【摘要】 将侧链偶氮聚电解质应用于聚苯乙烯胶体微球表面的静电层层自组装,得到了偶氮聚电解质和聚二烯丙基二甲基氯化铵多层膜覆盖的核壳微球.实验表明,组装后偶氮苯基团发生了一定程度的解聚集,得到的胶体微球可表现出明显的光色效应.研究进一步采用含肉桂酸酯的光敏聚电解质作为交联的保护壳层,并通过光交联反应使表面层发生交联固化反应.将上述具有核壳结构的胶体球溶解去除聚苯乙烯内核后,得到了含光响应聚电解质的空心微胶囊.更多还原

【Abstract】 In recent years,core-shell micro-particles and hollow capsules have aroused great research interests as new useful microstructures for many potential applications.In this work,core-shell spheres and hollow capsules containing azo polyelectrolytes were prepared by electrostatic layer-by-layer self-assembly and core-dissolution after the multiplayer deposition.In the electrostatic layer-by-layer self-assembling process,a side-chain azo polyelectrolytes （PEAPE） as polyanion was alternately adsorbed onto surfaces of polystyrene （PS） colloidal spheres together with a polycation of poly（diallyldimethylammonium chloride） （PDAC）.PEAPE is a random copolymer composed of acrylic and azobenzene-containing acrylate units.PEAPE samples with degree of functionalization （DF） of 9.3% and 41.4% were used.Solutions of the polyelectrolytes （PEAPE and PDAC） in water and an aqueous medium of 0.1 mol/L NaCl were alternately added into the diluted suspension of PS latex for electrostatic layer-by-layer adsorption.After 15 min,PS spheres were separated and washed by high-speed centrifuge （ultracentrifuge,Hitachi CR 22G）.Then the sediment was dispersed in Milli-Q water again for further experiment.The experiment steps were repeated several times until the required layer number was reached.The resulted core-shell particles were characterized by transmission electron microscopy （TEM,JEM-1200EX） and dynamic light scattering （DLS,Malvern Zetasizer 3000 HS）.The layer-by-layer adsorption of PEAPE and PDAC was evidenced by the diameter increase from the TEM images and DLS measurements.The oscillation of Zete-potenctial after each adsorption step,which indicates the over charge compensation,also confirmed the successive self-assembly of azo polyelectrolytes.Changing the ionic strength of PDAC solution （in water or in aqueous medium of 0.1 mol/L NaCl） could obviously shift the Zete-potenctial of the colloids,but had little influence on the diameter increasing of the colloidal spheres.The photoisomerization of the azobenzenes was studied by UV-Vis spectroscopy.These azobenzene-containing core-shell particles show typical photochromic effect upon UV light irradiation.After adsorbed to colloidal surfaces,the H-aggregation of azobenzene groups decreased in certain degree and resulted in red shifts in UV-Vis spectrum.As a consequence,the azobenzene chromophores exhibited quickly photo-response behavior upon UV irradiation.To obtain hollow capsules with stable shells,a photosensitive cinnamate-containing polyelectrolyte （PAAEH,DF=27%）,synthesized in authors’ lab,was applied to induce covalent crosslinking in the shells of colloidal spheres.In the process,PAAEH was adsorbed onto the core-shell particles of PS/（PDAC/PEAPE）₃ through electrostatic self-assembly together with PDAC.In the process,PAAEH was dissolved in Milli-Q water with a concentration of 1 mg/mL and used as polyanions.After two or three layers of PDAC/PAAEH adsorbed,the core-shell colloidal spheres were exposed to UV light （18 mW/cm²） for 30 min.The photosensitive shells were cross-linked upon UV-light radiation.Then PS core of colloidal spheres was removed by dissolving with tetrahydrofuran/H₂O （V∶V=1∶1）.Finally,hollow capsules containing azo chromophores were obtained.Due to their photoresponsive composition, the core-shell particles and hollow capsules may have potential applications in areas such as bio-medicine and photoelectronics.更多还原