Multifunctional Polymer Materials: From Synthesis to Disinfection

Polymer materials have wide applications in many industries, such as the food, pharmacy, construction, textile, and cosmetics industries. For the past few years, polymer materials have drawn the attention of scientists and engineers as a good disinfectant due to their advanced manufacturing methods, large surface areas, good stability, and lowcost. More importantly, polymer materials can be functionalized with various chemical groups to increase their affinity towards microorganisms and broaden their applications. In this thesis, four types of multifunctional polymer materials were synthesized to investigate their disinfection ability on bacterial cells.By using molecular imprinting technology, a small molecule-chloramphenicol-imprinted polymer material of nanometer size was prepared via precipitation polymerization, and large bacteria-imprinted polymer materials of micrometer size were synthesized via surface imprinting-Pickering emulsion polymerization. Both materials had highly specific binding to the targeted template and could be used as adsorbents. In precipitation polymerization, 3-(acrylamido)phenylboronic acid was added to introduce boronic acid on the material surface. In neutral and basic aqueous solutions, boronic acid groups formed reversible boronate ester bonds with the cis-diol groups of the polysaccharides on bacterial surfaces. The release of chloramphenicol led to a high antibiotic concentration around the bacterial cells, which killed the cells. In Pickering emulsion polymerization, positively charged vinyl-functionalized polyethylenimine self-assembled with negatively charged bacterial cells and acted as a stabilizer for the emulsion. Therefore, bacteria-recognition sites based on the bacteria’s physical property formed on the surface of polymer beads after crosslinking polymerization. Ag+ was released from the preloaded hydrophobic Ag nanoparticles in the polymer beads to deactivate the bound bacterial cells.To realize multifunctional materials for antibacterial applications, nanometer sized polymer materials were prepared with glycidyl methacrylate by precipitation polymerization and microemulsion polymerization. The epoxide groups were opened by polyethylenimine, which was further used to stabilize Ag nanoparticles. The final material selfassembled with bacterial cells via electrostatic interactions. The amino groups and Ag nanoparticles endowed the composite material with disinfection ability. The molecular spectra of bacteria could also be acquired via surfaceenhanced Raman scattering from the surface Ag nanoparticles.In addition to spherical polymer materials, temperature tunable deactivation polymers were also synthesized with (methacryloyloxy)ethyl]trimethylammonium by atom transfer radical polymerization, which was initiated by an initiator containing a boronic acid group. By further modification of the terminal alkyl bromide, a fluorescent molecule,fluorescein 5(6)-isothiocyanate, was added to the polymer chain. The obtained polymers self-assembled with bacterial cells via reversible boronate ester bonds and electrostatic interactions. At 40 ℃, the polymers showed effective deactivation of bacterial cells via a synergistic effect. At 20 ℃, the polymers displayed lower or no toxicityto bacterial cells and could be used to label bacterial cells in flow cytometry and fluorescence imaging

Synthesis of Bacteria Imprinted Polymers by Pickering Emulsion Polymerization

Molecularly imprinted polymers have been studied for a long time and have found useful applications in many fields. In most cases, small organic molecules are used as templates to synthesize imprinted polymers. In contrast to low molecular weight targets, large biological molecules and cells are more challenging to use as templates to synthesize cell-recognizing materials. This chapter presents an interfacial imprinting method to synthesize bacteria-recognizing polymer beads using Pickering emulsion polymerization. The tendency of bacteria to reside between two immiscible liquids is utilized to create surface-imprinted binding sites on cross-linked polymer microspheres

