The postgrafting of hydrophobic poly (glycidyl methacrylate-co-methyl methacrylate), P (GMA-co, -MMA), to grafted hydrophilic poly (ethyleneimine) on carbon blacks, CB-graft-PEI, and their dispersibility were investigated. The grafting of PEI onto carbon black surface was achieved by the direct condensation of surface carboxyl groups on carbon black with PEI in the presence of N, N'-dicyclohexylcarbodiimide as a condensing agent. The postgrafting of P (GMA-co-MMA) to CB-graft-PEI was successfully proceeded in N, N-dimethylformamide at 80°C to give branched polymer-grafted carbon black : total grafting increased to 45-60%. CB-graft-PEI gave a stable colloidal dispersion in water, but precipitated in toluene, because of hydrophilic nature of the surface. By postgrafting of P (GMA-co-MMA) to CB-graft-PEI, the carbon black lost its good dispersibility in water, but uniformly and stably dispersed in toluene, because of the hydrophobic nature of postgrafted P (GMA-co-MMA). When P (GMA-co-MMA) -postgrafted CB-graft-PEI was dispersed in water/toluene binary mixture, the water droplets (about 1-3-mm d.) stabilized with P (GMA -co-MMA) -postgrafted CB-graft-PEI was gathered in the intermediate layer. This result indicated that water droplets are surrounded by P (GMA-co-MMA) -postgrafted CB-graft-PEI particles in the same manner as surfactant molecules : grafted PEI and postgrafted P (GMA-co-MMA) chains had good affinity for water and toluene, respectively.
Diarylethene derivatives having one or two chiral l-menthyl substituents were synthesized for the examination of an asymmetric photocyclization reaction. The compounds have been prepared from the corresponding carboxylic derivatives and l-menthol in the presence of dicyclohexylcarbodiimide. Upon irradiation with UV light these open form diarylethenes were converted into the corresponding closed-ring forms. Two diastereomers of the closed-ring form were separated by HPLC equipped with a silica-gel column, and their absorption spectra and CD spectra were measured. The two diastereomers gave the same absorption maximum and coefficient. The absolute stereochemistry of one of the diastereomers was determined by the CD spectrum. These compounds were found to undergo diastereoselective photocyclization reactions in the amorphous state. The product distribution between the diastereomers was almost 1 : 1 in a solution, but it deviated from 1 : 1 in the amorphous state. The predominantly formed diastereomer was (R, R) isomer : in case of the compound having twoBl-menthyl group, a diastereomer excess as large as 37.4% d. e. was obserbed in the amorphous state.
The cathodic delamination of polyethylene-coated steel pipe was investigated. The steel pipe had three layers of coatings structure ; polyethylene, adhesive polyethylene, and amine cured epoxy primer. The cathodic delamination length of polyethylene coating was strongly dependent on the concentration of epoxy group in amine-cured epoxy primer. The polyethylene coating with greater resistance to cathodic delamination was obtained when the concentration of epoxy group was higher. In the case that the mixing ratio of epoxide to amine was constant, higher concentration of epoxy group surpressed oxygen permeability through the epoxy primer to the interfacial region between the steel pipe and the epoxy primer because of denser cross-linking of the epoxy primer. In the case that epoxide was in excess against amine curing agent, the cathodic delamination length was also shortened with the increase concentration of epoxy group. The result can not be explained by the cross-linking density or acid-base interaction between amino group and the steel at the interface. The excess of epoxy group was found to promote bonding at the interface with the steel, which resulted in the good resistance for the cathodic delamination.