接枝聚合制备具有超低介电常数聚酰亚胺纳米复合物材料

PREPARATION OF FLUORINATED POLYIMIDE/POSS NANOCOMPOSITES WITH ULTRA-LOW DIELECTRIC CONSTANT BY GRAFT COPOLYMERIZATION

通过热引发甲基丙烯酸环戊基-立方低聚倍半硅氧烷(R7R'Si8O12,POSS)(MA-POSS)与臭氧预处理的含氟聚酰亚胺(FPI)自由基接枝共聚制得了含多面体低聚倍半硅氧烷(POSS)的FPI纳米复合物.用核磁共振(NMR)、X-射线衍射(XRD)及场发射扫描电镜(FESEM)等手段对POSS/FPI纳米复合物的化学组成及其形貌结构进行了表征.POSS/FPI纳米复合物薄膜与原始FPI薄膜相比具有更低的、可调的介电常数,它的介电常数(κ)在2.5～2.1之间.

Nanocomposites of fluorinated polyimides （FPI） with covalently grafted polymethacrylate side chains containing polyhedral oligomeric silsesquioxane （ R7 R＇ Si8 O12 or POSS） units were prepared by thermally-initiated free-radical graft polymerization of methacrylcyclopentyl-POSS （MA-POSS） with the ozone-pretreated FPI. The chemical composition and structure of the FPI with grafted methacrylcyclopentyl-POSS side chains were characterized by nuclear magnetic resonance （1^H-NMR） and X-ray diffraction （XRD）. The morphology of the POSS/FPI nanocomposite films was observed by field-emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）. A layer-by-layer structure was revealed, which supports the formation of an ordered architecture by POSS crystallites in the FPI matrix, as the result of self-assembled POSS units of MA-POSS side chains. The POSS/FPI nanocomposite films had both lower and tunable dielectric constants,in comparison with that of the pristine FPI films. Dielectric constants （k＇ s） of about 2.5 to 2.1 were obtained. The reduction of dielectric constant was most likely due to a combined contribution of the nanoporosity of the POSS units and the extemal porosity introduced by the grafting of MA-POSS to the FPI chains.