Composition dependent changes in the swelling and mechanical properties of nanocomposite hydrogels

L. Janovák, J. Varga, L. Kemény, I. Dékány

Research output: Contribution to journalArticle

Abstract

We are synthetized thermo- and pH-sensitive gels, which are then tested as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth. During the polimerization reaction we are produced copolymers with varyable composition, which are proceed from two acrylic compounds [N- isopropyl- acrylamide (NIPAAm), and acrylamide (AAm)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na- montmorillonite (Na- m.) and with alkyl- ammonium ion organophilized Na- montmorillonites [(C n - m.), n = 4, 12, 18]. With this method we are synthetized composite- hydrogels. The filler content of composites varies between 1 and 25 wt%. We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1-5 wt%) resulted in more extensive swelling and stronger gel structure. In the course of the experiments the monomer composition of the gels (0/100-100/0 mol% NIPAAm/AAm) and in the case of composites, the quality (montmorillonite and organophilized montmorillonite) and quantity (1-25 wt%) of fillers are varied. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters. In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH m ) corresponding to the actual water contents were also determined by thermoanalytical measurements (DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the system, i.e. the polymer skeleton, the filler and water molecules. We found that water molecules within the gel matrix are bound to the 3-D polymer lattice with bonds of different strengths and the strength of these interactions are dependent on both hydrophilicity and charge conditions. In the case of hydrophobic NIPAAm composites a more extensive swelling can be achieved by applying montmorillonite fillers with hydrophobized surfaces, whereas in the case of hydrophilic AAm-based composites the use of hydrophilic montmorillonite fillers ensure more extensive swelling.

Original languageEnglish
Pages (from-to)13-32
Number of pages20
JournalNanopages
Volume4
Issue number1
DOIs
Publication statusPublished - Apr 1 2010

Keywords

  • DSC
  • clay- mineral composites
  • copolymers
  • mechanical properties
  • skin expander
  • swelling hydrogel

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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