Ind. Eng. Chem. Res. 2007, 46, 6425-6429
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Fabric Treated with Antimicrobial N-Halamine Epoxides Jie Liang,† Yongjun Chen,‡ Xuehong Ren,† Rong Wu,† Kevin Barnes,† S. D. Worley,*,† R. M. Broughton,§ Unchin Cho,§ Hasan Kocer,§ and T. S. Huang| Departments of Chemistry and Biochemistry, Polymer and Fiber Engineering, and Nutrition and Food Science, Auburn UniVersity, Auburn, Alabama 36849, and HaloSource Inc., 1631 220th Street SE, Bothell, Washington 98021
A series of new N-halamine epoxide precursors, 3-glycidyl-5,5-dialkylhydantoins (GH’s), has been synthesized by a very facile and economic method. Cellulose surfaces can be treated with GH’s and rendered biocidal by exposure to halogen solutions after curing the treated material. The biocidal efficacy tests showed that the chlorinated treated cellulose surfaces were antimicrobial with contact times required for 6-7 log reductions of Staphylococcus aureus and Escherichia coli O157:H7 of 5-30 min. It was found in simulated washing tests that celluloses, such as cotton swatches, treated with 3-glycidyl-5,5-dimethylhydantoin were quite stable and could survive more than the equivalent of 50 repeated home launderings with very little loss. Upon loss of the biocidal property due to long-term use, the treated surfaces could be recharged by further exposure to dilute bleach to regain antimicrobial activity. In addition, since only water was used as a solvent for the synthesis of GH’s at room temperature, the reaction solution could be directly used as a treatment solution. Stability tests showed that the reaction solutions were relatively stable at room temperature and more stable at 5 °C over a period of at least 30 d. Preliminary experiments have shown that polyester swatches can also be treated with GH’s and be rendered biocidal upon treatment with household bleach. The entire process should be economical for commercial application. Introduction
Scheme 1. Synthesis of 3-Glycidyl-5,5-dialkylhydantoins (GH’s)
The increasing awareness of healthcare has stimulated a wide range of research on antimicrobial materials.1-5 N-Halamines have been demonstrated to be efficient, direct-contact biocides due to the oxidative properties of halamine moieties (N-X) in contact with micro-organisms.6,7 A series of novel antimicrobial N-halamine monomers and polymers has been developed in these laboratories including hydantoin derivatives,8,9 N-halamine siloxanes,10-12 N-halogenated poly(styrenehydantoins),13-17 and copolymers of N-halamine/quat siloxane.18 The N-chlorohydantoinyl siloxanes are particularly useful biocidal treatment materials applicable to a variety of surfaces such as cellulose,11,19 polyvinyl chloride,19 silica gel,20 polyurethanes,21 and sand.22 Clothing and other textile materials are environments for survival and growth of bacteria, fungi, and viruses. Contamination of the textile materials by such microorganisms, especially in hospitals or other public venues, can cause extensive transmission of infections.23,24 Producing antimicrobial properties on the textile materials should effectively block the microorganism contamination of them. In the development of commercial antimicrobial textiles, many factors such as cost, lifetime, antimicrobial efficiency, and washing durability should be considered. Of the numerous antimicrobial textiles developed in recent years, durable and rechargeable ones such as those having N-halamine bound moieties have great potential for use. In this study, a series of new N-halamine epoxide precursors (GH’s) has been synthesized and employed to react on the surfaces of cotton and polyester swatches. Their structures are shown in Scheme 1. Since GH’s contain both an N-halamine * To whom correspondence should be addressed. Tel.: (334) 8446980. Fax: (334) 844-6959. E-mail:
[email protected]. † Department of Chemistry and Biochemistry, Auburn University. ‡ HaloSource Inc. § Department of Polymer and Fiber Engineering, Auburn University. | Department of Nutrition and Food Science, Auburn University.
