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Physical ageing phenomena in poly( tert ‐butylacetylene): influence of the microstructure
Author(s) -
Costa Giovanna,
Chikhaoui Saida,
Turturro Antonio,
Carpaneto Luca
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980202
Subject(s) - differential scanning calorimetry , microstructure , endotherm , tacticity , polymer , solvent , polymer chemistry , materials science , sphere packing , ageing , crystallography , chemistry , thermodynamics , composite material , physics , organic chemistry , genetics , biology , polymerization
Ageing phenomena in cast films of poly( tert ‐butylacetylene) (PTBA) of different tacticity were studied by dilatometric and calorimetric techniques and by morphological observations. Films of different density ( p ) obtained by varying solvent evaporation times, both from cis / trans or 100% cis PTBA, show during the first dilatometric run the presence of a temperature T p at which a packing effect occurs. Therefore, first dilatometric curves show two linear tracts, the latter representing the sum of thermal dilation and simultaneous packing induced by molecular motions leading to a better packing. Following measurements show a linear increase of the specific volume. The packing process is also revealed by differential scanning calorimetry as a broad endotherm. Δρ is the more pronounced the lower the initial density of the sample for mixed cis / trans PTBA, but, quite surprisingly, in 100% cis PTBA the trend is opposite and, in this case, denser samples undergo a more relevant packing. A tentative explanation is inferred on the basis of a conformational model recently proposed. An improvement of the chain packing is responsible of the fast ageing process of this polymer, as suggested by a preliminary X‐ray diffraction analysis.