Reactive and Functional Polymers (v.114, #C)

Water sorption isotherms of molecularly imprinted polymers. Relation between water binding and iprodione binding capacity by Manal Bitar; Gaëlle Roudaut; Jacqueline Maalouly; Stéphane Brandès; Régis D Gougeon; Philippe Cayot; Elias Bou-Maroun (1-7).
Molecularly imprinted polymers are often used in aqueous medium in order to recognize specifically a target molecule. The molecular recognition is usually based on hydrogen bonding. In this case, water molecule presents a serious competition towards the target molecule. In this study, the water sorption by molecularly imprinted polymers was studied in aqueous medium. The molecularly imprinted polymers were specific for iprodione fungicide and were prepared using a 24 full factorial experimental design. They were synthesized using EGDMA or TRIM as crosslinker, methacrylamide or styrene as functional monomer and using bulk or precipitation polymerization. The water sorption isotherms were established in a range of water activities 0.05–0.90 at 25 °C. The kinetics of water sorption by the polymers were modeled using Peleg's equation. This model shows that polymers having the highest water sorption capacities have high values of imprinting factor. The Guggenheim–Anderson–de Boer isotherm equations were used to fit the equilibrium data and the corresponding parameters were calculated. This model shows that polymers synthesized with EGDMA have higher water sorption capacities than those synthesized with TRIM due to the higher hydrophobicity of the latter. Peleg and Guggenheim–Anderson–de Boer equations satisfactorily modeled the water sorption on the imprinted and non-imprinted polymers. The results obtained from both equations were practically coincident. Principal component analysis was used as a chemometric tool in order to demonstrate that a polymer having a low adsorption energy and a high capacity of water retention could be applied to extract a target molecule from aqueous media.
Keywords: Molecularly imprinted polymers; Water sorption; Iprodione; Peleg's model; GAB model;

Antibacterial electrospun fibrous membranes are widely applied as dressings for treatment the wounds and burns. However, developing long-term gelatin-based fibrous membrane is still the main challenge inhibiting their uses for long-term treatments. Novel antibacterial electrospun gelatin-based mats were introduced by combining gelatin, glycerol, glucose and silver nanoparticles (Ag NPs), which together could exhibit optimal physicochemical characteristics as long-term electrospun fibrous mats. Therefore, Ag NPs were synthesized in-situ within the acidic electrospun solutions during preparing electrospun gelatin-glycerol-Ag NPs (GEL-GLY-Ag) and gelatin-glycerol-glucose-Ag NPs (GEL-GLY-GLU-Ag) mats. Conventional spectroscopic techniques based on XRD, FTIR, SEM, DTA, and water uptake-degradation tests and antibacterial studies were used to characterize the preparations. The results showed that the electrospun gelatin-based composites mats revealed free beads dense fibrous textures, and exhibited a high water uptake and long-term degradation behavior. The Ag NPs could be successfully synthesized in-situ within electrospinning solutions and the results confirmed that the in-situ prepared Ag NPs enhanced the antibacterial activity of electrospun mats against positive and negative bacteria.
Keywords: Silver nanoparticles; Electrospun gelatin; Glycerol; Glucose; In-situ preparation;

Polymeric quaternary ammonium salts (PQAS) have been widely used to prevent microbial contamination, but little is known about their activity against phytopathogenic fungi. Our previous report described the synthesis of two novel PQAS, namely a homopolymer of (2-methacrylamido) propyltetrabenzyldimethylammonium chloride (PQD-BC) and dimethylaminopropyl benzyl chloride-grafted polysiloxanes (PDMS-g-BC); we demonstrated their structure-activity relationship against phytopathogenic fungi such as R. solani and Fusarium oxysporum f. sp. cubense tropical race 4 (Foc4). Here, we analyzed the structure-activity relationship and toxicity mechanism of these compounds at the molecular level against Foc4 compared with the low molecular-weight quaternary ammonium salt benzalkonium chloride (BC). The results revealed that PQD-BC and PDMS-g-BC application inhibited the growth of Foc4 in a concentration-dependent manner and that PDMS-g-BC exhibited higher activity than PQD-BC. In addition, these polymers were found to induce cell death in Foc4 by disrupting the cellular structure integrity, such as the loss of the cell wall and plasma membrane integrity and oxidative stress (lipid peroxidation), leading to the release of intracellular contents and inducing mitochondrial dysfunction and interference with genomic DNA. The newly elucidated mechanism provides possible applications in which PQAS can be used against phytopathogenic fungi.
Keywords: Polymeric quaternary ammonium salts; Antifungal bioassay; Mechanism of antifungal action;

