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Article

Polymer-Metallic Systems Functionalizing Polylactide Nonwovens as a Greener Alternative to Modified Polypropylene-Based Textiles

by
Maria Czajka
,
Dawid Stawski
*,
Lucyna Herczyńska
and
Michał Puchalski
Textile Institute, Lodz University of Technology, Żeromskiego 116, 90-924 Łódź, Poland
*
Author to whom correspondence should be addressed.
Coatings 2025, 15(9), 996; https://doi.org/10.3390/coatings15090996
Submission received: 3 August 2025 / Revised: 20 August 2025 / Accepted: 25 August 2025 / Published: 28 August 2025
(This article belongs to the Section Bioactive Coatings and Biointerfaces)
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Abstract

This study focuses on functionalized nonwoven fabrics, modified with complexes of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) and divalent metal ions (M2+). A bioactive PDMAEMA with tertiary amines was synthesized and applied to nonwoven fabrics using a spray-coating method. Functionalization was achieved by in situ complexation on PDMAEMA-modified nonwovens with solutions of divalent metal salts. The aim of the study was to demonstrate that the proposed textiles can serve as biologically active materials, effectively inhibiting the growth of harmful bacteria. The modification process was designed to ensure that the amount of PDMAEMA was sufficient to cover the entire surface of the nonwoven fabric. The weight efficiency of the polymer application was approximately 1.4% and 2.0%. The presence of the polymer was confirmed through functional group analysis and electrokinetic property measurements. The PDMAEMA surface layer on the nonwoven fabrics was subsequently cross-linked by divalent metal ions (M2+), supplied from aqueous solutions of the corresponding salts, thereby converting the modifier into an insoluble form. Morphological changes in the functionalized nonwoven fabrics demonstrated the effect of the complexes on surface topography. Energy-dispersive X-ray microanalysis confirmed the presence of metal ions on the functionalized nonwoven fabrics. The modified polylactide (PLA) nonwoven fabrics exhibited antibacterial properties against Escherichia coli.

1. Introduction

Antimicrobials, such as antibiotics, disinfectants and antiseptics, are the basis of pathogen control. However, their excessive (and often unwise) use has led to the emergence of new, drug-resistant strains of microorganisms, which greatly limits the effectiveness of traditional methods of treatment and infection prevention. The problem of antimicrobial resistance has been recognized by the World Health Organization (WHO) as one of the greatest challenges of modern medicine, which has resulted in the development of the global strategy to combat antimicrobial resistance [1]. A key element of this strategy is the development of new technologies and materials that can provide an effective alternative to conventional antimicrobials. In recent years, special attention has been paid to the use of functional materials in medicine, including medical textiles, which not only play a protective role but can also actively counteract the spread of microorganisms. Contrary to expectations, hospital environments often become a place of intense spreading of pathogens, especially those that are resistant to many drugs. The bacteria can be transmitted on various types of textiles, such as medical gowns, bedding, curtains, or hospital drapes. These contaminated surfaces can act as reservoirs of pathogens, contributing to the development of nosocomial infections. Therefore, the use of textiles with antimicrobial properties has become extremely important, especially in the context of ensuring the safety of patients and medical staff. One of the substances that has a well-documented antimicrobial potential and can be easily applied to flat textile products is poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA).
PDMAEMA is a hydrophilic synthetic cationic polymer known for its pH and temperature responsiveness. In our previous work, we presented the use of a polymer modifier, known as poly(N,N-dimethylaminoethyl methacrylate), as a surface layer modifier in flat textile products. This is a polyelectrolyte with many important chemical and physical properties, and above all, it offers a wide range of interesting biological properties. The most important properties of the polymer are its wide solubility, bioactivity against different types of bacteria, hydrophilicity, gene transfer ability, and interesting hydrodynamic parameters [2,3,4].
The aim of this work is to develop innovative medical textiles with antimicrobial properties, with potential applications as nonwoven fabrics designed to inhibit the spread of hospital infections. These materials are based on the use of the functional polymer PDMAEMA, which is already known for its antibacterial activity.
The research gap addressed in this study concerns the lack of systematic investigations on complexes formed between PDMAEMA and divalent metal ions (Fe, Zn, Cu, and Co). The novelty of this work lies in exploring such complexes as a strategy to evaluate their influence on the biological properties of the obtained materials. Particular emphasis is placed on the use of biodegradable polylactide-based nonwovens as a more sustainable alternative to conventional polypropylene textiles. Finally, the antimicrobial effectiveness of the developed materials is evaluated against key hospital pathogens, including Escherichia coli.
In particular, we propose the innovative use of the combined effect of polymeric quaternary ammonium salts and different metals. Our intention is that the application of an active multi-component system on a nonwoven fabric made of biodegradable polymer will open new possibilities for the production of highly active disposable medical products.

2. Materials and Methods

2.1. Materials

The basic objects for modification were two polylactide nonwoven materials with different surface masses and, to compare and assess the possibility of using the selected technique, a polypropylene nonwoven material. The basic parameters of the modified nonwovens are shown in Table 1.
The following materials were used in the study: N,N-dimethylaminoethyl methacrylate (DMAEMA) (Merck KGaA, Darmstadt, Germany), which was distilled under reduced pressure (1 mmHg); azobisisobutyronitrile (AIBN, Merck, Darmstadt, Germany); zinc chloride—ZnCl2 (POCH, Gliwice, Poland); zinc sulphate heptahydrate—ZnSO4 x 7H2O (POCH, Gliwice, Poland); cobalt (II) acetate hydrate—(CH3COO)2Co x H2O (POCH, Gliwice, Poland); iron(II) sulphate heptahydrate—FeSO4 x 7H2O (POCH, Gliwice, Poland); copper (II) nitrate trihydrate—Cu(NO3)2 x 3H2O (Chempur, Piekary Śląskie, Poland).

2.2. Procedures

2.2.1. Polymerization of Methacrylate-N,N-Dimethylaminoethyl

PDMAEMA was prepared by the polymerization of N,N-dimethylaminoethyl methacrylate initiated with azobisisobutyronitrile. The average molecular weight (Mv = 447,000 g/mol) was determined using the viscosity method with an Ubbelohde viscometer. The ‘K’ value and constants for the Mark–Houwink equation were determined for a given polymer/solvent/temperature system by the fractionation method [5].

2.2.2. Applying PDMAEMA Solution to the Surface of Nonwovens

An alcoholic polymer solution was prepared in ethanol at a concentration of 0.17 mol/L (2.6%). The solution was then diluted five times to obtain a concentration of 0.034 mol/L (0.52%). The purpose of diluting the solution was to ensure the appropriate viscosity for applying it to the surface of the nonwovens. The obtained modifier application levels were 1.365% for sample 1, 1.415% for sample 2, and 2.155% for sample 3.

