3 nm were synthesized. The particle size distributions were characterized by vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) (see Additional file 1: SI-1). In order to improve their colloidal stability, the cationic particles were further coated by poly(acrylic acid) oligomers with molecular weight 2,000 × g mol−1 using the precipitation-redispersion process described previously [60]. The hydrodynamic sizes found in γ-Fe2O3-PAA2K dispersions were 5 nm (34 nm) above that of the bare particles (29 nm), indicating the presence of
a 2.5-nm PAA2K brush surrounding the particles (see in Figure 1). The fully characterizations of the bare and coated particles was shown in Table 1. Figure 1 Schematic description of bare γ -Fe 2 O 3 nanoparticles (left) and PAA 2K polymer coatings around particle (right). selleckchem The organic functionalities were adsorbed on the particle surfaces through electrostatic complexation. Table 1 Characteristics of the particles used in this work γ-Fe2O3 Characteristics Values D VSM(nm) 8.3 s VSM 0.26 D TEM(nm) 9.3 s TEM 0.18 5.8 × 106 3.8 × 106 29 34
470 ± 30 12,500 ± 50 WhereD VSM is the median diameter of the bare particles determined by VSM; s VSM is the polydispersity of the selleck products size distribution of the bare particles determined by VSM; D TEM is the median diameter of the bare particles from TEM; s TEMis the polydispersity of the size distribution of the bare particles determined by TEM; is the molecular weight of the bare particles derived from static light scattering experiments; is the molecular weight of the bare particles derived from the size distribution measured by TEM; is the hydrodynamic diameter of the bare particles, as determined by DLS; is the hydrodynamic diameter Edoxaban of the PAA2K-coated particles, as determined by DLS; is the Nutlin-3a cost number of PAA2Kpolymers adsorbed on the 8.3-nm particles and is the number of carboxylate groups available at the surface of the particle. As reported before, the anionically charged NPs have been co-assembled with a cationic-neutral diblock copolymers [48, 50], referred to as poly(trimethylammonium ethylacrylate)-b-poly(acrylamide)
(PTEA11K-b-PAM30K, M w = 44,400 g mol−1). The copolymers were synthesized by MADIX® controlled radical polymerization, which is a Rhodia patented process [61, 62]. Light scattering experiment was performed on the copolymer aqueous solutions to determine the weight-averaged molecular weight M w(44,400 ± 2,000 g mol−1) and mean hydrodynamic diameter D H (11 nm) of the chains [63]. The molecular weights targeted by the synthesis were 11000-b-30000 g mol−1, corresponding to 41 monomers of trimethylammonium ethylacrylate methylsulfate and 420 monomers of acrylamide, in fair agreement with the experimental values. In the following, this polymer will be abbreviated as PTEA11K-b-PAM30K[63]. The polydispersity index was determined by size exclusion chromatography at 1.6.