Polyimides are mostly synthesized from the condensation between dianhydride
and diamine, known for their excellent thermal stability, good chemical resistance,
and outstanding mechanical properties (Liaw et al. 2012). Besides, polyimides are
also inherently resistant to combustion and do not usually need to be mixed with
flame retardants to get a UL-94 V-0 or VTM-0 rating. Therefore, copolymerizing
aromatic imide groups into the main chain of a TLCP is well-established to enhance
the thermal stability and flame retardance of the resulting polymers (Vlad-Bubulac
et al. 2006; Yang et al. 2009). Serbezeanu et al. synthesized a series of novel
phosphorus-containing polyester-imides via high-temperature polycondensation
in o-dichlorobenzene, in which 1,4-bis[N-(4-hydroxyphenyl) phthalimidyl-5-carboxylate]-2-(6-oxido-6H-dibenzoxaphosphorin-6-yl)-naphtalene derived from
Table 3 Structure composition, thermal transition temperature, liquid crystalline phase, and
decomposition residue of the synthesized copolyesters (Vlad-Bubulac and Hamciuc 2009;
Serbezeanu et al. 2010a)
R
Unit ratio
Thermal transition from DSC
a
LC
phase
Residue
(wt%)
b
X: Y
T g
(
C)
T m1
(
C)
T m2
(
C)
T i
(
C)
–
0: 1
147
268
–
295
Nematic
28
–(CH 2 ) 2 –
0.5: 0.5
138
216
235
309
Nematic
23
–(CH 2 ) 3 –
0.5: 0.5
125
259
282
317
Nematic
22
–(CH 2 ) 4 –
0.5: 0.5
114
236
258
283
Nematic
20
–(CH 2 ) 6 –
0.5: 0.5
102
215
232
298
Nematic
17
–(CH 2 ) 12 – 0.5: 0.5
89
173
199
253
Smectic
14
–(CH 2 ) 12 – 0.95: 0.05 –
181
225
–
Smectic
6
–(CH 2 ) 12 – 0.8: 0.2
–
183
260
–
Smectic
7
–(CH 2 ) 12 – 0.6: 0.4
–
175
256
325
Smectic
11
–(CH 2 ) 12 – 0.4: 0.6
–
173
268
323
Smectic
14
–(CH 2 ) 12 – 0.2: 0.8
–
143
163
312
Nematic
15
T g glass transition temperature, T m1 , T m2 multiple melting temperatures, T i isotropic temperature,
LC liquid crystalline
a Peak temperatures from DSC were taken as the phase transition temperature; (À) denoted transition
not observed
b
Residue at 700
C were detected by TGA at a heating rate of 10
C min
À1 under nitrogen
atmosphere
Scheme 5 Chemical structure of phosphorus-containing main-chain TLCP from sebacoyl chloride, where X and 1-X denote the overall composition, not the block length (Qian et al. 2009)
560
L. Chen and Y.-Z. Wang
and diamine, known for their excellent thermal stability, good chemical resistance,
and outstanding mechanical properties (Liaw et al. 2012). Besides, polyimides are
also inherently resistant to combustion and do not usually need to be mixed with
flame retardants to get a UL-94 V-0 or VTM-0 rating. Therefore, copolymerizing
aromatic imide groups into the main chain of a TLCP is well-established to enhance
the thermal stability and flame retardance of the resulting polymers (Vlad-Bubulac
et al. 2006; Yang et al. 2009). Serbezeanu et al. synthesized a series of novel
phosphorus-containing polyester-imides via high-temperature polycondensation
in o-dichlorobenzene, in which 1,4-bis[N-(4-hydroxyphenyl) phthalimidyl-5-carboxylate]-2-(6-oxido-6H-dibenzoxaphosphorin-6-yl)-naphtalene derived from
Table 3 Structure composition, thermal transition temperature, liquid crystalline phase, and
decomposition residue of the synthesized copolyesters (Vlad-Bubulac and Hamciuc 2009;
Serbezeanu et al. 2010a)
R
Unit ratio
Thermal transition from DSC
a
LC
phase
Residue
(wt%)
b
X: Y
T g
(
C)
T m1
(
C)
T m2
(
C)
T i
(
C)
–
0: 1
147
268
–
295
Nematic
28
–(CH 2 ) 2 –
0.5: 0.5
138
216
235
309
Nematic
23
–(CH 2 ) 3 –
0.5: 0.5
125
259
282
317
Nematic
22
–(CH 2 ) 4 –
0.5: 0.5
114
236
258
283
Nematic
20
–(CH 2 ) 6 –
0.5: 0.5
102
215
232
298
Nematic
17
–(CH 2 ) 12 – 0.5: 0.5
89
173
199
253
Smectic
14
–(CH 2 ) 12 – 0.95: 0.05 –
181
225
–
Smectic
6
–(CH 2 ) 12 – 0.8: 0.2
–
183
260
–
Smectic
7
–(CH 2 ) 12 – 0.6: 0.4
–
175
256
325
Smectic
11
–(CH 2 ) 12 – 0.4: 0.6
–
173
268
323
Smectic
14
–(CH 2 ) 12 – 0.2: 0.8
–
143
163
312
Nematic
15
T g glass transition temperature, T m1 , T m2 multiple melting temperatures, T i isotropic temperature,
LC liquid crystalline
a Peak temperatures from DSC were taken as the phase transition temperature; (À) denoted transition
not observed
b
Residue at 700
C were detected by TGA at a heating rate of 10
C min
À1 under nitrogen
atmosphere
Scheme 5 Chemical structure of phosphorus-containing main-chain TLCP from sebacoyl chloride, where X and 1-X denote the overall composition, not the block length (Qian et al. 2009)
560
L. Chen and Y.-Z. Wang