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Structural and thermodynamic features of the polyhydroxybutyrate physical gels
Author(s) -
Cesàro Attilio,
Fabri Deborah,
Sussich Fabiana,
Paradossi Gaio
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991380121
Subject(s) - polyhydroxybutyrate , materials science , chemical engineering , phase diagram , phase (matter) , morphology (biology) , chemistry , organic chemistry , genetics , bacteria , engineering , biology
The structural and thermal properties of polyhydroxybutyrate (PHB) gels in dimethylformamide (DMF) are presented and discussed. The dilute and semi‐dilute mixed PHB/DMF system undergoes a phase separation on cooling at a temperature T gel, producing a gel in which the crystalline fraction is of the order of 50‐60% and the diffraction pattern is that of disperse nano‐crystals, with the same unit cell of the pure crystalline PHB. Upon heating, two melting peaks are normally observed at T m1 and T m2 (always higher than T gel ). Shapes of the peaks, temperatures and enthalpies of melting depend slightly on scanning rate on heating but on the procedure of gel preparation. Reproducibility and reversibility have always been found with repeated thermal cycles. A thermodynamic phase diagram is therefore constructed and discussed, although the morphology of the system may be subject to the experimental conditions under which the gel is prepared.