Electrochemical Deposition and Surface-Initiated RAFT Polymerization: Protein and Cell-Resistant PPEGMEMA Polymer Brushes

Multistage Anticoagulant Surfaces: A Synergistic Combination of Protein Resistance, Fibrinolysis, and Endothelialization

Anticoagulant surface modification of blood-contacting materials has been shown to be effective in preventing thrombosis and reducing the dose of anticoagulant drugs that patients take. However, commercially available anticoagulant coatings, that is, both bioinert and bioactive coatings, are typically based on a single anticoagulation strategy. This puts the anticoagulation function of the coating at risk of failure during long-term use. Considering the several pathways of the human coagulation system, the synergy of multiple anticoagulation theories may provide separate, targeted effects at different stages of thrombosis. Based on this presumption, in this work, negatively charged poly(sodium p-styrenesulfonate-co-oligo(ethylene glycol) methyl ether methacrylate) and positively charged poly(lysine-co-1-adamantan-1-ylmethyl methacrylate) were synthesized to construct matrix layers on the substrate by electrostatic layer-by-layer self-assembly (LBL). Amino-functionalized β-cyclodextrin (β-CD-PEI) was subsequently immobilized on the surface by host-guest interactions, and heparin was grafted. By adjusting the content of poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), the interactions between modified surfaces and plasma proteins/cells were regulated. This multistage anticoagulant surface exhibits inertness at the initial stage of implantation, resisting nonspecific protein adsorption (POEGMA). When coagulation reactions occur, heparin exerts its active anticoagulant function in a timely manner, blocking the pathway of thrombosis. If thrombus formation is inevitable, lysine can play a fibrinolytic role in dissolving fibrin clots. Finally, during implantation, endothelial cells continue to adhere and proliferate on the surface, forming an endothelial layer, which meets the blood compatibility requirements. This method provides a new approach to construct a multistage anticoagulant surface for blood-contacting materials.

Synthesis of hyperbranched polymer films via electrodeposition and oxygen-tolerant surface-initiated photoinduced polymerization

HYPOTHESIS

Hyperbranched polymers, not only possess higher functionality, but are also easier to prepare compared to dendrimers and dendric polymers. Combining electrodeposition and surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) polymerization is hypothesized to be a novel strategy for preparing hyperbranched polymer films on conductive surfaces without degassing.

EXPERIMENTS

Polymer brush grafted films with four different architectures (i.e. linear, branched, linear-block-branched, and branched-block-linear) were prepared on gold-coated glass substrates using electrodeposition, followed by SI-PET-RAFT polymerization. The resulting film structure and thickness, surface topology, absorption property, and electrochemical behavior were confirmed by spectroscopy, microscopy, microbalance technique, and impedance measurement.

FINDINGS

These hyperbranched polymer brushes were capable of forming a thicker but more uniformly covered films compared to linear polymer brush films, demonstrating that hyperbranched polymer films can be potentially useful for fabricating protective polymer coatings on various conductive surfaces.

Polymer brushes for friction control: Contributions of molecular simulations

When polymer chains are grafted to solid surfaces at sufficiently high density, they form brushes that can modify the surface properties. In particular, polymer brushes are increasingly being used to reduce friction in water-lubricated systems close to the very low levels found in natural systems, such as synovial joints. New types of polymer brush are continually being developed to improve with lower friction and adhesion, as well as higher load-bearing capacities. To complement experimental studies, molecular simulations are increasingly being used to help to understand how polymer brushes reduce friction. In this paper, we review how molecular simulations of polymer brush friction have progressed from very simple coarse-grained models toward more detailed models that can capture the effects of brush topology and chemistry as well as electrostatic interactions for polyelectrolyte brushes. We pay particular attention to studies that have attempted to match experimental friction data of polymer brush bilayers to results obtained using molecular simulations. We also critically look at the remaining challenges and key limitations to overcome and propose future modifications that could potentially improve agreement with experimental studies, thus enabling molecular simulations to be used predictively to modify the brush structure for optimal friction reduction.

