Unusual polymerization of 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride on PET substrates Samiha Mohamed Abo El Ola a , Richard Kotek b, * , W. Curtis White c , John Allan Reeve c , Peter Hauser b , Joon Ho Kim d a Textile Research Division, National Research Center, Dokki, Cairo, Egypt b College of Textiles, Textile Engineering Chemistry and Science, North Carolina State University, Box 8301, Raleigh, NC 27695-8301, USA c AEGIS ENVIRONMENTS, 2525 Washington Ave., Suite 500, Midland, MI 48642-4619, USA d School of Textiles, Yeungnam University, 214-1 Daedong, Kyongsan 712-749, South Korea Received 4 September 2003; received in revised form 19 December 2003; accepted 16 February 2004 Abstract 3-(Trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (AEM 5700) is a trifunctional monomer that can be polymerized under acidic conditions at temperatures greater than 100 8C. Under such conditions, coatings based on AEM 5700 formed on PET substrates are relatively hydrophobic and exhibit rewetting times higher than 100 min. Hydrophilic coatings exhibiting a rewetting time of 2.8 min can be also formed when AEM 5700 is initially hydrolyzed under alkaline conditions and then polymerized under acidic conditions. This effect could be related to the accessibility of unreacted hydroxyl groups and quaternary ammonium groups for interaction with water. Excellent antimicrobial action was demonstrated for all coatings based on AEM 5700 on PET substrates. Polyester fabrics having AEM 5700 coating can be dyed with direct dyes. The loss of hydrophilic properties for AEM 5700 coatings is observed after dyeing with direct dyes. q 2004 Elsevier Ltd. All rights reserved. Keywords: Silane polymerization; Trimethoxysilane; Ammonium salts 1. Introduction Demand for antimicrobial fabrics in domestic and international markets has grown significantly in recent years because of public awareness of the potential threat of spreading diseases [1,2]. Bio-protective clothing such as medical, protective garments, and institutional and hygienic textiles are the main applications of antimicrobial fabrics [2]. Silanes have been well published on and their associative and bonding capacities to themselves and to other surfaces has been studied by many researchers. It was determined that antimicrobial organofunctional silanes could be chemi- cally bound to receptive substrates such as cellulose, by what were believed to be Si–O linkage. The method was described as orienting the organofunctional silane in such a way that hydrolysable groups on the silicon atom were hydrolyzed to silanols formed chemical bonds with each other and the substrate. The resultant surface modification, when an antimicrobial moiety such as quaternary nitrogen was included, allowed the antimicrobial to be oriented away from the surface [3]. The attachment of this chemical to surfaces appears to involve two processes. First and most important is the very rapid process which coats the substrate with cationic species one molecule deep. This is an ion exchange process by which the cation of silane quaternary ammonium compound replaces protons from water on the surface. It has long been known that most surfaces in contact with water generate negative electrical charges at the interface between the water and the surface (even on sur- faces which contain no functionality). The second process is unique to materials such as silane quaternary ammonium compounds, which have silicon functionality, enabling them to polymerize after they have coated the surfaces and to become almost irremovable from these surfaces. Covalent bonding to that surface may also occur, and it is also possible to have intermolecular polymerization [4]. It is 0032-3861/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2004.02.041 Polymer 45 (2004) 3215–3225 www.elsevier.com/locate/polymer * Corresponding author. Tel.: þ 1-919-515-6585; fax: þ1-919-515-6532. E-mail address: rkotek@unity.ncsu.edu (R. Kotek).