碩士
國立臺北科技大學
有機高分子研究所
96
When the insulating polymers mixed with conductive material, like metal powder, graphite, carbon black(CB), carbon nanotubes(CNTs), which can improve the conductivity ...property. In the filler of conductive material, among the available fillers, CB has been used extensively because of the relative advantages of technology, low cost, and high conductivity properties. In this investigate to use conductive material is nano carbon black(VXC72), but carbon black due to aggregation behavior, account for the difficult in the industry like spinning when carbon black agglomerate too large which make the spin pack of sieve to choke and then can not spinning favorably, the spinning process must to stop. To obtain a well dispersed carbon black matrix, a high-temperature-endurable dispersant and a special two-screw extruder are two crucial issues. In this investigate, we used the copolymer which contain sulfonate(SO3-) and solubility in the water. Due to the dispersant has high-temperature-endurable
博士
國立清華大學
化學工程學系
102
Polyamidoamine (PAMAM) dednrimer bearing well-defined number of amine groups can be protonated under physiological or acidic condition to generate the macrocations capable of ...forming electrostatic complex (called “dendriplex”) with DNA for gene delivery. Using small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS), here we constructed the morphological map of the complex of DNA with PAMAM dendrimer of generation four (G4) in terms of the dendrimer charge density and the nominal N/P ratio given by the feed molar ratio of dendrimer amine group to DNA phosphate group. With the increase of dendrimer charge density under a given nominal N/P ratio, the structure was found to transform from square columnar phase (in which the DNA chains packed in square lattice were locally straightened) to hexagonally-packed DNA superhelices (in which the DNA chains organizing in a hexagonal lattice twisted moderately into superhelices) and finally to beads-on-string structure (in which DNA wrapped around the dendrimer to form nuclesome-like array). The phase transition sequence was understood from the balance between the bending energy of DNA and the free energy of charge matching governed by the entropic gain from counterion release. Decreasing nominal N/P ratio under fixed dendrimer charge density was found to exert the same effect as increasing dendrimer charge density; that is, the structure with higher DNA curvature tended to form at lower nominal N/P ratio, in particular for the dendriplex with low dendrimer charge density. The effect of N/P ratio was attributed to the tendency of the system to increase the translational entropy of the counterions released to the bulk solution by reducing the concentration of free DNA or dendrimer remained in the solution. The experimental results presented here thus demonstrated the crucial role of counterion entropy in the structural formation of DNA-dendrimer complexes, and this entropic contribution was governed by the dendrimer charge density, the nominal N/P ratio, and the initial concentrations of DNA and dendrimer used for complex preparation. The dominant role of counterion entropy was further verified by examining the effect of protonic acid on the nanostructure of the dendriplex, where the dendrimer was also protonated by multivalent acids, including H2SO4 and H3PO4.
