Bioinspired self-adhesive polymer for surface modification to improve antifouling property

The catechol functional group of dopamine (3,4-dihydroxyphenethylamine) forms a strong coordinate bond with both inorganic and organic substrates in a wet environment. The nonfouling surfaces required for this process are typically prepared through the immobilization of poly(ethylene glycol), so-called, PEGylation. In this work, polyaspartamides containing adhesive catechol and methoxy PEG pendants were synthesized from polysuccinimide through successive aminolysis reactions. The adhesion and crosslinking of the polyaspartamide derivatives in pH-controlled aqueous media was successfully utilized to modify a glass surface using a simple immersion method. Contact angle, α-step profiler, SEM and EDS, XPS, and AFM were used to characterize and verify the surface coating. In addition, the biocompatibility and antifouling properties of the modified surface were elucidated with a cell viability test, and a protein adsorption experiment, respectively. This biocompatible polymer system has biomedical application potential for use in adhesives and the surface coating of various biomaterials.     

Silver‐releasing and antibacterial activities of polyphenol‐based polyurethanes

Inspired by mussel adhesive proteins, catechol functional groups play an important role in the ability of the mussel to adhere to organic and inorganic surfaces. A novel functional polyurethane (PU) based on hydrolysable tannins that contain a number of catechol groups was successfully synthesized and characterized. These catechol groups were used as a reducer for Ag (I) to form Ag (0), and to prepare polyurethane/silver nanoparticles composites. These kinds of polyurethane containing Ag nanoparticles showed obvious inhibition of bacterial growth because of the conjunct actions of the well‐known antibacterial property of silver and the antifouling property of PEG. It is possible for these materials to be applied widely into antibacterial adhesive coatings for surface modification due to their low cost and the material‐independent adhesive property of catechol groups in tannins. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41349.     

Bioinspired and biocompatible adhesive coatings using poly(acrylic acid)‐grafted dopamine

Poly(acrylic acid) (PAA) was grafted with dopamine to increase its adhesion force to metal surface. Nitinol plate surfaces were then modified by coating with PAA‐g‐dopamine. To synthesize PAA‐g‐dopamine, PAA was first activated by dicyclohexylcarbodiimide and N‐hydroxysuccinimide (NHS) to form PAA–NHS. Dopamine was then copolymerized with PAA–NHS in an aqueous medium at pH 8.5. We propose to increase the adhesion of adhesive PAA‐g‐dopamine on nitinol to improve its durability. In this article, we studied wettability, surface elemental composition, and surface morphology. Biocompatibility was also assessed by L929 fibroblast cells in vitro. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improvement in the adhesion of polyimide/epoxy joints using various curing agents

An improvement in the adhesion strength of polyimide/epoxy joints was obtained by (1) introducing a functional group on the polyimide surface, (2) improving the mechanical properties of the epoxy adhesive, (3) increasing the curing temperature, and (4) using polyamic acid as an adhesion‐promoting layer. The functional group on polyimide was introduced via treatment with aqueous KOH. An adhesion‐promoting layer was formed by spin coating polyamic acid onto a modified polyimide surface. The maximum adhesion strength of the polyimide/epoxy joint was obtained using polyamic acid as both the adhesion‐promoting layer and as the curing agent. The surface energy of the modified polyimide was examined using contact angle measurements and Fourier transform infrared spectroscopy, and the peel strength was determined by the T‐peel method. The peeled surfaces were analyzed using scanning electron microscopy and X‐ray photoelectron spectroscopy.© 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 812–820, 2002     

Adhesion of polyethylene plates photografted with methacrylic acid and acrylic acid with enzymatically modified chitosan solutions and X‐ray photoelectron spectroscopy analysis of failed surfaces

An investigation was carried out on the application of dilute chitosan solutions modified by a tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to the adhesion of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) plates photografted with carboxyl‐group‐containing hydrophilic monomers, such as methacrylic acid (MAA) and acrylic acid (AA). In the case where photografting was carried out at lower monomer concentrations or at lower temperatures, the adhesive strength sharply increased with lower grafted amounts. A sharp increase in the adhesive strength was found to be due to the formation of shorter grafted polymer chains at lower monomer concentrations and/or the restriction of the location of grafting to the outer surface region at lower temperatures. In addition, the adhesive strength also sharply increased at even lower grafted amounts for photografting onto the HDPE plates and/or that of AA because the location of grafting was restricted to the outer surface region. For the AA‐grafted LDPE and HDPE plates, substrate breaking was observed. This was attributed to the coverage of the substrate surfaces with grafted poly(acrylic acid) chains at lower grafted amounts and a high water absorptivity of the grafted layer. X‐ray photoelectron spectroscopy (XPS) analysis of the grafted LDPE plates incubated in a dopamine solution containing tyrosinase suggested that the increase in the adhesive strength was caused by the penetration of enzymatically modified chitosan solutions in the grafted layers and the subsequent reaction of quinone derivatives enzymatically generated with grafted polymer chains. In addition, the surface analysis of the failed surfaces by XPS showed that as the adhesive strength increased, the location of failure was shifted from the interface between the layers mixed with enzymatically modified chitosan materials and grafted polymer chains to the inside the grafted layer containing enzymatically modified chitosan materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of silver nanoparticle immobilized fibrillar silicate by poly(dopamine) surface functionalization

