Chemistry Reference
In-Depth Information
HS
R
O
5
OH
HO
HO
OH
2, 4 o r 6
S
O
OH
2, 4 o r 6
AIB N/60 °C
(excess)
8
O
120 °C,
p
-to luenesulfonic acid
R
O
6
R
O
O
R
HS
5
OH
HO
OH
2, 4 o r 6
HO
OH
R=
n
-C
8
H
17
S
O
O
S
x
AIB N/60 °C
8
8
x
=2,4or6
Scheme 4.14 The synthesis of diols using 2ME. The actual synthesis utilized
soybean methyl esters, which contain linoleic acid methyl ester as
their main component.
45
decomposing thermally in nitrogen at 261-272 1C. The T
g
values of the
PUs were T
g
(monoamido diols)4T
g
(diamido diols)4T
g
(monoester diols) 4T
g
(diester diols). Mostly, increasing the number of CH
2
groups in the
diols led to lower T
g
values. The amide groups probably catalyzed the
reactions, since the PUs from amides had shorter gel times than the PUs
from esters.
Lluch et al.
48
coupled a thiol with oleic, 10-undecylenic acid and 10-
undecylenic acid triglyceride with 3-mercaptopropionic acid to obtain
compounds with two or three carboxylic acid groups (Scheme 4.16). Next, the
carboxylic groups were converted to mixed anhydrides with acetic anhydride,
followed by melt condensation (see Scheme 4.17), to obtain polymeric an-
hydrides. The formed anhydrides were cast and their degradation in pH 7.4
buffer was observed. A fast degradation of the polymer (more than 50% in
24 h) was observed. In addition, polymers were prepared with a hydrophobic
dye (rhodamine B) cast in the polymer as a model drug. Most of the drug was
released within 60 h in the pH 7.4 buffer.
More et al.
50
reported the successful addition of 2-mercaptoacetic acid
methyl ester to undecylenic acid methyl esters under mild conditions (35 1C,
or UV light at room temperature). The ester groups were successfully con-
verted to diisocyanate (1-isocyanato-10-(isocyanatomethyl)thio]decane
(DITD), Scheme 4.18) and reacted with diols to form PU. Compared to
1,8-diisocyanatooctane, DITD was less stable when exposed to air. This
observation was explained by the sulfur atom increasing the reactivity of the
nearby isocyanate group. PU formed with DITD, showed several transition
peaks in a DSC thermogram, which were explained by the enhanced flexibility
of the hydrocarbon chain due to the presence of the sulfur atoms.
T¨r¨nç and Meier
43
synthesized several derivatives of 10-undecylenic
acid and 10-undecylenic alcohol using the thiol-ene reaction (Scheme 4.19).
Next, a polycondensation reaction was carried out using the triazabicyclode-
cene (TBD) base catalyst to form several polyester compounds. The so-formed
polymers had number-average molecular weights (M
n
) of 3.9 to 9.4 kDa,
and polydispersities (M
w
/M
n
) of 1.87 to 3.37. The DSC thermogram showed
sharp endothermic peaks, indicating that the polymers were semi-crystalline.
