic hydrolyzable diblock copolymer additive were prepared and their potential as marine antifouling and antiadhesion materials was tested. The block copolymer additive consisted of a PDMS first block and a random poly(trialkylsilyl methacrylate (TRSiMA, R = butyl, isopropyl)-co-poly(ethyleneglycol) methacrylate (PEGMA) copolymer second block. PDMS-b-TRSiMA block copolymer additives without PEGMA units were also used as additives. The amphiphilic character of the coating surface was assessed in water using the captive air bubble technique for measurements of static and dynamic contact angles. The attachment of macro- and microorganisms on the coatings was evaluated by field tests and by performing adhesion tests to the barnacle Amphibalanus amphitrite and the green alga Ulva rigida. All the additive-based PDMS coatings showed better antiadhesion properties to A. amphitrite larvae than to U. rigida spores. Field tests provided meaningful information on the antifouling and fouling release activity of coatings over an immersion period of 23 months.