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Isotactic cis‐1,4‐poly(3‐methyl‐1,3‐pentadiene): a new conformation for isotactic cis‐1,4‐polydienes
Author(s) -
Meille Stefano Valdo,
Capelli Silvia,
Allegra Giuseppe,
Ricci Giovanni
Publication year - 1995
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.1995.030160416
Subject(s) - tacticity , helix (gastropod) , materials science , crystallography , polymer chemistry , polymer , chemistry , composite material , polymerization , biology , ecology , snail
Oriented specimens of isotactic cis‐1,4‐poly(3‐methyl‐1,3‐pentadiene) exhibit two crystalline modifications characterized, respectively, by the expected two‐fold helical conformation with a fiber repeat of 8,02 Å and by a three‐fold helix with c = 9,97 Å. The latter highly contracted structure is prevalent in fibers and is the only one observed in unoriented bulk specimens. Consistent with these findings conformational calculations indicate that the three‐fold helix is substantially more stable than the two‐fold one.