Effects of graft length and density of well-defined graft polymers on the thermoresponsive behavior and self-assembly morphology
A series of well-defined thermoresponsive graft polymers with different lengths and graft densities, poly(glycidyl methacrylate)- graft -poly( N -isopropylacrylate) (PGMA- g -PNIPAM), were successfully prepared by combination of controlled/living free radical polymerization and click chemistry. Effects of grafting length and density on the thermoresponsive behavior, aggregating mean diameter, and self-assembly morphology are systematically investigated. The thermosensitive characteristics of graft polymers in aqueous solution prove that the length and graft density had positive co-relationship with the lower critical solution temperature value and mean diameter of micelles as well as the size distribution, while the effect of graft length of polymers is more significant than that of density. Transmission electron microscopy analysis shows that the conformations of PGMA 45 - g -PNIPAM 20 and PGMA 45 - g -PNIPAM 46 with longer length and bigger grafting density in aqueous solutions are spherical nanoparticles with the increasing trend of the diameters, while that of PGMA 45 - g -PNIPAM (73, 50%) shows a spherical-like morphology, which indicates that the graft length and density have a significant effect on the mean diameter of micelle but not on the self-assembly morphology. These results reveal that to obtain desired thermoresponsive behavior and self-assembly morphology of functional polymers, it is essential to design and fabricate the structure of graft polymers with proper length and graft density. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52 , 2442–2453
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