2.2.3. Complexation of PDMAEMA with Selected Divalent Metal Salts

Specific aqueous solutions of divalent metal salts were prepared at a concentration of 0.2%. These aqueous metal salt solutions were subsequently applied onto nonwoven samples that had previously been modified with a PDMAEMA polymer solution. The quantity of metal salt applied was equimolar relative to the amount of polymer previously deposited on the nonwoven substrates.
The list of sample codes and abbreviations used throughout the manuscript is provided in the Supplementary Information (Table S1).

2.3. Characterization

2.3.1. Scanning Electron Microscopy

Images of PDMAEMA functionalized polylactide and polypropylene nonwovens were recorded by an FEI NOVA NanoSem 230 (FEI Company, Hillsboro, OR, USA, SE Detector, voltage: 15 kV, rough vacuum: 0.3 Torr). high-resolution scanning electron microscope (SEM) with a field emission gun. The observations were carried out under low-vacuum conditions (0.6 Torr), at an electron beam energy of 10 keV, and at 800× and 1000× magnifications. The elementary chemical microanalysis of samples was investigated using an EDAX Apollo 40 SDD X-ray micro-analyzer (FEI Company, Hillsboro, OR, USA), with an electron beam energy of 18 keV and under low-vacuum conditions (0.6 Torr). Quantitative analysis was performed using the ZAF procedure.

2.3.2. Streaming Potential

The flow potential and surface charge of the nonwovens were determined using a Mütek PCD 03 particle charge analyzer (BTG Instruments, Weßling, Germany). The nonwoven fabric samples were ground manually. Titration was performed using standard solutions (cationic titrant PDADMAC (0.001N) and anionic titrant PCD (0.001N)) in tap water, with a pH of 7.2 and conductivity of approximately 350 μS/cm at room temperature (25 ± 2 °C). The neutralization point was defined as the moment of change in the sign of the flow potential. Surface charge was calculated from the equation:
q = VC/W
where
V—the amount of titrant needed to reach the charge neutralization point (l);
C—the titrant concentration (eq/L);
W—the mass of the sample (g).

2.3.3. Antimicrobial Activity of Functionalized Nonwovens

Antimicrobial studies were performed using the ASTM E2149-10 Standard Test Method for Determining Antimicrobial Activity of Immobilised Antimicrobials Under Dynamic Contact Conditions [6]. The method of assessing antimicrobial activity under dynamic contact conditions is a quantitative study. A culture of Escherichia coli test microorganisms (DSM 1576) was diluted in a sterilized buffer (KH2PO4 buffer solution at 0.3 mM and pH 7.2). Then, about 1 g of the nonwoven sample was soaked in the buffer for 1 h and placed in flasks with 50 mL of the buffer containing the bacterial culture. The flasks were incubated and shaken (at 120 rpm) for 6 h. Samples were taken for analysis at specified intervals. To assess the number of viable bacteria, 1 mL of shaken solution was transferred to petri dishes (10 mm × 90 mm) containing nutrient agar. The petri dishes were incubated at 35 °C for 24 h. The number of colonies in petri dishes after incubation was converted to the number of colony-forming units per milliliter (CFU/mL). Antimicrobial activity was calculated as a percentage against a control sample, using the equation:
R = ((A − B)/A) × 100%
where
R—Inhibition of bacterial growth (%);
A—Number of bacteria recovered from control flasks (CFU);
B—Number of bacteria recovered from flasks containing test specimens (CFU).
Each experiment was conducted three times for each composition, and the results are presented as an average value (ASTM E2149-10, 2013).

3. Results

3.1. Deposition of the Polymeric Layer

The first stage of the modification consisted of the application of poly(N,N-dimethylaminoethyl methacrylate) as a bioactive polymer. PDMAEMA stands out from other polymers due to the presence of tertiary amino groups, which give it unique properties. This polymer is effective against a wide range of microorganisms, including Gram-positive and Gram-negative bacteria, viruses, and fungi [4,7,8,9]. One of the advantages of PDMAEMA is its bioactivity, which is already visible in the form containing tertiary nitrogen. Moreover, the process of nitrogen quaternization further increases its biological activity, making it a material with the potential for even wider applications. Samples with an inserted polymer layer were named by adding the letter ‘a’ to the name of the unmodified material. Gravimetric analysis of the polymer deposit levels yielded the plots shown in Table 2.
The data shown in Table 2 indicate that the actual polymer application on PLA nonwovens was at a similar level (approx. 1.4%). PLA nonwoven fabric is characterized by its high stiffness, resulting from its compact structure. Such an arrangement of fibers favored the placement of the modifier on the surface of the nonwoven fabric. However, the polymer solution had difficulty penetrating deep into the PLA nonwoven fabric, resulting in a lower degree of application. In the case of PP nonwoven fabric, the amount of polymer applied was close to the assumed values (2.5% wt.). This was due to the looser spatial structure of PP nonwoven fabrics, obtained by a different production technology than in the case of PLA nonwoven fabrics. The less compact arrangement of fibers in the PP nonwoven fabric allowed the PDMAEMA polymer to settle throughout its space.
Nonwovens subjected to the PDMAEMA modification process were subjected to a set of tests examining their structure.

3.1.1. Scanning Electron Microscopy

After the first stage of polymer modification, the nonwovens were subjected to scanning electron microscopy analysis, which allowed for a detailed assessment of morphological changes on the surface of the nonwovens. SEM was used to visualize the surface of the nonwovens and assess the distribution of the PDMAEMA polymer on their surface. The analysis provided key information on the quality and efficiency of the modifications, enabling the identification of microstructural characteristics, such as uniformity of coverage, the presence of agglomerates, or changes in surface topography. Sample SEM images of unmodified and modified samples are given in Figure 1 (Figures S1 and S2).
The SEM images of modified nonwovens confirm that the modification process affected the topography of the fiber surface, causing noticeable changes in their morphology. Fragments of nonwovens after modification give the impression of being covered with an additional layer, which suggests effective embedding of the polymer on their surface. In addition, modified nonwovens show the presence of areas of varying contrast intensity (so-called ‘shadows’), which are not visible in unmodified nonwovens. This phenomenon may be related to the deposition of a polymer layer or changes in the surface topography resulting from the modification process. Similar changes were observed by the authors [2] when introducing PDMAEMA on polypropylene nonwovens (polymer deposition at a level of 6.3%).

