Biomedical Engineering Reference
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OH
O
OH
H
O
HO
O
O
+
O
CH
3
+
aq. NaOH
pH = 8
CH
3
NH
2
O
N
N
HO
Cl
CH
3
CH
3
NH
H
3
C
-
CH
3
-
OH
Cl
Cl
+
Quat-188
-
N
CH
3
Cl
H
3
C
CH
3
Chitosan Quat-188
Figure 2.5
Reaction of chitosan with 3-chloro-2-hydroxypropyl trimethylammonium chloride (Quat-188).
2.3.3 Quaternization of Chitosan using Other Quaternizing Agents
De Britto and Assis [24] synthesized TMC by using dimethylsulfate as the methylating
agent. They suggested that dimethylsulfate is less expensive and less toxic than
iodomethane. Moreover, it has a higher boiling point than iodomethane and no solvent is
required for the reaction. The quaternization of chitosan was performed in mixtures of
sodium hydroxide solution and sodium chloride and refluxed with a methylating agent at
room temperature or at 70°C. They found that DQ was in the range of 15-52%, depending
on reaction time and temperature. Moreover, undesirable O-methylation and polymeric
degradation were also observed to have taken place in the reaction.
2.3.4 Quaternization of Chitosan Derivatives
Alkylation of TMC produces amphiphilic polymeric molecules because it possesses both
charged groups and nonpolar linear hydrocarbon branches in the chitosan backbone. Kim
H
3
COC
OH
NH
+
OH
O
l
2
+
HO
15% (w/v) NaOH
CH
3
O
CH
3
O
N
O
+
Cl
N
O
HO
CH
3
CH
3
pH = 8
NH(R)
CH
3
-
OH
CH
3
-
Cl
Cl
Chitosan or Chitosan derivatives
Quat-188
CH
3
H
3
C
CH
3
+
-
Cl
OH
H
3
COC
O
NH(R)
NH
HO
HO
O
O
O
O
O
O
HO
NH
O
OH
HO
HO
-
Cl
+
-
+
Cl
R = H
N
S
H
3
C
N
N
H
3
C
CH
3
X
X = H, CH
3
, OH, OCH
3
,
F, Cl, Br, CF
3
, NO
2
, COOH
H
3
C
CH
3
H
3
C
Chitosan derivatives Quat-188
Figure 2.6
Synthesis of quaternized chitosan and quaternized
N
-aryl chitosan derivatives using Quat-188.
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