In this work we have designed a simple, eco-friendly, one-pot method for the synthesis of palladium nanoparticles of quantum dot dimension (PdQDs) using a non-toxic, biocompatible block co polymer which functions as a reducing and stabilizing agent during the synthesis. The entire synthesis is free from any especial experimental set up and reaction conditions. These QDs were characterized by several well know characterization techniques such as UV–vis spectroscopy (UV–vis), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), dynamic light scattering (DLS), and ξ potential measurements. The transformation of a yellow solution into dark brown solution was indicative of the formation of the PdQDs. The kinetics of this reaction was monitored using a time scan absorption measurement which reveals a sigmoidal curve, a signature of noble metal nanoparticles. The rate of nucleation and growth were calculated using Finke and Watzky model. The synthesized colloidal PdQDs were employed for the reduction of environmentally toxic Cr(VI) to safer Cr(III). The reaction was catalyzed by the PdQDs in presence of acetic acid and was dependent on the concentration of both. The order and rate constant of the reduction reaction was calculated. A comparatively faster and complete reduction of Cr(VI) to Cr(III) using this catalysis was achieved at room temperature in presence γ irradiation, thus making the method more effective in its approach for bulk remediation of Cr(VI).
Keywords: PdQDs; Block co polymer; Colloidal; Growth kinetics; Finke-Watzky model; Dichromate;

Nano-sized polyacrylate colloids (< 200 nm) at high solids level (~ 60 wt%) are prepared via non-aqueous dispersion (NAD) semibatch polymerization using n-butyl methacrylate (BMA)-based macromer dispersants of varying chain lengths and levels of functionality provided by incorporation of 2-hydroxyethyl methacrylate (HEMA) comonomer. The effect of building the complexity of the core polymer recipe from methyl acrylate homopolymer to a five-monomer composition is systematically studied. While average particle size increased with the introduction of functional comonomers, the resulting NAD systems remained stable for all core compositions using both BMA macromers and a copolymer macromer containing 5 mol% HEMA. However, introduction of the HEMA functionality to the dispersant at levels of > 5 mol% led to destabilization of the dispersion. The polarity differences between the core compositions and dispersant polymers and the mixed continuous medium, as represented by Hansen solubility parameters, are qualitatively used to interpret the nucleation of particles and the effectiveness of the dispersants.Display Omitted
Keywords: Macromer dispersant; Hydroxyl functionality; Non-aqueous dispersion; Functionalized copolymers; Solubility parameters;

Natural based eumelanin nanoparticles functionalization and preliminary evaluation as carrier for gentamicin by Antonella De Trizio; Pathomthat Srisuk; Rui R. Costa; Alexandra G. Fraga; Tiziana Modena; Ida Genta; Rossella Dorati; Jorge Pedrosa; Bice Conti; Vitor M. Correlo; Rui L. Reis (38-48).
Purpose of the work was to modified natural based eumelanin nanoparticles surface by dopamine self-polymerization (FEUNp), facilitating conjugation through polydopamine bioactive functional groups and improving nanoparticle surface hydrophilicity. SEM, TEM, and AFM characterization confirmed FEUNp spherical shape (230.04 ± 8.25 nm) and their polydopamine coating. Individual indole or indoline structure spectrum at 1600 cm− 1 and C:N mass 9.08 was highlighted by FTIR and XPS analysis respectively. Quartz-crystal microbalance with dissipation monitoring (QCM-D) and thermal gravimetric analysis (TGA) showed successful polydopamine adsorption to eumelanin nanoparticles surface, a weight ratio of eumelanin nanoparticles/dopamine of 1/2.46 in the wet state and 1/0.20 in the dry state; the − 36.60 ± 0.45 mV negatively surface charges confirms the presence of PD covering. FEUNp were loaded with gentamicin sulfate, for application in infectious diseases therapies, such as osteomyelitis. Nanoparticles drug entrapment efficiency was 32.42 ± 3.21%, and ζ-potential close to neutrality (− 1.84 ± 0.58 mV). FEUNp-GS antimicrobial effect was tested on Staphylococcus aureus and Escherichia coli showing gentamicin 24 h sustained release from FEUNp-GS. IC50 and IC90 were 110.60 μg/mL and 216.39 μg/mL against S. aureus, and 54.13 μg/mL and 101.25 μg/mL against E. coli. The results are promising for FEUNp-GS as delivery system potentially useful diverse administration routes.
Keywords: Eumelanin nanoparticles; Polydopamine; Surface modification; Gentamicin; Drug delivery systems;