3.1.2. EDX Analysis

X-ray microanalysis of PDMAEMA-modified nonwovens was used to detect the elements present on the surface of the tested materials. PDMAEMA contains tertiary amino groups (–N(CH3)2); therefore, the detection of nitrogen in PDMAEMA-modified samples is evidence of the effective introduction of amino groups on the surface of modified nonwovens. The results of the analysis provided information on the percentage of elements by mass.
Figure 2, Figure 3 and Figure 4 present the results of the EDX analysis in the form of X-ray energy spectra for individual elements (signal intensity as a function of energy) and histograms showing the weight content of the elements. The EDX spectra for PLA nonwovens (Figure 2A and Figure 3A indicate the dominance of carbon (CKα) and oxygen (O Kα) signals, which is consistent with their organic chemical structure. In addition, a nitrogen signal (N Kα) is visible in these samples, which indicates the presence of amino groups introduced by the PDMAEMA modification. For sample 3a (Figure 4), the EDX spectra show carbon signal dominance, which is due to the fact that polypropylene is composed of carbon and hydrogen. A signal coming from nitrogen (N Kα) is present in the spectrum of sample 3a, which confirms the presence of the PDMAEMA modifier in the structure.
The histograms represent the weight content of elements in the analyzed samples. For PLA nonwovens (Figure 2B and Figure 3B), the nitrogen content of about 10% confirms the effective introduction of amino groups derived from PDMAEMA onto the fiber surface. In contrast, sample 3a (PP + PDMAEMA) shows a nitrogen content of 2.34%, which also indicates modification but with lower efficiency compared to PLA nonwovens.
For most materials, the depth of EDX analysis is between 1 and 2 μm [10]; therefore, the structure of the studied materials affects the detection of individual elements [11]. The analyzed PP nonwovens, produced by needle punch technology, are characterized by a loose and fluffy structure. This design allowed the PDMAEMA modifier to penetrate the free spaces between the fibers, which limited the homogeneous coverage of the surface layer. As a result, despite the larger amount of polymer applied to the PP nonwoven fabric (approx. 2%), compared to PLA nonwovens (approx. 1.4%), a lower nitrogen content was determined in the surface layer of PP nonwovens. PLA nonwovens, on the other hand, were characterized by a compact arrangement of fibers. The PDMAEMA modifier has been deposited on the surface layer, providing a greater number of amino groups on the surface of the nonwoven fabric. EDX microanalysis confirmed the presence of nitrogen in PDMAEMA-modified samples. The high nitrogen content in samples 1a and 2a confirms the effective introduction of amino groups from PDMAEMA to the surface of the PLA nonwoven fabric. The presence of 3a in the sample also indicates a modification; however, in the case of this nonwoven fabric, part of the polymer applied fills the spaces between the fibers, and only a small amount of it covers the fibers’ surface layers, which results from the different structure of the PP nonwoven fabric.

3.1.3. Electrokinetic Analysis

To evaluate the effectiveness of modification of PLA nonwovens with PDMAEMA, an analysis of electrokinetic properties was also performed. The research included the measurement of flow potential and the amount of surface charge in the water. The values of the flow potential allow for the assessment of the changes in the nature of the surface (cationic or anionic), while the amount of surface charge reflects the efficiency of modification and the degree of interaction between the surface of the nonwoven fabric and the water medium. The results of the above measurements are shown in Table 3.
The tested samples, in contact with the measuring medium (water), showed that the unmodified PLA samples (samples 1 and 2) have a negative flow potential (from −9.5 mV to −44 mV), with a small amount of charge in the range 0.6–0.8 × 106 (eq/g). The presence of a negative surface charge is typical of PLA, which can contain acidic functional groups, such as end groups (−COOH). After the application of PDMAEMA (samples 1a and 2a), the character of the surface has changed to a positive and the amount of charge is 25–29 × 106 (eq/g), which indicates the effective modification and presence of amino groups of PDMAEMA, which is a positive polyelectrolyte.
The unmodified PP nonwoven fabric has a negative flow potential, much lower than that of PLA (−98 mV). This may be due to other surface properties of polypropylene (low surface energy and lack of polar groups). For PDMAEMA (3a) functionalized PP nonwovens, the flow potential is also positive, but the charge is lower than that of the PLA samples and is 0.15 × 106 (eq/g). This could mean that, not only the degree of PDMAEMA deposit but also the surface structure and chemical interactions play a key role in generating surface charge. With a flat and more homogeneous surface, PLA makes better use of the cationic properties of PDMAEMA, while polypropylene (with its extensive structure) can reduce the amount of polymer in the outer layer. The above quantitative results showing a smaller amount of modifier in the outer layer of the needled nonwoven fabric than in the nonwoven fabric obtained by the spunbond method are consistent with the results obtained by the EDX technique.
In the study [2], PP nonwovens modified with the PDMAEMA layer were examined in the amount of 6.3% by weight. The flow potential was determined as being positive, while the amount of charge was determined at 20 × 106 (eq/g). In the conducted research, the nonwoven fabric obtained in the melt-blown technology was modified. The PDMAEMA layer on PLA nonwovens was deposited on the surface, as confirmed by the EDX analysis. This maximized the surface charge, even with a lower degree of application (approx. 1.4%).
Additionally, reflectance ATR-FTIR (Nicolet 6700, Thermo Electron Corp., Madison, WI, USA) spectra were recorded after the polymer modification step. For PLA-based samples, only subtle changes were visible due to overlapping carbonyl signals of PLA and PDMAEMA (see Figure S3), whereas for PP-based samples, the carbonyl peak from PDMAEMA was clearly distinguished (Figure S4).

3.2. Metallic Complexation

In compounds with divalent metals, tertiary nitrogen in the side group of PDMAEMA can act as an electron donor, donating its lone pair of electrons to the unoccupied metal orbitals. The metal then acts as an electron acceptor, allowing the formation of a coordination bond between the metal and the amino group [12]. This interaction is depicted schematically in Figure 5.
The next stage of modification (after applying the bioactive polymer PDMAEMA to the surface) was cross-linking the resulting structures with divalent metal solutions (zinc chloride, zinc sulphate heptahydrate, cobalt (II) acetate hydrate, iron(II) sulphate heptahydrate, and copper (II) nitrate trihydrate). The aim of this stage was to obtain a cross-linked spatial structure in the polymer, transforming the polymer modifier into an insoluble form. A quaternary ammonium salt formed as a result of the complexation process, which is characterized by a set of interesting bioactive properties, significantly exceeding tertiary nitrogen in this respect. In addition, the action of quaternary ammonium salts was enhanced by the use of the bioactive action of metals.