precursor moiety (hydantoin ring) and an active tethering group (epoxide ring), they can be covalently bound to cotton and then chlorinated with household bleach. The treated cotton swatches have been tested for biocidal efficacy against Gram-positive and Gram-negative bacteria, Staphylococcus aureus and Escherichia coli O157:H7, respectively. It will be shown that of these GH’s, 3-glycidyl-5,5-dimethylhydantoin exhibits excellent washing stability during laundering. Washing tests will demonstrate that cotton swatches treated with 3-glycidyl-5,5-dimethylhydantoin can survive more than the equivalent of 50 machine washings with very little loss. Experimental Section Materials. All chemicals were obtained from the Aldrich Chemical Co., Milwaukee, WI and used as received without further purification unless otherwise noted. The fabrics used were Style 400 Bleached 100% Cotton Print Cloth (Testfabics, Inc., West Pittston, PA) and polyester 100% Dacron Type 54 (Testfabrics, Inc., Middlesex, NJ). The bacteria employed were Staphylococcus aureus ATCC 6538 and Escherichia coli O157: H7 ATCC 43895 (American Type Culture Collection, Rockville, MD). The Trypticase soy agar used was from Difco Laboratories, Detroit, MI.
10.1021/ie0707568 CCC: $37.00 © 2007 American Chemical Society Published on Web 08/18/2007
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Instruments. The NMR spectra were obtained using a Bruker 400 MHz spectrometer, while the IR data were obtained with a Shimadzu IR Prestige-21 FTIR spectrometer. Mass spectra were obtained using a Micro Mass Trio 2000 instrument. Synthesis of 3-Glycidyl-5,5-dialkylhydantoins. 5,5-Dimethylhydantoin is commercially available. The other 5,5dialkylhydantoin derivatives were prepared by reaction of the appropriate dialkylketone with ammonium carbonate and either sodium or potassium cyanide in a molar ratio of about 0.67: 2.0:1.0, respectively, in a water/ethanol (1:1 by volume) solvent mixture at 50-60 °C for 4-10 h. For example, 5-methyl-5propylhydantoin was prepared by first mixing 86.4 g (0.90 mol) of ammonium carbonate with 29.3 g (0.45 mol) of potassium cyanide in 125 mL of water in a 500 mL round-bottom flask. To this solution was added 25.8 g (0.30 mol) of 2-pentanone in 125 mL of ethanol. The reaction mixture was heated to 5055 °C while being stirred for 6 h. After cooling to ambient temperature, the reaction mixture was slowly poured into 200 mL of a 10% HCl solution. The resulting crude white solid product was collected by filtration and purified by recrystallization from a water/ethanol mix to produce 41.2 g of white crystals (88% yield) which exhibited the following properties: mp 124-125 °C; 1H NMR (CDCl3) ∂ 0.93 (t, 3H), 1.23-1.80 (m, 4H), 1.45 (s, 3H), 6.30 (s, 1H); 13C NMR (CDCl3) ∂ 13.9, 16.9, 23.8, 39.9, 64.8, 156.2, 177.3; IR (KBr) 3233, 1767, 1712, 1433, 775, 449 cm-1; m/z 156. Other 5,5-dialkylhydantoins were prepared by an analogous procedure, and their structures were verified by NMR, IR, and mass spectrometry. In this manner, 2-pentanone, 2-octanone, acetophenone, and cyclohexanone were employed to synthesize 5-methyl-5-propylhydantoin, 5-hexyl-5-methylhydantoin, 5-methyl-5-phenylhydantoin, and 5,5-pentamethylenehydantoin, respectively. Then each of the 5,5-dialkylhydantoin derivatives was converted to its sodium or potassium salt by being stirred for 5-10 min in aqueous NaOH or KOH (equimolar mixture of base and hydantoin derivative). Then without actual isolation of the salts, the same molar concentration of epichlorohydrin was added to the solution, and the mixture was stirred for 6-10 h at ambient temperature. For example, 0.05 mol of 5,5-dimethylhydantoin was mixed with 0.05 mol of NaOH in 40 mL of water in a 100 mL beaker. After stirring for 5-10 min at ambient temperature, 0.05 mol of epichlorohydrin was added followed by stirring for 10 h at ambient temperature. Then most of the water was removed by evacuation, and 50 mL of acetone was added to dissolve the produced hydantoin epoxide, which was then isolated by filtration of the NaCl byproduct and evaporation of the acetone solvent. Crude 3-glycidyl-5,5-dimethylhydantoin (8.46 g) was recovered as an oil, and, after purification by column chromatography, 4.72 g of white solid product was obtained. 1H NMR (d-acetone): ∂ 1.38 (s, 6H), 2.52-2.71 (m, 2H), 3.10 (m, 1H), 3.48-3.65 (m, 2H); m/z: 184. The yield of the purified product was 51.30%, but generally the unpurified product or reaction solution was directly used for the surface-binding studies. Treatment and Chlorination Procedures. Typically a bath containing the same molar concentration (0.26) of each 3-glycidyl-5,5-dialkylhydantoin in a 1:1 by weight solution of acetone and water was prepared. Swatches of 100% Cotton Print Cloth were soaked in the bath without agitation for about 15 min, producing a wet add-on weight percentage of about 175%, then dried at 95 °C for 1 h, and then further cured at 145 °C for 20
