Thermal characterization of the interaction
of poly(3-hydroxybutyrate) with maleic anhydride
J. L. Souza
•
A. F. Santos
•
M. S. Crespi
•
C. A. Ribeiro
CBRATEC7 Conference Special Issue
Ó Akade
´
miai Kiado
´
, Budapest, Hungary 2011
Abstract Poly(3-hydroxybutyrate), PHB, has been
structurally modified with maleic anhydride, MA, in the
presence of triethylamine, TEA. Glass transition, melting,
and crystallization temperature, obtained from DSC curves,
and thermal degradation temperatures obtained from TG
ones, were employed to evaluate the influence of the MA
proportion on the modification in the PHB chain. Accord-
ing to the results, most of chain modification reactions are
the 80/20 and 90/10 proportions. Observations suggest that
most chain modification reactions occur when the ratio of
PHB/MA is 80/20 or 90/10. This suggests that modifica-
tions of PHB in the presence of MA involve main chain
scission.
Keywords Transesterification reaction Á
Poly(3-hydroxybutyrate) Á Maleic anhydride
Introduction
Poly(3-hydroxybutyrate) (PHB) is a biopolymer produced
and accumulated intracellular by a wide variety of bacteria
during unbalanced growth from renewable carbon sources
in a controlled biotechnological process [1–3]. Ralstonia
eutropha has been used to produce the polymer with the
PHB content nearly 70% of dry weight [4]. The prospective
market for PHB is the general packages, injected products,
disposable materials in cosmetic industries [5], and it is
also a highly potential biomaterial in biomedical applica-
tions such as scaffolds for bone reconstruction, sutures
surgical fibers [6], and capsules for drug delivery [7], due
to its biocompatibility and absorption in the organism [8–
10]. Nevertheless, PHB is thermal unstable, brittle, and
presents high melting crystalline temperature (e.g.,
165 °C). In order to improve these disadvantages, some
alkanoates monomers have been introduced in the polymer
chain during the biosynthesis, as an example the 3-hy-
droxyvalerate, thus obtaining a random copolymer [11, 12].
The transesterification reaction conditions were carried out
at 110 °C, during 1 h and with triethylamine (TEA) con-
centration in 5% v/v [13, 14]. The main purposes of this
article are to evaluate the thermal behavior of the PHB
homopolymer and PHB structurally modified with maleic
anhydride (MA) in different proportions (w/w of PHB/MA)
by differential scanning calorimetry (DSC) and thermo-
gravimetric analysis (TG).
Experimental
Film preparation
Pre-treating
PHB homopolymer (PHB Industrial, Serrana, Brazil) with
average molecular weight 300848 Dalton [15, 16] were
added in 2 mL of chloroform (J T Baker) in sealed vials
(8 mL). MA (MERCK) was prepared in the same way. The
sealed vials were kept at 100 °C during 10 min and stirred
(90 RPM) during 20 h for complete dissolution of the
polymer. After the stirring period, the MA solution was
completely transferred to PHB solution to obtain a different
ratio (w/w) of PHB/MA, according to Table 1.
J. L. Souza Á A. F. Santos Á M. S. Crespi Á C. A. Ribeiro (&)
Instituto de Quı
´
mica, Universidade Estadual Paulista-UNESP,
Araraquara, SP, Brazil
e-mail: ribeiroc@iq.unesp.br
123
J Therm Anal Calorim (2011) 106:453–458
DOI 10.1007/s10973-011-1706-3