Novel, iodine-containing compound, preparation thereof and block copolymer comprising the same

A process for preparing a block copolymer having a number average molecular weight of from 1.times.10.sup.3 to 1.times.10.sup.6 comprising at least two types of blocks in a molecule wherein at least one block is a homopolymeric or random copolymeric block comprising at least one block selected from the group consisting of:

• (a) a block consisting of at least two repeating units selected from the formulae:
• --(CH.sub.2 CF.sub.2 CF.sub.2 O).sub.a --
• --(CHClCF.sub.2 CF.sub.2 O).sub.b --
• --(CCl.sub.2 CF.sub.2 CF.sub.2 O).sub.c --
• --(CHFCF.sub.2 CF.sub.2 O).sub.d --
• --(CFClCF.sub.2 CF.sub.2 O).sub.e --
• --(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.f --
• a, b, c, d, e and f are each 0 or a positive integer and satisfy the following equations:
• 2 .ltoreq.a+b+c+d+e+f.ltoreq.200 and
• 1 .ltoreq.a+c+d+f,
• (b) a block consisting of the repeating units of the formula:
• ##STR20## wherein p, q and r are each 0 or a positive integer and satisfy the following equations:
• 2.ltoreq.p+q+r.ltoreq.200 and
• .ltoreq. p+q,
• (c) a block consisting of the repeating units of the formula:
• ##STR21## wherein R.sub.f1 and Rf.sub.2 are the same or different and C.sub.1 -C.sub.3 perfluoroalkyl, k and m are each a positive integer and satisfy the equations:
• .ltoreq. k+m.ltoreq.50 and
• 0.2.ltoreq.m/(k+m),
• and n is an integer of 0 to 10, and
• (d) a block consisting of repeating units of the formula:
• --(CF.sub.2 CFCl).sub.x --
• wherein x is an integer of 2 to 11,
• and at least one block is a homopolymeric or random copolymeric block consisting of repeating units of the formula:
• --(CF.sub.2 CXY)--
• wherein X is hydrogen or fluorine, Y is hydrogen, chlorine, fluorine, difluoromethyl or C.sub.1 -C.sub.8 perfluoroalkyl or perfluoroalkoxy, provided that when the former block consists of the repeating unit (d) alone, the combination of X=fluorine and Y=chlorine is excluded, wherein the content of the latter block is 1 to 95 % by weight based on the total weight of the block copolymer which process comprises polymerizing at least one fluorine-containing olefin of the formula:
• CF.sub.2 .dbd.CXY
• where X and Y are as defined above, in the presence of a radical-generating source and at least one compound selected from the group consisting of:
• (a) an iodine-containing compound consisting of at least two repeating units selected from the formulae:
• --(CH.sub.2 CF.sub.2 CF.sub.2 O).sub.a --
• --(CHClCF.sub.2 CF.sub.2 O).sub.b --
• --(CCl.sub.2 CF.sub.2 CF.sub.2 O).sub.c --
• --(CHFCF.sub.2 CF.sub.2 O).sub.d --
• --(CFClCF.sub.2 CF.sub.2 O).sub.e --
• --(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.f --
• wherein
• a, b, c, d, e, and f are each 0 or a positive integer and satisfy the following equations:
• a+b+c+d+e+f.ltoreq.200 and
• a+c+d+f
• and an iodine atom at least at one end of a molecule,
• (b) an iodine-containing compound consisting of at least two repeating units of the formula ##STR22## wherein p, q and r are each 0 os a positive inteqer and satisfy the following equations:
• p+q+r <200 and
• p+q
• and an iodine atom at least at one end of a molecule, (c) an iodine-containing compound consisting of the repeating units of the formula:
• ##STR23## wherein R.sub.f1 and Rf.sub.2 are the same or =perfluoroalkyl, k and m are each a positive integer and satisfy the equations:
• 2.ltoreq.k+m.ltoreq.50 and
• 0. 2.ltoreq.m/(k+m),
• and n is an integer of 0 to 10, and an iodine atom at least at one end of a molecule, and
• (d) an iodine-containing compound consisting of the repeating units of the formula:
• --(CF.sub.2 CFCl).sub.x --
• wherein x is an integer of 2 to 11, and an iodine atom at least at one end of a molecule.
• to thereby form said block copolymer.