Enhanced Water Vapor Transmission through Porous Membranes Based on Melt Blending of Polystyrene Sulfonate with Polyethylene Copolymers and Their CNT Nanocomposites

A novel concept for the use of an immiscible and non-meltable polymer, such as sodium polystyrene sulfonate (PSSNa), in order to prepare polyethylene non-woven breathable membranes is described. Membranes were fabricated by melt compounding of properly functionalized PE (P(E-co-AA)) and PSSNa (P(SSNa-co-GMA)) copolymers in the presence of water soluble polyethylene glycol (PEG). The inability of PSSNa derivatives to be melted was overcome by using PEG, which was easily meltable thus inducing PSSNa processability improvement. PEG was removed after membrane fabrication and therefore also acted as a porogen. Carbon nanotubes, functionalized with PSSNa moieties or alkyl groups, were also incorporated in the membranes with the aim of improving the porous connectivity and increasing the water vapor transmission rate. The morphology of the membranes was investigated through Scanning Electron Microscopy (SEM). Water vapor transmission rate (permeation) (WVTR) measurements for the porous membranes showed increased values in comparison with the neat PE ones. A further increase of WVTR was observed with the addition of CNTs to the polymer membranes

Environmentally Friendly Hybrid Organic–Inorganic Halogen-Free Coatings for Wood Fire-Retardant Applications

Wood and wood-based products are extensively used in the building sector due to their interesting combination of properties. Fire safety and fire spread, however, are of utmost concern for the protection of buildings. Therefore, in timber structures, wood must be treated with fire-retardant materials in order to improve its reaction to fire. This article highlights the flame retardancy of novel hybrid organic–inorganic halogen-free coatings applied on plywood substrates. For this purpose, either a huntite-rich mineral (H5) or its modified nano-Mg (OH)2 type form (H5-m), acting as an inorganic (nano) filler, was functionalized with reactive oligomers (ROs) and incorporated into a waterborne polymeric matrix. A water-soluble polymer (P (SSNa-co-GMAx)), combining its hydrophilic nature with functional epoxide groups, was used as the reactive oligomer in order to enhance the compatibility between the filler and the matrix. Among various coating compositions, the system composed of 13% polymeric matrix, 73% H5 and 14% ROs, which provided the best coating quality and flame retardancy, was selected for the coating of plywood on a larger scale in one or two layers. The results indicated that the novel plywood coating systems with the addition of ecological coating formulations (WF-13, WF-14 and WF-15), prepared at two layers, reached Euroclass B according to EN13501-1, which is the best possible for fire systems applied to wood

Environmentally Friendly Cross-Linked Antifouling Coatings Based on Dual Antimicrobial Action

The synthesis of environmentally friendly antimicrobial polymeric coatings, especially in the case of aquaculture, that inhibit the growth of bio-deposits is a very important issue that will contribute to the cost reduction of nets’ cleaning process as well as the protection of the submarine wealth from the biostatic substances used so far. In the present work, the antimicrobial polymers P(SSAmC16-co-VBCHAMx) and the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) were synthesized, bearing quaternary ammonium compounds, electrostatically bound and covalently attached at the same polymer chain. The combination of the two types is of particular importance, as it can provide effective antimicrobial polymeric materials with self-polishing capabilities as a result of the released nature of the antimicrobial, in combination with the permanent local action of the immobilized species. The cross-linking reaction of the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) with the homopolymer polyacrylic acid (PAA) was tested at 120 °C in terms of the equivalent ratio between epoxy and carboxyl groups. The synthesized polymers were further used for the coating of aquaculture nets and tested in terms of antifouling efficiency in lab and scale-up conditions. Uncoated nets were also used in all applications for comparison reasons. The coated nets performed efficiently for 35 days in lab-scale and 66 days in scale-up conditions, showing a high antifouling activity in both fields compared to the uncoated nets