Surface modified fibrillar silicate (FS) was prepared by dopamine oxide polymerization and self‐assembly of poly(dopamine) (PDA) on the FS surface, presynthesized silver nanoparticles subsequently adhered to the PDA functionalized FS (FS‐PDA) surface by simply dipping FS‐PDA in silver nanoparticles solution, owing to the metal‐binding ability of catechol and nitrogen‐containing groups on the PDA coating on the surface of FS. The chemical composition of the modified FS surface was determined by X‐ray photoelectron spectroscopy. Surface morphological changes of the FS nanofibers were observed by transmission electron microscopy. The results indicated that the in situ spontaneous oxidative polymerization of dopamine on the FS surface and the immobilization of Ag nanoparticles on the surface of FS were successful. The FS‐PDA/Ag demonstrated a significant enhancement in antibacterial properties compared to the pristine FS by using Escherichia coli as model strain. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39859.     

Application of enzymatically gelled chitosan solutions to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semidilute chitosan solutions. The viscosity of the chitosan solutions increased highly by the tyrosinase‐catalyzed reaction and the subsequent reactions between o‐quinone compounds and chitosan. These highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and held them in water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. The increase in the amino group concentration of the chitosan solutions and the molecular mass of the chitosan used effectively led to the increase in adhesive strength of the glass slides. In addition, in the case where the chitosan solution was gelled by the enzymatic reaction with dopamine in the presence of poly(ethylene glycol), adhesive strength sharply increased at shorter reaction times concomitantly with the increase in the viscosity of the chitosan solutions because the tyrosinase activity effectively was retained by poly(ethylene glycol). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1818–1827, 2007     

Direct introduction of phosphonate by the surface modification of polymers enhances biocompatibility

A novel chemical method for the modification of polystyrene and nylon polymers by the reaction of diaryl carbenes permits the direct and efficient introduction of phosphonate residues upon the polymer surface. The method is simple to execute, involving solution coating to adsorb the reactive coating agent, followed by drying and thermolysis at temperatures not greater than 150 °C. This material can be further modified to the calcium phosphonate derivative, by treatment with aqueous calcium hydroxide. The modified polymers show enhanced biocompatibility of the modified polymer, as evidenced by the improved growth of MG63 human osteosarcoma cell line on the surface. This method is of significance since it offers a simple chemical protocol for the tailoring of the surface properties of materials, it avoids the need to construct ab initio new polymers for a given application, it provides an alternative to existing surface modification protocols, and it extends the range of polymers suitable as biocompatible materials .     

Reinforced soy protein isolate–based bionanocomposites with halloysite nanotubes via mussel‐inspired dopamine and polylysine codeposition

Fully renewable soy protein isolate (SPI)–based film with rigid strength and sufficient water resistance is difficult to attain. In this study, the mussel‐inspired surface chemistry of ?‐poly‐L‐lysine (?‐PL)/dopamine was exploited for codeposition onto halloysite nanotubes (HNTs) to engineer a multinetwork of HNT/SPI bionanocomposite films via physicochemical bonds. A series of ?‐PL/dopamine aqueous solutions at different concentration ratios were employed. The ?‐PL with abundant cationic amine groups could prevent the overoxidation of dopamine on HNT surfaces, thus maintaining sufficient free catechol groups for highly active reactions that improve the biphase interfacial adhesion. Moreover, HNTs surface entangled by ?‐PL chains could be more compatible with peptides. This codeposition of ?‐PL/dopamine on HNT (DLHNT) surfaces was analyzed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis. Compared to the control SPI film, the tensile strength of the nanocomposite film (DLHNTs0.5/SPI) was increased from 5.9 MPa to 8.25 MPa, the Young's modulus was improved by 166.4%, and the moisture absorption was reduced to 56.1% (87.2% of the control). In summary, a facile and mild bioinspired surface chemistry of ?‐PL/dopamine codeposition onto HNT surfaces was performed to prepare SPI‐based nanocomposite films with improved interfacial adhesion and benign compatibility. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46197.     

