The colloidal crystal template or opal with a closed-packed face-centered cubic （fcc） lattice was prepared from monodisperse polystyrene （PS） spheres by vertical sedimentation. The template provided void space for...The colloidal crystal template or opal with a closed-packed face-centered cubic （fcc） lattice was prepared from monodisperse polystyrene （PS） spheres by vertical sedimentation. The template provided void space for infiltration of monomer precursor composed of acrylate acid, acrylamide and ammonium-persulfate, as well as microgel from the subsequent copolymerization. The sample was immersed in dimethylbenzene for completely removing PS spheres to form PAM inverse opal hydrogels （IOHPAM） or PAM/PAA inverse opal hydrogels （IOHPAM/PAA） photonic crystals. The PS spheres were replaced by air spheres, which interconnected each other through the windows. The study of responses to pH show that there are two peaks for both IOHPAM and IOHPAM/PAA films, but the IOHPAM/PAA peaks shift to higher pH, and the peaks are independent with the AA content.展开更多
There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is ...There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is by a physical method to suppress chain termination and to prolong radical lifetime. Here we report a new method called Graduation Initiating Radical Polymerization System for realizing “controlled/living radical polymerization”. Its principle and experimental setup are as follows: firstly, initiatable groups(i.e. peroxide groups) were introduced onto the polymer substrates like LDPE film by photo-oxidation reaction; secondly, the films carried peroxide groups were put and fixed to the bottom of polymerization bottle containing monomer and solvent. Afterwards, they were made to produce radicals(by heating or reductive agent), and finally the system polymerization was initiated. Once these radicals are produced on the surface of these films, they will undergo three different processes: terminating by combination, diffusing to monomer solution and taking in monomers(polymerizing). The reactive diffusion makes this system produce “two graduation”: one is the graduation of radical concentration(i.e. the farther away from the surface of the film, the lower radical concentration); the other is the length-graduation of living chains,\{i.e.\} the farther away from the surface of the film the longer the propagating chains. By this way, we could obtain a polymerization field where the radical concentration is very low and there are no primary free radicals approximately, which are benefit to realize “controlled/living radical polymerization”. This communication reports the first experimental results based on the above idea: with benzophenone(BP) as photo-catalyst and peroxide groups introduced on the LDPE surface in a concentration 10^-8 mol/cm^2; by these peroxided films as the sources of free radicals, polyacrylamide and polyacrylic acid were obtained with molecular weights more than 20 millions.展开更多
基金supported by the National Natural Science Foundation of China(No.50473044).
文摘The colloidal crystal template or opal with a closed-packed face-centered cubic （fcc） lattice was prepared from monodisperse polystyrene （PS） spheres by vertical sedimentation. The template provided void space for infiltration of monomer precursor composed of acrylate acid, acrylamide and ammonium-persulfate, as well as microgel from the subsequent copolymerization. The sample was immersed in dimethylbenzene for completely removing PS spheres to form PAM inverse opal hydrogels （IOHPAM） or PAM/PAA inverse opal hydrogels （IOHPAM/PAA） photonic crystals. The PS spheres were replaced by air spheres, which interconnected each other through the windows. The study of responses to pH show that there are two peaks for both IOHPAM and IOHPAM/PAA films, but the IOHPAM/PAA peaks shift to higher pH, and the peaks are independent with the AA content.
文摘There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is by a physical method to suppress chain termination and to prolong radical lifetime. Here we report a new method called Graduation Initiating Radical Polymerization System for realizing “controlled/living radical polymerization”. Its principle and experimental setup are as follows: firstly, initiatable groups(i.e. peroxide groups) were introduced onto the polymer substrates like LDPE film by photo-oxidation reaction; secondly, the films carried peroxide groups were put and fixed to the bottom of polymerization bottle containing monomer and solvent. Afterwards, they were made to produce radicals(by heating or reductive agent), and finally the system polymerization was initiated. Once these radicals are produced on the surface of these films, they will undergo three different processes: terminating by combination, diffusing to monomer solution and taking in monomers(polymerizing). The reactive diffusion makes this system produce “two graduation”: one is the graduation of radical concentration(i.e. the farther away from the surface of the film, the lower radical concentration); the other is the length-graduation of living chains,\{i.e.\} the farther away from the surface of the film the longer the propagating chains. By this way, we could obtain a polymerization field where the radical concentration is very low and there are no primary free radicals approximately, which are benefit to realize “controlled/living radical polymerization”. This communication reports the first experimental results based on the above idea: with benzophenone(BP) as photo-catalyst and peroxide groups introduced on the LDPE surface in a concentration 10^-8 mol/cm^2; by these peroxided films as the sources of free radicals, polyacrylamide and polyacrylic acid were obtained with molecular weights more than 20 millions.
