ISSN:
0887-6266
Keywords:
polymer gel
;
poly(N-isopropylacrylamide)
;
PNIPA
;
volume phase transition
;
hydrogen bond
;
hydrophobic interaction
;
free volume
;
positronium
;
positron annihilation
;
methanol-water mixed solvent
;
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The macroscopic volume shrinkage and swelling of poly(N-isopropylacryl-amide) (PNIPA) gel induced by the compositional change in the methanol-water mixed solvent is correlated to the change in the nanoscopic free volume size and numerical concentration formed in the PNIPA gels. The free volume size and numerical concentration are estimated from the longest component appearing in the positron annihilation lifetime curves. The apparent free volume fraction calculated by the free volume size and numerical concentration, and dispersion of the free volume deduced by the size distribution are utilized to analyze the origin and location of the free volumes. The free volume parameters obtained by analysis of the positron annihilation data show various nanoscopic phases occuring within the PNIPA gels during the volume change, implying the variation of the strength of the interactions among the solvent molecules and the polymer chains of the PNIPA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1141-1151, 1998
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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