Surface-initiated Photopolymerization Research Articles

Surface-Initiated Polymerizations Mediated by Novel Germanium-Based Photoinitiators.

Since surface-initiated photopolymerization techniques have gained increasing interest within the last decades, the coupling of photoinitiators to surfaces and particles has become an important research topic in material and surface sciences. In terms of surface modification and functionalization, covalently coupled photoinitiators and subsequent photopolymerizations are employed to provide a huge variety of surface properties, such as wettability, stimulus responsive features, antifouling behavior, protein binding, friction control, drug delivery, and many more. For this purpose, numerous type I and type II photoinitiators or other photosensitive moieties have been attached to different substrates so far. In our studies, a convenient and straightforward synthetic protocol to prepare a novel germanium-based photoinitiator (bromo-tris(2,4,6-trimethylbenzoyl)germane) in good yields was developed. The immobilization of this photoinitiator at the surface of silicon wafers and quartz plates was evidenced by X-ray photoelectron spectroscopy (XPS). Employing visible-light-triggered surface-initiated polymerization of different functional monomers, including acrylamide, perfluorodecyl acrylate, and fluorescein-o-acrylate, surfaces with various features such as hydrophilic/hydrophobic and fluorescent properties were prepared. This was also achieved in a spatially resolved manner. The polymer layers were characterized by contact angle measurements, UV-vis/fluorescence spectroscopy, spectroscopic ellipsometry, and XPS. The thicknesses of the surface grafted polymer layers ranged between 10 and 126 nm.

Tunable Luminescence and Enhanced Polar Solvent Resistance of Perovskite Nanocrystals Achieved by Surface-Initiated Photopolymerization.

Colloidal lead halide perovskite nanocrystals (PNCs) have demonstrated great potential as materials of light-emitting diodes if their colloidal and compositional instability could be addressed. Herein, we reported a facile surface-initiated photopolymerization method that introduced polymers on a CsPbBr3 PNC surface to achieve improved stability and regulated halide exchange of PNCs in polar solvents. Synthetic polymers grafted from the surface of an individual PNC surface stabilized the PNCs, in which the multidentate linkage initiators and the extending polymers were two essential factors. The polymer-grafted PNCs showed composition-dependent colloidal dispersity and structural stability in various polar organic solvents and aqueous condition. It was found that changing the polarity of dispersing solvents effectively switched the swelling and collapsed states of surface polymers on the PNC-polymer nanoparticles, which provided an on-off mechanism to regulate the permeation of halide anions into the PNC cores. Thus, halide exchange of polymer-grafted PNCs in a good solvent for polymers varied the composition of PNCs and their emissive color, while switching the nanoparticles into a poor solvent, for example, ethanol and water, collapsed the surface polymer, prohibited the halide exchange, and consequently retained the color stability. It was demonstrated that different CsPbX3 PNCs with collapsed surface polymers could coexist into one solvent medium, achieving simultaneous emission with a white display. We believe this work provided insights into the rational functionalization of PNC materials using well-defined synthetic polymers toward tunable emission and outstanding stability in polar media.

Design of a Composite Based on Polyamide Fabric-Hydrogel-Zinc Oxide Particles to Act as Adsorbent and Photocatalyst.

Surface-initiated photopolymerization has been run to synthesize a hydrogel with ZnO particles distributed uniformly along its structure, which has been loaded onto a polyamide fabric. Three samples have been obtained at different concentrations of zinc nitrate (10% (sample PA10); 20% (sample PA20) and 30% (sample PA30) of the weight of the fabric, respectively)) and subjected to gravimetric analysis, scanning electron microscopy and transmission electron microscopy. The effect of the adsorption parameters of the composite material on the removal Drimaren Rot K-7B dye from water has been studied. The Freundlich isotherm describes this process better than the Langmuir isotherm. As the results of the adsorption kinetics show, the process fits well with a pseudo-second-order equation and depends both on the boundary layer and on the structure of the adsorbent itself. The thermodynamic parameters have demonstrated that the process is endothermic and physical. When exposed to ultraviolet light, the discoloration of the dye solution accelerates due to the photocatalytic properties of the composite materials. The addition of H2O2 also speeds up further the process, while the reuse of the materials slows it down, gradually changing the kinetic parameters. The reaction has been attributed to first-order kinetic model, when the active centers of the materials and the number of oxidative radicals formed are numerous and to the second-order kinetic model at a lower reaction activity. Moreover, 52% decolorization of the dye solution (50 mg L−1) in the dark was achieved from composite material PA 30 (13.3 g L−1) in 120 min and 89% under UV light irradiation. The H2O2 addition (0.14 mmol L−1) enhanced it up to 98%. In the second and third use of the photocatalyst, the dye removal decreased to 80% and 60%. Composite material PA30 exhibits antibacterial activity against Gram-negative bacteria E. coli, being most effective at eliminating Gram-positive bacteria S. aureus.

