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Structure and dynamics of melt poly( ε ‐caprolactone) from inverse rheological calculation
Author(s) -
Gimenez J.,
Cassagnau P.,
Fulchiron R.,
Michel A.
Publication year - 2000
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/(sici)1521-3935(20000301)201:5<479::aid-macp479>3.0.co;2-f
Subject(s) - caprolactone , polymer chemistry , polymer , materials science , polymerization , rheology , rheometer , viscoelasticity , alkoxy group , molar mass distribution , chemical engineering , composite material , chemistry , organic chemistry , alkyl , engineering
Abstract The linear viscoelastic behavior of poly( ε ‐caprolactone) (PCL) in situ synthesized between the plates of the rheometer was investigated. The polymerization of ε ‐caprolactone was initiated and catalyzed by titanium tetrapropoxide. These polymers are very sensitive to hydrolysis of the alkoxy‐titanium bonds included in the polymer chains. Two different forms of PCL can be studied: hydrolyzed or non‐hydrolyzed PCL. However, only the molecular weight distribution (MWD) of the hydrolyzed chains can be accessed from size exclusion chromatography (SEC) analysis. The MWD of the in‐situ synthesized poly( ε ‐caprolactone) was calculated by solving the inverse problem of determination of the MWD from rheological data. A continuous form of the relaxation function was derived and an a priori shape (Wesslau or bi‐modal Wesslau) of the MWD was assumed. Then MWDs calculated from complex moduli curves were used to investigate the structure of the poly( ε ‐caprolactone) at the end of the polymerization process. About 85% of the polymer chains consist of a single branched linear structure. The remaining 15% are assumed to be mainly two fold branched. The presence of star structures cannot be precluded. The present work describes an illustrative example of the suitability of the quasi on‐line estimation of the MWD from the inversion data.