论文部分内容阅读
Polymer-grafted nanoobjects(PGNOs)are a kind of nanoparticles with persistent geometric shape and densely tethered polymer hairs.[1] They are very important materials,exhibiting many fantastic applications including loading catalysts,delivering drugs,medical diagnosing and imaging,and improving performances of polymer materials as nanofillers.We reported a useful method to prepare PGNOs with different shapes from one block copolymer,so all the shaped PGNOs have the same molecular weight of tethered polymer hairs.A block copolymer poly-(3-(triethoxysilyl)propyl methacrylate)-block-polystyrene(PTEPM134-b-PS623)was synthesized by RAFT mediated radical polymerization.It is well know that the morphology of self-assembly of a block copolymer is controlled by the volume fraction of two blocks.[2-4] Since the low molecular weight polystyrene(e.g.PS58 here)easily diffused into the PS microdomains of the block copolymers,the total volume fraction of PS component in the blend increased with adding PS58,and then the morphology of the casting films can be changed from the lamellae to the cylinders to the spheres(Figure 1).Finally,ethoxylsilanes contained in PTEPM domain could be cross-linked and the PGNOs with different shapes were obtained by dispersing the bulk samples in solvent and removing PS58.PGNOs/polystyrene nanocomposites were prepared using a precipitation technique.The well dispersions of PGNOs in the polymer matrix were validated by transmission electron microscopy(TEM).The rheological features of PGNOs with different shapes but same tethered polymer hairs(MW and volume fraction)are investigated for the first time.The influence of concentrations and ratio of MW of hair to MW of matrix are discussed as well(Figure 2).