A Versatile Hydrophilic and Antifouling Coating Based on Dopamine Modified Four-Arm Polyethylene Glycol by One-Step Synthesis Method

A versatile hydrophilic and antifouling coating was designed and prepared based on catechol-modified four-arm polyethylene glycol. The dopamine (DA) molecules were grafted onto the end of the four-arm polyethylene glycol carboxyl (4A-PEG-COOH) through the amidation reaction, which was proven by ¹H NMR and FTIR analysis, assisting the strong adhesion of PEG on the surface of various types of materials, including metallic, inorganic, and polymeric materials. The reduction of the water contact angle and the bacteria-repellent and protein-repellent effects indicated that the coating had good hydrophilicity and antifouling performance. Raman spectroscopy analysis demonstrated the affinity between the polymeric surface and water, which further confirmed the hydrophilicity of the coating. Finally, in vitro cytotoxicity assay demonstrated good biocompatibility of the coating layer.

Probing polymer brushes with electrochemical impedance spectroscopy: a mini review

Polymer brushes are frequently used as surface-tethered antifouling layers in biosensors to improve sensor surface-analyte recognition in the presence of abundant non-target molecules in complex biological samples by suppressing nonspecific interactions. However, because brushes are complex systems highly responsive to changes in their surrounding environment, studying their properties remains a challenge. Electrochemical impedance spectroscopy (EIS) is an emerging method in this context. In this mini review, we aim to elucidate the potential of EIS for investigating the physicochemical properties and structural aspects of polymer brushes. The application of EIS in brush-based biosensors is also discussed. Most common principles employed in these biosensors are presented, as well as interpretation of EIS data obtained in such setups. Overall, we demonstrate that the EIS-polymer brush pairing has a considerable potential for providing new insights into brush functionalities and designing highly sensitive and specific biosensors.

Surface Grafting "Band-Aid" for "Everyone": Filter Paper-Assisted Surface-Initiated Polymerization in the Presence of Air

We report herein a facile and generalized approach to the modification of solid surfaces with polymer brushes under ambient conditions: filter paper-assisted surface-initiated Cu0 -mediated controlled radical polymerization (PSI-CuCRP). The polymerization solution wetted filter paper is sandwiched between a copper plate and an initiator-modified substrate, which allows the creation of a surface-initiated polymerization (SIP) "band-aid" so that everyone can perform the surface grafting selectively with good control over the quality of the polymer brushes employing low concentration and microliter amounts of the monomer solution. The versatility of this method is demonstrated by grafting different homo-, block-, and multicomponent polymer brushes by using the same activation system and reaction conditions, the polymerization process can be precisely controlled to yield uniform polymers and show high chain-end functionality which is exemplified by in situ tetra-copolymerization. The combination of photolithography and paper cutting enables to prepare arbitrary three-dimensional patterned polymer brushes on the surface.

PPEGMEMA-based cationic copolymers designed for layer-by-layer assembly

We have synthesized three PPEGMEMA-based cationic copolymers with similar amine contents but with systematic variation in the average length of the PEG side chains. The positively charged copolymers were paired with alginate to fabricate layer-by-layer assembled multilayered films. It was demonstrated that the polymeric design, in terms of the systematic variation in the average length of the PEG units, affects the polyelectrolyte multilayer growth mechanism and can be used to tune the structural properties and the water content of the layers. In addition, by partial cross-linking of the amine groups present in the copolymer backbone, disintegration of the film induced by pH changes was prevented. Finally, it was demonstrated how the cross-linked multilayered film can exhibit cationic, zwitterionic and anionic properties depending on the pH value and how these changes are associated with swelling, layer contraction and changes in water content.

PPEGMEMA-based cationic copolymers were synthesized and utilized in a layer-by-layer assembly process to prepare a multilayered film. Film properties were tuned with systematic variation in the average length of the PEG side chains.

Electrochemically Mediated Reversible Addition-Fragmentation Chain-Transfer Polymerization

An electrochemically mediated reversible addition-fragmentation chain-transfer polymerization (eRAFT) of (meth)acrylates was successfully carried out via electroreduction of either benzoyl peroxide (BPO) or 4-bromobenzenediazonium tetrafluoroborate (BrPhN2+) which formed aryl radicals, acting as initiators for RAFT polymerization. Direct electroreduction of chain transfer agents was unsuccessful since it resulted in the formation of carbanions by a two-electron transfer process. Reduction of BrPhN2+ under a fixed potential showed acceptable control, but limited conversion due to the generation of a passivating organic layer grafted on the working electrode surface. However, using fixed current conditions, easier to implement than fixed potential conditions, conversions > 80% were achieved. Well-defined homopolymers and block copolymers with a broad range of targeted degrees of polymerization were prepared.

