Degree Of Quaternization Research Articles

Poly(vinyl pyridine) and Its Quaternized Derivatives: Understanding Their Solvation and Solid State Properties

A series of N-methyl quaternized derivatives of poly(4-vinylpyridine) (PVP) were synthesized in high yields with different degrees of quaternization, obtained by varying the methyl iodide molar ratio and affording products with unexplored optical and solvation properties. The impact of quaternization on the physicochemical properties of the copolymers, and notably the solvation properties, was further studied. The structure of the synthesized polymers and the quaternization degrees were determined by infrared and nuclear magnetic spectroscopies, while their thermal characteristics were studied by differential scanning calorimetry and their thermal stability and degradation by thermogravimetric analysis (TG-DTA). Attention was given to their optical properties, where UV-Vis and diffuse reflectance spectroscopy (DRS) measurements were carried out. The optical band gap of the polymers was calculated and correlated with the degree of quaternization. The study was further orientated towards the solvation properties of the polymers in binary solvent mixtures that strongly depend on the degree of quaternization, enabling a better understanding of the key polymer (solute)-solvent interactions. The assessment of the underlying solvation phenomena was performed in a system of different ratios of DMSO/H2O and the solvatochromic indicator used was Reichardt’s dye. Solvent polarity parameters have a significant effect on the visible spectra of the nitrogen quaternization of PVP studied in this work and a detailed path towards this assessment is presented.

Quaternized Polysaccharide-Based Cationic Micelles as a Macromolecular Approach to Eradicate Multidrug-Resistant Bacterial Infections while Mitigating Antimicrobial Resistance.

Microbial infections and microbial resistance lead to a high demand for new antimicrobial agents. Quaternized polysaccharides are cationic antimicrobial candidates; however, the limitation of homogeneous synthesis solvents that affect the molecular structure and biological activities, as well as their drug resistance remains unclear. Therefore, the authors homogeneously synthesize a series of quaternized chitin (QC) and quaternized chitosan (QCS) derivatives via a green and effective KOH/urea system and investigate their structure-activity relationship and biological activity in vivo and in vitro. Their study reveals that a proper match of degree of quaternization (DQ) and degree of deacetylation (DD') of QC or QCS is key to balance antimicrobial property and cytotoxicity. They identify QCS-2 as the optimized antimicrobial agent with a DQ of 0.46 and DD' of 82%, which exhibits effective broad-spectrum antimicrobial properties, good hemocompatibility, excellent cytocompatibility, and effective inhibition of bacterial biofilm formation and eradication of mature bacterial biofilms. Moreover, QCS-2 exhibits a low propensity for development of drug resistance and significant anti-infective effects on MRSA in vivo comparable to that of vancomycin, avoiding excessive inflammation and promoting the formation of new blood vessels, hair follicles, and collagen deposition to thus expedite wound healing.

Development of recoverable adsorbents for Cr(VI) ions by grafting of a dimethylamino group-containing monomer on polyethylene substrate and subsequent quaternization

ABSTRACT A polymeric adsorbent for removal of hexavalent chromium (Cr(VI)) ions was developed by the photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to a polyethylene (PE) mesh and subsequent quaternization with iodoalkanes of different alkyl chain lengths. The grafting of DMAEMA and subsequent quaternization were verified by the FT-IR and XPS measurements. The Cr(VI) ion adsorption capacity of the DMAEMA-grafted PE meshes had the maximum value at the grafted amount of 2.6 mmol/g in a 0.20 mM K2Cr2O7 solution at pH 3.0 and 30°C. The adsorption behaviour obeyed the pseudo-second order kinetic model and well expressed by Langmuir isotherm. These results suggest that the Cr(VI) ion adsorption occurs through the electrostatic interaction mainly between protonated dimethylamino groups and hydrochromate (HCrO4 -) ions. The adsorption capacity of the quaternized PE-g-PDMAEMA meshes increased with an increase in the degree of quaternization and/or the alkyl chain length of the iodoalkanes used and the maximum adsorption ratio was obtained at the degree of quaternization of 54.2% for the iodoheptane-quaternized PE-g-PDMAEMA (PE-g-QC7PDMAEMA) mesh. This value was about 1.86 times higher than that of the PE-g-PDAMEMA mesh. Cr(VI) ions were successfully desorbed from the PE-g-PDMAEMA and PE-g-QC7PDMAEMA meshes in eluents such as NaOH, NaCl, and NH4Cl. In 0.50 M NaCl, 0.10 M NH4Cl, and 0.50 mM NaOH, the adsorption and desorption process was repeatedly performed without any considerable decrease and the desorption behaviour obeyed the pseudo-second order kinetic model. These results emphasise that the PE-g-PDMAEMA meshes and their quaternized products can be applied as an adsorbent for Cr(VI) ions.