Kinetic study of the alcoholic fermentation in the presence of new biocatalysts

Reversed Flow Gas Chromatography (R.F.G.C.) was used for thedetermination of rate constants for each alcoholic fermentation phase andthe calculation of produced ethanol in the presence of new biocatalysts.The rates for each alcoholic phase were determined in real time from themeasurement of the concentration of produced ethanol. This can be carriedout by developing an appropriate mathematical model for the analysis ofthe experimental data obtained from a versatile gas chromatographictechnique. R.F.G.C is a time-honoured method which involves the change ofthe carrier gas flow direction at various time intervals. It has a vast numberof applications in a wide scientific field such as the determination ofdiffusion and mass transfer coefficients, adsorption equilibrium constantsLenard-Jones parameters, activity coefficients, rate constants, etc.In the present work, the yeast strain used was Saccharomycescerevisiae (ΑΧΑΖ-1), a cryotolerant and alcohol resistant strain, which wasisolated from a Greek vineyard area and is maintained in the collection ofthe Food Technology Laboratory of the Chemistry department at theUniversity of Patras. The immobilization carriers used where differentsources of starch such as raw materials from which starch is derived (wheat,corn and barley grains as well as potato pieces), starch from gel (wheat,corn) and pure starch (wheat, corn).Furthermore, in order to verify the accuracy of the developedmathematical model and of the R.F.G.C. technique to measure ethanolconcentration, the results were compared with those obtained fromconventional Gas Chromatography (G.C.) and distillation as well. Theimmobilization of yeast cells on the above carriers was confirmed byscanning electron microscope. Repeated batch fermentations with glucoseculture medium and must were performed for free and immobilized cellsshowing that biocatalysts lead to shorter fermentation time. From kineticsof the fermentation processes wheat grains seems to be more efficientsupporters than barley, corn, rice grains and potato pieces. Moreover, the corn starch gel prevailing wheat starch gel, as it provides higher rateconstant values as they were determined with R.F.G.C. The kineticparameters confirm the predominance of the biocatalysts against free cellsystems in the fermentation process. The calculated kinetic parameters forthe second phase of the fermentation were one order of magnitude smallerthan those reported for the other two phases. In all cases the same amountsof the produced ethanol were determined at the end of the fermentationeither by measuring it with conventional methods (gas chromatography anddistillation) or with R.F.G.C. This reveals the fact that, R.F.G.C. is atrustworthy method which can be used not only for the determination ofethanol but also for the calculation of rate constants at each alcoholicfermentation phase. In addition to this, the reaction rate constants for eachphase were determined during the alcoholic fermentation processesconducted in a bioreactor of 100 L using as immobilization carrier wheatgrains.Main purpose of this work was also to establish the applicability ofGravitational Field Flow Fractionation (Gr.F.F.F.) technique in order tostudy the affection of environmental conditions, such as external pH andtemperature, on the fermentation kinetics and the proliferation of thealcohol-resistant and psychrophilic Saccharomyces cerevisiae (AXAZ-1) yeaststrain, in the presence or absence of wheat and corn starch granules asimmobilization carrier. Differences in the fractograms monitored byGr.F.F.F., at different values of temperature and pH, make evident thedifferent fermentation