Surface modification of UHMWPE/fabric composite membrane via self‐polymerized polydopamine followed by mPEG‐NH2 immobilization

In this work, a novel approach to improve the antifouling properties of membrane surfaces was developed. First, a polydopamine layer was attached onto the surface of an ultrahigh molecular weight polyethylene/fabric composite microporous membrane based on dopamine self‐polymerization and adhesive behavior. Then, methoxy polyethylene glycol amine was covalently bonded with the polydopamine layer via a Schiff base reaction. The physicochemical properties of the modified composite membrane surface were investigated, and the results indicated this modification could effectively enhance the membrane surface hydrophilicity. Furthermore, the protein fouling resistance of both dopamine‐coated and methoxy polyethylene glycol amine immobilized composite membranes was evaluated. It was found that a dopamine coating cannot obviously enhance the membrane antifouling properties due to its strong bioadhesion behavior. However, the antifouling properties of the composite membranes were significantly improved after being immobilized with a methoxy polyethylene glycol amine layer. Consequently, a layer‐by‐layer modified composite membrane with excellent antifouling property was obtained. The pure water flux and flux recovery ratio of the resultant membrane were 764 L m^?2 h^?1 and 83%, respectively. The aim of this paper was to provide an effective approach to optimizing the separation efficiency and antifouling performance of the ultrahigh molecular weight polyethylene/fabric composite membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46428.     

Bioinspired Fabrication of Insensitive HMX Particles with Polydopamine Coating

The development of a facile method for large scale production of insensitive HMX particles is of great importance for energetic materials, especially for insensitive munitions. Inspired by mussels, HMX particles with a thin, robust, wettable and uniform coating based on the self‐polymerization of dopamine were prepared by one‐step solution stirring processes in the study. The as‐prepared HMX@PDA particles showed stable shape, size, and polymorphy compared with original HMX particles. With PDA (polydopamine) coating, the HMX@PDA particles exhibited better wettability, which could improve the adhesive properties between particles and other liquid components in a PBX (plastic bonded explosive). Furthermore, the mechanical sensitivities were decreased for the HMX@PDA particles because of the uniform and smooth PDA coating decreasing the hot spots on the surface of the HMX particles. HMX@PDA particles produced by a facile scalable process might provide a promising substitute for sensitive HMX particles to enhance the safety and adhesive properties when used in PBX.     

Application of chitosan solutions gelled by melB tyrosinase to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by melB tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semi‐dilute chitosan solutions. The viscosity of the chitosan solutions highly increased by the tyrosinase‐catalyzed quinone conversion and the subsequent nonenzymatic reactions of o‐quinones with amino groups of the chitosan chains. The viscosity of chitosan solutions highly increased in shorter reaction times by addition of melB tyrosinase. Therefore, in this study, the gelation of a chitosan solution was carried out without poly(ethylene glycol) (PEG), which was added for the gelation of chitosan solutions using mushroom tyrosinase. The highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and were held under water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. An increase in either amino group concentration of the chitosan solutions or molecular mass of the chitosan samples used effectively led to an increase in adhesive strength of the glass slides. Adhesive strength obtained by chitosan materials gelled enzymatically was higher than that obtained by a chitosan gel prepared with glutaraldehyde as a chemical crosslinking agent. In addition, the use of melB tyrosinase led to a sharp increase in adhesive strength in shorter reaction times without other additives such as PEG. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyelectrolytes to promote adhesive bonds of laser-structured aluminium

Aluminium is one of the most popular construction materials in machine and equipment manufacture as well as vehicle and aircraft construction. Particularly, in automotive and aircraft industries, the adhesive bonding of aluminium requires the pre-treatment of the adhesive surfaces. In this study laser pre-treatments were used to laterally control the surface roughness and clean the substrate surfaces by forming fresh aluminium oxide layers. In order to keep the adhesive properties stable over time, the laser pre-treated aluminium surfaces were subsequently coated with weak polyelectrolytes. The applied polyelectrolytes lower the driving forces for the adsorption of unwanted surface contaminations and provide reactive amino groups for the subsequent coupling of reactive adhesives. The surface topographies of the laser-treated aluminium surfaces were investigated in relation to the applied laser parameters (such as pulse frequency, and laser power) by means of scanning electron microscopy (SEM) and light-microscopic techniques (confocal microscopy). The adsorption of the polyelectrolytes was studied by X-ray photoelectron spectroscopy (XPS). Inverse water contact angle measurements using captive air bubbles were carried out to study the wettability (hydrophilicity/hydrophobicity) of the modified aluminium surfaces. Single lap joint tests carried out on joined AlMg3 sheets showed that the shear strengths can be significantly increased by pre-treatment with laser and coating of the alloy surfaces with weak polyelectrolytes. Furthermore, the application of polyelectrolytes improved the stability against corrosion. The article shows the increase of tensile shear strengths at adhesively bonded single lap shear samples after laser pre-treatment and also an increase in long-term stability due to of the combination of laser pre-treatment and coating with polyelectrolytes. Adhesive bonds of laser treated samples with and without polyelectrolyte coating have a higher stability against corrosion compared to untreated samples.     