One-step zwitterionization and quaternization of thick PDMAEMA layer grafted through subsurface-initiated ATRP for robust antibiofouling and antibacterial coating on PDMS

In this work, we demonstrate the grafting of thick poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) layer on PDMS via subsurface-initiated atom transfer radical polymerization (SSI-ATRP). The self-migration of DMAEMA monomers into the subsurface of PDMS is proven to be the dominant factor for the success of SSI-ATRP. The as-prepared thick microscale graft layer on PDMS shows much better abrasion resistance than nanoscale graft layer obtained by conventional surface-initiated atom transfer radical polymerization (SI-ATRP) under identical condition. Taking advantage of the tertiary amines of PDMAEMA, the simultaneous zwitterionization and quaternization of the PDMAEMA thick layer is realized through a facile one-step process. The effect of zwitterionization and quaternization degree on the antibiofouling and antibacterial properties is investigated. The results show that a relatively high zwitterionization degree (75 mol%) and a low quaternization degree (25 mol%) exhibit a good well-balanced effect on both fouling repellence and bactericidal activity. This work may lead to the development of robust bifunctional antibiofouling and antibacterial surfaces via SSI-ATRP strategy.

Synthesis and structural characterization of N,N,N‐trimethyl chitosan

AbstractN,N,N‐trimethyl chitosan (TMC) with molar mass 29 ~ 136 kg/mol and degree of quaternization 70% ~ 82% was synthesized from chitosan via N,N‐dimethyl chitosan (DMC) by a two‐step method. Size exclusion chromatography (SEC) coupled with multiangle laser light scattering was employed to characterize the molar mass and chain conformation of DMC and TMC. Nearly no degradation was found for DMC, but degradation by ~50% was observed from TMC. Apart from degradation, the shift of SEC peak toward higher elution volume for N‐methylated chitosan was attributed to the increase in chain flexibility. It was shown that chitosan, DMC, and TMC took a random coil conformation in 200 mM acetate buffer, with persistence length decreased from 10 nm for chitosan, to 5.7 nm for DMC and 3.2 nm for TMC. The significant increase in chain flexibility upon N‐methylation is most probably due to the breakage of intramolecular hydrogen bonds between chitosan repeating units.

Responsive Quaternized PDMAEMA Copolymers with Antimicrobial Action.

In this work, the antimicrobial action of partially quaternized poly(2-(dimethylamino)ethyl methacrylate) (PQDMAEMA) copolymers using different alkyl halides is presented. The poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) homopolymer was synthesized by group transfer polymerization, followed by the modification of its tertiary amine groups, using bromoethane, iodoethane, bromohexane and bromoethanol, to introduce permanent cationic, quaternary ammonium salt moieties, randomly distributed along the polymer chains. In all cases, the degree of quaternization was low, at ~10 mol%, as verified by proton nuclear magnetic resonance spectroscopy to preserve the thermo-responsive character of the PDMAEMA precursor polymer. The biocidal activity of the lightly quaternized PQDMAEMA copolymers against Escherichia coli and Staphylococcus aureus was evaluated by calculating the minimum inhibitory concentration (MIC) as well as the minimum bactericidal concentration (MBC) of the polymers and by comparing them to the respective values of the precursor non-quaternized PDMAEMA homopolymer. The antibacterial mechanism of action in the solution was studied by zeta potential measurements, scanning electron microscopy and protein leakage tests signifying the disruption of the outer membrane of the bacterial cells to release their periplasmic proteins.