kinetic profiles and can be related with the unlikecell growth. Gr.F.F.F. can provide valuable information about yeast cell sizedistribution, density and shape from the determination of retention valuesand the different peak profiles. In addition to this, to confirm thecorrespondence between the fractograms obtained by Gr.F.F.F. with thekinetics of the fermentation processes, analysis of residual sugar (withH.P.L.C.) and ethanol concentration (with G.C.) were performed. Theresults indicate that both systems (free and immobilized cells) performedbetter at 30ºC, whereas at lower temperatures decreases in thefermentation rate and in the number of viable cells were observed. Moreover the pH of the medium (pH=5) resulted in higher fermentationrates and ethanol productivities. The duration and the rate of thefermentation process were shorter in the case of immobilized cells ascompared with free cells, which is in accordance with literature. Moreover,wheat starch granules proved to be a more efficient than corn starchgranules as it provided shorter fermentation times, and higher values ofreaction rate constants and immobilized cells. The activation energy for thefermentation processes was reduced in the case of immobilized cells ascompared with free cells. The above mentioned results confirm thecatalytic activity of both immobilization carriers, with starch granulesprevailing corn grains.The results obtained from the kinetic study of the alcoholicfermentations with the R.F.G.C. and Gr.F.F.F. techniques, led to acomparison between them and confirmed the accuracy and the precision ofthese methods.Η Αέρια Χρωματογραφία Αναστρεφόμενης Ροής (Α.Χ.Α.Ρ.)χρησιμοποιήθηκε για τον προσδιορισμό των σταθερών ταχύτητας σε κάθεφάση της αλκοολικής ζύμωσης καθώς και της παραγόμενης αλκοόλης(αιθανόλης), παρουσία νέων βιοκαταλυτών. Οι σταθερές ταχύτητας σε κάθεφάση της αλκοολικής ζύμωσης προσδιορίστηκαν με την εξαγωγή ενόςμαθηματικού μοντέλου το οποίο συνδέει τα πειραματικά μετρούμενα μεγέθη(ύψος κορυφών έκλουσης) με τη συγκέντρωση της παραγόμενης αιθανόλης.Η τεχνική της Α.Χ.Α.Ρ. στηρίζεται στην απλή ή διπλή αναστροφή της ροήςτου φέροντος αερίου ανά τακτά χρονικά διαστήματα και επιτρέπει τονπροσδιορισμό φυσικοχημικών μεγεθών. Έχει εφαρμοστεί με επιτυχία στονπροσδιορισμό των συντελεστών διάχυσης και μεταφοράς μάζας, τωνσταθερών ισορροπίας προσρόφησης, των παραμέτρων Lennard-Jones,καθώς και στον προσδιορισμό σταθερών ταχύτητας, κ.α.Στην παρούσα διατριβή το είδος της ζύμης που χρησιμοποιήθηκε ήταντο ψυχρόφιλο και αλκοολοανθεκτικό στέλεχος, Saccharomyces cerevisiaeAXAZ-1, το οποίο απομονώθηκε από μια Ελληνική αγροτική περιοχή καιφυλάσσεται στο Εργαστήριο Τεχνολογίας Τροφίμων του Τμήματος Χημείαςτου Πανεπιστημίου Πατρών. @ς φορέας ακινητοποίησης χρησιμοποιήθηκε,για πρώτη φορά το άμυλο σε διαφορετικές μορφές: πρώτες ύλες από τιςοποίες προέρχεται το άμυλο (σιτάρι, κριθάρι, αραβόσιτος, πατάτα, ρύζι),ζελατινοποιημένο άμυλο (σιτάρι, αραβόσιτος), καθώς και καθαρό άμυλο(σιτάρι, αραβόσιτος).Επιπλέον, με σκοπό την πιστοποίηση της ακρίβειας τόσο τουμαθηματικού μοντέλου όσο και της τεχνικής της Α.Χ.Α.Ρ. για τη μέτρηση τηςπαραγόμενης αιθανόλης, πραγματοποιήθηκαν μετρήσεις με δύο επιπλέονμεθόδους: την κλασσική χρωματογραφία και την απόσταξη και έγινεσύγκριση των αποτελεσμάτων. Η ακινητοποίηση των κυττάρων της ζύμηςστους φορείς επιβεβαιώθηκε με φωτογραφίες όπως αυτές ελήφθησαν με τοηλεκτρονικό μικροσκόπιο σάρωσης. Οι επαναλαμβανόμενες αλκοολικέςζυμώσεις, που πραγματοποιήθηκαν σε θρεπτικό γλυκόζης, και εν συνεχεία σε μούστο, απέδειξαν ότι τα ακινητοποιημένα κυτταρικά συστήματαοδήγησαν σε μικρότερους χρόνους ζύμωσης συγκριτικά με τα ελεύθερα.