Arginine-Based Polymer Brush Coatings with Hydrolysis-Triggered Switchable Functionalities from Antimicrobial (Cationic) to Antifouling (Zwitterionic)

Arginine polymer based coatings with switchable properties were developed on glass slides (GS) to demonstrate the smart transition from antimicrobial (cationic) to fouling-resistant (zwitterionic) surfaces. l-Arginine methyl ester-methacryloylamide (Arg-Est) and l-arginine-methacryloylamide (Arg-Me) polymer brushes were grafted from the GS surface via surface-initiated reversible addition-fragmentation chain-transfer (SI-RAFT) polymerization. In comparison to the pristine GS and Arg-Me graft polymerized GS (GS-Arg-Me) surfaces, the Arg-Est polymer brushes-functionalized GS surfaces exhibit a superior antimicrobial activity. Upon hydrolysis treatment, the strong bactericidal efficacy switches to good resistance to adsorption of bovine serum albumin (BSA), the adhesion of Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli, as well as the attachment of Amphora coffeaeformis. In addition, the switchable coatings are proven to be biocompatible. The stability and durability of the switchable coatings are also ascertained after exposure to filtered seawater for 30 days. Therefore, deposition of the proposed "smart coatings" offers another environmentally friendly alternative for combating biofouling.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

A hemocompatible polyurethane surface having dual fibrinolytic and nitric oxide generating functions

Thrombus formation remains a serious problem in developing blood compatible materials. Despite continuous, intensive efforts over many years to prepare surfaces that prevent clotting, such surfaces have not been achieved; indeed it seems that surface-induced clotting is inevitable. An alternative approach is to accept that clotting will occur and to design surfaces so that small, nascent clots will be lysed before they can cause harm. The generation of plasmin, as in the fibrinolytic system, may be adopted for this purpose. The vascular endothelium (the inner surface of intact blood vessels) releases nitric oxide (NO) on a continuous basis. NO protects against platelet activation and aggregation, and also has an anti-proliferative effect on smooth muscle cells (SMCs). Based on these two important functions of the vascular system, the approach of constructing a fibrinolytic surface that generates NO is developed in the present work. Poly(oligo(ethylene glycol) methyl ether methacrylate-co-6-amino-2-(2-methacylamido)-hexanoic acid) (poly(OEGMA-co-LysMA)) was attached to a vinyl-functionalized polyurethane (PU) surface by graft polymerization giving a surface (PU-POL) with protein-resistant properties (via poly(OEGMA)) and clot lysing properties (via poly(LysMA)). Selenocystamine, which catalyzes S-nitrosothiol decomposition to generate NO in the vasculature, was then immobilized on the PU-POL surface via covalent attachment. A dual functioning surface with fibrinolytic activity (lysis of nascent clots) and NO releasing ability (inhibition of platelet adhesion and SMC adhesion as well as proliferation) was thereby constructed.

Zwitterionic materials for antifouling membrane surface construction

Membrane separation processes are often perplexed by severe and ubiquitous membrane fouling. Zwitterionic materials, keeping electric neutrality with equivalent positive and negative charged groups, are well known for their superior antifouling properties and have been broadly utilized to construct antifouling surfaces for medical devices, biosensors and marine coatings applications. In recent years, zwitterionic materials have been more and more frequently utilized for constructing antifouling membrane surfaces. In this review, the antifouling mechanisms of zwitterionic materials as well as their biomimetic prototypes in cell membranes will be discussed, followed by the survey of common approaches to incorporate zwitterionic materials onto membrane surfaces including surface grafting, surface segregation, biomimetic adhesion, surface coating and so on. The potential applications of these antifouling membranes are also embedded. Finally, we will present a brief perspective on the future development of zwitterionic materials modified antifouling membranes.