Quaternary Trimethyl Chitosan Chloride Capped Bismuth Nanoparticles with Positive Surface Charges: Catalytic and Antibacterial Activities

Quaternary trimethyl chitosan-stabilized bismuth nanoparticles (QTMC-BiNPs) with positive surface charges were uniquely synthesized and fully characterized. In the synthesis, Quaternary Trimethyl Chitosan (QTMC), a water-soluble derivative of chitosan (CTS) was prepared using two-step reductive methylation. The new biopolymeric functionalized ligand was further used as capping agent for the synthesis of QTMC-BiNPs which was applied as antibacterial and catalytic agents. The reaction was carried out at room temperature without the use of energy consuming or high-cost instruments. The QTMC and nanocomposites were characterized by proton nuclear magnetic resonance (1H NMR), attenuated total reflection Fourier-transform infrared, UV–visible, X-ray diffraction, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopic techniques. The topology and morphology of the composites were examined with scanning electron microscopy and high-resolution transmission electron microscopy. Thermogravimetric and differential thermal gravimetric analysis were also conducted. The degree of quaternization and degree of dimethylation values of 63.33 and 11.75%, respectively obtained for QTMC confirmed that the main product is a quaternary derivative. The average particle size of QTMC-BiNPs was evaluated to be between 30 and 45 nm. The QTMC-BiNPs revealed clear and uniform lattice fringes with an estimated interplanar d-spacing of 0.32 nm confirming the formation of highly crystalline nanocomposites. A further insight into the antibacterial activities of this nanomaterial were carefully examined on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) using resazurin based microdilution method for Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). The obtained results revealed that both bacteria pathogens were effectively inhibited/killed by the QTMC-BiNPs at very low concentrations. The MIC of 15.63 and 125 µg/mL were recorded against E. coli and S. aureus, respectively while the MBC of 31.25 and 500.00 µg/mL were estimated against E. coli and S. aureus, respectively. An extensive evaluation of the catalytic capability of the nanocomposites towards the reduction of 4-nitrophenol to 4-aminophenol was also carried out with highly promising result.

Facile synthesis of Antibacterial, Biocompatible, quaternized Poly(ionic liquid)s with pendant saccharides

Glycopolymer has been developed in bactericidal applications, but the traditional synthesis, such as click chemistry, needs poly-step reactions and complicated processes. Herein, incorporating the glyco-units into the polymers by quaternization has been exploited to give a facile strategy by Copper-mediated reversible deactivation radical polymerization (Cu(0)-RDRP) to prepare quaternized poly(ionic liquid)s (PILs) with pendant saccharide. The obtained PILs have the suitable property of killing typical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Simultaneously, they perform the lower hemolytic rate of blood cells, higher selectivity index against bacteria, and higher affinity with Concanavalin A (ConA) than those quaternized by bromohydrin at the same quaternization degree. This result demonstrated that the introduced saccharide units, such as glucose and mannose, could maintain the electrostatic interaction to kill bacteria, perform lectin recognition behavior and interaction with ConA, and relatively harmlessness against red blood cells. Moreover, the sugar-containing PILs became insoluble and still antibacterial after anion exchange reaction. These new findings illuminated that such quaternized antibacterial agents with saccharide units that are easy-to-prepare, low cytotoxic could pave the way for further water disinfectant and pathogen control application.

Synthesis, Characterization and Antibacterial Activity of Novel β-cyclodextrin Polyurethane Materials

