Synthesis and characterization of novel nanostructured, organosoluble, thermally stable and wholly aromatic poly(amide-imide)s from a new diimide-diacid monomer by direct polycondensation

Figures & data

Figure 1. FT-IR spectrum of diimide-diacid (6).

Figure 2. ¹H-NMR spectrum of the diimide-diacid (6).

Figure 3. FT-IR spectra of the PAI8d (a) and PAI8f (b).

Figure 4. ¹H NMR spectra of the PAI8d (a) and PAI8f (b).

Figure 5. XRD patterns of PAI8a, PAI8c and PAI8f.

Figure 6. FE-SEM images of PAIs.

Figure 7. UV–vis transmission spectra of PAIs film.

Figure 8. The TGA (a) and DTG (b) curves of PAIs.

Scheme 1. Synthesis of diimide-diacid (6).

Scheme 2. Synthesis of PAIs.

Table 1. Synthesis and some physical properties of PAIs.

Diamine	Polymer	Yield (%)^a	ηinh^b	Color
7a	PAI8a	83	0.42	Light yellow
7b	PAI8b	87	0.39	Light yellow
7c	PAI8c	91	0.48	Light yellow
7d	PAI8d	89	o.45	Yellow
7e	PAI8e	86	0.51	Yellow
7f	PAI8f	87	0.37	Brown

^a Polymers were precipitated in methanol.

^b Measured at a concentration of 0.5 g dL⁻¹ in NMP at 25 °C.

Table 2. FT-IR and ¹H NMR data of the PAIs.

Polymer	Spectral data
PAI8a	FT-IR (KBr, cm^−1): 3381 (N–H stretching), 2990 (Ar–H stretching), 1773 (C=O imide, asymmetric stretching), 1715 (C=O imide, symmetric stretching), 1661 (C=O amide, stertching), 1604 (C=C aromatic), 1517 (N–H bending), 1387 (CNC axial stretching), 1187 (CNC transverse stretching), 721 (CNC out-of-plane bending). ^1H NMR (400 MHz, DMSO-d6, ppm): 7.39–8.21 (Ar–H), 10.68 (N–H).
PAI8b	FT-IR (KBr, cm^−1): 3376 (N–H stretching), 3083 (Ar–H stretching), 1776 (C=O imide, asymmetric stretching), 1714 (C=O imide, symmetric stretching), 1658 (C=O amide, stertching), 1607 (C=C aromatic), 1510 (N–H bending), 1377 (CNC axial stretching), 1196 (CNC transverse stretching), 723 (CNC out-of-plane bending).
PAI8c	FT-IR (KBr, cm^−1): 3379 (N–H stretching), 3100 (Ar–H stretching), 1775 (C=O imide, asymmetric stretching), 1718 (C=O imide, symmetric stretching), 1658 (C=O amide, stertching), 1603 (C=C aromatic), 1510 (N–H bending), 1377 (CNC axial stretching), 1192 (CNC transverse stretching), 1059 (C–O stretching), 726 (CNC out-of-plane bending). ^1H NMR (400 MHz, DMSO-d6, ppm): 7.27–8.57 (Ar–H), 10.68 (N–H).
PAI8e	FT-IR (KBr, cm^−1): 3379 (N–H stretching), 3108 (Ar–H stretching), 2983 (C–H stretching, aliphatic) 1773 (C=O imide, asymmetric stretching), 1719 (C=O imide, symmetric stretching), 1657 (C=O amide, stertching), 1600 (C=C aromatic), 1512 (N–H bending), 1379 (CNC axial stretching), 1190 (CNC transverse stretching), 728 (CNC out-of-plane bending).

Table 3. Elemental analysis of PAIs.

Polymer	Formula (formula weight)^a		Elemental analysis (%)
			C	H	N
PAI8a	(C43H23N5O8)n	Calcd.	69.94	3.11	9.49
	(737.74)n	Found.	69.38	3.27	9.21
PAI8c	(C49H27N5O9)n	Calcd.	70.85	3.25	8.43
	(829.84)n	Found.	70.18	3.47	8.59
PAI8e	(C50H29N5O8)n	Calcd.	72.47	3.50	8.45
	(827.86)n	Found.	71.92	3.79	8.11
PAI8f	(C62H35N5O8)n	Calcd.	76.07	3.57	7.15
	(978.04)n	Found.	75.23	3.66	7.39

^a The polymer sample was dried in vacuum at 80 °C for 5 h.

Table 4. Quantitative solubility^a of the PAIs.

Polymer	Solvent
	NMP	DMAc	DMF	DMSO	m-Cresol	Py	DO	CHCl3
PAI8a	++	+	+	+	±	±	–	–
PAI8b	++	++	++	++	+	+	–	–
PAI8c	++	++	++	++	±	±	–	–
PAI8d	++	++	++	++	±	±	–	–
PAI8e	++	++	++	++	±	+	–	–
PAI8f	++	++	++	++	±	±	–	–

Note: (++) Soluble at room temperature, (+) soluble after heating, (±) partially soluble, (–) insoluble.

^a Measured at a polymer concentration of 0.05 g/ml.

Table 5. Optical properties of the PAIs.

Polymer	λmax (nm)		λonset (nm)		λ0 (nm)
	Solution^a	Film^b	Solution^a	Film^b
PAI8a	301	307	421	411	459
PAI8b	297	303	409	420	463
PAI8c	305	294	427	431	465
PAI8d	298	308	436	415	473
PAI8e	311	302	417	429	468
PAI8f	304	299	403	414	471

^a From UV–vis absorption spectra measured in NMP solution (0.2 g/dL) at room temperature.

^b The cut off wavelengths (λ₀) from the transmission UV–vis spectra of PAI films.

Table 6. Thermal characteristic data of PAIs.

Polymer	Decomposition temperature (°C)				CR^c	LOI^d	∆Hcomb(kJ/g)^e
	Ti ^a	T5 ^a	T10 ^a	Tmax ^b
PAI8a	412	428	503	536	71.3	46.0	17.4
PAI8b	407	421	499	521	63.1	42.7	18.7
PAI8c	413	431	461	483	57.4	40.4	19.8
PAI8d	417	437	453	492	60.0	41.5	19.3
PAI8e	396	413	446	481	53.4	38.9	20.5
PAI8f	433	476	537	539	75.9	47.9	16.7

^a The initial decomposition temperature and temperature at which 5 and 10% weight loss was recorded by TGA at a heating rate of 20 °C/min in a nitrogen atmosphere.

^b The temperature of the maximum speed of decomposition at a heating rate of 20 °C/min in a nitrogen atmosphere.

^c Percentage weight of material left undecomposed after TGA analysis at 800 °C in a nitrogen atmosphere.

^d LOI evaluating at char yield at 800 °C.

^e The specific heat of combustion evaluating at LOI.