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Characterization of two polypentadienes of differing tacticity by physical methods
Author(s) -
FieldingRussell G. S.,
Smith G. H.
Publication year - 1970
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1970.070140321
Subject(s) - tacticity , materials science , vulcanization , glass transition , polymer chemistry , polymer , characterization (materials science) , atmospheric temperature range , isomerization , composite material , thermodynamics , natural rubber , catalysis , polymerization , chemistry , organic chemistry , nanotechnology , physics
The preparation of isotactic and syndiotactic 1,4‐polypentadienes with a cis content of at least 70%–75% using i‐Bu 2 AlH/Ti(i‐OPr) 4 and AlEtCl 2 /thiophene/Co(acetylacetonate) 2 catalysts, respectively, is reported. Physical characterization of the vulcanizates, prepared by a common recipe, involving infrared analysis, DTA, simple stress–strain and swelling measurements, and dynamic mechanical measurements over a frequency range of 2 decades and temperature range of −60°C to +20°C indicated that no isomerization had taken place during vulcanization and that stereoregularity of the polymer chains affected the resultant cure: the isotactic form was found to have a greater crosslink density than the syndiotactic form. Master curves covering an extended frequency range were constructed from the reduced dynamic mechanical data and the calculated quantities—thermal expansion coefficients of free volume and the fractional free volumes at the glass transition temperatures—agree with the accepted values. Glass transition temperatures of the isotactic and syndiotactic polymers are −37°C and −42°C, respectively, and for their vulcanizates, −33°C and −40°C, respectively.