Κατά την κινητική μελέτη των αλκοολικών ζυμώσεων καλύτεροι φορείςακινητοποίησης στην κατηγορία των πρώτων υλών ήταν το σιτάρι, ενώ σεαυτήν του ζελατινοποιημένου αμύλου ο αραβόσιτος, καθώς παρουσίασανυψηλότερες τιμές σταθερών ταχύτητας έναντι των υπολοίπων φορέων, όπωςυπολογίστηκαν με την Α.Χ.Α.Ρ. για κάθε φάση της αλκοολικής ζύμωσης.Αξίζει να σημειωθεί πως οι σταθερές ταχύτητας που υπολογίστηκαν για τηδεύτερη φάση της αλκοολικής ζύμωσης είναι μιας τάξης μεγέθουςμικρότερες σε σχέση με εκείνες που εμφανίζονται στις άλλες δύο φάσεις. Σεόλες τις περιπτώσεις δεν παρατηρήθηκαν διαφορές στα ποσά τηςπαραγόμενης αιθανόλης που προσδιορίστηκαν στο τέλος των αλκοολικώνζυμώσεων είτε με την Α.Χ.Α.Ρ., είτε με τις μεθόδους της κλασσικήςχρωματογραφίας και της απόσταξης. Από τα παραπάνω συμπεραίνουμε, πωςη Α.Χ.Α.Ρ. παρέχει αξιόπιστα αποτελέσματα συγκριτικά με τις άλλες δύομεθόδους και επιτρέπει τον ταυτόχρονο προσδιορισμό των σταθερώνταχύτητας σε κάθε φάση της αλκοολικής ζύμωσης καθώς και τηςπαραγόμενης αιθανόλης. Επιπλέον, προσδιορίστηκαν οι σταθερές ταχύτηταςγια κάθε φάση των αλκοολικών ζυμώσεων που πραγματοποιήθηκαν σεβιοαντιδραστήρα 100 L χρησιμοποιώντας τον βέλτιστο βιοκαταλύτη(σταθερότητα δραστικότητας του βιοκαταλύτη, σταθερές ταχύτητας για κάθεφάση της ζύμωσης) από την κατηγορία των πρώτων υλών, το σιτάρι.Ένας από τους κύριους σκοπούς της παρούσας διατριβής ήταν ημελέτη της κινητικής των αλκοολικών ζυμώσεων των ελεύθερων καιακινητοποιημένων κυττάρων ΑΧΑΖ-1 σε καθαρό άμυλο (σιτάρι, αραβόσιτος),σε διαφορετικές τιμές θερμοκρασίας και pH, μέσω της ΜονοφασικήςΧρωματογραφίας Βαρυτικού Πεδίου (Μ.Χ.Β.Π.) και η σύγκριση τωναποτελεσμάτων με τα αντίστοιχα που ελήφθησαν με την Α.Χ.Α.Ρ. Η μέθοδοςαυτή (Μ.Χ.Β.Π.) είναι κατάλληλη για τoν χαρακτηρισμό των κυττάρων τωνζυμών και τη μελέτη της βιωσιμότητας και της δραστικότητάς τους.Iιαφορές που εμφανίζονται στις καμπύλες έκλουσης σχετίζονται άμεσα μετις διαφορετικές κατανομές των κυττάρων της ζύμης, τις διαφορετικέςπυκνότητες, τη μορφολογία και/ή το μέγεθός τους. Η Μ.Χ.Β.Π. μπορεί να μας δώσει πολύτιμες πληροφορίες για την κατανομή του μεγέθους τωνκυττάρων της ζύμης, την πυκνότητα και το μέγεθός τους. Για νααποδείξουμε τη σχέση μεταξύ των μεταβολών που παρατηρούνται στιςκορυφές έκλουσης με την κινητική των αλκοολικών ζυμώσεων,πραγματοποιήθηκαν επιπλέον αναλύσεις για τον υπολογισμό της τελικήςσυγκέντρωσης σακχάρου με Υγρή Χρωματογραφία Υψηλής Απόδοσης(H.P.L.C.) καθώς και της % v/v συγκέντρωσης της αιθανόλης με κλασσικήΑέρια Χρωματογραφία (G.C.). Τόσο τα ακινητοποιημένα όσο και ταελεύθερα συστήματα λειτούργησαν καλύτερα στη θερμοκρασία των 30ºCπαρουσιάζοντας τις υψηλότερες τιμές σταθερών ταχύτητας. Η μείωση τηςθερμοκρασίας οδήγησε σε μείωση των σταθερών ταχύτητας της ζύμωσηςκαθώς και του αριθμού των ακινητοποιημένων κυττάρων. Επιπλέον, στο pHτου θρεπτικού υγρού (pH=5), παρατηρήθηκαν υψηλότερες ταχύτητεςζύμωσης καθώς και μεγαλύτερα ποσοστά παραγωγής αιθανόλης. Η διάρκειατων αλκοολικών ζυμώσεων καθώς και οι σταθερές ταχύτητας αυτώνπαρουσίασαν μικρότερες τιμές στα ακινητοποιημένα κύτταρα, συγκριτικά μετα ελεύθερα, γεγονός που συμφωνεί με τη βιβλιογραφία. Τέλος,συγκρίνοντας τα συστήματα των ακινητοποιημένων κυττάρων καλύτεροιχρόνοι ζύμωσης και υψηλότερες τιμές σταθερών ταχύτητας, παρατηρήθηκανόταν σαν φορέας χρησιμοποιήθηκε άμυλο από σιτάρι. Επιπλέον,διαπιστώνουμε πως οι ενέργειες ενεργοποίησης των αλκοολικών ζυμώσεωνεμφανίζουν μικρότερες τιμές παρουσία των φορέων ακινητοποίησης σε κάθετιμή pH. Τα ανωτέρω επιβεβαιώνουν την καταλυτική ικανότητα και των δύοφορέων ακινητοποίησης με το σιτάρι να πλεονεκτεί έναντι του αραβόσιτου.Τα αποτελέσματα που ελήφθησαν από την κινητική μελέτη τωναλκοολικών ζυμώσεων με τις τεχνικές της Α.Χ.Α.Ρ. και της Μ.Χ.Β.Π.οδήγησαν σε σύγκριση των δύο μεθόδων και επιβεβαίωση της ακρίβειας καιαξιοπιστίας τους