STATEMENT OF SIGNIFICANCE

Membrane fouling is a severe problem hampering the application of membrane separation technology. The properties of membrane surfaces play a critical role in membrane fouling and antifouling behavior/performance. Antifouling membrane surface construction has evolved as a hot research issue for the development of membrane processes. Zwitterionic modification of membrane surfaces has been recognized as an effective strategy to resist membrane fouling. This review summarizes the antifouling mechanisms of zwitterionic materials inspired by cell membranes as well as the popular approaches to incorporate them onto membrane surfaces. It can help form a comprehensive knowledge about the principles and methods of modifying membrane surfaces with zwitterionic materials. Finally, we propose the possible future research directions of zwitterionic materials modified antifouling membranes.

Surface PEGylation of intraocular lens for PCO prevention: An in vivo evaluation

Posterior capsular opacification (PCO) is a common complication in cataract surgery. The development of PCO is attributed to the combination of adhesion, migration, proliferation, and transdifferentiation of the residual lens epithelial cells (LEC) onto the interface of intraocular lens (IOL) material and lens posterior, in which the initial adhesion is the beginning step and plays important roles. In the present study, hydrophilic polyethylene glycol (PEG) was immobilized onto IOL surface via plasma-aided chemical grafting procedure. The attenuated total reflection - Fourier transform infrared (ATR-FTIR) and contact angle (CA) - measurements indicate the successful surface PEGylation, as well as the excellent hydrophilicity of the surfaces. Compared with pristine IOL, the PEGylation does not influent its optical property, whereas the initial adhesion of LEC is greatly inhibited. In vivo ocular implantation results show that the PEGylated IOL presents good in vivo biocompatibility, and can effectively prevent the PCO development.

Bottom-Up Fabrication of PEG Brush on Poly(dimethylsiloxane) for Antifouling Surface Construction

Poly(dimethylsiloxane) silicones have found many applications in biomedical devices, whereas their surface hydrophobicity always brings about unexpected bioadhesion, causing complications of the implanted biomedical devices. In this work, surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization was utilized to generate PEG brushes on silicone surface, obtaining highly hydrophilic surface coatings. Such PEG brush coated silicone presents excellent antifouling to protein, cells, and bacteria, which may have great potential in implantable biomaterial surface modifications.

Mussel-Inspired Photografting on Colloidal Spheres: A Generalized Self-Template Route to Stimuli-Responsive Hollow Spheres for Controlled Pesticide Release

A thermo-controlled pesticide release system composed of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) thin film grafted polydopamine (PDA) (PDMAEMA-g-PDA) microcapsules is reported. SiO2 microparticles are used as a template to prepare PDA-coated SiO2 microparticles. The thermally-responsive PDMAEMA thin films are grafted on PDA surfaces using a metal-free surface-initiated photopolymerization approach without adding any photo-initiator or photosensitizer under UV light irradiation. The subsequent acid etching yields PDMAEMA-g-PDA hollow microcapsules. PDMAEMA-g-PDA microcapsules exhibit well-controlled release of avermectin (Av). The results show that the loading ability of PDMAEMA-g-PDA microcapsules of Av is up to 52.7% (w/w). The release kinetics of Av demonstrate that Av@PDMAEMA-g-PDA microcapsules exhibit temperature-controlled release performance. This work is significant for controlled release systems. This simple design is expected to be used in various applications, such as in controlled drug release and agriculture-related fields.

Polymer brush coatings regulating cell behavior: passive interfaces turn into active

Material technology platforms able to modulate the communication with cells at the interface of biomaterials are being increasingly experimented. Progress in the fabrication of supports is simultaneously introducing new surface modification strategies aimed at turning these supports from passive to active components in engineered preparations. Among these platforms, polymer brushes are arising not only as coatings determining the physical and (bio)chemical surface properties of biomaterials, but also as smart linkers between surfaces and biological cues. Their peculiar properties, especially when brushes are synthesized by "grafting-from" methods, enable closer mimicking of the complex and heterogeneous biological microenvironments. Inspired by the growing interest in this field of materials science, we summarize here the most prominent and recent advances in the synthesis of "grafted-from" polymer brush surfaces to modulate the response of adhering cells.