min. After the curing process, the swatches were soaked in a 0.5% detergent solution for 15 min, washed with water, and dried in an oven at 70 °C. The typical dry add-on weight percentage was about 1.6%. At this point the fibers declined in tensile strength by about 14%. Then the swatches were soaked in a 10% solution of household bleach (0.65% NaOCl) (pH adjusted to 7) without stirring at ambient temperature for 45 min, rinsed with water, and dried at 45 °C for 1 h. This procedure was sufficient to remove any free chlorine adhered to the swatches. Chlorination did cause a loss of about 40% in tensile strength of the fibers relative to untreated cotton fibers. Similar procedures were employed for polyester (poly(ethylene terepthalate)) swatches except that generally the swatches were pretreated with dilute sodium hydroxide (0.5-2.0 N) at temperatures up to 100 °C for time periods of 5-60 min in order to promote hydrolysis of some surface ester linkages. Then they were exposed to a bath containing 10% by weight 3-glycidyl5,5-dimethylhydantoin for 30 min at ambient temperature without agitation, squeezed on a padding machine, dried at 60 °C for 60 min, and cured at temperatures ranging from 75 to 175 °C for time periods ranging from 5 to 120 min. Chlorination was performed as described for the cotton swatches. Measurement of add-on weights of the polyester swatches and tensile strengths of the fibers before and after treatment were not performed. Analytical Titration Procedure. For the determination of oxidative chlorine (Cl+) content on the cotton or polyester swatches, a standard iodometric/thiosulfate titration procedure was employed. For example, about 0.5 g of pieces of treated and chlorinated cotton swatches were suspended in 50 mL of a 0.1 N acetic acid solution. After addition of 0.3 g of KI, and 1 mL of 0.5% of starch water solution as an indicator, the solution was titrated with 0.0375 N of sodium thiosulfate until the blue color disappeared at the end point. The weight percent Cl+ on the cotton swatches could then be determined from the equation below
% Cl+ ) [N × V × 35.45 /(2 × W)] × 100% where N and V are the normality (eqv/L) and volume (L), respectively, of the Na2S2O3 consumed in the titration, and W is the weight in g of the cotton or polyester swatch sample. Durability Tests. Washing tests were performed on swatches of cotton treated with GH’s. Two-thirds of the treated cotton swatches were chlorinated before the wash tests, and the others were not chlorinated. Then all types of treated swatches were subjected to laundry washing cycles using the AATCC Test Method 61 (Test 2A Procedure). In this procedure stainless steel canisters (1.5 × 2 in.) containing 150 mL of 0.15% AATCC detergent water solution and 50 stainless steel balls were fixed in a Launder-O-meter and rotated at 42 rpm and 49 °C for 45 min. Each test sample was rinsed three times with distilled water and then dried in air at ambient temperature. In this method each wash cycle is considered to be the equivalent of 5 machine washings. Samples were evaluated after 1, 2, and 10 washing cycles for retention of the GH’s and/or chlorinated GH’s. Those samples not chlorinated before washing were chlorinated by the procedure described above in order to assess how much chlorine could be loaded after variable numbers of washing cycles. Those chlorinated before washing were divided into two groups with half being assessed for chlorine loading without rechlorination, the other half being rechlorinated and then assessed for chlorine loading. Chlorinated polyester swatches treated with 3-glycidyl5,5-dimethylhydantoin were subjected to analogous washing tests.
Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007 6427 Scheme 2. Previous Reported Method for Synthesis of 3-Glycidyl-5,5-dimethylhydantoin
Antimicrobial Efficacy Testing. One inch square cotton swatches, some untreated to serve as controls, others treated with GH’s, but unchlorinated, to serve as a second type of control, and others treated with GH’s, but chlorinated, served as samples for antimicrobial efficacy testing. Dried swatches were challenged with either Staphylococcus aureus ATCC 6538 or Escherichia coli O157:H7 ATCC 43895 using a “sandwich test”. In this test, 25 µL of bacterial suspension was placed in the center of a swatch, and a second identical swatch was laid upon it which was held in place by a sterile weight to ensure good contact of the swatches with the inoculum. The bacterial suspensions employed for the tests contained from 106 to 107 colony forming units (CFU), the actual number determined by counting after spread-plating on Trypticase soy agar plates. There was no significant evaporation of water from the inocula during the tests. After contact times of 5, 10, and 30 min, the various swatches were placed in sterile conical centrifuge tubes, each containing 5.0 mL of sterile 0.01 M sodium thiosulfate to quench any oxidative free chlorine which might have been present, and vortexed for 250 s to remove bacteria. Then the swatches were removed, and serial dilutions of the quenched solutions were plated on Trypticase soy agar. The plates were incubated at 37 °C for 24 h and then counted for viable CFU of bacteria. Polyester samples were not tested for biocidal efficacy. Results and Discussion Synthesis and Treatment with 3-Glycidyl-5,5-dialkylhydantoins (GH’s). Hydantoins are very stable N-halamine precursors and contain both amide and imide groups. For producing antimicrobial properties on the surface with covalent binding, the amide group can be used to bind oxidative halogen to form N-halamines, and the imide group can be used to bind an active functional group for tethering. In our previous work, a series of N-halamines with siloxane as the tethering functional group has been developed.10-12,18-22 In this report an epoxide was employed as the tethering functional group. The synthesis of 3-glycidyl-5,5-dimethylhydantoin had been reported (see Scheme 1).25 In this reported synthesis method, epichlorohydrin was used as both reactant and solvent so that the molar ratio between 5,5-dimethyhydantoin and epichlorohydrin was 1:30. In order to reduce the cost for the preparation of 3-glycidyl5,5-dialkylhydantoins, a modified method (Scheme 2) was developed in these laboratories to prepare 3-glycidyl-5,5dialkylhydantoins. This method is very suitable for industrial production at large scale. Water was used as the solvent, and no heating was required for this reaction. More importantly, the reaction solutions could be directly used as treatment solutions without any prior workup. Of these GH’s, only 3-glycidyl-5,5-dimethylhydantoin was very soluble in water; the other GH’s were not completely miscible in water. In order to use the same condition for treatment with each GH, mixed solvents of water and acetone (1:1 w/w) were used to prepare 0.26 molar concentration of treatment solution for each GH. After treating and curing, the GH’s were covalently bound onto the cotton swatches. Com-
Scheme 3. Preparation of GH’s-Based Antimicrobial Cellulose
Table 1. Stability of Treatment Solutions Prepared with Isolated Products of 3-Glycidyl-5,5-dialkylhydantoins (GH’s) at 25 °C and 5 °Ca treatment solution
Cl+% (A)b
Cl+% (B)b
Cl+% (C)b
Cl+% (D)b
Cl+ % (E)b
initial after 1 d (25 °C) after 1 d (5 °C) after 10 d (25 °C) after 10 d (5 °C) after 20 d (25 °C) after 20 d (5 °C) after 30 d (25 °C) after 30 d (5 °C)
0.14 0.13 0.13 0.14 0.14 0.13 0.14 0.14 0.15
0.19 0.19 0.20 0.19 0.21 0.19 0.21 0.18 0.20
0.96 0.76 0.95 0.64 0.81 0.69 0.81 0.70 0.81
0.29 0.27 0.28 0.28 0.30 0.29 0.30 0.31 0.32
0.16 0.17 0.16 0.15 0.16 0.11 0.13 0.12 0.15
a The error in the measured Cl+ weight percentage values was (0.01. A, 3-glycidyl-5,5-dimethylhydantoin; B, 3-glycidyl-5-methyl-5-propylhydantoin; C, 3-glycidyl-5-hexyl-5-methylhydantoin; D, 3-glycidyl-5methyl-5-phenylhydantoin; E, 3-glycidyl-5,5-pentamethylenehydantoin.