The advanced water treatment taken by organic micro-pollution or microbiological pollution water resource has been a hot issue of public concern. In this article, novel quaternary ammonium salt functionalized β-cyclodextrin polyurethane (QAS-β-CDPU) microparticles were successfully constructed for above-mentioned pollutants removal. By adjusting the proportion of the chlorine-containing monomers, we studied the effect of different quaternization degree (0%, 20%, 40%, 60%) on solvent resistance and thermal stability. Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) are recognized as significant human bacterial pathogens, which were used as model bacteria to investigate the antibacterial activity by contact-killing tests. Methylene blue (MB) served as a toxic organic model to quantify the dye wastewater remediation efficiency. Research shows that the reaction of β-cyclodextrin and diisocyanate can form a cyclodextrin-based carbamate network structure. Since both the cyclodextrin cavity and the carbamate network may remove the dye, the obtained polymer has a double advantage. Besides, the presence of quaternary ammonium groups enables QAS-β-CDPU microparticles to possess good bactericidal properties. When the quaternization degree is 60%, sterilization rates of QAS-β-CDPU microparticles are over 96% for S. aureus and E. coli. On basis of this simple, green and economical synthetic route, QAS-β-CDPU microparticles have the potential to become an ideal multifunctional material in water purification. Novel quaternary ammonium salt functionalized β-cyclodextrin polyurethane (QAS-β-CDPU) microparticles were successfully constructed for removing bacteria and dyes from wastewater.

A Molecular Shape Recognitive HPLC Stationary Phase Based on a Highly Ordered Amphiphilic Glutamide Molecular Gel.

Chiral glutamide-derived lipids form self-assembled fibrous molecular gels that can be used as HPLC organic phases. In this study, HPLC separation efficiency was improved through the addition of branched amphiphilic glutamide lipids to the side chains of a terminally immobilized flexible polymer backbone. Poly(4-vinylpyridine) with a trimethoxysilyl group at one end was grafted onto the surface of porous silica particles (Sil−VP15, polymerization degree = 15), and the pyridyl side chains were quaternized with a glutamide lipid having a bromide group (BrG). Elemental analysis indicated that the total amount of the organic phase of the prepared stationary phase (Sil−VPG15) was 38.0 wt%, and the quaternization degree of the pyridyl groups was determined to be 32.5%. Differential scanning calorimetric analysis of a methanol suspension of Sil−VPG15 indicated that the G moieties formed a highly ordered structure below the phase transition temperature even on the silica surface, and the ordered G moieties exhibited a gel-to-liquid crystalline phase transition. Compared with a commercially available octadecylated silica column, the Sil−VPG15 stationary phase showed high selectivity toward polycyclic aromatic hydrocarbons, and particularly excellent separations were obtained for geometrical and positional isomers. Sil−VPG15 also showed highly selective separation for phenol derivatives, and bio-related molecules containing phenolic groups such as steroids were successfully separated. These separation abilities are probably due to multiple interactions between the elutes and the highly ordered functional groups, such as the pyridinium and amide groups, on the highly ordered molecular gel having self-assembling G moieties.

Effect of Trimethyl Chitosan with Different Degrees of Quaternization on the Properties of Tablets Prepared using Charged Model Drugs

Trimethyl chitosan (TMC) has demonstrated effectiveness as an absorption enhancer for hydrophilic and high molecular weight (MW) drugs across the intestinal epithelium. However, the effects of degrees of quaternization (DQ) of TMC on the absorption of negatively and positively charged drugs have not been investigated. This investigation aimed to determine the properties of the tablets formulated using TMC with different DQ. In this study, TMC with DQ of 20 % (TMC-20), 40 % (TMC-40) and 60 % (TMC-60) were synthesized and subsequently characterized. Cetirizine dihydrochloride (CHC) and hyoscine butylbromide (HBB) were used as negatively and positively charged model drugs. Eight tablet formulations were prepared using the wet granulation method. The formulated tablets were evaluated regarding their properties in terms of thickness and hardness, weight variation, disintegration time, and dissolution profile. These tablets were evaluated according to the standards set by the United States Pharmacopeia (USP41) guidelines. The results showed that TMC with all DQ have the MW and an intrinsic viscosity less than starting chitosan. The MW and an intrinsic viscosity of the synthesized TMC decreased with increasing DQ. In order to evaluate the effect of TMC with various DQ on the properties of the formulated tablets, all tablet formulations prepared had good characteristics and were found to be within the acceptable range based on the requirements of USP. In conclusion, TMC had a minor retarding effect on the dissolution profiles of CHC from the formulated tablets. Still, TMC was able to significantly delay the release of HBB from the formulated tablets (p > 0.05). When TMC with various DQ were compared, TMC-60 showed higher drug release than TMC-20 and TMC-40. In our study, we observed a possible interaction between the model drugs and TMC. This warrants the need for further studies. HIGHLIGHTS Degree of quaternization represents the charge density of trimethyl chitosan (TMC) Degradation of the polymer backbone occurred in the synthesis reaction step TMC affects dissolution profiles of a negative charged drug Ionic interaction and viscous gel layer of TMC affects the model drug release

