Thermoresponsive Self-Assemblies of Cyclic and Branched Oligosaccharide-block-poly(N-isopropylacrylamide) Diblock Copolymers into Nanoparticles

• Published in: Biomacromolecules 2012-05, Vol.13 (5), p.1458-1465
• Main Authors: Otsuka, Issei, Travelet, Christophe, Halila, Sami, Fort, Sébastien, Pignot-Paintrand, Isabelle, Narumi, Atsushi, Borsali, Redouane
• Format: Article
• Language: English
• Subjects: Acrylamides - chemical synthesis; Acrylamides - chemistry; Acrylic Resins; Applied sciences; Catalysis; Chemical modifications; Chemical reactions and properties; Chemical Sciences; Copper - chemistry; Cyclization; Exact sciences and technology; Material chemistry; Molecular Structure; Nanoparticles - chemistry; Oligosaccharides - chemical synthesis; Oligosaccharides - chemistry; Organic polymers; Physicochemistry of polymers; Polymers; Polymers - chemical synthesis; Polymers - chemistry; Temperature
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm300167e

This paper discusses the thermoresponsive nanoparticles obtained by self-assemblies of nonlinear oligosaccharide-based diblock copolymer systems. These diblock copolymers were synthesized by Cu(I)-catalyzed 1,3-dipolar azide/alkyne cycloaddition (“click” reaction) of propargyl-functionalized β-cyclodextrin (βCyD) and xyloglucooligosaccharide (XGO) with poly(N-isopropylacrylamide) (PNIPAM) having a terminal azido group prepared by atom transfer radical polymerization (ATRP). Elastic and quasi-elastic light scattering analysis of the dibock copolymers in H2O indicated that thermodynamic phase transitions of the PNIPAM blocks at their cloud points (T cps ≈ 34 °C), around lower critical solution temperatures (LCSTs), triggered their self-assemblies into the nanoparticles. These nanoparticles had narrow size distributions and small interphases (i.e., sharp boundaries). The mean hydrodynamic radii (R hs) of the βCyD and XGO-based nanoparticles were determined to be around 150 and 250 nm upon slow heating (i.e., step-by-step heating), and 364 and 91.5 nm upon fast heating, respectively, depending on a predominance of the interchain association or the intrachain contraction. Transmission electron microscope (TEM) and field emission gun-scanning electron microscopy (FEG-SEM) images of the nanoparticles clearly showed compact spherical nanoparticles whose cores are mainly made with the PNIPAM blocks, whereas the rough shells consist in the oligosaccharidic blocks.