b
mercially available household bleach solution was used to chlorinate the treated cotton swatches to form antimicrobial N-halamine epoxides on the cotton (Scheme 3). Here oxidative chlorine percentage (Cl+%) is a key parameter. Higher Cl+% generally indicates increased biocidal capacity and also higher concentrations of GH’s bound on the cotton swatches. For commercial applications, the stability of treatment solutions is very important. Table 1 shows the stability of treatment solutions prepared with unpurified products of GH’s. For each GH, 0.022 mol of crude product was dissolved in acetone/H2O (1:1 w/w) to produce a total of 80.00 g of treatment solution. All treatment solutions with different storage times at room temperature (25 °C) and lower temperature (5 °C) were tested. The data indicate that after storage for 1 month at both room temperature and lower temperature, all treatment solutions were still suitable for use, and after chlorination of the treated cotton swatches, the same level of Cl+% could be obtained as compared to fresh treatment solutions. As mentioned above, the reaction solutions for preparation of hydantoin epoxides can be directly used as treatment solutions. Table 2 shows the stability of treatment solutions employed directly from reaction solutions. For each reaction solution, 0.022 mol of 5,5-dialkylhydantoin was added to a given amount of water containing the same molar concentration of NaOH, and then 0.022 mol of epichlorohydrin was added. The reaction mixture was stirred at room temperature for 6-10 h, and then a measured amount of acetone was added to prepare a total of 80.00 g of treatment solution. It was found that all reaction solutions were quite stable under storage, especially at lower temperature. Durability Evaluation. Cotton swatches treated with GH’s were subjected to laundry washing cycles using the AATCC Test Method 61 (Test 2A Procedure) as described earlier. The
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Table 2. Stability of Treatment Solutions Prepared Directly from Reaction Solutions of 3-Glycidyl-5,5-dialkylhydantoins (GH’s) at 25 °C and 5 °Ca treatment solution
Cl+% (A)b
Cl+% (B)b
Cl+% (C)b
Cl+% (D)b
initial after 1 d (25 °C) after 1 d (5 °C) after 10 d (25 °C) after 10 d (5 °C) after 20 d (25 °C) after 20 d (5 °C) after 30 d (25 °C) after 30 d (5 °C)
0.18 0.16 0.17 0.16 0.17 0.16 0.17 0.15 0.18
0.35 0.33 0.33 0.30 0.33 0.28 0.34 0.26 0.32
0.79 0.66 0.76 0.65 0.74 0.67 0.74 0.68 0.78
0.23 0.17 0.22 0.17 0.19 0.17 0.18 0.19 0.21
a The error in the measured Cl+ weight percentage values was (0.01. A, 3-glycidyl-5,5-dimethylhydantoin; B, 3-glycidyl-5-methyl-5-propylhydantoin; C, 3-glycidyl-5-hexyl-5-methylhydantoin; D, 3-glycidyl-5methyl-5-phenylhydantoin.
