Preparation And Characterization Of New Temperature-sensitive Microgels

Temperature-sensitive microgel has attracted intensive interest because of it's thermosensitivity. At the present, most of the monomers that are used to polymerize the microgel are N-isopropylacrylamide (NIPAM). PolyNIPAM microgel's polymerization method is emulsion polymerization in the previous days, because surfactant is used in the conventional emulsion polymerization, there are some questions about the surfactant contamination. That the mono-disperse cationic microgels that NIPAM acts as main monomer, dimethylaminoethyl methacrylate (DMAEMA) as co-monomer, methylene bisacrylamide (MBA) as crosslinker by surfactant-free emulsion polymerization has been studied in this thesis. Because no any surfactant was used in the polymerization the microgels are clean. Such microgels exhibit outstanding capabilities for the separation and immobilization of protein, nucleic acid and other biologically- active macromolecules and they are to be used in the protein separation, gene diagnosis field and so on.The size of the microgels can be controlled by the concentration of DMAEMA, the pH value of polymerization medium affects the size of the microgels, the microgel's volume phase transition temperature(VPTT) is about 32 ℃, but with the increase of DMAEMA concentration the VPTTrange become broader and the swelling ratio is decreasing gradually.The surfactant-free emulsion polymerization kinetic analysis of the hydrophobic monomer ( styrene, for instance)has been studied by others, but our monomers are hydrophilic, the microgels are thermosensitive , the nucleation process is different. We think the nucleation mechanism is homogeneous nucleation, the nucleation period is short and the polymerization rate increases with the DMAEMA concentration by measuring NIPAM conversion versus reaction time and tracing the microgel's propagation process during the early phase by DLS and TEM. A strong dependence of water soluble polymer (WSP) formation on DMAEMA concentration was found by analyzing the amount and content of water soluble polymer. Poly(NIPAM-co-DMAEMA) copolymer is situated at the surface of the particle.Synthesis Silica/Poly NIP AM core-shell particle by colloid-templated polymerization, then get rid of the silica core by HF and form hollow Poly NIP AM sphere. The sphere has thermosensitivity in the water, The VPTT is about 32℃ , with the swelling of the sphere in the water, the wall of the sphere is from the state of "OFF" to "ON" , this property makes the sphere be used to encapsulate and release biologically-active macromolecules such as enzyme, protein and nucleic acid.