The effect of chain stereoregularity on inborn entanglement and solubility of polyacrylonitrile (PAN) was examined. The three PAN samples of various stereoregularity were prepared by three different ways, namely matrixanionic polymerization (MAP), radiation-induced radical polymerization and aqueous suspension radical polymerization. The inborn entanglement index (EI) is defined by (M~r^o-M~r^e)/M~r^9, where M~r^o and M~r^e are the measured apparent molecular weights (M~r) of PAN before and after shear modification, and the the triad tacticity was measured by IR spectroscopy. It is shown that under nearly the same chain stereoregularity, the value of EI increases with the increasing M~r, while, the solubility of PAN samples decrease with 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 PAN chain. The experimental results suggested that EI may not always consistent with solubility of PAN.

Key words: POLYACRYLONITRILE, WATER SOLUBILITY, ENTANGLEMENT