b
Table 3. Stability of 3-Glycidyl-5,5-dialkylhydantoins (GH’s) Reacted onto Cotton Subjected to Washing Cyclesa
3-glycidyl-5, 5-dialkylhydantoins 3-glycidyl-5,5-dimethylhydantoin
3-glycidyl-5-methyl5-propylhydantoin
3-glycidyl-5-hexyl5-methylhydantoin
3-glycidyl-5-methyl5-phenylhydantoin
3-glycidyl-5,5-pentamethylenehydantoin
chlorination after washing % Cl+ washing % Cl+ after control swatches (% Cl+)e cyclesb remainingc recharged 0
0.15
0.15
0.15
1 2 10 0
0.01 0.22
0.12 0.12 0.10 0.22
0.15 0.14 0.14 0.22
1 2 10 0
0.01 0.81
0.14 0.09 0.07 0.81
0.13 0.11 0.07 0.81
1 2 10 0
0.32 0.19 0.01 0.27
0.43 0.35 0.13 0.27
0.26 0.13 0.06 0.27
1 2 10 0
0.19
0.07 0.07 0.07 0.19
0.12 0.11 0.09 0.19
1 2 10
-
0.13 0.11 0.09
0.16 0.15 0.14
a The error in the measured Cl+ weight percentage values was (0.01. One washing cycle is considered to be equivalent to 5 machine washings. c The initial weight % Cl+ for chlorinated swatches before washing given at 0 cycles. d Rechlorination after washing swatches. e Chlorination of washed unchlorinated swatches. b
data in Table 3 indicate that the cotton swatches treated with 3-glycidyl-5,5-dimethylhydantoin were most stable as compared to ones treated with other hydantoin epoxides. Even though the oxidative chlorine dissociates from the hydantoin ring during washing, the hydantoinyl moiety remains attached to the cotton through its condensation with the epoxide moiety, such that it can be recharged repeatedly with free chlorine (bleach). Furthermore, if bleach were added to each wash cycle, then the treatment could be maintained with oxidative chlorine and, hence, remain antimicrobial, probably throughout the lifetime of the cotton fabric. Similar washing testing was performed for the cotton swatches treated with 3-glycidyl-5-methyl-5-propylhydantoin, 3-glycidyl-5-hexyl-5-methylhydantoin, 3-glycidyl-5-methyl-5phenylhydantoin, and 3-glycidyl-5,5-pentamethylenehydantoin. Although higher initial chlorine loadings were obtained for all of these as compared to 3-glycidyl-5,5-dimethylhydantoin
discussed above, there were greater losses of the hydantoinylepoxy treatments during washings as evidenced by lesser recharge abilities following the equivalent of 10 washing cycles (50 machine washings). Even though these hydantoin epoxides, with the exception of 3-glycidyl-5,5-dimethylhydantoin, are sparingly soluble in water, a portion of them can still physically bond to cotton swatches after treatment and rinsing. These physically absorbed hydantoin epoxides could be easily washed off compared to covalently bound ones to cause greater losses of hydantoin epoxides on cotton. It should be noted that the swatches containing all of the covalently bonded GH’s are stable in storage. For the polyester swatches treated with 3-glycidyl-5,5dimethylhydantoin the best results were obtained for swatches pretreated with 1 N sodium hydroxide at 60 °C for 60 min, soaked in 10% epoxy solution containing 1% sodium hydroxide for 30 min at 60 °C, and cured for 1 h at 60 °C followed by 10 min at 150 °C. These swatches loaded 0.21% oxidative chlorine initially, which disappeared after the equivalent of 5 machine washings, but could be replenished to 0.16% even after the equivalent of 50 machine washings. Thus the epoxide treatment itself was quite firmly bound to the polyester fibers. Failure to pretreat the polyester swatches with base resulted in little reaction between the polyester and the epoxide. Biocidal Efficacy Evaluation. The biocidal efficacy data for chlorinated cotton swatches treated with GH’s against Grampositive S. aureus and Gram-negative E. coli O157:H7 are presented in Table 4. The tabulated chlorine concentrations are presumed to be completely available for disinfection and are directly related to the amount of GH bonded to the fibers. As can be seen from the results in Table 4, all of the chlorinated swatches provided complete inactivation of S. aureus within a contact time of 30 min. It is evident that the control samples only provided a loss of about one log or less of the bacteria; thus, most of the losses noted for the chlorinated samples can be attributed to true inactivation of the bacteria. Similar results were obtained for E. coli with a complete inactivation of this bacterium (6.65 logs) within 10 min contact for all