Antimicrobial PVK:SWNT nanocomposite coated membrane for water purification: performance and toxicity testing

This study demonstrated that coated nitrocellulose membranes with a nanocomposite containing 97% (wt%) of polyvinyl-N-carbazole (PVK) and 3% (wt%) of single-walled carbon nanotubes (SWNTs) (97:3 wt% ratio PVK:SWNT) achieve similar or improved removal of bacteria when compared with 100% SWNTs coated membranes. Membranes coated with the nanocomposite exhibited significant antimicrobial activity toward Gram-positive and Gram-negative bacteria (≈ 80-90%); and presented a virus removal efficiency of ≈ 2.5 logs. Bacterial cell membrane damage was considered a possible mechanism of cellular inactivation since higher efflux of intracellular material (Deoxyribonucleic acid, DNA) was quantified in the filtrate of PVK-SWNT and SWNT membranes than in the filtrate of control membranes. To evaluate possible application of these membrane filters for drinking water treatment, toxicity of PVK-SWNT was tested against fibroblast cells. The results demonstrated that PVK-SWNT was non toxic to fibroblast cells as opposed to pure SWNT (100%). These results suggest that it is possible to synthesize antimicrobial nitrocellulose membranes coated with SWNT based nanocomposites for drinking water treatment. Furthermore, membrane filters coated with the nanocomposite PVK-SWNT (97:3 wt% ratio PVK:SWNT) will produce more suitable coated membranes for drinking water than pure SWNTs coated membranes (100%), since the reduced load of SWNT in the nanocomposite will reduce the use of costly and toxic SWNT nanomaterial on the membranes.

Controlled protein absorption and cell adhesion on polymer-brush-grafted poly(3,4-ethylenedioxythiophene) films

Tailoring the surface of biometallic implants with protein-resistant polymer brushes represents an efficient approach to improve the biocompability and mechanical compliance with soft human tissues. A general approach utilizing electropolymerization to form initiating group (-Br) containing poly(3,4-ethylenedioxythiophen)s (poly(EDOT)s) is described. After the conducting polymer is deposited, neutral poly((oligo(ethylene glycol) methacrylate), poly(OEGMA), and zwitterionic poly([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide), poly(SBMA), brushes are grafted by surface-initiated atom transfer radical polymerization. Quartz crystal microbalance (QCM) experiments confirm protein resistance of poly(OEGMA) and poly(SBMA)-grafted poly(EDOT)s. The protein binding properties of the surface are modulated by the density of polymer brushes, which is controlled by the feed content of initiator-containing monomer (EDOT-Br) in the monomer mixture solution for electropolymerization. Furthermore, these polymer-grafted poly(EDOT)s also prevent cells to adhere on the surface.

Characterization of Polymer Brush Membranes via HF Etch Liftoff Technique

Surface modification using end-tethered polymer brushes is an attractive, versatile, and effective method of tailoring the surface properties of a material. However, because the chains are covalently attached, characterization of these films is limited. When polymer brushes are detached in their native state, as opposed to fabricating a cross-linked initiator support, additional analytical techniques can be employed. We report lifting off patterned polymer brush membranes from a silicon oxide surface via a hydrofluoric acid etch. This method allows examination of polymer brushes via TEM and thus provides information regarding the perfection of initiator self-assembled monolayer formation and brush growth, as well as the effect of different cross-linking procedures.

Enhancement of surface graft density of MPEG on alginate/chitosan hydrogel microcapsules for protein repellency

Alginate/chitosan/alginate (ACA) hydrogel microcapsules were modified with methoxy poly(ethylene glycol) (MPEG) to improve protein repellency and biocompatibility. Increased MPEG surface graft density (n(S)) on hydrogel microcapsules was achieved by controlling the grafting parameters including the buffer layer substrate, membrane thickness, and grafting method. X-ray photoelectron spectroscopy (XPS) model was employed to quantitatively analyze n(S) on this three-dimensional (3D) hydrogel network structure. Our results indicated that neutralizing with alginate, increasing membrane thickness, and in situ covalent grafting could increase n(S) effectively. ACAC(PEG) was more promising than ACC(PEG) in protein repellency because alginate supplied more -COO(-) negative binding sites and prevented MPEG from diffusing. The n(S) increased with membrane thickness, showing better protein repellency. Moreover, the in situ covalent grafting provided an effective way to enhance n(S), and 1.00 ± 0.03 chains/nm(2) was achieved, exhibiting almost complete immunity to protein adsorption. This antifouling hydrogel biomaterial is expected to be useful in transplantation in vivo.

