Indian Journal of Fibre & Texti le Research Vol. 30, J une 2005, pp. 204-206

Short Communications Use of polyaniline as an antimicrobial agent

in textiles

Devender T Seshadri & Narendra V Bhat"

Bombay Textile Research Association, L B S Marg, Ghatkopar (W), Mumbai 400 0 19, India

Received 16 April 2004; accepted 6 August 2004 The conductive cotton + PANi (polyani l ine) fabrics have been

prepared by ill sitll polymerization of ani l ine monomer and their antimicrobial properties studied. It is observed that the fabrics have good antibacterial and antifungal properties. The antibacterial activity for gram positive bacteria reduces by 95 % while for gram negative bacteria it is 85 %.

Keywords: Antimicrobial agent, Cotton, Conductive fabric, Polyani l ine

IPC Code: Int. CI .7 A61 L l 5100, DO l F I 1100, D06B5/00

Conducting polymers have assumed a great importance in recent years. The synthesis, structure and properties of several conducting polymers, l ike polypyrrole, polyaniline (PANi) and poly thiophene have been reported 1,2 since their discoveries in 1977. Of these, PANi has additional advantages, l ike low cost, changes in colour, facile chemistry and better processabi lity. The studies on PANi reveal that it has good crystal line structure and possibility of polymerization even at low concentrations of oxidane. These electroactive polymers have capabi lity to act as 'smart materials' as they respond to electrical, mechanical and environmental stimulation4,5. The stabi lity and util ity have been improved by making composites with other polymers and fibres6. Thus, these materials can be easily used for several applications like gas sensors, pressure transducers, electronic components and anticorrosive paint. Their role in 'wearable electronics7 and other biotechnological applications are now evident.

Out of many antibacterial agents proposed for the development of antimicrobial textiles, viz. chitosan, cations of heavy metals (copper, silver, mercury and zinc), alcohols, oxidizing agents which release

"To whom all the correspondence should be addressed.

Phone: 2500365 1 , Fax: +9 1 -22-25000459;

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halogen atoms or cations, organic acids attached to alkyl or aryl groups, aldehydes, surfactants, antibiotics, quarternary ammonium salts (QAS) and halamines8-1 1 , latter two draw the attention and curiosity as they had similar moieties as polyani line (charged nitrogen atom and chloride ions) (Fig. 1 ) . It has been reported that the antibacterial activity of these QAS and halamines is due to both the charged nitrogen as wel l as due to the chloride ions. This was the perfect recipe needed to make an antibacterial agent out of polyaniline, which is known to have both these. This was really a striking feature and our focus shifted from just electrical conduction to make the fabrics antibacterial as well . Unl ike the other organic QAS or halamines where large quantities would be required to serve the purpose, here even a small quantity would suffice because of the polymeric nature. The advantage of using polyanil ine is that it is insoluble in water unlike QAS and halamines. Hence, it can be repeatedly used even after regular washing or in other words, durability and regenerabil ity would be good.

Antibacterial agents are incorporated in fabrics to make them bacteria resistant8- 1 1 • These fabrics can be used in innerwear, as surgical gowns, by mil itary personnel, in sanitary wears, etc . The antibacterial agents either kill or inhibit the growth of bacteria, i .e. they are either bactericidal or bacteriostatic and hence result in safe and foul odour free garments, especially for military personnel who are engaged in warfare over long periods in remote places.

In the present work, the conductive cotton+PANi fabrics have been prepared by in situ polymerization of anil ine monomer and their antimicrobial properties studied.

Grey cotton fabric was obtained from Century Mills . Aniline and ammonium persulphate were obtained from S.D. Fine Chemicals, India. Cotton fabric was desized using 5 gIL diestase enzyme with 1 0 gIL sodium chloride at 65 DC for 2 h and scoured using 3 % sodium hydroxide (owf) and 1 gIL nonionic detergent at boil for 3 h. The fabric was thoroughly washed with boiling water after each process and lastly washed with 1 gIL acetic acid to neutralize the sodium hydroxide. The fabric was further washed

SHORT COMMUNrCA nON 205

H Halamine

R. I CI R - N +- R

1 I 3 R2 where R I , R2, R3, R4 are alkyl groups

Quarternary Ammonium Sail

where, y � I -x Polyanilin.