Boronic Acid Functionalized Nanosilica for Binding Guest Molecules

Dendritic fibrous nanosilica (DFNS) has very high surface area and well-defined nanochannels; therefore, it is very useful as supporting material for numerous applications including catalysis, sensing, and bioseparation. Due to the highly restricted space, addition of molecular ligands to DFNS is very challenging. This work studies how ligand conjugation in nanoscale pores in DFNS can be achieved through copper-catalyzed click reaction, using an optional, in situ synthesized, temperature-responsive polymer intermediate. A clickable boronic acid is used as a model to investigate the ligand immobilization and the molecular binding characteristics of the functionalized DFNS. The morphology, composition, nanoscale pores, and specific surface area of the boronic acid functionalized nanosilica were characterized by electron microscopy, thermogravimetric and elemental analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption measurements. The numbers of boronic acid molecules on the modified DFNS with and without the polymer were determined to be 0.08 and 0.68 mmol of ligand/g of DFNS, respectively. We also studied the binding of small cis-diol molecules in the nanoscale pores of DFNS. The boronic acid modified DFNS with the polymer intermediate exhibits higher binding capacity for Alizarin Red S and nicotinamide adenine dinucleotide than the polymer-free DFNS. The two types of boronic acid modified DFNS can bind small cis-diol molecules in the presence of large glycoproteins, due in large part to the effect of size exclusion provided by the nanochannels in the DFNS

Recyclable nanoparticles based on a boronic acid–diol complex for the real-time monitoring of imprinting, molecular recognition and copper ion detection

Molecularly imprinted polymers (MIPs) have now become one of the most remarkable materials in the field of molecular recognition. Although many efforts have been made to study the process and mechanism of molecular imprinting, it has not been possible to monitor the interactions between the template and the growing polymer chains under real-time experimental conditions. The behavior of the template–monomer complex during the whole polymerization process has remained largely unknown. In this work, we introduce a fluorescence technique that allows monitoring of the template–functional monomer complex during an actual imprinting process, as well as the real-time signaling of template binding and dissociation from the imprinted polymer. For the first proof-of-principle, we select Alizarin Red S (ARS) and 4-vinylphenylboronic acid as the template and functional monomer, respectively, to synthesize MIP particles via precipitation polymerization. As the formation of the template–functional monomer complex leads to strong fluorescence emission, it allows the status of the template binding to be monitored throughout the whole reaction process in real time. Using the same fluorescence technique, the kinetics of template binding and dissociation can be studied directly without particle separation. The hydrophilic MIP particles can be used as a scavenger to remove ARS from water. In addition, the MIP particles can be used as a recyclable sensor to detect Cu ions. As the Cu ion forms a stable complex with ARS, it causes ARS to dissociate from the MIP nanoparticles, leading to effective fluorescence quenching. The non-separation analytical method based on fluorescence measurement provides a convenient means to study molecular imprinting reactions and the kinetics of molecular recognition using imprinted polymers. The recyclable nanoparticle sensor allows toxic Cu ions to be detected directly in water in the range of 0.1–100 μM with a recovery of 84–95%

Hydroxide conducting BAB triblock copolymers tailored for durable high-performance anion exchange membranes

Well-designed block copolymers with a controlled co-continuous microphase morphology can be applied as efficient anion exchange membranes (AEMs) for fuel cells and water electrolyzers. In the present work, we have prepared and studied a series of BAB triblock copolymers consisting of a central cationic polyfluorene A block with flanking hydrophobic polystyrene B blocks, where the fluorene units of the A block carried double pairs of piperidinium cations via flexible hexyl spacer chains. First, a polyfluorene tethered with bromohexyl chains was prepared by superacid-mediated polyhydroxyalkylation, and then modified to produce a bi-directional macroinitiator for atom transfer radical polymerization (ATRP). Next, ATRP of styrene was carried out to form BAB triblock copolymers with different lengths of the B blocks. Finally, the polyfluorene block was densely functionalized with piperidinium cations by Menshutkin reactions. Small angle X-ray scattering of block copolymer AEMs indicated the presence of both block copolymer phase domains (d~15 nm) and ionic clusters (d~6 nm). Atomic force microscopy showed clearly phase-separated morphologies with seemingly well-connected hydrophilic nanophase domains for ion transport. The AEMs reached hydroxide conductivities up to 161 mS cm-1 at 80 ºC. Moreover, the AEMs decomposed only above 250 °C and possessed excellent alkaline stability with no degradation detected by 1H NMR analysis after storage in 2 M aq. NaOH, at 90 °C during 672 h. Notably, the current block copolymer AEMs showed higher alkaline stability and hydroxide conductivity compared to AEMs based on corresponding statistical copolymers

