Dense and uniform layers of a biologically active carbonatecontaining hydroxyapatite can be formed on various kinds of organic polymers by the following biomimetic method. First, a substrate is set in contact with particles of CaO-Si0,-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma for forming the apatite nuclei on the substrate. Second, the substrate is soaked in another solution highly supersaturated with respect to the apatite, e.g., with ion concentrations 1.5 times those of SBF (IJSBF) for making the apatite nuclei grow on the substrate in situ. The induction period for the apatite nucleation, which is defined as the time of the first treatment required for forming enough of the apatite nuclei to make the continuous layer after the second treatment, was almost 24 h for most of the examined polymers. The adhesive strength of the formed apatite layer to the polymers was as high as 3 to 4 MPa for poly(ethy1ene terephthalate), poly-ether sulfone, and poly (vinyl alcohol) hydrogel. This type of apatite-organic polymer composite is expected to be useful for repairing not only living hard tissues but also soft ones.
The present paper focuses on the atom transfer radical polymerization (ATRP) of vinyl ether (VE) based macromonomers with a methacryloyl group at the chain end. Living cationic polymerization of isobutyl VE (IBVE) initiated with the HCl adduct of a VE carrying a pendant methacryloyl group in conjunction with ZnI 2 yielded the macromonomer (MA-PIBVE) with a narrow molecular weight distribution (MWD) (M h w/M h n < 1.1). The ATRP of MA-PIBVE was carried out using a halide initiator and the CuBr/4,4′-di-n-heptyl-2,2′-bipyridine catalytic system. The number-average molecular weight of the polymacromonomer increased in proportion to the monomer conversion, while the MWDs stayed fairly narrow (M h w/M h n ∼ 1.2). Thus a novel type of polymacromonomers with controlled chain lengths for both the backbone and the side chain have been synthesized through a combination of living cationic polymerization and ATRP techniques.
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