Philippe Roger

Poly(ionic liquid) and macrocyclic polyoxometalate ionic self-assemblies: new water-insoluble and visible light photosensitive catalysts

Several poly(ionic liquid)s (PILs) were synthesized and assembled with a multielectronic-process sustaining polyoxometalate (POM) into new green and water-insoluble nanomaterials (POM@PILs). They are visible light photosensitive, unlike their two components. A synergic effect was highlighted for the first time. POM@PILs achieve complete photodegradation of AO7 in aerobic media. The photocatalysts were recoverable and recyclable.

Mechanical Behavior of a Bacillus subtilis Pellicle

Bacterial biofilms consist of a complex network of biopolymers embedded with microorganisms, and together these components form a physically robust structure that enables bacteria to grow in a protected environment. This structure can help unwanted biofilms persist in situations ranging from chronic infection to the biofouling of industrial equipment, but under certain circumstances it can allow the biofilm to disperse and colonize new niches. Mechanical properties are therefore a key aspect of biofilm life. In light of the recently discovered growth-induced compressive stress present within a biofilm, we studied the mechanical behavior of Bacillus subtilis pellicles, or biofilms at the air-liquid interface, and tracked simultaneously the force response and macroscopic structural changes during elongational deformations. We observed that pellicles behaved viscoelastically in response to small deformations, such that the growth-induced compressive stress was still present, and viscoplastically at large deformations, when the pellicles were under tension. In addition, by using particle imaging velocimetry we found that the pellicle deformations were nonaffine, indicating heterogeneous mechanical properties with the pellicle being more pliable near attachment surfaces. Overall, our results indicate that we must consider not only the viscoelastic but also the viscoplastic and mechanically heterogeneous nature of these structures to understand biofilm dispersal and removal.

Surface initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA-ATRP) of 4-vinylpyridine on poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) substrates were modified by means of surface-initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA-ATRP) of 4-vinylpyridine (4VP). Substrates were pretreated in order to graft chloromethylbenzene (CMB) units capable of initiating the radical polymerization reaction of 4VP units. Surface characterization techniques, including Water Contact Angle (WCA), Attenuated Total Reflection (ATR), X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) showed a successful grafting of a stable, smooth and homogenous layer of p4VP. This process offers the advantages of a rapid, simplified and low cost strategy to chemically modify polymer substrates with covalently bonded layer of the pH responsive p4VP for different applications. Moreover, by using TOF-SIMS profiling, we were able to track a density gradient along the z-axis generated by the interpenetrating phases of the different layers of the final modified surface. Fact that we correlated to the various positions of initiation sites within the polyethylenimine (PEI) used for PET aminolysis prior to CMB grafting. Our strategy will be used in future work to graft other polymers for different applications where industrial scale viable options are needed.

The design of new photochromic polymers incorporating covalently or ionically linked spiropyran/polyoxometalate hybrids

The incorporation of highly photochromic polyoxometalates (POMs) with spiropyran (SP) appended groups into polymeric matrices has been investigated via two synthetic approaches. First of all, a new unsymmetrical Anderson-type POM bearing both a photochromic SP entity and a methacrylate (MA) unit has been synthesized (SP-POM-MA). This compound has been copolymerized with methylmethacrylate (MMA) as a monomer leading to a covalently linked SP-POM polymer material (poly(SP-POM-MA-co-MA)). In a second part, a symmetrical Anderson-type POM functionalized by two SP units (SP-POM-SP) has been ionically associated with the cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (poly(SP-POM-SP-DMAEMA+)). The different hybrid materials elaborated have been fully characterized via1H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and size exclusion chromatography, assessing unambiguously the integrity of the SP-POM units once introduced into the polymer. The solid-state photophysical properties of these materials have been fully investigated under ambient conditions. The ionic poly(SP-POM-SP-DMAEMA+) polymer with 7.7% weight in SP, exhibits highly efficient photochromic performances including a fast and intense coloration response under low power UV irradiation, a strong photocoloration contrast, and a very slow thermal fading process. This can be explained by the great stabilization of the photogenerated zwitterionic merocyanine form in the polar cavities of the cationic polymer. In addition, this material exhibits a relatively low photofatigue. For the covalent poly(SP-POM-MA-co-MA) polymer containing 1.1% weight in SP, as expected the photocoloration contrast is lower, but noticeably, showing that even low loading in SP-POM can afford photoresponsive materials.