3.2.1. Complexes with Zinc

The importance of Zn(II) coordination complexes stems from their versatile applications, including therapeutic action against biologically relevant peptides and proteins [13], anticancer properties [14], and applications in chemical and biological sensors [15,16]. In the research, ZnCl2 and ZnSO4 salts were used to create PDMAEMA-Zn2+ complex systems (Table 4). It was assumed that chloride (Cl−) or sulfate (SO42−) anions can affect the process of forming coordination complexes, modifying their structure and morphology. PDMAEMA is an excellent material for this type of research because of its ability to form coordination bonds with metal ions. In the following analysis, carried out by scanning electron microscopy (SEM), complexes that formed on different nonwovens were subjected to a comparative evaluation. The aim was to determine the effect of the type of substrate on the morphology of the resulting complexes and to investigate the differences resulting from the use of different zinc salts. The samples were modified with zinc, as follows:
SEM Analysis
Scanning electron microscopy was used to image the surface of nonwovens containing PDMAEMA-Zn2+ complexes. The analysis was carried out at magnifications of 1000× and 2000×.
The obtained images (Figure 6) indicate a clear influence of the developed complexes on the topography of the surface of the nonwovens. The presence of layers surrounding the fiber structure and irregularly shaped microparticles was observed. No significant effect of the type of substrate on the structure of the resulting complexes was observed. The literature [17] describes the effect of zinc salt anions on the morphology of Zn sediments. Chlorides promote the formation of flake aggregates, while sulphates lead to more ordered structures. This phenomenon is explained by the preferential adsorption of anions on various crystal planes of zinc [18]. In the present study, it was shown that zinc complexes with PDMAEMA also show differences in morphology depending on the type of zinc salt. The PDMAEMA + ZnSO4 · 7H2O arrangement provided a more regular complex layer on the nonwovens (Figure 6 and Figure S5), whereas the PDMAEMA+ ZnCl2 arrangement led to the formation of flake-like aggregates (Figure 6 and Figure S6). The results obtained confirm that zinc salt anions have a significant impact on the process of forming layers and microstructures on the surface of nonwovens, which may be related to preferential interactions during the formation of complexes.
EDX Analysis
Figure 7 and Table 5 present the results of the EDX analysis in the form of X-ray energy spectra and the weight content of elements in individual functionalized nonwovens. Particular attention was paid to the analysis of nitrogen (N) and zinc (Zn), which are key indicators of the introduction of the PDMAEMA modifier and polymer–metal complexes in samples of selected nonwovens. Below is an analysis for complex systems using ZnCl2 and ZnSO4 salts.
The EDX spectra for PLA nonwovens (Figure 7) show an intense nitrogen signal (N Kα), which is confirmed by the presence of amino groups introduced by the PDMAEMA modification and a zinc signal (Zn Kα), derived from polymer–metal complexes. On the other hand, in the case of PP nonwovens with a polymer–metal complex (Figure 7C,F), a lower intensity of the nitrogen signal (N Kα) was observed, with a clearly higher zinc signal (Zn Kα). This may be because heavier elements (such as Zn) are deposited on the outer layers of the fluffy sample (which was confirmed by SEM analysis), so their signal may be relatively stronger. This is due to the higher energy of the Zn X-ray lines and the shorter path that the radiation can move in the material, which results in an increase in signal intensity (Zn Kα) in the EDX spectra for the modified PP samples.
Table 5 presents the results of the quantitative analyses performed based on the ZAF procedure. In the case of PLA nonwovens, the zinc content is at the level of 0.38–1.88%, while for polypropylene samples, it is 4.65% for zinc chloride and 2.93% for sulfate. X-ray microanalysis was used to determine the negligible residues of unreacted salts, which served as donors of the element zinc during the complexation process. Data from the literature indicate the presence of salt residues after the in situ complexation process [4,19]. Consequently, even after the purification step has been applied, they can be detected by EDX methods or other analytical techniques. The results obtained allowed for the formulation of the conclusion that the content of complexed elements in the surface layer depends on the number of modifiers introduced and the structure of the nonwovens. EDX microanalysis confirmed the presence of both nitrogen and zinc in the samples modified with the PDMAEMA polymer, demonstrating the effectiveness of the metal–polymer modification and complexation process. Differences in the content of elements between PLA and PP nonwovens may be related to differences in the structure of the nonwovens and the adsorption capacity of the surface.

3.2.2. Complexes with Iron

Because of its versatile properties, iron is widely used in various industries. Fe2+ ions are commonly used in materials chemistry as components of catalysts, magnetic compounds, and in environmental purification technologies [20,21,22]. Iron complexes with polymers are also used in medicine and biomaterials, including dressing materials, due to their antibacterial properties [23,24]. In this study, ferrous sulfate was used to produce polymer–metal complexes on PLA and PP nonwovens. The main objective of the modification was to investigate the effect of Fe2+ ions on the process of forming complexes in situ and on the potential antibacterial properties of the obtained nonwovens. The samples were labeled as 1c (PLA 1 + PDMAEMA + Fe), 2c (PLA 2 + PDMAEMA + Fe), and 3c (PP + PDMAEMA + Fe).
SEM Analysis
The figures below show electron microscopy images of modified samples.
Scanning electron microscopy (SEM) was used to image the surface of nonwovens containing PDMAEMA-Fe2+ complexes and to assess their distribution and structure. The obtained images (Figure 8) confirm the influence of the formed complexes on the surface topography. In the analyzed nonwovens, the presence of microparticles was observed, which evenly cover their surface. In the case of the 2c nonwoven fabric, characteristic structures were noted, forming a layer on the fibers and resembling a ‘sticky’ coating, containing microparticles in its structure. The analysis also clearly showed the effect of the added modifier: introducing a larger amount of polymer and metal resulted in a clearer coating of the nonwoven fabric. Similar microparticle structures were described in a paper on layer-by-layer (LbL) functionalization of cotton fibers. In that study, after applying two layers of a modifier containing a MIL-100(Fe) complex (metal–organic framework (MOF), which consists of iron (Fe) ions and organic ligands), characteristic microparticle formations were observed on the surface of the material, which was confirmed by SEM analysis. The results suggest the efficient deposition of iron complexes on cotton fibers, similar to the current study in which polymer–Fe2+ complexes were produced on in situ-modified nonwovens. These results suggest that similar mechanisms of complex deposition may occur in the case of in situ-modified materials [25]. In addition, the elongated and sharp structures observed in the present study may show morphological similarity to the structures described in the publication on the synthesis of iron oxide nanoparticles using FeSO4 salts as a precursor. In the literature, structures described as having an elongated shape have been referred to as ‘nanorod’. Although PDMAEMA-Fe2+ complexes were produced in the present study, the morphology of the described structures may indicate similar mechanisms of object formation with FeSO4 [26]. SEM analysis confirmed the presence of characteristic structures of PDMAEMA-Fe+ complexes on the surface of PLA and PP nonwovens. The observations showed the effect of the amount of modifier on the nonwoven fabric coating and displayed morphological similarities to structures described in the literature as ‘nanorod’, as well as complexes obtained by the LbL method. These results indicate the possibility of a controlled formation of complex structures containing iron in the process of modifying fibrous materials.
EDX Analysis
Figure 9 and Table 6 present the results of EDX analysis in the form of X-ray energy spectra and the elemental weight content. Particular attention is given to the analysis of nitrogen and iron, which serve as key indicators of the presence of the PDMAEMA modifier and the formation of polymer–metal complexes in the 1c, 2c, and 3c nonwoven samples.
The EDX spectra for PLA nonwovens (Figure 9A,B) show clear nitrogen signals (N Kα), confirming the presence of amino groups introduced by PDMAEMA modification, and an iron signal (Fe Kα), derived from polymer–metal complexes. For PP samples with the PDMAEMA-Fe complex (Figure 9C), the signal intensity of nitrogen (N Kα) was lower compared to PLA nonwovens, while the iron signal (Fe Kα) reached a higher value (about 55 cps). The weight content of elements in the analyzed samples showed that, for PLA nonwovens (Table 6), the nitrogen content is approx. 9%, while iron content is 0.43% and 1.99%, respectively. In sample 3c, the nitrogen content is 4.09%, while the iron content is 5.1%. The observed differences in the intensity of nitrogen and iron peaks between PLA and PP nonwovens may be related to the differences in the structure of the nonwovens and the adsorption properties of their surfaces. As in the case of zinc complexes, anionic residues (which are salt residues) were found in the iron-modified samples. EDX microanalysis confirmed the presence of nitrogen and iron in samples modified with PDMAEMA polymer, which confirms the effectiveness of the metal–polymer modification and complexation process.