Antifouling and chlorine-resistant cyclodextrin loose nanofiltration membrane for high-efficiency fractionation of dyes and salts

Antifouling loose nanofiltration membranes are prepared for effective fractionation of dyes and salts by the construction of a porous cyclodextrin polymer layer on membrane substrate. Octopus-shaped cyclodextrin macromonomers with pendant vinyl groups can be facilely prepared via a union of controlled radical polymerization and esterification reaction, which are then used to fabricate membrane. The surface-initiated photopolymerization of β-cyclodextrin-centered macromonomers could yield a porous polymer layer on the surface of the PVDF substrate. The porous structure could be well-tuned by adjusting the concentration of macromonomers or regulating the polymerization time. The optimal loose nanofiltration membranes have demonstrated high-efficiency separation ability for different dyes and low rejection ability for salts (<10%), owing to the selective layer of porous cyclodextrin polymer. Meanwhile, it maintains a high Congo red (CR) retention (∼99%) in a long-term filtration test. Furthermore, the cyclodextrin polymer layer also endows the membranes with predominant chlorine-resistance performance even after 15 days of immersion in sodium hypochlorite solution. The flux recovery ratio value of optimal membrane towards bovine serum albumin is 97.6% even after 5 antifouling cycles, and the antifouling ability is more than 10 times higher than that of the pristine PVDF membrane depending on the degree of membrane fouling by CR. The proposed strategy could provide helpful guidance in preparing antifouling loose nanofiltration membranes.

Phototethering of Collagen onto Polyetheretherketone Surfaces to Enhance Osteoblastic and Endothelial Performance

Polyetheretherketone (PEEK) is a candidate material for bone implants as an alternative to metals. However, PEEK exhibits poor osseointegration and low endothelial compatibility. This study demonstrates the phototethering of collagen onto PEEK surfaces to facilitate osteoblastic and vascular endothelial performance. In particular, collagen with methacryloyl groups is covalently tethered to the PEEK surface via surface-initiated photopolymerization. This process is simpler than the conventional method of collagen-tethering and can be extended to the surface-patterning treatment of collagen. The collagen is confirmed to be tethered to the PEEK surface using attenuated total reflection Fourier transform infrared measurements, bicinchoninic acid assays, and atomic force microscopic observations. When human bone marrow-derived mesenchymal stem cells (HbmMSCs) are cultured on collagen-tethered PEEK (COL-PEEK) surfaces, the cells favorably adhere and proliferate. After inducing osteogenic differentiation, the cells on the COL-PEEK surfaces show higher expression levels of osteoblast-related genes and mineralization than those on the PEEK surface. Moreover, the tethering of collagen greatly improves endothelial proliferation. The COL-PEEK surfaces promotes endothelial networking in coculture with HbmMSCs. These results suggest that COL-PEEK is highly compatible with both osteoblasts and vascular endothelial cells. COL-PEEK is a promising implant that induces osteogenesis and angiogenesis to repair bone tissues.

Chemically Tuned Intracellular Gene Delivery by Core-Shell Nanoparticles: Effects of Proton Buffering, Acid Degradability, and Membrane Disruption.

