Thermoreversible Thickening and Self-assembly Behaviors of pH/Temperature Dually Responsive Microgels with Interpenetrating Polymer Network Structure

The pH /temperature dually responsive microgels of interpenetrating polymer network( IPN) structure composed of poly( N-isopropylacrylamide)( PNIPAM) network and poly( acrylic acid)( PAA) network( PNIPAM /PAA IPN microgels) were synthesized by seed emulsion polymerization. The results obtained by dynamic laser light scattering( DLLS) show that the microgels have good pH /temperature dual sensitivities. The temperature sensitive component and the pH sensitive component inside the microgels have little interference with each other. The rheological properties of the concentrated PNIPAM /PAA IPN microgel dispersions as a function of temperature at pH 4. 0 or 7. 0 were investigated by viscometer,and the results displayed that only at pH 7. 0 the dispersions presented thermoreversible thickening behavior. Then the PNIPAM /PAA fibers were prepared by self-assembly of the PNIPAM /PAA IPN microgels in the ice-crystal templates formed by unidirectional liquid nitrogen freezing method. Field emission scanning electron microscopy( FESEM) images indicate that the PNIPAM /PAA fibers are rounded,randomly orientated and interweaved.

ClO_4^--directed Assembly of Two Co^ⅡComplexes Based on Flexible N-donor Ligands:Syntheses,Crystal Structures and Magnetic Properties

The reaction of Co^II ions with 1,4-bis（imidazol）butane（bimb） or 1,4-bis（triazol）butane（bitb） in the presence of ClO4^-, respectively affords two CoII coordination complexes, namely {[Co（bimb）3]·2ClO4}n（I） and {[Co（bitb）3]·2ClO4}n（II）. Single-crystal X-ray analysis indicates that both complexes I and II show the same α-Po topological structures. However, complex I exhibits a 2-fold interpenetrating network, while complex II features a 3-fold interpenetrating network. In addition, solid-state properties such as thermal stabilities and magnetic properties of two complexes were also investigated.