Binary copolymerizations of acetaldehyde, propionaldehyde,
n-butyraldehyde and iso-butyraldehyde were investigated using Et
2AlNPh
2 as catalyst at -78°C. All the copolymers obtained were crystalline and had the lattice constants varying in a continuous way according to the copolymer composition. The infrared absorption bands due to the ethereal linkage of the copolymer also showed a continuous variation in relation to the compositions. The copolymers of some limited compositions, unlike the both homopolymers and the copolymers of other compositions, were completely soluble in toluene, chloroform or carbon tetrachlorides, but could not be separated into fractions having different properties with usual organic solvents. From these results it was concluded that these copolymers were to be a “cocrystalline copolymer”, which falls into the category of the isomorphous phenomenon of monomeric units.
Such a cocrystalline copolymer was also obtained by the use of EtAl (NPh
2)
2, Al (NPh
2)
3, AlR
3, Al (OR)
3 or ZnR
3 as catalyst.
The copolymerizations of a higher aldehyde, such as
n-heptanal or
n-octanal, with some lower aldehydes gave also the cocrystalline copolymers, however, in these cases the cocrystalline copolymers obtained showed different types of X-ray diffraction patterns in regard to the composition of the charged monomer.
The copolymer polymerized with Et
2AlNPh
2 was shown to have a terminal group of -NPh
2 by UV-absorption method.
The thermal decomposition of the copolymer of acetaldehyde and
n-butyraldehyde was investigated at various temperatures and the solution viscosities of the decomposed polymers were determined. From these results the mechanisms of the thermal decomposition was discussed in some detail. The apparent activation energy of the scission of the polymer chain was calculated to be 34kcal/mol.
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