Hydroxypropyltrimethyl ammonium chloride chitosan-based hydrogel as the split H5N1 mucosal adjuvant: Structure-activity relationship

In this study, 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC)-based hydrogel was devised as a mucosal adjuvant for H5N1 vaccine. Aimed to investigate the structure activity relationship between HTCC hydrogel and immune response, we prepared a series of HTCC hydrogel with defined quaternization degrees (DQs, 0%, 21%, 41%, 60%, 80%). Results suggested that with DQ increasing, the positive charge and gelation time of HTCC hydrogel increased but the viscosity decreased. We applied in vivo imaging system and found that the moderate DQ 41% prolonged antigen residence time in nasal cavity, resulting in the most potent systemic responses (IgG, IgG1, IgG2a, HI). While, the lowest DQ 0% produced the best mucosal IgA antibody responses, most likely due to the closer contact with mucosa. Furthermore, the influence of animal gender was also discussed. These data add to the growing understanding of the relationship between physicochemical features of chitosan-based hydrogel and how they influence the immune responses.

Microwave assisted quaternized cyclodextrin grafted chitosan (QCD-g-CH) nanoparticles entrapping ciprofloxacin

In the present study quaternized cyclodextrin grafted chitosan (QCD-g-CH) nanoparticles entrapping ciprofloxacin were prepared for the development of sustained release system. The QCD-g-CH is prepared by microwave assisted synthesis technique using 3-chloro-2-hydroxypropyl trimethyl ammonium chloride as cationic reagent. The QCD-g-CH entrapping ciprofloxacin nanoparticles are prepared by ionic gelation method using NaTPP as a cross linker. The prepared QCD-g-CH nanoparticles were characterized by FTIR, DSC, X-RD and FESEM-EDS. The average p-size of the drug loaded QCD-g-CH nanoparticles was found in the range 176 to 642 nm whereas the % encapsulation efficiency of different batches was found to be in the range of 80 to 92%. The % degree of tosylation, substitution and quaternization were calculated by 1H NMR and it was found to be1.27, 5.07 and 66.66%. The antimicrobial activity was studied using bacterial and fungal strains. The in vitro release study of QCD-g-CH-CPFX NPs in PBS buffer (pH 7.4) showed sustained release behavior during 24 h study.

Aliphatic Polyurethane Elastomers Quaternized with Silane-Functionalized TiO2 Nanoparticles with UV-Shielding Features.

The design of high-performance nanocomposites with improved mechanical, thermal or optical properties compared to starting polymers has generated special interest due to their use in a wide range of targeted applications. In the present work, polymer nanocomposites composed of polyurethane elastomers based on polycaprolactone or polycaprolactone/poly(ethylene glycol) soft segments and titanium dioxide (TiO2) nanoparticles as an inorganic filler were prepared and characterized. Initially, the surface of TiO2 nanoparticles was modified with (3-iodopropyl) trimethoxysilane as a coupling agent, and thereafter, the tertiary amine groups from polyurethane hard segments were quaternized with the silane-modified TiO2 nanoparticles in order to ensure covalent binding of the nanoparticles on the polymeric chains. In the preparation of polymer nanocomposites, two quaternization degrees were taken into account (1/1 and 1/0.5 molar ratios), and the resulting nanocomposite coatings were characterized by various methods (Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, contact angle, thermogravimetric analysis, dynamic mechanical thermal analysis). The mechanical parameters of the samples evaluated by tensile testing confirm the elastomeric character of the polyurethanes and of the corresponding composites, indicating the obtaining of highly flexible materials. The absorbance/transmittance measurements of PU/TiO2 thin films in the wavelength range of 200–700 nm show that these partially block UV-A radiation and all UV-B radiation from sunlight and could possibly be used as UV-protective elastomeric coatings.

