Thermoresponsive Interpolymeric Complex Assemblies from Co-association of Linear PAAc Homopolymers with PNIPAAm Segments Containing PAAc-Based Graft Copolymer

In aqueous solution at pH 3.0 and 20 degrees C, poly(acrylic acid)-g-poly(N-isopropylacrylamide)/monomethoxy poly(ethylene glycol) (PAAc-g-PNIPAAm/mPEG) can assemble spontaneously with linear poly(acrylic acid) homopolymers (homoPAAc) into interpolymeric complexes (IPC). The resultant IPC assemblies exhibit a core-corona structure consisting of a hydrophobic PAAc/PNIPAAm complex core surrounded by hydrated PNIPAAm/mPEG coronas. At temperatures above 30 degrees C, the assemblies transform into a core-shell-corona micelle. Highly loose, irregular IPC assemblies developed at a reduced weight ratio of homoPAAc with the graft copolymer at 20 degrees C show particle size enlargement and structural variation above 30 degrees C. By contrast, co-assembly of long homoPAAc chains with the copolymer leads to large aggregates comprising several IPC assemblies interconnected by homoPAAc chain segments.