Oil-core microcapsules may be produced by dispersing a calcium solution-oil emulsion into an alginate solution. The release of calcium from the emulsion leads to the gelation of alginate around the oil droplet and therefore to the formation of microcapsules. This work aims to propose a new method of microcapsule production by dispersion-inverse gelation technique. Therefore, W/O emulsions were dispersed in alginate solution and led to the formation of capsules with varying diameters depending on the stirring rate of the alginate bath. The membrane thickness varied between 35 and 200 μm depending on the type of emulsion destabilization treatment used. Oil was encapsulated at a yield of 100% allowing the extrapolation of this method at pilot scale. In addition, microcapsules released hydrophilic dye in few hours while hydrophobic dye was retained in the core due to interaction with the oil phase. Core-shell alginate microcapsules produced by dispersion-inverse gelation technique displayed interesting property suitable for applications where actives need to be retained during long times or for volatile compounds.
Keywords: Oil; Encapsulation; Inverse gelation; Dispersion; Alginate;

Effect of ionic and covalent crosslinking agents on properties of chitosan beads and sorption effectiveness of Reactive Black 5 dye by Tomasz Jóźwiak; Urszula Filipkowska; Paula Szymczyk; Joanna Rodziewicz; Artur Mielcarek (58-74).
This study compared properties of hydrogel chitosan sorbents crosslinked with eight agents, including four ionic ones: sodium citrate, sodium tripolyphosphate, sulfosuccinic acid, and oxalic acid and four covalent ones: glutaraldehyde, epichlorohydrin, trimethylpropane triglycidyl ether, and ethylene glycol diglycidyl ether. The effect of crosslinking process conditions (pH, temperature) and dose of the crosslinking agent on chitosan sorbent stability during sorption and on the effectiveness of Reactive Black 5 dye sorption were examined. The optimal parameters of crosslinking ensuring sorbent stability in acidic solutions and high sorption capability were established for each crosslinking agent tested. The susceptibility of crosslinked sorbents to mechanical damages was analyzed as well.The process of ionic crosslinking was the most effective at the pH value below which hydrogel chitosan sorbent began to dissolve (pH 4). The crosslinking temperature ranging from 25 to 60 °C had no effect upon sorbent stability. The higher temperature during ionic crosslinking, however, slightly decreased RB5 sorption effectiveness. The ionic crosslinking significantly decrease the susceptibility of chitosan hydrogels to mechanical damages. In the case of covalent crosslinking of chitosan hydrogel beads, the effect of process conditions (pH, temperature) on the properties of the crosslinked sorbent depended on the type of crosslinking agent. The sorbents crosslinked with covalent agents were usually harder but also more fragile, and therefore more susceptible to mechanical damages.Display Omitted
Keywords: Chitosan; Crosslinking; Covalent crosslinking agents; Ionic crosslinking agents; Reactive Black 5;

Photo-crosslinked thiol-ene based hybrid polymeric sensor for humidity detection by Aslı Beyler Çiğil; Hüsnü Cankurtaran; Memet Vezir Kahraman (75-85).
This study describes the preparation and characterization of new surface modified carbon nanotube particles (CNT) containing thiol-ene based hybrid polymers by photo-polymerization of pentaerythritol tetrakis, glyoxal bis(diallyl acetal), trimethylol propane triacrylate monomers and their usage for humidity sensing. CNT surface was photografted with polyethylene glycol acrylate (PEGA) to produce hydroxyl groups. Hydroxyl functionalized CNT/PEGAs were acrylated using isocyanatoethyl methacrylate (IEM) in order to improve the dispersion and interfacial interaction in composites. Furthermore, different amounts of gold nanoparticles containing compositions were also prepared. The humidity sensing properties of two samples were investigated by impedance measurements. The effects of CNT/Au modification, the applied potential bias and alternating current frequency on the electrical properties and the humidity sensitivity were determined. FCNT0 and FCNT5Au0.5 exhibit extremely high selectivity against humidity compare to various solvents; ethanol, acetone, methyl acetate and chloroform. FCNT0 has a reasonable good sensor performance for humidity measurements. It has high sensitivity, selectivity, stability, response/recovery and linear response properties in a full range of humidity measurements.
Keywords: Humidity sensor; Carbon nanotube; Uv-curable polymer composite; Photograft; Thiol-ene based polymer;