Synthesis and characterization of glycosylated nano particles

Abstract Functionalized polymer nanoparticles have been synthesized by emulsifier-free emulsion polymerization of styrene with amino-functionalized monomers. Two monomers were used: the well-known 2- aminoethylmethacrylate and a new monomer with a styrenic polymerizable function, 4-(2-aminoethylthio)methylstyrene. The latexes were characterized by gravimetry, dynamic light scattering and colorimetric titration in order to obtain the styrene conversion, the hydrodynamic diameter, the particle size distribution and the concentration of surface amino groups, respectively. Then, glycosydic molecules such as maltose, lactose, maltotriose and galactopyranosylethanal were covalently grafted to the nanoparticles by amidation or reductive amination.

Poly(4-vinylpyridine)-modified silica for efficient oil/water separation

Silica particles were modified with a poly(4-vinylpyridine) (P4VP) for efficient separation of oil-in-water emulsions. Using a 3-(aminopropyl) triethoxysilane (APTES)-based molecule coupled to an appropriate radical initiator, P4VP chains were built from silica surfaces under mild reaction conditions using surface-initiated supplemental activator and reducing agent atom transfer radical polymerization. P4VP-modified silica particles were successfully used as a pH-switchable barrier for oil/water separation and proved to be efficient in removing oil from an oil-in-water nanoemulsion.

Biomodification Strategies for the Development of Antimicrobial Urinary Catheters: Overview and Advances

Abstract Microbial burden associated with medical devices poses serious health challenges and is accountable for an increased number of deaths leading to enormous medical costs. Catheter‐associated urinary tract infections are the most common hospital‐acquired infections with enhanced patient morbidity. Quite often, catheter‐associated bacteriuria produces apparent adverse outcomes such as urosepsis and even death. Taking this into account, the methods to modify urinary catheters to control microbial infections with relevance to clinical drug resistance are systematically evaluated in this review. Technologies to restrict biofilm formation at initial stages by using functional nanomaterials are elucidated. The conventional methodology of using single therapeutic intervention for developing an antimicrobial catheter lacks clinically meaningful benefit. Therefore, catheter modification using naturally derived antimicrobials such as essential oils, curcumin, enzymes, and antimicrobial peptides in combination with synthetic antibiotics/nanoantibiotics is likely to exert sufficient inhibitory effect on uropathogens and is extensively discussed. Futuristic efforts in this area are projected here that demand clinical studies to address areas of uncertainty to avoid development of bacterial resistance to the new generation therapy with minimum discomfort to the patients.

Hydrophobization of chitosan films by surface grafting with fluorinated polymer brushes

Chitosan with its surface-properties and biodegradability is a promising biomaterial for green packaging applications. Till now, this application is still limited due to chitosan high sensitivity to water. Some existing studies deal with the incorporation of hydrophobic additives to enhance water-proof performances of chitosan films. As these additives may impair the film properties, our study focuses on chitosan efficient hydrophobization by means of simple and successful surface grafting reactions. Chitosan films prepared by solvent casting were modified by means of surface-initiated activators regenerated by electron transfer atom radical polymerization (SI-ARGET-ATRP) of 2-hydroxyethyl methacrylate (HEMA) followed by esterification reaction with fluorinated acyl compound. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) highlighted the surface chemical changes after each step. Surface properties were investigated by contact angle measurements and surface energy calculations. Hydrophobic surfaces with low surface energy and good water-repellent properties were obtained using a simple handling polymerization procedure. This is the first study in applying ARGET ATRP to prepare hydrophobic biopolymer films offering potential applications in packaging.