Synthesis and self-assembly of polyzwitterionic phenylboronic acid-containing double hydrophilic block copolymers

Double hydrophilic block copolymers self-assemble into smart materials with promising applications in nanomedicine. However, such practical applications require thoroughly understanding the underlying mechanisms of this self-assembly process and the effects of external stimuli on the resulting materials. Thus, we report the post-polymerization modification of a pH-responsive double hydrophilic diblock copolymer (poly(ethylene oxide)-b-poly(4-vinyl pyridine)) by stimuli-responsive, diol-binding 2-bromomethyl-4-fluorophenylboronic acid and the comprehensive study of the self-assembly properties of this polyzwitterionic polymer for potential applications in the delivery of functional diols, including pharmaceutical drugs, steroids and sugars. For this purpose, we performed simple, robust and reproducible quaternization reactions at three different degrees (25, 50 and 100%) by varying the composition of the initial mixture and confirmed full control over the degree of quaternization by proton nuclear magnetic and infrared spectroscopy. Our results show that the degree of quaternization strongly affects the solubility of these polymers in basic solutions because PBA adopts a tetragonal conformation with a negative charge on boron at pH values higher than the pKA of PBA. Nevertheless, the specific PBA (anionic vs neutral) form of these polymers can be differentiated by 11B NMR, regardless of the degree of quaternization. In turn, the pH of the solvent affected the intensity of the NMR signals, thus suggesting the formation of kinetically frozen nanoparticles, in line with the results from both static and dynamic light scattering, with no indication of particle dissociation at low concentrations. Moreover, electrophoretic light scattering showed linear, albeit opposite (direct and inverse) correlations between the degree of quaternization and the zeta potential in water and 0.1 M HCl, respectively. When adsorbed to a mica surface, these nanoparticles predominantly displayed globular shapes under atomic force microscopy. Therefore, our high-throughput and low-cost nanofabrication method combining the stimuli-responsive behavior of a double hydrophilic block copolymer with the unique chemical properties of pH-responsive diol-binding phenylboronic acid functional groups establishes an experimental paradigm for preparing nanocarriers for biomedical applications, such as targeted drug delivery.

Antifungal properties of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and quaternized derivatives

A series of poly[2-(dimethylamino)ethyl methacrylate]s (PDMAEMAs) of different molar mass were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were subsequently treated with two different alkyl halides (1-iodobutane (BuI) and iodomethane (MeI)) to obtain a library of 21 PDMAEMAs with different degree of quaternization (DQ). This is the first report where the antifungal activity of these polymers is assessed for different fungi relevant in biomineralization and aesthetic biodeterioration of stone surfaces. The antifungal activity was assessed with the minimum inhibitory concentration (MIC), the minimum fungicidal concentration (MFC) and the mycelia growth inhibition in plate for the most promising materials. The obtained results demonstrated that all evaluated polymers possess certain level of antifungal activity against the evaluated fungi (even unquaternized PDMAEMAs). However, polymers of low molar mass (series III) revealed predominantly fungicidal activity at low values of MFC (from 2500 to 9.7 μg mL−1). Unexpectedly, the performed mycelia growth inhibition tests showed that the DQ has a less significant effect on the antifungal properties of the polymers than the polymer molar mass. Hence, the antifungal activity of these polymers may depend to a great extent on the physiological and morphological characteristics of the fungi, wherein the best antifungal activity was observed in III-M2, III-B1 and III-B2. It is worth mentioning that this detailed screening contributes to a better understanding of PDMAEMA-based composites that can be utilized in the development and optimization of low-cost and accessible antimicrobial protective coatings for petrous surfaces in cultural heritage monuments or modern buildings.