3.2.3. Complexes with Cobalt

Cobalt, as a transition element, is widely used in various areas of industry due to its magnetic, catalytic, and antimicrobial properties [27,28,29,30]. Co2+ ions exhibit the ability to form stable complexes with ligands, which makes them attractive in the context of polymer–metal materials. These complexes can be used in medicine, environmental protection, and materials engineering. In particular, their antibacterial properties result from interfering with bacterial metabolic processes and generating reactive oxygen species (ROS). The production of PDMAEMA-Co2+ complexes allows for the assessment of the effect of cobalt ions on the physicochemical properties of nonwovens, including their antimicrobial potential. The results of this research can provide the basis for the development of new functional materials with a wide range of applications. The following system uses cobalt acetate to produce polymer–metal complexes. The aim of the modification was to investigate the effect of cobalt ions on the formation of complexes in situ and on the potential antibacterial properties of the produced nonwovens. The samples were labeled as 1d (PLA 1 + PDMAEMA + Co), 2d (PLA 2 + PDMAEMA + Co), and 3d (PP + PDMAEMA + Co).
SEM Analysis
The figures below show electron microscopy images of modified samples.
The obtained images from SEM analysis (Figure 10) confirmed the influence of the developed complexes on the topography of the surface of the nonwovens. Both PLA and PP nonwoven fabrics contain complexes with a characteristic flake structure, the amount and distribution of which may depend on the structure of the nonwovens that have been obtained by different methods. SEM analysis also indicated the presence of aggregates on the surface of the modified nonwovens, which take on a hairline structure. The aggregation of complexes may result from interactions between complexes and the surface of the nonwoven fabric or intermolecular interactions under in situ synthesis conditions. In the studies carried out by [31], cobalt(II) complexes were synthesized using Schiff base derivatives and subsequently applied to modify cotton fabrics. The synthesis process involved the reaction of cobalt salts with ligands in solution, leading to the formation of complexes in situ. SEM analysis revealed that structures with hair-flap morphology formed on the surface of the fabrics, indicating effective functionalization of the material. Similar structures were observed in the present study on PP nonwovens with PDMAEMA-Co2+ complexes, suggesting that the formation process of such morphologies may be independent of the type of substrate and result from the properties of the cobalt complexes themselves. In addition, in studies on Co(II) complexes with poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride) polymer, the formation of characteristic aggregates in the form of thin flakes was observed, which was confirmed by SEM analysis. A similar phenomenon was observed in the present study, where complex aggregate structures were also formed on the surface of PP nonwovens with PDMAEMA-Co2+ complexes, which may indicate common features of the process of forming these structures under in situ synthesis conditions [32]. The SEM analysis confirmed the presence of PDMAEMA-Co2+ complexes in the form of lobular-hair-shaped structures with a tendency to aggregate. The similarity of the morphology of the complexes on different substrates suggests that their formation may be independent of the type of base material. Further research is needed to understand the mechanisms of shaping these structures and the factors influencing their formation in more detail.
EDX Analysis
Figure 11 and Table 7 present the results of EDX analysis in the form of X-ray energy spectra and elemental weight content. Particular attention is given to nitrogen and cobalt, which serve as key indicators of the presence of the PDMAEMA modifier and the formation of polymer–metal complexes in the 1d, 2d, and 3d nonwoven samples.
The EDX spectra for PLA nonwovens (Figure 11A,B) show a nitrogen (N Kα) signal with an intensity of about 20 cps, which confirms the presence of amino groups introduced by the PDMAEMA modification, and a cobalt (Co Kα) signal, indicating the formation of polymer–metal complexes. In the case of PP nonwoven fabric (Figure 11C), the signal intensity of nitrogen (N Kα) was about 15 cps, while the signal of cobalt (Co Kα) reached a higher value, at about 30 cps. Table 7 shows that, for PLA nonwovens (samples 1d and 2d), the nitrogen content is about 10% and the cobalt content is 0.22% and 0.19%, respectively. In the PP sample (sample 3d), the nitrogen content is lower (6.16%), while the cobalt content is much higher (2.26%). This trend was also observed for complexes formed by PDMAEMA with the previously discussed elements.

