Effect of Crosslinkers on the Microstructure and Swelling Properties of the N-Isopropyl Acrylamide Gels: A Positron Annihilation Study
The Poly N-Isopropyl acrylamide (PNIPA) gels were prepared in different synthesis media by crosslinking with acrylate monomers with varying chain length. The microstructural characterization in terms of the free volume fractions and distributions were studied using positron annihilation lifetime spectroscopy (PALS). The equilibrium swelling of the PNIPA in distilled water was measured. An attempt has been made to understand the correlations between microscopic free volumes and the equilibrium swelling of the gels. The free volume fraction of the gels prepared in Dimethyl formamide (DMF) was directly correlated with swelling while it varied inversely with chain length of the crosslinker. The microstructure of the gels was found to be very sensitive to the solvent/medium used for polymerization. Our studies show that the swelling property is influenced by the free volumes, chain relaxation as well as the chemical nature of the cross linkers.
Jozef Krištiak, Jan Kuriplach and Pradeep K. Pujari
P. N. Patil et al., "Effect of Crosslinkers on the Microstructure and Swelling Properties of the N-Isopropyl Acrylamide Gels: A Positron Annihilation Study", Materials Science Forum, Vol. 733, pp. 155-158, 2013