Clevertex - Grado Zero Espace Srl

increasing quantities of the aqueous liquid. This process would normally lead to a complete solution of
the polymer. However, due to the crosslinking between the polymer chains of the absorbent polymer,
only the formation of a gel takes place, precluding its solution. The water is strongly bonded by means
of hydrogen bonds in the gel.
Superabsorbent polymers can swell up to hundreds of times their own weight in aqueous media. Their
swelling behaviour is characterised mainly by the amount of water they absorb and the rate of
absorption.
At the North Carolina State University, U.S., a project is going on (since 2001) to develop stimulisensitive
polymers. To this end, the molecular and physicochemical principles accompanying the
changes of these polymers will be studied. The aim is to extrude fibres completely made of stimulisensitive
polymers. One starts from fibres based on polyacrylic acid, carboxymethyl cellulose and
chitosan and one proceeds according to the wet spinning process.
Drug delivery systems
Textile materials in drug delivery systems are a topic of increasing interest and research in the last
years. As textile materials are characterised by their open permeable structure and large surface area,
they are applied in in- and ex-vivo drug delivery systems. Research is going on in the field of textile
slow release systems like fibres bearing cyclodextrins, ion-exchange fibres, microparticles and
nanofibres containing drugs produced by electrospinning.
Fibres bearing cyclodextrins
Cyclodextrins are able to form complexes with a variety of long chain aliphatic or aromatic molecules
like drugs, detergents and fragrances, for example. The group of drugs that can be bonded to
cyclodextrins is quite large, because the complex formation is largely independent of the chemical
properties of the drug molecule. Thus different types of drugs have been investigated, varying from
neutral to ionic and from basic to acidic. Van der Waal’s forces play a significant role in the formation
of a drug-cyclodextrin complex. Both, the complexation as well as the decomplexation, namely the
release of the drug from the cyclodextrin, are equilibrium processes. Cyclodextrins can be fixed either
permanently or non-permanently to the surface of a fibre. Grafting of cyclodextrins on textiles turned
out to be very promising. Different types of cyclodextrins have already been grafted on textile fibres
like cotton, Tencell, wool, polyester and polypropylene.
Ion-exchange fibres
Besides in wastewater purification, uranium enrichment from seawater, ion-exchange fibres are also
applied in textile drug delivery systems. With characteristics like a fast ion-exchange rate and a high
124