Nanoparticles consisting of a condensed nucleic acid core surrounded by protective layers which aid to overcome extracellular and intracellular hurdles to gene delivery (i. e., core-shell nanoparticles, CSNPs) synthetically mimic viruses. The outer shells shield the core and are particularly designed to enable facilitated release of the gene payload into the cytoplasm, the major limiting step in intracellular gene delivery. The hypothetical proton sponge effect and degradability in response to a stimulus (i. e., mildly acidic pH in the endosome) are two prevailing, although contested, principles in designing effective carriers for intracellular gene delivery via endosomal escape. Utilizing the highly flexible chemical-tuning of the polymeric shell via surface-initiated photo-polymerization of the various monomers at different molecular ratios, the effects of proton buffering capacity, acid-degradability, and endosomal membrane-lysis property on intracellular delivery of plasmid DNA by CSNPs were investigated. This study demonstrated the equivalently critical roles of proton buffering and acid-degradability in achieving efficient intracellular gene delivery, independent of cellular uptake. Extended proton buffering resulted in further improved transfection as long as the core structure was not compromised. The results of the study present a promising synthetic strategy to the development of an efficient, chemically-tunable gene delivery carrier.

Freeform Three-Dimensionally Printed Microchannels via Surface-Initiated Photopolymerization Combined with Sacrificial Molding.

Precise freeform microchannels within an aqueous environment have several biomedical applications but remain a challenge to fabricate. Carbohydrate glass materials have shown potential for three-dimensionally (3D) printing precise, microscale structures and are suitable as a sacrificial material to reconstruct complex channel architectures, but due to the rapid dissolution kinetics in hydrogels and the aqueous environment, protective coatings are required. Here, conformal coatings were applied to carbohydrate structures via surface-initiated photopolymerization (SIP) by incorporating a photoinitiator (PI) into freeform 3D printed isomalt structures using a custom 3D printer. Structures were then immersed into a photocurable prepolymer bath and exposed to light for reaction initiation. To achieve uniform distribution of photoinitiator molecules in 3D printed constructs, miscibility between commercial photoinitiators and isomalt was modeled using the group contribution method. A dye-based, type-two photoinitiator, Eosin Y disodium salt (EY), was selected for its miscibility with isomalt and stability under high temperature. A previously described Eosin Y (EY)/triethanolamine (TEA) radical polymerization system was used to polymerize poly(ethylene glycol) diacrylate (PEGDA). Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), surface morphology, and swelling ratio characterizations via SIP were performed. Coatings around freeform structures and solid surfaces were presented to demonstrate the capability of coating complex architectures. This coating method should facilitate the application of 3D sacrificial molding in a variety of hydrogels toward building biomimetic vascular constructs.

Enhanced adhesion effect of epoxy resin on carbon fiber-reinforced Poly(etheretherketone) via surface initiated photopolymerization of glycidyl methacrylate

Adhesives for carbon fiber-reinforced poly (etheretherketone) (CFR-PEEK) have attracted the interest of researchers as an effective means for bonding this newly developed lightweight and high-performance composite structures. In this study, we developed a method to overcome the lack of interaction between adherends and adhesives through the modification of glycidyl methacrylate (GMA) brushes via surface-initiated photopolymerization. To achieve a better formation of PGMA brushes, some parameters of the surface-initiated photopolymerization, for example, light intensities (e.g., 2, 4, and 8 mW/cm2) and exposure durations (e.g., 15, 30, 45, 60, 90, 120 min) of ultraviolet (UV) treatment, were optimized. The joints using the adherends with an optimized PGMA layer exhibited more than a two-fold increase in the ultimate lap shear strength compared to that using the bare CFR-PEEK adherends, when a commercially available epoxy film adhesive, FM 309-1, is utilized. The influence of the UV intensities was further revealed via a double cantilever beam test, and the adherends with the modification under 4 mW/cm2 of UV irradiation for 2 h exhibited the best performance, owing to the higher grafting density of the PGMA brushes.

Adhesion enhancement of Poly(etheretherketone) via surface-initiated photopolymerization of glycidyl methacrylate

Poly(etheretherketone) (PEEK) is a high-performance engineering thermoplastic with high heat deflection temperature. Owing to its low surface free energy, the untreated PEEK adherend may exhibit low bond shear strength with epoxy adhesives. This work presents a method to improve the adhesion performance of PEEK with epoxy adhesives through poly(glycidyl methacrylate) (PGMA) grafting. The PGMA-grafted PEEK (PEEK-g-PGMA) was prepared via surface-initiated photopolymerization under 2 and 8 mW/cm2, respectively. The influence of the irradiation duration and the removal of the polymerization inhibitor from the monomer on PGMA grafting are discussed herein. The results showed that (1) the PEEK-g-PGMA is obtained from the photopolymerization under 2 and 8 mW/cm2 of UV irradiation; (2) the long durations of the UV exposure promoted the formation of brushes; and (3) the polymerization inhibitor only slightly inhibited the polymerization, but effectively prevented the auto-polymerization of monomer solution during the UV irradiation. The enhanced performance of the epoxy adhesives was demonstrated by the single-lap shear tests using PEEK-g-PGMA joints. Under optimized concoctions, the lap shear strength of PEEK-g-PGMA was significantly enhanced to 15.1 MPa which is seven times higher than that of unmodified PEEK (2.5 MPa).