Development of Antifouling Coatings Based on Quaternary Ammonium Compounds through a Multilayer Approach

The development of polymeric materials as antifouling coatings for aquaculture nets is elaborated in the present work. In this context, cross-linked polymeric systems based on quaternary ammonium compounds (immobilized or releasable) prepared under mild aqueous conditions were introduced as a more environmentally friendly methodology for coating nets on a large scale. To optimize the duration of action of the coatings, a multilayer coating method was applied by combining the antimicrobial organo-soluble copolymer poly(cetyltrimethylammonium 4-styrenesulfonate-co-glycidyl methacrylate) [P(SSAmC16-co-GMA20)] as the first layer with either the water-soluble copolymer poly(vinylbenzyl trimethylammonium chloride-co-acrylic acid) [P(VBCTMAM-co-AA20)] or the water-soluble polymers poly(acrylic acid) (PAA) and poly(hexamethylene guanidine), PHMG, as the second layer. The above-mentioned approach, followed by thermal cross-linking of the polymeric coatings, resulted in stable materials with controlled release of the biocidal species. The coated nets were studied in terms of their antifouling efficiency under accelerated biofouling conditions as well as under real conditions in an aquaculture field. Resistance to biofouling after three water-nutrient replenishments was observed under laboratory accelerated biofouling conditions. In addition, at the end of the field test (day 23) the uncoated nets were completely covered by marine contaminants, while the coated nets remained intact over most of their extent

