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Structures of vinylidene chloride–vinyl chloride copolymers

1964; Inderscience Publishers; Volume: 2; Issue: 4 Linguagem: Inglês

10.1002/pol.1964.100020418

1542-6246

Kensuke Okuda,

Advanced Polymer Synthesis and Characterization

Abstract The relationships between composition and structure of vinylidene chloride (VDC)–vinyl chloride (VC) copolymer were investigated by various methods such as x‐ray wide‐angle and small‐angle scattering, electron diffraction and microscopy, thermal analysis, and high resolution nuclear magnetic resonance. The copolymers used were made by suspension copolymerization below 5% conversion. The crystalline regions are fundamentally ismorphous to polyvinylidene chloride (PVDC) for the VDC–VC copolymers in the composition range from 1 to 0.560 in terms of the molar fraction of VDC (0.560 VDC). In the composition range below 0.145 VDC, the copolymers form crystallites isomorphous to polyvinyl chloride. The copolymers having the intermediate compositions are amorphous. In the composition range above 0.560 VDC, the average crystallite sizes of the uniaxially oriented specimens are almost constant; on the contrary, the long periods increase with decrease of the molar fraction of VDC. The intensities of the long‐period diffraction peaks show a maximum for the copolymer in which the molar fraction of VDC is 0.685. The crystallinities, which were estimated from the x‐ray method, decrease with decrease of the VDC fraction. The melting point depression is so small that it cannot be explained by Flory's equation. The results of NMR indicate that a large percentage of VC monomer units exists as sequences even in VDC‐rich copolymers. PVDC and the VDC–VC copolymers higher than 0.745 VDC crystallize in the form of layer crystal aggregates from monochlorobenzene solutions. The molecules are sharply folded within these layers. The average crystallite sizes and long periods of the solution growth crystals are almost constant. These experimental facts cannot be interpreted in the terms of the structure which is expected by the copolymerization theory, but may be explained only on the basis of the molecular structure model which means the copolymer has a kind of block‐type structure.