Functionalization of cotton with polyNiPAAm/chito

Authors: Pavla Križman Lavrič Brigita Tomšič Barbara Simončič Marijn M C G Warmoeskerken Dragan Jocic

Publish Date: 2011/12/07

Volume: 19, Issue: 1, Pages: 273-287

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Abstract

An innovative strategy for functional finishing of cotton involves application of stimuliresponsive surface modifying system based on temperature and pHresponsive polyNiPAAm/chitosan microgel The stimuliresponsiveness implied to cotton is the consequence of swelling/collapse of the microgel particles incorporated to the fibre surface which produces an active liquid management system The performance of functionalized cotton fabric in terms of liquid management properties was assessed by choosing appropriate techniques water uptake thinlayer wicking water retention capacity and drying capability and discussion of the results was based on the types of water that are expected to be present in hydrated cotton and stimuliresponsive microgelThermophysiological comfort relates to the ability of the fabric to maintain thermal equilibrium between the human body and the environment through its moisture and liquid management abilities ie wicking wetting and water vapour transport properties Zhou et al 2007 which can be efficiently controlled by redesigning textile material surface Pastore and Kiekens 2001Currently available approaches to implement moisture and liquid management properties to cotton fabrics are based on composite textile structures multilayered fabrics combining fabric and polymer films combining fabric and membrane etc microencapsulation technology eg encapsulated phasechange materials—PCMs and moisture management finishes eg silicone microemulsions and thermoreactive polyurethane Holme 2007 Nevertheless the latest concepts from the emerging areas of responsive polymers and surface modification techniques enable taking cotton moisture management one step further—to develop stimuliresponsive material which can actively control material performance by polymer grafting Hu et al 2006 Liu et al 2009 Save et al 2005 or functional finishing by application of microgel based on stimuliresponsive polymers Jocic 2008 Microgel based surface modifying system shows specific volume phasetransition swelling and shrinking which can be triggered by various stimuli eg temperature pH humidity and it is expected to lead to adjusting the liquid management of textiles Jocic 2009 Jocic et al 2009Currently wide variety of available stimuliresponsive polymeric systems is reported addressing diverse range of applications Cohen Stuart et al 2010 Meng and Hu 2010 Since temperature and pH have a physiological significance versatile dual responsive hydrogels have been reported mainly for biomedical applications Kopecek and Yang 2007 Kumar et al 2007 Mano 2008 Simultaneously an increasing amount of research is being done on functional finishing of textile materials by incorporating stimuliresponsive polymeric systems which resulted in publishing two extensive review papers Crespy and Rossi 2007 Liu and Hu 2005 Due to the need for biocompatibility and biodegradability biopolymer based dual responsive hydrogels prepared by combining with a thermoresponsive synthetic polymer are currently of great interest Prabaharan and Mano 2006 Biopolymer chitosan as an aminerich linear β14linked polysaccharide similar to cellulose that is obtained by the partial deacetylation of chitin offers unique physicochemical properties naturally renewable source nontoxic nonallergenic antimicrobial biocompatible and biodegradable Ravi Kumar 2000 Rinaudo 2006 Chitosan is a typical pHsensitive polymer its primary amino groups have pKa values of about 63 which responds to the changes in the pH of the surrounding medium by protonation/deprotonation of its amino groups Vårum et al 1994 This process induces phase transition which results in increase/decrease of the hydrodynamic volume of the polymer which when polymer is present in the form of hydrogel or microgel particles shows the macroscopic response in varying dimensions swelling/deswellingAmong synthetic polymers polyNisopropylacrylamide polyNiPAAm is the most intensively investigated thermoresponsive polymer especially in the fields of biotechnology bioengineering and medicine Klouda and Mikos 2008 As a consequence of the rather complex polarity of the molecule a balance between hydration at amido groups and hydrophobic aggregation of isopropyl groups it exhibits a volume phase transition at ~32 °C LCST—lower critical solution temperature which is exactly between human body temperature and room temperature Schild 1992 The origin of polyNiPAAm temperature sensitivity has been fully explained by the cooperative hydration mechanism Okada and Tanaka 2005 Below the LCST the amide group binds water molecules via hydrogen bonding ie it hydrates to form an expanded structure above the LCST hydrogen bonds break and the polymer expels water and precipitates ie its chains dehydrate to form a shrunken structure The result of copolymerization of polyNiPAAm with an ionizable polymer such as chitosan is a microgel that is responsive to both temperature and pH However because of its hydrophilic nature affected by pH the incorporation of chitosan bearing a large amount of hydrophilic groups into the polyNiPAAm hydrogel network is expected to greatly influence the above explained interactionsIn this study dualstimuli responsive microgel was prepared from chitosan and polyNiPAAm with the aim to obtain a surface modifying system that is capable of changing its structure as well as its physicochemical characteristics when responding to changes in pH and temperature PolyNiPAAm/chitosan PNCS microgel was subsequently incorporated onto cotton by a paddrycure process using 1234butanetetracarboxylic acid BTCA as crosslinker Kulkarni et al 2010 Both PNCS microgel synthesis and incorporation to cotton are thoroughly explained in Part I of this paper Krizman Lavric et al 2011 While the Part I established that moisture management properties of microgel functionalized cotton depend on the temperature and humidity this study assesses the liquid management properties of the same material including a pH of the liquid as another stimulus apart from the temperature and humiditySince cotton is highly absorptive fibre both the amount of liquid that can be absorbed wetting and the rate of the liquid spreading wicking can affect the comfort of apparel directly The abundant hydroxyl groups of cotton cellulose are responsible for bonding water but extremely complex morphology of a fibre makes predicting the moisture and liquid transport phenomena a difficult task and the measurements of moisture regain MR moisture sorption isotherms water retention and absorptive capacities are regularly done Zeronian 1984 However having in mind that water is the driving force for the microgel responsiveness in this study some additional techniques are required to investigate liquid management ability of textile material treated with PNCS microgel The capability of functionalized material to respond to different stimuli pH temperature humidity is studied through swelling/shrinking or hydration/dehydration kinetics and equilibrium using a gravimetric method ie the determination of water uptake—WU The spreading of liquid driven into a functionalized cotton fabric by capillary forces is determined by using a thinlayer wicking TLW method Water retention capacity WRC is used to estimate the swelling capacity of fibres as determined by the amount of water retained imbibed water by waterswollen samples after centrifugation The capacity to discharge the absorbed water during drying is evaluated by assessment of the drying curves of the fabric Fangueiro et al 2010 Li 2001 Männer et al 2004 Above methods can give insight to the question of how much liquid water is held by capillary forces and how much is absorbed within the PNCS functionalized cotton The understanding of interactions between water moisture vapour and liquid water and microgel functionalized cotton on a fundamental level is necessary for further optimization and development of such a materialCotton fabric 100 cotton plainweave fabric of 105 g/m2 weight per unit area desized double scoured was supplied by Vlisco The Netherlands PolyNiPAAm/chitosan microgel PNCS has been prepared according to the procedure of Lee et al 2003 and incorporated to cotton fabric using paddrycure process Kulkarni et al 2010 For the purpose of this study the functionalized cotton sample CoPNCS/BTCA with 2 addon of the surface modifying system has been prepared 100 pickup during padding Untreated sample CoUT was used as the reference in all characterization methods Moreover for the purpose of BTCA influence assessment a sample treated with BTCA only has been prepared CoBTCA Both microgel synthesis and cotton fabric incorporation procedures have been thoroughly described in Part I of this paper Krizman Lavric et al 2011

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