Surface characterization and properties of functionalized nonwoven

Nonwoven materials have been increasingly used in many industries. The surface properties of nonwoven materials are of importance in these applications. In this study, functional nonwoven materials were prepared by sputtering deposition of copper (Cu), zinc oxide (ZnO), and polytetrafluoroethylene (PTFE) on the surface of polypropylene (PP) fibers. Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM) were employed to study the surface morphology and chemical compositions. The observations by AFM revealed the formation of functional nanostructures on the fibre surfaces and the ESEM examination confirmed the formation of functional compositions on the fiber surface. The metallic coating of Cu significantly improved the surface conductivity of the material. The transmittance analysis indicated that the ZnO coating obviously increased the ultra‐violet absorption of the material. The surface hydrophobicity of the nonwoven material was enhanced by the sputter coating of PTFE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication of highly efficient ultraviolet absorbing PVDF membranes via surface polydopamine deposition

Polydopamine (PDA) layers and particles self‐polymerized by dopamine have ultraviolet (UV) absorbing property besides versatility and adhesive ability. Herein, a facile strategy for preparing poly(vinylidene fluoride) (PVDF) membrane coated with a thick PDA layer was developed to decrease UV transmittance through the surface modification of PVDF membrane. The PVDF membrane was modified by PDA deposition after pretreated with KOH/alcohol and KMnO₄/KOH solution. Furthermore, we investigated the effect of coating conditions such as concentration of dopamine and Tris–HCl buffer solution, coating time, and temperature on the performance of membranes. The characterization results indicated that it is more conductive for PDA deposition on the surface PVDF‐OH films than original PVDF films. Most importantly, UV transmittance of PVDF‐OH film modified in dopamine solution under optimum condition for one time can decrease to as low as 0.122% at 320 nm, which showed excellent UV‐shielding property. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45746.     

Mussel‐Inspired Hydrogel Composite with Multi‐Stimuli Responsive Behavior

A mussel‐inspired adhesive hydrogel with pH, temperature, and near‐infrared (NIR) light–responsive behavior is designed. The hydrogel system is formulated by combining chitosan modified with catechol motifs, thermo‐responsive poly(N‐isopropylacrylamide) terminated with catechols, and light‐absorbing polypyrrole nanoparticles (PpyNPs). The effects of catechol concentration, molar ratio of Fe³⁺ to catechol units, pH, and the incorporation of the PpyNPs on the mechanical property of the formed hydrogel are investigated. The responsive behaviors of the resulting hydrogel composite to pH, temperature, and NIR light are also demonstrated. The obtained hydrogel also shows promising adhesive property to glass and steel substrates. It is anticipated that the fabricated adhesive hydrogel with multi‐responsive behavior, especially NIR light response, can potentially be useful in a wide range of biomedical applications, such as remotely controlled release systems and removable sealant materials.     

The Effect of Different Surface Pretreatment Methods on Nano-adhesive Application in High Strength Steel and Aluminum Bonding

Epoxy adhesives (single and two components) modified with SiO₂ nano-particles were used in this investigation to glue aluminum alloy and also two types of high strength steel (dip-galvanized steel DP 600 and micro-alloyed steel ZStE340). To improve the adhesion between metal surfaces and adhesives, the metal surfaces were pretreated with: a self-indicating pretreatment (SIP^*); corundum blasting; corundum blasting + a SIP coating; and a Pyrosil^® treatment + SurALink^® primer (PG 15 for epoxy adhesive). A single-lap shear tension test, done in accordance to DIN EN 1465, was used to determine the adhesive strength. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis were used to analyze fractures that took place in the samples. The results showed that the adhesion strength of glued samples, containing the nano-particles modified adhesive, had significantly higher strength than unmodified ones. Pretreatment of the metal surfaces affected the adhesion, using nano-adhesives, only slightly. The adhesive strength values for single component epoxy resins were higher than those for two component epoxy resins. It was found that steel samples fractured adhesively at the steel surfaces. Aluminum treated samples indicated after pretreatment an increase in adhesive strength and the fracture occurred adhesively at the aluminum surfaces. Aluminum glued with two-component adhesives and pretreated with corundum blasting plus a SIP coating showed a mixed fracture mode; adhesively at the aluminum surface and cohesively in the adhesive layer.     

