Magnetic temperature-sensitive polymer nanocapsules preparation and characterization

Title: Magnetic temperature-sensitive polymer nanocapsules preparation and characterizationAuthor: Zhang FengDegree-granting units: Fudan UniversityKeywords: environmental responsiveness;; temperature-sensitive polymer;; core / shell structure microspheres;; seed emulsion polymerization;; poly (N-isopropyl acrylamide) (PNIPAM);; magnetic nanoparticles;; co-precipitation law;; temperature hydrolysis;; nanocapsules;; multifunctional materials;; one-dimensional self-assembly;; SiO_2;; surface modification;; precipitation polymerizationSummary:Environmental response of the material is a class of small changes in the external environment stimulation, self-certain physical or chemical properties will change accordingly to change materials in separation, catalysis, drug delivery, sensors, etc. have many Neodymium Magnets potential applications. Temperature responsive polymers and nano-materials is to study the magnetic environment more responsive material, which is not easy to control due to changes in temperature, but can be easily applied in vitro and in vivo, and magnetic nano-materials can be easily controlled by an external magnetic field . Structural stability of the polymer nanocapsules, their internal hollow area can accommodate a large number or large guest molecules, which aroused great interest. This paper around with temperature and magnetic response of the polymer nanocapsules prepared to start, mainly to obtain a result of the following aspects:(1) to develop a simple and efficient preparation of temperature-sensitive poly (N-isopropyl acrylamide) (PNIPAM) nanocapsules method. First, soap-free emulsion polymerization prepared monodisperse P (St-co-NIPAM) microspheres, then P (St-co-NIPAM) microspheres as seeds, seed emulsion was prepared P (St-co-NIPAM ) / PNIPAM core / shell structure microspheres. P (St-co-NIPAM) microspheres particle size can be added to the reaction system by sodium dodecyl sulfate (SDS), the amount of control. When the amount of added SDS increased from 0 to 0.20 g, the dynamic light scattering (DLS) measured microsphere size decreases from 268 nm to 43 nm. PNIPAM http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets shell thickness shell monomer can adjust the amount of added NIPAM, while keeping the shell cross-linking (cross-linker N, N'-methylene acrylamide (MBA) and NIPAM molar ratio) 10%, NIPAM monomer addition is at 0.5, 1.0 and 2.0 g, 25 ℃ under the DLS measured the thickness of the PNIPAM shell, respectively 31, 67 and 89 nm. Core / shell structure microspheres with temperature-sensitive PNIPAM shell cross-linking degree, and when the NIPAM monomer dosage of 1.0 g, with the shell cross-linking changes from 5% to 10% and 15%, slightly ball of swelling ratio (defined as (D_ (25 ℃) / D_ (45 ℃)) ~ 3) reduced from 16.1 to 11.8 and 7.9. PNIPAM nanocapsules by tetrahydrofuran (THF) solution to remove P (St-co-NIPAM) core obtained with FTIR, TEM and DLS PNIPAM nanocapsules were characterized. In the absence of P (St-co-NIPAM) core limit, hollow PNIPAM nanocapsules showed a stronger ability to swell and shrink.(2) the use of PSt / P (NIPAM-co-AA) core / shell structure microspheres and-NH_2 modified magnetic Fe_3O_4 @ SiO_2 particles were prepared for the functional module anchored surface magnetic particles of P (NIPAM-co-AA ) nanocapsules. First prepared by seeded emulsion polymerization PSt / P (NIPAM-co-AA) core / shell structure microspheres, by improving the St (o | ¨) ber Fe_3O_4 @ SiO_2 prepared magnetic particles and magnetic particles Fe_3O_4 @ SiO_2 surface-NH_2 modified. Then,-NH_2 Fe_3O_4 @ SiO_2 modified magnetic particles and PSt / P (NIPAM-co-AA) core / shell structure microspheres assembled together by electrostatic attraction, in the 1 - (3 - dimethylamino-propyl) - 3 - ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS), a common catalyst, core / shell structure microspheres of-COOH and-NH_2 magnetic particles on the occurrence of amidation reaction, thus between the two particles connected by covalent bond. PSt / P (NIPAM-co-AA) core / shell magnetic microspheres adsorbed Fe_3O_4 @ SiO_2 particle density can be joined by two particles in proportion to the amount of control. Dissolved with THF to remove PSt / P (NIPAM-co-AA) core / shell microspheres PSt core, has been connected with Fe_3O_4 @ SiO_2 surface of magnetic particles P (NIPAM-co-AA) nano-microcapsules, nanocapsules display the magnetic, pH and temperature of the multiple response.(3) weak ferromagnetic iron oxide nanoparticles for magnetic dipole-induced one-dimensional self-assembly and sol-gel reaction of TEOS to prepare a worm-like iron oxide / SiO_2 nanostructures, and on this basis, one-dimensional magnetic PNIPAM prepared nanocapsules. Were prepared using high temperature hydrolysis of magnetic iron oxide nanoparticles, nano-particle size can be added NaOH / DEG solution to control the volume, size of magnetic nanoparticles with the added NaOH / DEG solution volume increases. XRD and Raman spectroscopy results showed that the preparation of magnetic nanoparticles is Fe_3O +4 and a mixture of γ-Fe_2O_3, VSM and ZFC / FC results showed that the preparation of iron oxide nanoparticles at room temperature with a weak ferromagnetism. Induced in the magnetic interactions, the weak preparation of magnetic iron oxide nanoparticles can iron on the substrate and the colloidal dispersion in the self-assembly of nanoparticles into one-dimensional chain. The use of iron oxide nanoparticles in the colloidal dispersion of one-dimensional self-assembly, combined with the sol-gel reaction of TEOS was prepared by a one-dimensional worm-like iron oxide / SiO_2 nanostructures, one-dimensional iron oxide / SiO_2 morphology of nanostructures can be through the preparation process of ultrasonic power control, SiO_2 layer thickness can adjust the amount of added TEOS. One-dimensional iron oxide / SiO_2 nanostructures showed good magnetic response, in the external magnetic field, can be aligned along the field direction. NIPAM prepared by solution polymerization and γ-(methacryloyloxy) propyl trimethoxysilane (MPS) of the copolymer P (NIPAM-co-MPS), and P (NIPAM-co-MPS) grafted on one-dimensional iron oxide / SiO_2 nano-structured surface, and then by the precipitation polymerization of NIPAM in the one-dimensional iron oxide / SiO_2 outside coated with nano-structured cross-linked PNIPAM layer, and finally dissolved with NaOH to remove SiO_2, get a one-dimensional magnetic PNIPAM microcapsules .Degree Year: 2009