Polyaniline thermoset blends and composites by F.X. Perrin; C. Oueiny (86-103).
The blending of polyaniline (PANI) with insulating polymers is an active area of research which has been driven by the possibility to combine the good mechanical properties and processability of the polymer matrix with low electrical resistance. This review will focus on thermosetting polymer matrix composites or blends. A good dispersion of PANI in the thermoset matrix is essential for the enhanced mechanical and electrical properties of the material. Much effort has been exerted in attempts to improve the compatibility of PANI with thermoset matrices. Attention will be given to describe some of the processing parameters that affect the morphology of PANI thermoset blends and composites. In recent years, there has been renewed interest in PANI thermoset composites with the emergence of multifunctional ternary composites. The different approaches for the design of ternary composites will be reviewed. Additionally, promising applications of PANI thermoset composites in different fields will be described such as electromagnetic shielding and microwave absorption, static electricity dissipation, flame-retardant materials, conductive adhesives, coatings for anticorrosion protection, sensor materials and electro-stimulated drug delivery systems.
Keywords: Thermosetting resin; Conductive composites; Polyaniline; Smart materials; Electrical properties;

One-pot synthesis of supported hydrogel membranes via emulsion templating by Qixiang Jiang; Angelika Menner; Alexander Bismarck (104-109).
Supported hydrogel membranes were produced by one-pot synthesis by polymerisation of suitable emulsion templates. High internal phase emulsions (HIPEs) with styrene (St), divinylbenzene (DVB) and ethylhexyl acrylate (EHA) in the continuous phase and methacrylic acid (MAA) in the internal phase were polymerised to prepare poly(MAA) hydrogel grafted poly(St-co-DVB-co-EHA) poly(merised)HIPEs. By changing the concentration of the crosslinker, N,N′-methylenebisacrylamide, in the internal phase of the emulsion template the crosslinking density of the grafted poly(MAA) was tuned. The presence of the hydrogel was indicated by a change in pore morphology, e.g. coverage of the pore throats and the wrinkled pore wall surface, and the increase in the density of the composite polyHIPEs as compared to control polyHIPEs. Moreover, the increase in foam density and reduction of porosity were related to the crosslinking degree of the hydrogel. The water uptake of the composite polyHIPEs exceeded the pore volume of the polyHIPE scaffold supporting the grafted hydrogel. The permeability and rejection of aqueous solutions of polyethylene glycol (PEG) by the hydrogel grafted polyHIPE membranes were strongly pH dependent, the permeability decreased and the rejection of PEG increased with increasing pH due to the increased swelling of the hydrogel. A 91% rejection of 50 kDa PEG for polyHIPE supported hydrogel membranes has been identified, which qualifies such membranes for ultrafiltration applications.Display Omitted
Keywords: Emulsion templating; Macroporous polymers; PolyHIPE composites; Supported hydrogel membranes; Ultrafiltration;

