Thermoresponsive Vesicular Morphologies Obtained by Self-Assemblies of Hybrid Oligosaccharide-block-poly(N-isopropylacrylamide) Copolymer Systems

This work discusses the self-assembly properties of thermoresponsive hybrid oligosaccharide-block-poly(N-isopropylacrylamide) copolymer systems: maltoheptaose-block-poly(N-isopropylacrylamide) (Mal7-b-PNIPAMn) copolymers. Those systems at different molar masses and volume fractions were synthesized using Cu(I)-catalyzed 1,3-dipolar azide/alkyne cycloaddition, so-called “click” chemistry, between an alkynyl-functionalized maltoheptaose (1) and poly(N-isopropylacrylamide) having a terminal azido group (N3-PNIPAMn) prepared by atom transfer radical polymerization (ATRP). While the cloud point (Tcp) of the N3-PNIPAMn ranged from 36.4 to 51.5 °C depending on the degree of polymerization, those obtained of the diblock copolymers ranged from 39.4 to 73.9 °C. The self-assembly of such systems is favored due to the hydrophobicity of the PNIPAM in water above the Tcp. While the N3-PNIPAMn present polydisperse globular shape with a mean diameter of 500 nm, well-defined vesicular morphologies with an approximate diameter of 300 nm are obtained in diblock copolymer systems. These results were obtained and confirmed using static and dynamic light scattering as well as imaging techniques such as transmission electron microscope experiments.