Preparation of boronic acid-functionalized cryogels using modular and clickable building blocks for bacterial separation

Composite cryogels containing boronic acid ligands are synthesized for effective separation and isolation of bacteria. The large and interconnected pores in cryogels enable fast binding and release of microbial cells. To control bacterial binding, an alkyne-tagged boronic acid ligand is conjugated to azide-functionalized cryogel via the Cu(I)-catalyzed azide−alkyne cycloaddition reaction. The boronic acid-functionalized cryogel binds Gram-positive and Gram-negative bacteria through reversible boronate ester bonds, which can be controlled by pH and simple monosaccharides. To increase the capacity of affinity separation, a new approach is used to couple the alkyne-tagged phenylboronic acid to cryogel via an intermediate polymer layer that provides multiple immobilization sites. The morphology and chemical composition of the composite cryogel are characterized systematically. The capability of the composite cryogel for the separation of Gram-positive and Gram-negative bacteria is investigated. The binding capacities of the composite cryogel for Escherichia coli and Staphylococcus epidermidis are 2.15 × 109 and 3.36 × 109 cfu/g, respectively. The bacterial binding of the composite cryogel can be controlled by adjusting pH. The results suggest that the composite cryogel may be used as affinity medium for rapid separation and isolation of bacteria from complex samples

Ag−Polymer nanocomposites for capture, detection, and destruction of bacteria

Bacterial infection is one of the major problems for human health. To prevent outbreak of bacteria-caused diseases, early diagnosis of bacterial pathogen and effective destruction of pathogenic microorganisms are in urgent need. In this work, we developed a new multifunctional nanocomposite material that can effectively capture and destroy bacteria. Epoxide-modified nanoparticles were synthesized by microemulsion polymerization and precipitation polymerization. The epoxide groups on the particle surface were reacted with polyethylenimine to introduce cationic amine groups. The amine groups on the nanoparticle surface enhanced the colloidal stability of the particles’ suspension and provided multivalent interactions to bind and destroy the bacteria. After further modification with Ag nanoparticles, the final composite nanomaterial was able to not only capture and destroy Gram-negative bacteria but also allow the bacteria’s fingerprint spectra to be obtained through surface-enhanced Raman scattering.The multifunctional nanoparticles developed in this work offer a new approach toward fast capture, detection, and destruction of pathogenic bacteria

Photoconjugation of temperature- and pH-responsive polymer with silica nanoparticles for separation and enrichment of bacteria

A new photoconjugation approach was developed to prepare nanoparticle-supported boronic acid polymer for effective separation and enrichment of bacteria. The photo-activated polymer immobilization was demonstrated by coupling an azide-modified copolymer of N-isopropylacrylamide and glycidyl methacrylate to a perfluorophenyl azide-modified silica surface. The thermoresponsive polymer was synthesized using reversible addition fragmentation chain transfer polymerization followed by conversion of the pendant epoxides into azide groups. The perfluorophenyl azide-modified silica nanoparticles were synthesized by an amidation reaction between amino-functionalized silica and pentafluorobenzoyl chloride, and a subsequent treatment with sodium azide. Bacteria-capturing boronic acid was conjugated to the silica-supported polymer chains via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. The particle size, morphology and organic content of the composite nanoparticles were characterized systematically. The capability of the nanocomposite to bind Gram-positive and Gram-negative bacteria was investigated. The nanocomposite exhibited high binding capacities for E. coli (13.4 × 107 CFU/mg) and S. epidermidis (7.66 × 107 CFU/mg) in phosphate buffered saline. The new photoconjugation strategy enables fast and straightforward grafting of functional polymers on surface, which opens many new opportunities for designing functional materials for bioseparation and biosensing