Abstract
In aqueous solutions of pH 3.0 at 20 °C, linear homoPAAc and PAAc-g-PNIPAAm/mPEG graft copolymer co-associate spontaneously into IPC assemblies via mutual hydrogen bonds betweenAAcandNIPAAmresidues. The morphology of IPC assemblies and their thermoresponsive behavior are virtually governed by the molecular weight of homoPAAc andweight ratio of homoPAAc/copolymer. By co-assembly of the graft copolymer with short homoPAAc17 chains at a proper ratio, the resulting IPC assemblies (Dh ca. 60 nm) exhibit a well-defined structure comprising a hydrophobic PAAc/PNIPAAm complex core surrounded by well-mixed PNIPAAm/mPEG coronas. With the temperature being increased beyond 30 °C, IPC assemblies are transformed from the core-corona into core-shell-corona structure via microphase segregation of PNIPAAm/mPEG coronas and collapse of PNIPAAm grafts into dehydrated shells. While highly loose and hydrated IPC assemblies with a low homoPAAc 17 /copolymer ratio are developed at ambient temperature, IPC assemblies subsequently experience a considerable morphological transformation into amicellelike structure with an appreciably enlarged size and reduced size distribution by virtue of thermally driven co-association between loose IPCs acting as hydrophobic nuclei and graft copolymer originally uncomplexed upon temperature raise beyond the LCST of PNIPAAm. By contrast, co-assembly from long homoPAAc 208 chainswith the copolymer produces very large colloidal particles (Dh ca. 400 nm) composed of several individual IPC assemblies interconnected by homoPAAc208 chain segments unpaired with NIPAAm residues. These IPC assemblies display very weak thermoresponsive behavior. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.