Fig. I - Structures of halaminc, quatcrnary ammonium sail and polyan i l i ne

with running cold water thoroughly and dried before use, This dried cotton was referred to as 'control cotton' , Sodium chloride, sodium hydroxide and acetic acid, all of A,R, grade, were obtai ned from S,D, Fine Chemicals, Ani l ine was twice disti l led before use,

The preparation of cotton + PANi fabrics by the diffusion polymerization in a mixed bath (DPMB) process has been reported earl ier6, However, the procedure for the preparation of conductive cotton + PANi fabrics by in situ polymerization of ani l ine monomer is given below:

Pieces of control cotton fabrics of size 40 cm x 10 cm were dipped in 50 % (voLlwt.) monomer solution (an i l ine i n 1M HCI) on the weight of fabric, The solution was continuously stirred for 2 h so that an i l ine diffuses in the fabric, The solution was then cooled in an ice bath (0-5°C) and precooled oxidant sollltion of ammonium persulphate (50 % W,Lt. ani l ine) was gradual ly added over a period of 2 h with continuous stirring, The reactants were further stirred for additional 2 h, which i s the polymerization time for ani l ine by the standard methodl 2, The fabric was then removed from the bath and washed thoroughly with 1M acid followed by dist i l led water to remove the salt and excess acid 12, The fabric was allowed to dry at 65 % RH and 27 °C, This fabric was green i n color resembl ing polyani l i ne .

The antibacterial and antifungal properties of these fabrics were tested by the ASTM: E 2 149 - 01 procedure, which gives a quantitative estimate of the antibacterial and antifungal activities of fabrics, while qualitative tests were done by the AATCC 147 - 1 998 procedure (parallel streak method).

Circular fabric swatches of dimension 4 X 4.8 cm ± 0. 1 cm (- Ig) were kept with 1 .0 ± 0. 1 mL of bacterial i nnoculum in a 250 mL container. The i nnoculum was a nutrient broth culture contain ing 2 .7 X 105 / mL colony forming units (CFU) of bacteria, After test and control swatches had been in contact with bacteria over a desired period, These were transferred to 100 mL steri l ized disti l led water blanks and kept on a shaker for 30 min fol lowed by serial d i lutions. Appropriate d i lutions were placed on nutrient agar and incubated for 48 h at 37 °C, Viable colonies of bacteria on the agar plate were counted, and the reduction in number of bacteria was calculated using the fol lowing equation:

R = 100 (B - A) B " . ( 1 )

where R is the percentage reduction in bacteria/fungi by the treatment (% reduction) ; B, the no, of CFU of bacteria/fungi recovered from the i noculated treated test swatches in the jar immediately after inoculation (at '0' contact time); and A, the no. of CFU of bacteria/fungi recovered from the i noculated treated test swatches i n the jar incubated over 48 h period, The tests were performed in duplicate for two sets of samples. S imi larly, tests were also performed for antifungal activity.

Qual itative analysis reveals that the bacteria grow around the fabric while quantitative analysis shows reduction in bacterial counts for both gram positive and gram negative bacteria . The paral lel streak method is used for qual i tative est imation of agents, which leach out from the fabric i nto tne solution, The observation that no i nhibition is found around the fabric shows that the chloride ions do not leach out. 1 ;1is is because the chloride ions are strongly bonded to the charged n itrogen atoms in PANi molecules,

On quantitative test, it i s found that the cotton + PANi fabrics prepared w ith 50 % (owf) monomer (an i l i ne) show about 95 % reduction in bacterial activity of gram posit ive bacteria (Staphylococcus aureus) and 85 % reduction in bacterial activity of gram negative bacteria (Escherichia coli). Also these fabrics show good antifungal property with 92 % reduction i n CFU of Candida albicans. This is due to the attack on the cel l wall of the bacteria by the charged state of N and Cl ions of the PANi chain, The advantage of using PANi is that d ipping i n di lute HCI solution can regenerate the chloride ions. Thus, the

206 INDIAN J. F I B R E TEXT. R ES .. J U N E 2005

antibacterial/antifungal activity of such fabrics could be restored.

It is therefore inferred that the conductive fabrics of cotton + PANi having good antibacterial as wel l as antifungal actIvIty along with the e lectrical conductivity can be prepared.

Acknowledgement The authors express their thanks to Counci l of

Scientific and Industria l Research, New Delhi , for fund ing. Thanks are also due to Dr (Ms) S Nair of BTRA for carry ing out the antimicrobial te:;ts.

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