Durable hydrophilic surface modification for PTFE hollow fiber membranes by Haiming Song; Hongwei Yu; Lijing Zhu; Lixin Xue; Dichao Wu; Hao Chen (110-117).
A facile one-step process was developed to generate hydrophilic coating on polytetrafluoroethylene (PTFE) hollow fiber membranes based on co-deposition of polymerized dopamine (PDA) and poly (ethyleneimine) (PEI) from aqueous solutions. For comparison, step-by-step coating of PDA and PEI was also applied to modify PTFE membranes. ATR-FTIR, XPS, SEM, AFM and water contact angle measurements were applied to analyze the surface chemistry and morphology evolution of the modified PTFE membranes at varied grafting yields. PDA and PEI were successfully deposited on PTFE membranes while the hydrophilicity and wettability of the modified membrane were greatly improved. The modified PTFE membranes showed high water permeate fluxes, good long-term stability and durability in strong acidic aqueous solution. Although PTFE hollow fiber membranes samples modified by a step-by-step dip-coating process with PDA and PEI tent to lose their hydrophilicity in strong alkaline solutions, the co-deposited PTFE membranes with PDA and PEI were found to have good durability in aqueous solution at pH 13. This work provides a one-step method to improve the hydrophilicity and chemical stability of the PTFE hollow fiber membranes for water treatment applications.
Keywords: PTFE hollow fiber membrane; Hydrophilic; Surface modification; Polydopamine, Co-deposition;

Novel hybrid formulations based on chitosan and a siloxane compound intended for biomedical applications by Irina Elena Bordianu-Antochi; Mihaela Olaru; Corneliu Cotofana (118-126).
The present study reports on the obtaining of chitosan/siloxane–based microspheres by coacervation/precipitation method and their use as efficient drug delivery vehicles for ciprofloxacin, one antibacterial synthetic drug belonging to fluoroquinolones group. These new hybrid formulations were analyzed in terms of structural characterization (FTIR, SEM, TG, DSC techniques), swelling capacity and in vitro drug release. The release mechanism of the model drug was investigated by means of several kinetic models, i.e., zero order, first order, Higuchi model, Korsmeyer–Peppas model, Hixson–Crowell model, Baker–Lonsdal model, Weibull model and Schott model.
Keywords: Chitosan; Hybrid materials; Ciprofloxacin; Drug delivery; Schott model;

Fluoride removal from aqueous solution by Zirconium-Chitosan/Graphene Oxide Membrane by Jing Zhang; Nan Chen; Panyun Su; Miao Li; Chuanping Feng (127-135).
A Zirconium-Chitosan/Graphene Oxide (Zr-CTS/GO) Membrane adsorbent was applied for fluoride removal from aqueous solution. The effects of different compositions, dose, pH, and initial fluoride concentration were investigated. Results showed that the membrane could effectively remove fluoride within a wide pH range of 3–11. The data fitted the Freundlich isotherm model well, indicating that fluoride adsorption occurred on heterogeneous Zr-CTS/GO membrane surfaces probably in a multilayer form. The kinetic studies showed that the adsorption reached equilibrium within 45 min, and the maximum adsorption capacity was calculated to be 29.0588 mg/g by Two-site Langmuir isotherm model. X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy (EXAFS) were used to elucidate the adsorption mechanism. The results revealed that Zr(IV) species reacted with oxygen functional groups from the CTS/GO complex, and Zr―F species formed partly through fluoride ions exchanged with chloride ions and ―OH and partly through chemical rearrangement. The findings indicate that Zr-CTS/GO is a promising adsorbent for fluoride removal with a quite short contact time and a wide optimum pH range.Display Omitted
Keywords: Fluoride removal; Zirconium; Graphene oxide; Chitosan; Membrane;

Sol–gel derived multi-component silica composites are widely accepted as smart materials in orthopedic surgery as bone fillers and bioactive skeleton drug delivery systems. This paper discusses the effect of hydroxy-terminated polydimethylsiloxane (PDMS) (10, 20, 30 and 40% (w/w)) on the physicochemical properties of low temperature sol–gel processed polydimethylsiloxane/calcium phosphate/silica (PDMS-modified CaP/SiO2) composites. The micromolding technique was employed to obtain PDMS-modified CaP/SiO2 composites–monolithic granule-type formulations. The effectiveness of PDMS-modified CaP/SiO2 granules as potential skeleton drug delivery systems was studied in vitro using Rhodamine B (ROD) as a model for highly water-soluble molecules. Results indicated that the composites with PDMS contents at 20 and 30% (w/w) showed similar mechanical properties to those of human cancellous bones. The content of PDMS had a significant effect on the release of ROD. These results showed that PDMS-modified CaP/SiO2 granules with 20 and 30% (w/w) PDMS could provide the zero-order release profile of highly water-soluble molecules.
Keywords: Monolithic silica composites; Sol–gel process; Micromolding technique; Controlled release;