derivatives tested. It should be noted that the equivalent concentrations of free chlorine in aqueous solution would perform the inactivation of the two pathogens in a few seconds, but, for the combined chlorine in the GH’s, the disinfection time is extended to minutes as expected. These chlorinated GH’s are stable to the release of free chlorine at pH values at least as low as 4, such that there should be no danger of release of chlorine gas under use conditions. It can be concluded that the chlorinated 3-glycidyl-5,5-dialkylhydantoins are antimicrobial and could be used to create antimicrobial cellulose products. The polyester samples were not evaluated for biocidal efficacy, but previous work in these laboratories has demonstrated that chlorine loadings greater than 0.02% are sufficient to induce antimicrobial activity on all surfaces. Conclusion A series of new N-halamine epoxide precursors (GH’s) has been synthesized and reacted with cotton swatches. Upon chlorination, the cotton swatches treated with all of the GH’s provided reasonable antibacterial performances and durability toward washing. Since 3-glycidyl-5,5-dimethylhydantoin is a water-soluble N-halamine epoxide precursor, it could be dissolved in water to prepare treatment solutions to avoid the addition of organic solvents in real applications. This represents a substantial advantage for commercial use. Also, since it was synthesized from commercially available 5,5-dimethylhydantoin
Ind. Eng. Chem. Res., Vol. 46, No. 20, 2007 6429 Table 4. Antimicrobial Efficacies against S. aureus and E. coli O157:H7 for 3-Glycidyl-5,5-dialkylhydantoins Reacted onto Cotton Swatches 3-glycidyl-5,5-dialkylhydantoins cotton controlc 0 wt % Cl+ dimethyld 0 wt % Cl+ dimethyl-Cle 0.44 wt % Cl+ methyl propyl 0 wt % Cl+ methyl propyl-Cl 0.22 wt % Cl+ hexyl methyl 0 wt % Cl+ hexyl methyl-Cl 0.81 wt % Cl+ methyl phenyl 0 wt % Cl+ methyl phenyl-Cl 0.27 wt % Cl+ pentamethylene 0 wt % Cl+ pentamethylene-Cl 0.19 wt % Cl+
contact time (min)
log reduction of S. aureusa
log reduction of E. coli O157:H7b
5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30 5 10 30
0.66 0.66 0.74 0.81 0.90 1.01 3.81 3.95 6.98 0.65 0.92 0.97 3.62 3.65 6.98 0.14 0.26 0.38 4.47 4.78 6.60 NDf NDf 0.55 4.78 6.60 6.60 0.77 0.79 0.85 3.58 4.07 6.98
0.13 0.22 0.28 0.25 0.32 0.29 4.35 6.65 6.65 0.20 0.27 0.25 4.53 6.65 6.65 0.12 0.15 0.24 6.65 6.65 6.65 0.11 0.12 0.46 6.65 6.65 6.65 0.19 0.24 0.50 6.65 6.65 6.65
a Each sample was inoculated with 25 µL of bacterial suspension at 1.60 × 108 cfu/mL; errors are of the order (0.2 log. b Each sample was inoculated with 25 µL of bacterial suspension at 1.48 × 108 cfu/mL. c Untreated cotton; errors are of the order 0.2 log. d Cotton treated with chromatographically purified 3-glycidyl-5,5-dimethylhydantoin but not chlorinated. e Cotton treated with chromatographically purified 3-glycidyl5,5-dimethylhydantoin which was chlorinated. f No determination.
and epichlorohydrin in water without heating, the low cost for its production should be advantageous. Washing tests showed that 3-glycidyl-5,5-dimethylhydantoin bonded onto cotton exhibited excellent stability during laundering, and it could endure more than the equivalent of 50 machine washings with very little loss. Antimicrobial tests showed that the treated cotton possessed efficient antibacterial properties against Staphylococcus aureus and Eschericia coli O157:H7. Preliminary studies have shown that polyester treated with 3-glycidyl-5,5-dimethylhydantoin also loaded oxidative chlorine and thus should be antimicrobial. Having these excellent properties, 3-glycidyl-5,5dimethylhydantoin, as an N-halamine epoxide precursor, will have potential commercial applications, especially in the antimicrobial treatment of textiles. Acknowledgment The authors acknowledge the support of the U.S. Air Force through Contract FO8637-02-C-7020 and the National Textile Center for this work. Literature Cited (1) Sauvet, G.; Fortuniak, W.; Kazmierski, K.; Chojnowski, J. Amphiphilic Block and Statistical Siloxane Copolymers with Antimicrobial Activity. J. Polym. Sci. Part A: Polym. Chem. 2003, 41, 2939-2948.
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ReceiVed for reView May 30, 2007 ReVised manuscript receiVed July 6, 2007 Accepted July 15, 2007 IE0707568
