Characterisation of poly(N-isopropylacrylamide) by asymmetrical flow field-flow fractionation, dynamic light scattering, and size exclusion chromatography.
Asymmetrical flow field-flow fractionation (AsFIFFF) was used to determine the hydrodynamic particle sizes, molar masses, and phase transition behaviour of various poly(N-isopropylacrylamide) (PNIPAM) samples synthesised by reversible addition--fragmentation chain transfer (RAFT) and conventional free radical polymerisation processes. The results were compared with corresponding data obtained by dynamic light scattering (DLS) and size exclusion chromatography (SEC). Agreement between the three methods was good except at higher molar masses, where the molar mass averages obtained by SEC were much lower than those obtained by AsFIFFF and light scattering. The aggregation of the polymers, which are thermally sensitive, was studied by DLS and AsFIFFF at various temperatures. In deionised water there was an abrupt change in the particle size due to phase separation at approximately equal to 32-35 degrees C. The critical temperatures determined by AsFIFFF were 3-5 degrees C higher than those obtained by DLS.
Yohannes
Gebrenegus
G
Laboratory of Analytical Chemistry, Department of Chemistry, PB 55, FIN-00014 University of Helsinki, Finland.
Shan
Jun
J
Jussila
Matti
M
Nuopponen
Markus
M
Tenhu
Heikki
H
Riekkola
Marja-Liisa
ML
D000180:Acrylic Resins / Q000737:chemistry*; D002850:Chromatography, Gel; D031521:Fractionation, Field Flow; D015394:Molecular Structure; D008970:Molecular Weight; D012542:Scattering, Radiation; D013237:Stereoisomerism; D013696:Temperature
D000180:Acrylic Resins; C052970:poly-N-isopropylacrylamide