Continuous aerosol photopolymerization to coat de-agglomerated nanoparticles

A novel continuous aerosol photopolymerization technique to coat nanoparticles that have been previously de-agglomerated is presented. After de-agglomeration in a jet-impactor assisted fluidized bed, monomer vapors are condensed onto the surface of aerosolized nanoparticles via heterogeneous condensation. Photopolymerization is initiated through exposure to UV light. To demonstrate the process, titanium dioxide (TiO2) and methyl methacrylate (MMA) were selected as nanoparticle and organic monomer, respectively. We demonstrated this light-based technique, operated at ambient pressure and room temperature, is able to graft a PMMA-like film with a thickness of 1.5 nm on the surface of nanoparticles, confirmed by TEM and FTIR. XPS analysis confirmed formation of covalent bonds with the TiO2 surface, indicating a surface-initiated photopolymerization. Particle size measurements in suspension illustrated the efficiency of the de-agglomeration and subsequent coating process, as coated particles remained smaller than bare particles. UV–Vis absorbance spectra show that the coating facilitates dispersion in non-polar solvents. Finally, long-term stability experiment confirmed the suspension stability is enhanced not only because of the reduction of agglomerate sizes, but also as a result of the carbon coating that improves the interfacial interactions among particles, and between particles and solvent. This technique can be easily combined with any continuous inorganic nanoparticle generation process as a solvent-free post-synthesis approach to impart a functional coating.

Modulation of Foreign Body Reaction against PDMS Implant by Grafting Topographically Different Poly(acrylic acid) Micropatterns.

The surface of poly(dimethylsiloxane) (PDMS) is grafted with poly(acrylic acid) (PAA) layers via surface-initiated photopolymerization to suppress the capsular contracture resulting from a foreign body reaction. Owing to the nature of photo-induced polymerization, various PAA micropatterns can be fabricated using photolithography. Hole and stripe micropatterns ≈100-µm wide and 3-µm thick are grafted onto the PDMS surface without delamination. The incorporation of PAA micropatterns provides not only chemical cues by hydrophilic PAA microdomains but also topographical cues by hole or stripe micropatterns. In vitro studies reveal that a PAA-grafted PDMS surface has a lower proliferation of both macrophages (Raw 264.7) and fibroblasts (NIH 3T3) regardless of the pattern presence. However, PDMS with PAA micropatterns, especially stripe micropatterns, minimizes the aggregation of fibroblasts and their subsequent differentiation into myofibroblasts. An in vivo study also shows that PDMS samples with stripe micropatterns polarized macrophages into anti-inflammatory M2 macrophages and most effectively inhibits capsular contracture, which is demonstrated by investigation of inflammation score, transforming-growth-factor-β expression, number of macrophages, and myofibroblasts as well as the collagen density and capsule thickness.

Facile Fabrication of Hierarchically Thermoresponsive Binary Polymer Pattern for Controlled Cell Adhesion.

A versatile platform allowing capture and detection of normal and dysfunctional cells on the same patterned surface is important for accessing the cellular mechanism, developing diagnostic assays, and implementing therapy. Here, an original and effective method for fabricating binary polymer brushes pattern is developed for controlled cell adhesion. The binary polymer brushes pattern, composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly[poly(ethylene glycol) methyl ether methacrylate] (POEGMA) chains, is simply obtained via a combination of surface-initiated photopolymerization and surface-activated free radical polymerization. This method is unique in that it does not utilize any protecting groups or procedures of backfilling with immobilized initiator. It is demonstrated that the precise and well-defined binary polymer patterns with high resolution are fabricated using this facile method. PNIPAAm chains capture and release cells by thermoresponsiveness, while POEGMA chains possess high capability to capture dysfunctional cells specifically, inducing a switch of normal red blood cells (RBCs) arrays to hemolytic RBCs arrays on the pattern with temperature. This novel platform composed of binary polymer brush pattern is smart and versatile, which opens up pathways to potential applications as microsensors, biochips, and bioassays.