Magnetic DNA vector constructed from PDMAEMA polycation and PEGylated brush-type polyanion with cross-linkable shell

A novel magnetic-responsive complex composed of polycation, DNA, and polyanion has been constructed via electrostatic interaction. The magnetic nanoparticles (MNPs) were first coated with a polycation, poly[2-(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA(30)), and then binded with DNA through electrostatic interaction; the complexes were further interacted with the brush-type polyanion, namely poly[poly(ethylene glycol)methyl ether methacrylate]-block-poly[methacrylic acid carrying partial mercapto groups] (PPEGMA-b-PMAA(SH)). The resulting magnetic particle/DNA/polyion complexes could be stabilized by oxidizing the mercapto groups to form cross-linking shell with bridging disulfide (S-S) between PPEGMA-b-PMAA(SH) molecular chains. The interactions among DNA, Chol-PDMAEMA coated MNPs, and PPEGMA-b-PMAA(SH) were studied by agarose gel retardation assay. The complexes were fully characterized by means of zeta potential, transmission electron microscopy (TEM), dynamic light scattering (DLS) measurements, cytotoxicity assay, antinonspecific protein adsorption, and in vitro transfection tests. All these results indicate that this kind of magnetic-responsive complex has potential applications for gene vector.

Permeability of anti-fouling PEGylated surfaces probed by fluorescence correlation spectroscopy

The present work reports on in situ observations of the interaction of organic dye probe molecules and dye-labeled protein with different poly(ethylene glycol) (PEG) architectures (linear, dendron, and bottle brush). Fluorescence correlation spectroscopy (FCS) and single molecule event analysis were used to examine the nature and extent of probe-PEG interactions. The data support a sieve-like model in which size-exclusion principles determine the extent of probe-PEG interactions. Small probes are trapped by more dense PEG architectures and large probes interact more with less dense PEG surfaces. These results, and the tunable pore structure of the PEG dendrons employed in this work, suggest the viability of electrochemically-active materials for tunable surfaces.

Electropatterning of binary polymer brushes by surface-initiated RAFT and ATRP

A new, simple, and effective method for preparing binary patterned brushes by electrodeposition and self-assembly is presented. The technique involves the use of electrochemistry to immobilize a chain transfer agent (CTA) on a patterned conducting substrate that mediate surface-initiated polymerization (SIP) through a reversible addition-fragmentation chain transfer (RAFT) process. The non-electropatterned surfaces were then backfilled with self-assembly of an atom transfer radical polymerization (ATRP) silane initiator where the polymerization of the next brush was initiated. The use of techniques such as RAFT and ATRP is well known to give a controlled polymerization mechanism, which would be of great advantage in generating binary patterned brushes. FT-IR imaging was used to analyze these films.

Colloidally templated two-dimensional conducting polymer arrays and SAMs: binary composition patterning and chemistry

A facile approach and strategy toward binary-composition, two-dimensional (2D) patterned surfaces of conducting polymer periodic arrays, together with thiol self-assembled monolayers (SAMs) is described. The method involved a Langmuir-Blodgett (LB)-like deposition of latex microsphere particles, electropolymerization via cyclic voltammetric (CV) techniques, and self-assembly of an amphiphile. The LB-like technique enabled the monolayer deposition of different sizes of polystyrene (PS) particles in hexagonal packing arrangement on planar substrates. Combining the LB-like method with CV electropolymerization is advantageous because it provides deposition control of a polymer interconnected network, controlled composition ratio of polymer and SAMs, and control of 2D size and spacing of the spherical void pattern. Electrochemical-quartz crystal microbalance (EC-QCM) in situ monitoring of the film deposition quantified a constant and linear growth rate, with varying viscoelastic behavior of the conducting polymer adsorption on planar and PS-templated substrates. The dual-patterned surface provided a good imaging contrast as observed by atomic force microscopy (AFM). Complementary analyses such as X-ray photoelectron spectroscopy (XPS), attenuated total internal reflection infrared (ATR IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and static contact angle measurements were used to characterize the formation of the patterned surface. The versatility of the method enables the potential for making various types of quantitative binary compositions and patterned surfaces using different combinations of conducting polymer or functional SAMs, which can be extended in the future to polymer brushes and layer-by-layer assembly of various materials.