A versatile characterization of poly(N-isopropylacrylamide-co-N,N'-methylene-bisacrylamide) hydrogels for composition, mechanical strength, and rheology

A. Chetty, J. Kovács, Zs Sulyok, Á Mészáros, J. Fekete, A. Domján, A. Szilágyi, V. Vargha

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Poly(N-isopropylacrylamide-co-N,N'-methylene-bisacrylamide) (P(NIPAAm-co-MBA)) hydrogels were prepared in water using redox initiator. The copolymer composition at high conversion (> 95%) was determined indirectly by HPLC (high performance liquid chromatography) analysis of the leaching water and directly by solid state 13C CP MAS NMR (cross polarization magic angle spinning nuclear magnetic resonance) spectroscopy of the dried gels, and was found to be close to that of the feed. The effect of cross-linker (MBA) content in the copolymer was investigated in the concentration range of 1.1-9.1 mol% (R:90-10; R = mol NIPAAm/mol MBA) on the rheological behaviour and mechanical strength of the hydrogels. Both storage and loss modulus decreased with decreasing cross-linker content as revealed by dynamic rheometry. Gels R70 and R90 with very low cross-linker content (1.2-1.5 mol% MBA) have a very loose network structure, which is significantly different from those with higher cross-linker content manifesting in higher difference in storage modulus. The temperature dependence of the damping factor served the most accurate determination of the volume phase transition temperature, which was not affected by the cross-link density in the investigated range of MBA concentration. Gel R10 with highest cross-linker content (9.1 mol% MBA) behaves anomalously due to heterogeneity and the hindered conformation of the side chains of PNIPAAm.

Original languageEnglish
Pages (from-to)95-105
Number of pages11
JournalExpress Polymer Letters
Volume7
Issue number1
DOIs
Publication statusPublished - Jan 1 2013

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Keywords

  • Copolymer composition
  • Mechanical properties
  • PNIPAAm
  • Polymer gels
  • Rheology

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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