Preparation of Antimicrobial Coatings from Cross-Linked Copolymers Containing Quaternary Dodecyl-Ammonium Compounds

One of the concerns today’s societies face is the development of resistant pathogenic microorganisms. The need to tackle this problem has driven the development of innovative antimicrobial materials capable of killing or inhibiting the growth of microorganisms. The present study investigates the dependence of the antimicrobial activity and solubility properties on the hydrophilicity/hydrophobicity ratio of antimicrobial coatings based on quaternary ammonium compounds. In this line, suitable hydrophilic and hydrophobic structural units were selected for synthesizing the antimicrobial copolymers poly(4-vinylbenzyl dimethyldodecylammonium chloride-co-acrylic acid), P(VBCDDA-co-AA20) and poly(dodecyltrimethylammonium 4-styrene sulfonate-co-glycidyl methacrylate), P(SSAmC12-co-GMA20), bearing an alkyl chain of 12 carbons either through covalent bonding or through electrostatic interaction. The cross-linking reaction of the carboxylic group of acrylic acid (AA) with the epoxide group of glycidyl methacrylate (GMA) of these two series of reactive antimicrobial copolymers was explored in blends, obtained through solution casting after curing at various temperatures. The release of the final products in pure water and NaCl 1 M solutions (as analyzed by gravimetry and total organic carbon, TOC/total nitrogen, TN analyses), could be controlled by the coating composition. The cross-linked polymeric membranes of composition 60/40 w/w % ratios led to 97.8 and 99.7% mortality for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively, whereas the coating 20/80 w/w % resulted in 96.6 and 99.8% cell reduction. Despite the decrease in hydrophobicity (from a 16- to a 12-carbon alkyl chain), the new materials maintained the killing efficacy, while at the same time resulting in increased release to the aqueous solution

Flame Retardant Nano-Structured Fillers from Huntite/Hydromagnesite Minerals

In the current study, we propose a simple hydrothermal pathway to synthesize nano-structured Mg(OH)2 after application of thermal decomposition followed by hydration of commercial minerals based on hydromagnesite and huntite. The synthesis of nano-materials is performed without the use of any catalyst. The effect of decomposition temperature on the hydrothermal synthesis of Mg(OH)2 is extensively studied. It is shown that the morphology of resulting structures consists typically of particles ~200 nm in diameter and ~10 nm in thickness. Study of the structure at the molecular level designates the composition and supports the nano-sized characteristics of the produced materials. The associated thermal properties combined with the corresponding optical properties suggest that the material may be used as a flame retardant filler with enhanced transparency. In this concept, the flame retardancy of composite coatings containing the produced nano-sized Mg(OH)2 was examined in terms of limiting oxygen index (LOI), i.e., the minimum concentration of oxygen that just supports flaming combustion

Designing Antioxidant and Antimicrobial Polyethylene Films with Bioactive Compounds/Clay Nanohybrids for Potential Packaging Applications

