Influences of chain stereoregularity on inborn entanglement and solubilityof polyacrylonitrile

The effect of chain stereoregularity on inborn entanglement and solubility of polyacrylonitrile (PAN) was examined. The three PAN samples of various s tereoregularity were prepared by three different ways, namely matrixanionic polymerization (MAP), radiation - induced radical polymerization and aqueo us suspension radical polymerization. The inborn entanglement index (EI) is defined by (M-r(o) - M-r(e))/M-r(o), where M-r(o) and M-r(e) are the measu red apparent molecular weights (M-r) of PAN before and after shear modifica tion, and the triad tacticity was measured by IR spectroscopy. It is shown that under nearly the same chain stereoregularity, the value of EI increase s with the increasing M-r, while, the solubility of PAN samples decrease wi th the increasing M-r, and that under nearly the same M-r, the value of EI and the solubility decrease with the increasing triad content(mm) in the PA N chain. The experimental results suggested that EI may not always consiste nt with solubility of PAN.