Functional graphene oxide nanosheets modified with cyclodextrins for removal of Bisphenol A from water

A novel type of functional graphene oxide nanosheets (GNs) modified with β-cyclodextrins (β-CDs) have been developed by coating dopamine-functionalized cyclodextrin (DACD) molecules on GNs for removing Bisphenol A (BPA) molecules from water. The DACD molecules with both β-CD groups for achieving adsorption property and dopamine (DA) groups for achieving adhesion property are synthesized by grafting DA onto carboxymethyl-β-cyclodextrin (CmβCD). The proposed DACD molecules can be firmly coated on the surfaces of various inorganic and organic substrates. Due to the large specific surface area of GNs, DACD-coated GNs (DACD@GNs) are proposed for efficient adsorption separation of BPA molecules from water. Due to the host-gust complexation between the BPA molecules in water and β-CDs on DACD@GNs, the fabricated DACD@GNs exhibit excellent adsorption performances. The adsorption kinetics can be explained via the pseudo-second-order model effectively. The experimental adsorption capacity of DACD@GNs is 11.29 mg·g^-1 for BPA. Furthermore, after the adsorption process, the DACD@GNs can be easily separated from aqueous solutions via vacuum filtration with porous membranes, and then regenerated by simply washing with ethanol. The proposed strategy in this study can be used for effectively functionalizing the surfaces of various substrates with functional β-CDs, which is highly promising in applications in the field of adsorption separations, especially water treatments.     

Adhesion of DOPA-Functionalized Model Membranes to Hard and Soft Surfaces

The adhesive proteins secreted by marine mussels form a natural glue that cures rapidly to form strong and durable bonds in aqueous environments. These mussel adhesive proteins contain an unusual amino acid, 3,4-dihydroxy-L-phenylalanine (DOPA), which is largely responsible for their cohesive and adhesive strengths. In this study, we incorporated DOPA into diblock and triblock polymers and developed a membrane contact experiment to assess the adhesive interactions of these materials with TiO(2) and tissue surfaces. In a typical experiment a micrometer-thick DOPA-functionalized elastomeric membrane is attached to the end of a cylindrical glass tube. Application of a positive pressure to the tube brings the membrane into contact with the surface of interest. The negative pressure needed to separate the membrane from the substrate is a measure of the strength of the adhesive interaction. The test confirms previous results obtained with TiO(2) substrates. Because the membrane geometry is well suited for rough or chemically heterogeneous surfaces, it is ideal for studies of tissue adhesion. DOPA was found to give strong adhesion to tissue surfaces, with the strongest adhesion obtained when the DOPA groups were oxidized while in contact with the tissue surface.     

Rapid production of micropatterned surfaces using a fluid dynamical instability

The continuous, high speed patterning of polyethylene films with a micron‐structured silicone coating was investigated in a roll coating process that did not depend on the use of prestructured tools. Thermally curable polydimethylsiloxane (PDMS) resin was rheologically modified by the addition of highly agglomerated, aerosol‐derived silica and resulted in a Herschel–Bulkley fluid. Application of the modified siloxane in a roll coating process resulted in a fluid dynamical instability at high capillary numbers promoting the spontaneous formation of randomly branched surface structures. The shear‐thinning properties of the nanoparticle‐doped PDMS resin were adjusted as to preserve the wet, structured coating during the following thermal curing step. The highly regular pattern was characterized in terms of averaged branch width and could be controlled from micro‐ to millimeter size by adjusting coating roll velocity and roll gap distance. The adhesive properties of the structured coating were compared to unstructured conventional silicone coatings by measuring the release force of pressure‐sensitive adhesives. For rubber‐based tape, the release force of patterned PDMS was reduced by a factor of up to eight if compared to smooth reference silicone. These ultra‐low adhesive coatings may find applications in packaging, food processing, and for covering sanitary surfaces, offering a cost‐effective alternative to conventional surface structuring methods. POLYM. ENG. SCI., 46:1541–1547, 2006. © 2006 Society of Plastics Engineers