3.2.4. Complexes with Copper

Copper and its compounds are known for their potent antibacterial, antioxidant, and antifungal properties [32]. Copper complexes are also used in modern anticancer therapies, supporting the action of drugs and effectively destroying cancer cells [33,34]. In addition, copper compounds exhibit antiviral properties, including efficacy against coronaviruses, which makes them a promising material in reducing the risk of spreading infectious diseases [35,36]. Studies on PDMAEMA complexes with copper ions have shown their effectiveness against various strains of bacteria, both Gram-positive and Gram-negative. For example, the surface modification of PDMAEMA materials with copper ions led to coatings with increased antibacterial activity [2,4]. In the context of nonwovens, the use of PDMAEMA-Cu2+ complexes can lead to materials with improved antibacterial and antiviral properties, which is particularly important in medical and hygienic applications. Studies indicate that such modifications can also affect other physicochemical properties of materials, such as thermal stability and mechanical and conductive properties [37]. Overall, the functionalization of nonwovens with PDMAEMA with Cu2+ ions in a nonwoven matrix represents a promising strategy for producing materials with advanced antimicrobial and antiviral properties, justifying research into this system. The samples were labeled as 1e (PLA 1 + PDMAEMA + Cu), 2e (PLA 2 + PDMAEMA + Cu), and 3e (PP + PDMAEMA + Cu).
SEM Analysis
The figures below show electron microscopy images of modified samples.
The obtained images (Figure 12) for nonwovens 1e, 2e, and 3e confirm that the modification process significantly affected the topography of the nonwovens’ surface, causing noticeable changes in their morphology. Modified nonwovens show the presence of areas of varying contrast intensity (the so-called ‘shadows’), which occur in the case of nonwovens modified with the PDMAEMA polymer. Microparticles embedded in the shadows were observed in their structure, as clearly shown in Figure 12. In the publication “PLA nonwovens modified with poly (dimethylaminoethyl methacrylate) as antimicrobial filter materials for workplaces” [4], the authors described the modification of polylactide nonwovens (PLA) with poly(dimethylaminoethyl methacrylate) (PDMAEMA) and copper (Cu) complexes in order to obtain filter materials with antimicrobial properties. The SEM analysis showed the acquisition of structures with morphologies similar to those obtained in this study, which emphasizes the universal nature of the methodology for the production of such materials [4]. A group of scientists from Peru, looking for textiles that inhibit the spread of the coronavirus through textiles, carried out a modification of polyester–cotton fabrics in industrial conditions by depositing copper oxide particles. For this purpose, a commonly available precursor was used: hydrated copper (II) sulphate (VI) (CuSO4) [36]. In this work, copper (II) nitrate was used as a precursor for the synthesis of PDMAEMA-Cu2+ complexes. The SEM analysis showed that the obtained structures of copper particles on the nonwovens were similar in terms of morphology and uniformity of coating, despite differences in the starting compounds used. The publication [30] describes copper (Cu) complexes formed with a Schiff-base type aniline derivative, which were analyzed using SEM. The images showed the presence of fine, well-defined nanostructures on the surface of the modified cotton fabrics. Modification of the fabrics using copper complexes resulted in marked changes in their topography compared to the unmodified samples. The similarities in SEM results between the complexes described in the literature and the PDMAEMA-Cu2+ complexes in this study indicate the efficiency of complex deposition and the versatility of copper in the development of functional materials. The similarities between the results obtained in this work and the results described in the cited literature indicate the universality of copper nitrate as a precursor in the processes of modification of nonwovens and textiles. This is particularly important for the development of advanced materials with a wide range of application potential, such as antimicrobial filters or conductive materials.
EDX Analysis
Figure 13 and Table 8 present the results of EDX analysis in the form of X-ray energy spectra and elemental weight content. Particular attention is given to nitrogen (N) and copper (Cu), which serve as key indicators of the presence of the PDMAEMA modifier and the formation of polymer–metal complexes in the 1e, 2e, and 3e nonwoven samples.
The EDX spectrum of PP nonwoven fabric modified with the PDMAEMA-Cu complex shows a more intense characteristic band signal (Cu Kα) of copper in relation to the signal intensity of the nitrogen band (N Kα) (Figure 13C). For PLA nonwovens (Table 8), the nitrogen content is about 10% and the copper amount is 2.47% (sample 1e) and 1.44% (sample 2e), respectively. For sample 3e, the nitrogen content is 5.70% and copper is 5.29%. EDX microanalysis confirmed the presence of both nitrogen and copper in the samples modified with the PDMAEMA polymer, demonstrating the effectiveness of the metal–polymer modification and complexation process.

3.3. Studies on the Antibacterial Activity of Polylactide Nonwovens

Studies on the antibacterial activity of nonwovens subjected to complexes in situ were carried out based on the ASTM E2149-10 standard. PLA2 polylactide nonwovens, with a surface mass of 120 g/m2, were selected for the study, which were complexed using each of the possible systems described in the above work. The effect of modifiers on the growth of Escherichia coli bacteria was studied, and the results are shown in Table 9.
Analyzing the test results for the antibacterial activity of modified nonwovens found that all nonwovens showed 100% bactericidal activity against bacteria Echerichia Coli, achieving a reduction of 4Log10 (Table 9). The reduction in bacteria occurred after 6 h of exposure. The antibacterial properties of tertiary PDMAEMA have been thoroughly researched and described by Rawlinson [7]. Several studies have shown that PDMAEMA is effective in inhibiting the growth of Gram-negative bacteria such as E. coli, while its effect against Gram-positive bacteria is variable. The literature analysis [7,8,9] indicates that the time of exposure, the degree of inoculation, and the molecular weight of the polymer have a significant impact on antibacterial effectiveness. The higher molecular weight of PDMAEMA increases its antimicrobial effect, which is also confirmed in this paper. Gutarowska et al. [4] studied PLA nonwovens using PDMAEMA and its complexes with copper (PDMAEMA-Cu). Samples containing 1.1% PDMAEMA showed a reduction in bacteria of about 40% after 8 h of exposure. Increasing the polymer application to 2.7% resulted in an increase in the reduction of bacteria of up to 80%. On the other hand, PDMAEMA complexation with copper provided a 100% reduction in bacteria after 8 h. The results of the study indicated that the amount of PDMAEMA applied significantly improved its antibacterial properties, which allowed for the full elimination of bacteria in correctly modified samples.

4. Conclusions

This work focused on finding a way to solve a real problem: how to respond to the growing resistance of microbes to antimicrobial measures. Current biocides are often focused on a selected type or group of microorganisms. Meanwhile, the solution developed in this work proposes a material based on biodegradable polylactide, which is supposed to offer a wide range of biological activities, combining the effects (I) of a bioactive polymer with tertiary nitrogen, (II) selected metals, and (III) quaternary ammonium salts.
A scheme for the modification of a base of nonwovens was developed, which consisted of applying layers in stages and by spraying with popular and cheap solvents: water and ethanol.
The proposed method is inexpensive and straightforward in practice, as it does not require the design of new equipment or the development of specialized tools.
Surface-layer investigations by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDX) confirmed the formation of a stable polymer–metal complex on the modified nonwovens, while electrokinetic measurements further verified the successful deposition of the PDMAEMA layer.
In this work, PDMAEMA was quaternized to improve its antimicrobial properties. However, no significant differences were observed in the antibacterial activity of samples modified by a polymer complex with different metals because all modified polylactide nonwovens were characterized by a 100% reduction in Escherichia coli bacteria.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/coatings15090996/s1, Table S1. List of sample codes and abbreviations (Supplementary Information); Figure S1: SEM image of nonwovens after complexation. Sample 3b1—PP nonwovens modified with PDMAEMA and ZnCl2; magnification 2000×.; Figure S2: SEM image of nonwovens after complexation. Sample 3b2—PP nonwoven modified with the PDMAEMA + ZnSO4 x 7H2O; magnification 2000×; Figure S3. Representative ATR-FTIR spectra of the samples: 1—PLA nonwoven (black), PDMAEMA (blue), 1a—PLA nonwoven + PDMAEMA (red); Figure S4. ATR-FTIR spectrum of the samples: 3—PP nonwoven (black), PDMAEMA (blue), 3a—PP nonwoven + PDMAEMA (red); Figure S5. SEM image of nonwovens after complexation. Sample 3b1—PP nonwovens modified with PDMAEMA and ZnCl2; magnification 2000×; Figure S6. SEM image of nonwovens after complexation. Sample 3b2—PP nonwoven modified with the PDMAEMA + ZnSO4 x 7H2O; magnification 2000×.