Effect of alkyl chain length and fluorine content on the surface characteristics and antibacterial activity of surfaces grafted with brushes containing quaternized ammonium and fluoro-containing monomers

Although considerable efforts have been made to vary the alkyl chain length in the quaternary ammonium compounds (QACs) for optimizing the antibacterial activity, only few researchers have systematically investigated the combinatory effects of alkyl chain length and another acryl monomers with the different chemical configuration on the antibacterial activity of the modified substrate. In this study, by surface grafting of various copolymeric brushes, different modified cotton substrates were prepared by surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization reaction for exploring the effects of alkyl chain length of QACs and the fluorine content on antibacterial and anti-microbial adhesion characteristics. The quaternized monomers used were prepared by quaternization of 2-(dimethylamino) ethyl methacrylate (DMAEMA) with 1-bromooctane (DMAEMA + 8), and 1-bromopropane (DMAEMA + 3). The fluoro-containing monomer was 2,2,2-Trifluoroethyl methacrylate (TFEMA). Ethyl methacrylate (EMA) was also used for comparison. Results have shown that the optimal antibacterial and anti-microbial adhesion characteristics were noted on the substrates grafted with DMAEMA + 8 and TFEMA. This can be attributed to the enhanced degree of surface quaternization due to the hydrophobic interactions between the grafted TFEMA and DMAEMA + 8 chains, leading to an increase in antibacterial efficacy of modified cotton substrates.

Unexpected counterion exchange influencing fundamental characteristics of quaternary ammonium chitosan salt

N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan salt (HTCS) is used in applications benefiting from its strong cationic charge. The degree of quaternization (DQ) and the type of counterions are the HTCS fundamental characteristics. HTCS with DQ between 15 and 116% were synthesized by reaction between chitosan glucosamine unit and glycidyltrimethylammonium chloride. While this should lead to a chloride polysalt, we unexpectedly identified a massive spontaneous exchange of chloride counterions by other anions originated from aqueous environment during synthesis and purification. Up to 70% lower DQ was obtained by potentiometric titration of chloride counterions – the method widely used in literature. It was shown that the true DQ can be determined by NMR spectroscopy. The phenomenon of counterion exchange was further verified by XPS and demonstrated also for quaternized dextran. The underlying mechanism of the counterion exchange was explained. It should be considered for other polyelectrolytes especially in applications, where the counterion type is important.

Contributions to the quaternization description and kinetics illustrated on poly(dimethylaminoethyl methacrylate)

Using the effects of solvent polarity observed on the microstructure of reaction products and the viscosity of the reaction medium, the evolution of the polymer chain conformation when the conversion changes, as well as the corresponding reaction kinetics, are formulated to explain the characteristics of the quaternization reaction of poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA), a polymer with flexible side-chains ended by tertiary amine groups.So, the polymeric chain is fully extended in strongly polar solvents regardless of the degree of quaternization (DQ), leading to simple kinetics of the second order. In less polar solvents, the polymer chain has coil conformation, which causes the reaction to take place more on the coil edge, which in turn leads to quaternized block formation and auto-acceleration. Self-acceleration is explained by bringing the unreacted groups to the periphery of the coil by the solvent because it prefers them in the detriment of the reacted groups. The kinetics model for self-accelerated reactions is validated by finding that the fraction of peripheral unreacted amine groups is nearly constant during the entire reaction. Such kinetics could be applied for other polymer analogous reactions when the polymer chains take coil conformation or associate with each other in globules.

SYNTHESIS OF A HIGH-PERFORMANCE ANTIMICROBIAL O-QUATERNIZED ALGINATE – A PROMISING POTENTIAL ANTIMICROBIAL AGENT

Three novel biologically active quaternized sodium alginates were synthesized via the reaction of sodium alginate (SA) with 3-chloro-2-hydroxypropyl trimethylammonium chloride, at room temperature for different time intervals (1, 3 and 6 h), to produce quaternized sodium alginates designated as QSA1, QSA3 and QSA6. The percentage degree of quaternization (DQ%) significantly increased with increasing the reaction time. Images from FTIR, 1H-NMR, XRD and SEM have confirmed the chemical structures of the QSA samples. Their antimicrobial activity was investigated against bacteria and fungi using XTT assay, and the results showed that all QSA samples displayed high growth inhibition capacity of the tested microorganisms, compared to zero inhibition for SA, as shown by their lower minimum inhibitory concentration (MIC). The QSA6 was the best antimicrobial composite, displaying the same MIC value as that of the used reference drugs. The developed composites were found to be safe on normal human fibroblast cells (WI-38 cell line), by evaluating them using cytotoxic activity measurement, which makes QSA a promising material in biomedical and food applications.