96
C. Lorenzini et al. / Reactive and Functional Polymers 93 (2015) 95–100
fluorescens were purchased from Aldrich. Tetrabutylammonium bro-
mide (TBAB, N98%) were obtained from Fluka. Chloroform (analytical
grade), petroleum ether (analytical grade), and methylene chloride
were purchased from SDS and used without further purification.
Isosorbide (99%) and Irgacure 250 (iodonium salt) were kindly supplied
by Roquette Frères (Lestrem, France) and BASF Company respectively.
2.3.4. Synthesis of isosorbide diepoxy, DGEDAS
Diallyl isosorbide ether was prepared by the Williamson reaction.
Isosorbide (3 g, 20.4 mmol) was dissolved in a 50% aqueous NaOH (6 g,
107.2 mmol) solution. Allyl bromide (10 mL, 115.7 mmol) was used as
an alkylating agent in the presence of 4.6% of tetrabutylammonium
bromide (TBAB, 300 mg, 0.94 mmol) with respect to isosorbide. The
reaction was stopped after 4 h of heating at 65 °C and the mixture
was extracted with methylene chloride. Freshly prepared diallyl
isosorbide (3 g, 13.4 mmol) was then added slowly to a solution of m-
chloroperbenzoic acid (7 g, 40.6 mmol) in 12 mL of methylene chloride.
The reaction was stirred at a temperature of 20 °C for 72 h. The solution
was then filtrated and washed with a solution of 10% sodium bisulfate
followed by saturated sodium bicarbonate and distillated water. The
organic layer was then dried over magnesium sulfate. The yield of the
reaction is 60%.
2
.2. Instrumentation
1H and 13C NMR spectra were recorded on a Bruker Avance II NMR
spectrometer, working at 400 MHz (1H). The solvent peak (DMSO-d
was used as a reference. The FTIR spectra were recorded on a TENSOR
7 Bruker apparatus (Digi Tect DLaTGS detector, 32 scans, 4 cm−1).
6
)
2
Thermogravimetric analyses (TGAs) were performed on a Setaram
Setsys Evolution 16 apparatus, under argon atmosphere, with a heating
−
1
rate of 10 °C · min from 0 to 800 °C under argon atmosphere. Dynam-
ical mechanical thermal analysis (DMA Q800, TA, USA) were performed
on samples (20 mm × 5 mm) at a frequency of 1 Hz with a ramp rate of
2.3.5. Preparation of polyether–polyester networks
The photocurable formulations were prepared by adding increasing
amount of PHA diepoxy to 150 mg (Mn = 286 g/mol, 0.52 mmol) of
isosorbide diepoxy : 0, 10 (17 mg), 20 (38 mg), 25 (50 mg) wt. %
were added to the epoxy monomer. An actual amount of 3 wt.% of cat-
1
0 °C/min in the tensile configuration. The gel content was determined
on the cured films by measuring the weight loss after 24 h extraction
with methylene chloride at room temperature. Hydrolytical degrada-
tion was performed using a buffer solution at pH 7.4. The polymeric
coatings were dried into an oven at 100 °C for one night and weighted
to an accuracy of 0.1 mg. Each sample was placed into an individual
vial containing 5 ml of buffer solution incubated at 37 °C. The samples
were removed after different times, dried and reweighted. The degrad-
ability was evaluated by following the weight loss.
2 2
ionic photoinitiator I 250 and 0.5 mL of CH Cl were added to each for-
mulations. The photocurable products were introduced in a silicon mold
(4 cm × 2 cm) and irradiated at room temperature with a Hd-Xe lamp
from Hamamatsu (200 W, Lightning Cure LC8 (L8251)), coupled a flex-
ible light guide. The end of the guide was placed at a distance of 11 cm.
2
The light intensity on the surface of the sample was about 9 mW/cm .
After 5 min of irradiation, the formation of transparent film is achieved.
2
2
.3. Preparation and characterization of the samples
2
.3.6. Hydrolytic degradation of epoxy networks
Films (40 mg) were placed in a vial filled with 5 mL of phosphate
.3.1. Preparation of bis-hydroxylated PHA oligomers (PHA-diols) under
microwave irradiation
buffer, pH = 7.4. They were incubated under stirring in an oil bath at
37 °C for different period of time. The samples were washed 3 times
1
g of PHBHV (Mn = 90,000 g · mol−1, 1.1 × 10−5 mol) was dis-
solved in 10 mL of dried chloroform in a borosilicate glass tube fitted
to a microwave reactor. The reaction was performed under microwave
irradiation in a monowave 300 microwave synthesis reactor from
Anton Paar. The microwave source was a magnetron with a 2.5 GHz fre-
quency powered by a 900 W power generator. 0.37 mL of anhydrous
n
−
3
ethylene glycol (6.6 × 10
mol) and 1.24 mL of dibutyltin dilaurate
DBTDL
−
6
(
2.09 × 10 mol) were introduced and the mixture was heated from
2
4
0 to 140 °C for 3 min and then the temperature was maintained for
5 min. At the end, they were cooled at 40 °C in 2 min. The reaction
was maintained under stirring all along irradiation. After cooling to
room temperature, the solution was precipitated twice in petroleum
ether, filtrated and then dried under vacuum at 60 °C overnight. The
a) PHA diol
m < n
1
molar mass of the oligomers, were determinated by H NMR [25].
DBTDL
2
.3.2. Synthesis of PHA diallyl
.4 g of PHA-diol (Mn = 1500 g · mol 1, 1.6 × 10−3 mol) and 311 μL
−
2
−
3
(
3,52 × 10 mol) of allyl isocyanate were dissolved in 16 mL of dried
chloroform with 60 μL of DBTDL as catalyst. The mixture was allowed
reacting at 80 °C for 4 h. The solution was then precipitated in petro-
leum ether, filtered and then dried under vacuum at 60 °C overnight
in order to obtain the PHA diallyl.
b) PHA diallyl
m
m-CPBA
2
.3.3. Synthesis of PHA diepoxy
g of PHA diallyl (Mn = 1700 g · mol 1, 1.2 × 10−3 mol) was then
added slowly to a solution of m-chloroperbenzoic acid (611 mg,
−
2
.6 × 10− mol) in 2 mL of methylene chloride. The reaction was stirred
3
3
c) PHA diepoxy
at a temperature of 20 °C for 72 h. The solution was then filtrated and
washed with a solution of 10% sodium bisulfate followed by saturated
sodium bicarbonate and distillated water. The solution was then precip-
itated in petroleum ether, filtered and then dried under vacuum at 60 °C
overnight in order to obtain the PHA diepoxy.
m
Fig. 1. Reaction sequence for the synthesis of (a) the PHA diol, (b) the PHA diallyl and
(c) the PHA diepoxy.