Author Contributions

Conceptualization, D.S.; methodology, M.C. and D.S.; validation, M.C., D.S., and L.H.; formal analysis, M.C.; investigation, M.C.; resources, D.S. and M.P.; data curation, M.C.; writing—original draft preparation, M.C.; writing—review and editing, D.S., L.H., and M.P.; visualization, M.C.; supervision, D.S.; project administration, D.S.; funding acquisition, D.S. All authors have read and agreed to the published version of the manuscript.

Funding

The manuscript was financed from funds assigned for 14-148-1-21-28 statuary activity, by the Lodz University of Technology, Textile Institute, Poland.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study, including additional SEM images and raw measurements, are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare that the method presented in this article is protected by Polish Patent No. 246837. No commercial interest or external funding was involved at any stage of the research or patent application.

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Figure 1. SEM images at 1000× magnification of: (A) unmodified PLA nonwoven 1 (Sample 1), (B) unmodified PLA nonwoven 2 (Sample 2), (C) unmodified PP nonwoven (Sample 3), (D) PLA nonwoven 1 with deposited PDMAEMA (Sample 1a), (E) PLA nonwoven 2 with deposited PDMAEMA (Sample 2a), (F) PP nonwoven 3 with deposited PDMAEMA (Sample 3a).
Figure 1. SEM images at 1000× magnification of: (A) unmodified PLA nonwoven 1 (Sample 1), (B) unmodified PLA nonwoven 2 (Sample 2), (C) unmodified PP nonwoven (Sample 3), (D) PLA nonwoven 1 with deposited PDMAEMA (Sample 1a), (E) PLA nonwoven 2 with deposited PDMAEMA (Sample 2a), (F) PP nonwoven 3 with deposited PDMAEMA (Sample 3a).
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Coatings 15 00996 g002
Figure 2. EDX results of 1—base PLA nonwoven 1 and 1a—PLA nonwoven 1 modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
Figure 2. EDX results of 1—base PLA nonwoven 1 and 1a—PLA nonwoven 1 modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
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Coatings 15 00996 g003
Figure 3. EDX results of 2—base PLA nonwoven 2 and 2a—PLA nonwoven 2 modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
Figure 3. EDX results of 2—base PLA nonwoven 2 and 2a—PLA nonwoven 2 modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
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Coatings 15 00996 g004
Figure 4. EDX results of 3—PP nonwoven and 3a—PLA nonwoven modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
Figure 4. EDX results of 3—PP nonwoven and 3a—PLA nonwoven modified with PDMAEMA: (A) intensities of X-ray characteristic spectra; (B) quantitative analysis.
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Coatings 15 00996 g005
Figure 5. The graphical representation of polymer–metal complexation for the PDMAEMA-Copper2+ system.
Figure 5. The graphical representation of polymer–metal complexation for the PDMAEMA-Copper2+ system.
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Coatings 15 00996 g006
Figure 6. SEM images of nonwovens complexed with zinc chloride ((A)—sample 1b1, (B)—sample 2b1, (C)—sample 3b1) and zinc sulfate VI; (D)—sample 1b2, (E)—sample 2b2, (F)—sample 3b2).
Figure 6. SEM images of nonwovens complexed with zinc chloride ((A)—sample 1b1, (B)—sample 2b1, (C)—sample 3b1) and zinc sulfate VI; (D)—sample 1b2, (E)—sample 2b2, (F)—sample 3b2).
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Coatings 15 00996 g007
Figure 7. EDX results of (A) 1b1—PLA nonwoven 1 + PDMAEMA + ZnCl2, (B) 2b1—PLA nonwoven 2 + PDMAEMA + ZnCl2, (C) 3b1—PP nonwoven 1 + PDMAEMA + ZnCl2, (D) 1b2—PLA nonwoven 1 + PDMAEMA + ZnSO4, (E) 2b2—PLA nonwoven 2 + PDMAEMA + ZnSO4, and (F) 3b2—PP nonwoven + PDMAEMA + ZnSO4.
Figure 7. EDX results of (A) 1b1—PLA nonwoven 1 + PDMAEMA + ZnCl2, (B) 2b1—PLA nonwoven 2 + PDMAEMA + ZnCl2, (C) 3b1—PP nonwoven 1 + PDMAEMA + ZnCl2, (D) 1b2—PLA nonwoven 1 + PDMAEMA + ZnSO4, (E) 2b2—PLA nonwoven 2 + PDMAEMA + ZnSO4, and (F) 3b2—PP nonwoven + PDMAEMA + ZnSO4.
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Coatings 15 00996 g008
Figure 8. SEM images of nonwovens complexed with iron sulphate VI ((A)-sample 1c; (B)—sample 2c, (C)—sample 3c).
Figure 8. SEM images of nonwovens complexed with iron sulphate VI ((A)-sample 1c; (B)—sample 2c, (C)—sample 3c).
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Coatings 15 00996 g009
Figure 9. EDX results: signal intensities characteristic of: (A) 1c—PLA nonwoven 1 + PDMAEMA + FeSO4, (B) 2c—PLA nonwoven 2 + PDMAEMA + FeSO4, and (C) 3c—PP nonwoven + PDMAEMA + FeSO4.
Figure 9. EDX results: signal intensities characteristic of: (A) 1c—PLA nonwoven 1 + PDMAEMA + FeSO4, (B) 2c—PLA nonwoven 2 + PDMAEMA + FeSO4, and (C) 3c—PP nonwoven + PDMAEMA + FeSO4.
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Coatings 15 00996 g010
Figure 10. SEM images of nonwovens complexed with cobalt acetate ((A)-sample 1d, (B)-sample 2d, (C)-sample 3d).
Figure 10. SEM images of nonwovens complexed with cobalt acetate ((A)-sample 1d, (B)-sample 2d, (C)-sample 3d).