Multiple microarrays of non-adherent cells on a single 3D stimuli-responsive binary polymer-brush pattern.

We have developed a 3D smart binary polymer-brush pattern on the polymer substrate for inducing multiple cell microarrays aided by a lectin and temperature. The binary polymer-brush pattern composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(d-gluconamidoethyl methacrylate) (PGAMA) brushes is fabricated by combining the photolithography technique with a surface-initiated photo-polymerization (SIPP) method. We demonstrate that well-defined binary polymer-brush patterns with high resolution are fabricated using this facile method. The patterned hierarchical PNIPAM brushes exhibit reversible switching to the adhesion of red blood cells (RBCs) induced by thermo-responsiveness. The PGAMA brush domains resist adhesion of RBCs but bind specifically with concanavalin A (Con A), forming a lectin pattern to capture RBCs in a site-specific manner. Therefore, multiple cell microarrays on a single platform are generated with the aid of Con A and temperature. This novel platform composed of a smart binary polymer-brush pattern is versatile and specific, which opens up pathways to potential applications such as microsensors, biochips and bioassays.

Nanopatterned polymer brushes by reactive writing.

Polymer brush patterns were prepared by a combination of electron beam induced damage in self-assembled monolayers (SAMs), creating a stable carbonaceous deposit, and consecutive self-initiated photografting and photopolymerization (SIPGP). This newly applied technique, reactive writing (RW), is investigated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane SAM (PF-SAM) on silicon oxide, which, when modified by RW, can be selectively functionalized by SIPGP. With the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), we demonstrate the straightforward formation of polymer brush gradients and single polymer lines of sub-100 nm lateral dimensions, with high contrast to the PF-SAM background. The lithography parameters acceleration voltage, irradiation dose, beam current and dwell time were systematically varied to identify the optimal conditions for the maximum conversion of the SAM into a carbonaceous deposit. The results of this approach were compared to patterns prepared by carbon templating (CT) under analogous conditions, revealing a dwell time dependency, which differs from earlier reports. This new technique expands the range of CT by giving the opportunity to not only vary the chemistry of the created polymer patterns with monomer choice but also vary the chemistry of the surrounding substrate.

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.

Thermoresponsive PNIPAM/silica nanoparticles by direct photopolymerization in aqueous media

This article presents a simple and facile method to fabricate thermoresponsive polymer-grafted silica particles by direct surface-initiated photopolymerization of N-isopropylacrylamide (NIPAM). This method is based on silica particles bearing thiol functionalities, which are transformed into thiyl radicals by irradiation with UV light to initiate the polymerization of NIPAM in aqueous media at room temperature. The photopolymerization of NIPAM could be applied to smaller thiol-functionalized particles (approximate to 48 nm) as well as to larger particles (approximate to 692 nm). Hollow poly(NIPAM) capsules could be formed after etching away the silica cores from the composite particles. It is possible to produce tailor-made composite particles or capsules for particular applications by extending this approach to other vinyl monomers. (c) 2015 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 2015, 53, 1260-1267

Acid-degradable core–shell nanoparticles for reversed tamoxifen-resistance in breast cancer by silencing manganese superoxide dismutase (MnSOD)