In the present work, direct incorporation of bioactive compounds onto the surface and interlayer of nanoclays before their incorporation into the final polymeric film was conducted, based on a green methodology developed by our group that is compatible with food packaging. This will lead to the higher thermal stability and the significant reduction of the loss of activity of the active ingredients during packaging configuration. On this basis, the essential oil (EO) components carvacrol (C), thymol (T) as well as olive leaf extract (OLE), which is used for the first time, were incorporated onto organo-modified montmorillonite (O) or inorganic bentonite (B) through the evaporation/adsorption method. The prepared bioactive nanocarriers were further mixed with low-density polyethylene (LDPE), via melt compounding, in order to prepare films for potential use as fresh fruit and vegetable packaging material. Characterization of the bioactive nanocarriers and films were performed through XRD, TGA, tensile, antimicrobial and antioxidant tests. Films with organically modified montmorillonite loaded with carvacrol (OC), thymol (OT) and olive leaf extract (OOLE) at 5% wt. showed better results in terms of mechanical properties. The films with polyethylene and organically modified montmorillonite loaded with carvacrol or thymol at 20% wt. (PE_OC20 and PE_OT20), as well as with olive leaf extract at 5 or 10 %wt., clay:bioactive substance ratio 1:0.5 and 10% compatibilizer (PE_OOLE5_MA10 and PE_OOLE10_MA10) exhibited the highest antioxidant activity. The resulting films displayed outstanding antimicrobial properties against Gram-negative Escherichia coli (E. coli) with the best results appearing in the films with 10% OC and OT

Environmentally Friendly Hybrid Organic-Inorganic Halogen-Free Coatings for Wood Fire-Retardant Applications

Wood and wood-based products are extensively used in the building sector due to their interesting combination of properties. Fire safety and fire spread, however, are of utmost concern for the protection of buildings. Therefore, in timber structures, wood must be treated with fire-retardant materials in order to improve its reaction to fire. This article highlights the flame retardancy of novel hybrid organicâ\u80\u93inorganic halogen-free coatings applied on plywood substrates. For this purpose, either a huntite-rich mineral (H5) or its modified nano-Mg (OH)2 type form (H5-m), acting as an inorganic (nano) filler, was functionalized with reactive oligomers (ROs) and incorporated into a waterborne polymeric matrix. A water-soluble polymer (P (SSNa-co-GMAx)), combining its hydrophilic nature with functional epoxide groups, was used as the reactive oligomer in order to enhance the compatibility between the filler and the matrix. Among various coating compositions, the system composed of 13% polymeric matrix, 73% H5 and 14% ROs, which provided the best coating quality and flame retardancy, was selected for the coating of plywood on a larger scale in one or two layers. The results indicated that the novel plywood coating systems with the addition of ecological coating formulations (WF-13, WF-14 and WF-15), prepared at two layers, reached Euroclass B according to EN13501-1, which is the best possible for fire systems applied to wood. © 2022 by the authors

Evaluation of Antimicrobial Efficiency of New Polymers Comprised by Covalently Attached and/or Electrostatically Bound Bacteriostatic Species, Based on Quaternary Ammonium Compounds

In the present work a detailed study of new bacteriostatic copolymers with quaternized ammonium groups introduced in the polymer chain through covalent attachment or electrostatic interaction, was performed. Different copolymers have been considered since beside the active species, the hydrophobic/hydrophilic nature of the co-monomer was also evaluated in the case of covalently attached bacteriostatic groups, aiming at achieving permanent antibacterial activity. Homopolymers with quaternized ammonium/phosphonium groups were also tested for comparison reasons. The antimicrobial activity of the synthesized polymers after 3 and 24 h of exposure at 4 and 22 °C was investigated on cultures of Gram-negative (P. aeruginosa, E. coli) and Gram-positive (S. aureus, E. faecalis) bacteria. It was found that the combination of the hydrophilic monomer acrylic acid (AA), at low contents, with the covalently attached bacteriostatic group vinyl benzyl dimethylhexadecylammonium chloride (VBCHAM) in the copolymer P(AA-co-VBCHAM88), resulted in a high bacteriostatic activity against P. aeruginosa and E. faecalis (6 log reduction in certain cases). Moreover, the combination of covalently attached VBCHAM units with electrostatically bound cetyltrimethylammonium 4-styrene sulfonate (SSAmC16) units in the P(SSAmC16-co-VBCHAMx) copolymers led to efficient antimicrobial materials, especially against Gram-positive bacteria, where a log reduction between 4.9 and 6.2 was verified. These materials remain remarkably efficient even when they are incorporated in polysulfone membranes