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Figure 11. EDX results: signal intensities characteristic of: (A) 1d—PLA nonwoven 1 + PDMAEMA + (CH3COO)2Co, (B) 2d—PLA nonwoven 2 + PDMAEMA + (CH3COO)2Co, and (C) 3d—PP nonwoven + PDMAEMA + (CH3COO)2Co.
Figure 11. EDX results: signal intensities characteristic of: (A) 1d—PLA nonwoven 1 + PDMAEMA + (CH3COO)2Co, (B) 2d—PLA nonwoven 2 + PDMAEMA + (CH3COO)2Co, and (C) 3d—PP nonwoven + PDMAEMA + (CH3COO)2Co.
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Coatings 15 00996 g012
Figure 12. SEM images of nonwovens complexed with copper nitrate ((A)—sample 1e, (B)—sample 2e, (C)—sample 3e).
Figure 12. SEM images of nonwovens complexed with copper nitrate ((A)—sample 1e, (B)—sample 2e, (C)—sample 3e).
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Coatings 15 00996 g013
Figure 13. EDX results: signal intensities characteristic of: (A) 1e—PLA nonwoven 1 + PDMAEMA + Cu(NO3)2. (B) 2e—PLA nonwoven 2 + PDMAEMA + Cu(NO3)2 and (C) 3e—PP nonwoven + PDMAEMA + Cu(NO3)2.
Figure 13. EDX results: signal intensities characteristic of: (A) 1e—PLA nonwoven 1 + PDMAEMA + Cu(NO3)2. (B) 2e—PLA nonwoven 2 + PDMAEMA + Cu(NO3)2 and (C) 3e—PP nonwoven + PDMAEMA + Cu(NO3)2.
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Table 1. Basic parameters of modified nonwovens.
Table 1. Basic parameters of modified nonwovens.
Sample
Number		Type of PolymerType of
Nonwoven		Mass per
Unit Area
[g/m2]		Average Thickness of Nonwoven
[mm]		Average Fiber
Diameter in
Nonwoven
[µm]
1PLASpunbond400.299–10
2PLASpunbond1200.419–10
3PPNeedle punch651.9814–16
Table 2. Deposition percentage of PDMAEMA onto different materials.
Table 2. Deposition percentage of PDMAEMA onto different materials.
SampleMaterialAmount of PDMAEMA [%]
1aPLA1.365
2aPLA1.415
3aPP2.155
Table 3. Electrokinetic data of samples before and after PDMAEMA polymer deposition.
Table 3. Electrokinetic data of samples before and after PDMAEMA polymer deposition.
SamplePercentage of PDMAEMA [%]Streaming Potential [mV]Charge Density
×10−6 eq g−1
1-−9.50.80
1a1.365+15829.0
2-−440.61
2a1.415+18025.0
3-−982.6
3a2.155+1000.15
Table 4. Zinc modification systems.
Table 4. Zinc modification systems.
SampleNonwovenType of salt
1b1PLA1ZnCl2
1b2PLA1ZnSO4 · 7H2O
2b1PLA2ZnCl2
2b2PLA2ZnSO4 · 7H2O
3b1PPZnCl2
3b2PPZnSO4 · 7H2O
Table 5. The weight content of elements in functionalized nonwovens.
Table 5. The weight content of elements in functionalized nonwovens.
SampleElement Content (wt%)
CNOZn
1b142.019.7847.560.38
1b248.568.6942.020.56
2b143.759.0744.351.88
2b241.5310.6146.281.40
3b182.362.748.744.65
3b286.273.536.152.93
Table 6. The weight content of elements in functionalized nonwovens.
Table 6. The weight content of elements in functionalized nonwovens.
SampleElement Content (wt%)
CNOFe
1c42.378.9648.100.43
2c42.098.4447.071.99
3c81.264.098.455.10
Table 7. The weight content of elements in functionalized nonwovens.
Table 7. The weight content of elements in functionalized nonwovens.
SampleElement Content (wt%)
CNOCo
1d41.569.6448.580.22
2d42.209.8847.730.19
3d81.666.169.922.26
Table 8. The weight content of elements in functionalized nonwovens.
Table 8. The weight content of elements in functionalized nonwovens.
SampleElement Content (wt%)
CNOCu
1e44.009.4444.092.47
2e41.999.6246.951.44
3e79.035.709.355.29
Table 9. Antibacterial test results for the modified nonwoven fabrics. Test microorganism: E. coli (DSM 1576). The antimicrobial activity of the immobilized agents under dynamic contact conditions was determined according to ASTM E2149.
Table 9. Antibacterial test results for the modified nonwoven fabrics. Test microorganism: E. coli (DSM 1576). The antimicrobial activity of the immobilized agents under dynamic contact conditions was determined according to ASTM E2149.
SampleModifierCFU mL−1 at t0CFU mL−1 at t1Reduction (%)Log10
Reduction
Culture only (DK)—1.83 × 1051.73 × 105——
2 (PLA control)——7.06 × 1050—
2a PDMAEMA—01004
2b1PDMAEMA + Zn (ZnCl2)—01004
2b2PDMAEMA + Zn (ZnSO4)—01004
2cPDMAEMA + Co—01004
2dPDMAEMA + Fe—01004
2ePDMAEMA + Cu—01004
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MDPI and ACS Style

Czajka, M.; Stawski, D.; Herczyńska, L.; Puchalski, M. Polymer-Metallic Systems Functionalizing Polylactide Nonwovens as a Greener Alternative to Modified Polypropylene-Based Textiles. Coatings 2025, 15, 996. https://doi.org/10.3390/coatings15090996

AMA Style

Czajka M, Stawski D, Herczyńska L, Puchalski M. Polymer-Metallic Systems Functionalizing Polylactide Nonwovens as a Greener Alternative to Modified Polypropylene-Based Textiles. Coatings. 2025; 15(9):996. https://doi.org/10.3390/coatings15090996

Chicago/Turabian Style

Czajka, Maria, Dawid Stawski, Lucyna Herczyńska, and Michał Puchalski. 2025. "Polymer-Metallic Systems Functionalizing Polylactide Nonwovens as a Greener Alternative to Modified Polypropylene-Based Textiles" Coatings 15, no. 9: 996. https://doi.org/10.3390/coatings15090996

APA Style

Czajka, M., Stawski, D., Herczyńska, L., & Puchalski, M. (2025). Polymer-Metallic Systems Functionalizing Polylactide Nonwovens as a Greener Alternative to Modified Polypropylene-Based Textiles. Coatings, 15(9), 996. https://doi.org/10.3390/coatings15090996

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