Drug resistance acquired by cancer cells is a significant challenge in the clinic and requires impairing the responsible pathological pathway. Administering chemotherapeutics along with silencing resistance-basis activity using RNA interference (RNAi) is expected to restore the activity of the chemotherapeutic and generate synergistic cancer eradication. This study attempted to reverse tamoxifen (TAM)-resistance in breast cancer by silencing a mitochondrial enzyme, manganese superoxide dismutase (MnSOD), which dismutates TAM-induced reactive oxygen species (ROS) (i.e., superoxide) to less harmful hydrogen peroxide and hampers therapeutic effects. Breast cancer cells were co-treated with TAM and MnSOD siRNA-delivering nanoparticles (NPs) made of a siRNA/poly(amidoamine) (PAMAM) dendriplex core and an acid-degradable polyketal (PK) shell. The (siRNA/PAMAM)-PK NPs were designed for the PK shell to shield siRNA from nucleases, minimize detrimental aggregation in serum, and facilitate cytosolic release of siRNA from endosomal compartments. This method of forming the PK shell around the siRNA/PAMAM core via surface-initiated photo-polymerization enables ease of tuning NPs' size for readily controlled siRNA release kinetics. The resulting NPs were notably homogenous in size, resistant to aggregation in serum, and invulnerable to heparan sulfate-mediated disassembly, compared to siRNA/PAMAM dendriplexes. Gel electrophoresis and confocal microscopy confirmed efficient siRNA release from the (siRNA/PAMAM)-PK NPs upon stimuli-responsive hydrolysis of the PK shell. Sensitization of TAM-resistant MCF7-BK-TR breast cancer cells with (MnSOD siRNA/PAMAM)-PK NPs restored TAM-induced cellular apoptosis in vitro and significantly suppressed tumor growth in vivo, as confirmed by biochemical assays and histological observations. This study implies that combined gene silencing and chemotherapy is a promising strategy to overcoming a significant challenge in cancer therapy.

Photofunctional Construct That Interfaces Molecular Cobalt-Based Catalysts for H2 Production to a Visible-Light-Absorbing Semiconductor

Molecular cobalt-containing hydrogen production catalysts are grafted to a visible-light-absorbing semiconductor. The attachment procedure exploits the UV-induced immobilization chemistry of vinylpyridine to p-type (100) gallium phosphide (GaP). Single step surface-initiated photopolymerization yields a covalently attached polymer with pendent pyridyl groups that provide attachment points for assembling cobaloxime catalysts. Successful attachment is characterized by grazing angle attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR), which shows distinct vibrational modes associated with the catalyst, as well as X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure spectroscopy (XANES) that confirm the presence of intact Co(III) complex on the surface. The Co-functionalized photocathode shows significantly enhanced photoelectrochemical (PEC) performance in aqueous conditions at neutral pH, compared to results obtained on GaP without attached cobalt complex. PEC measurements, at 100 mW cm(-2) illumination, yield a 2.4 mA cm(-2) current density at a 310 mV underpotential.

Melamine-imprinted polymer grafts through surface photopolymerization initiated by aryl layers from diazonium salts

In this work, diazonium-based photoinitiators were electrografted on gold electrodes to provide specific, selective and ultrasensitive molecularly imprinted polymer (MIP) grafts for the detection of melamine. This toxic molecule was used as a template, while methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were the functional and crosslinking monomers, respectively. Surface-initiated photopolymerization was conducted because it is a simple and versatile mean for making ultrathin MIP grafts (∼25 nm thick). Both cyclic and square wave voltammetry (SWV) were used for investigating rebinding melamine by the MIP grafts. However, the latter permitted to achieve ultrasensitive detection down to 7.7 × 10−10 mol/L in PBS and 3.1 × 10−10 mol/L in milk. Recovery was found to be very good, levelling off at 92%.

Comparative Aminolysis Kinetics of Different Active Ester Polymer Brush Platforms in Postpolymerization Modification with Primary and Aromatic Amines

The kinetics of aminolysis between two different active ester polymer brush platforms, poly(4-pentafluorophenyl acrylate) (poly(PFPA)) and poly(N-hydroxysuccinimide-4-vinyl benzoate) (poly(NHS4VB)), are compared using primary and aromatic amines with varying reactivity toward postpolymerization modification. UV–vis was used to monitor the aminolysis of both brush platforms with 1-aminomethylpyrene (AMP), 1-aminopyrene (AP), and Ru(bpy)2(phen-5-NH2)(PF6) (Ru2+A). Using a pseudo-first-order kinetics model, the pseudo-first-order rate constant (k′) was calculated for each system. The k′ of poly(PFPA) modified with AMP, AP, and Ru2+A were 2.46 × 10–1, 5.11 × 10–3, and 2.59 × 10–3 s–1, respectively, while poly(NHS4VB) can only be functionalized with the alkyl amine, albeit at a slower rate constant, k′ of 3.49 × 10–3 s–1, compared to that of poly(PFPA) with AMP. The kinetics of surface-initiated photopolymerization of PFPA from oxide surfaces was also investigated as an effective method to control grafting den...