Design, synthesis, characterization, and applications of diol monomers, polyimides, and co-polyimides

Figures & data

Figure 1. FT-IR spectrum of diol monomer IVa and polyimide PI-1.

Figure 2. ¹H-NMR spectrum of N,N′-bis(4-hydroxynaphthyl)oxydiphthalic diimide.

Figure 3. ¹³C-NMR spectrum of N,N′-bis(4-hydroxynaphthyl)oxydiphthalic diimide.

Table 1. Properties of PIs and co-PIs.

PIs and co-PIs	IVa	IVb	Yield (%)	ηinh^a (dL/g)	FT-IR (KBr) (cm^−1)	Dielectric constant (εr)
PI-1	100	–	80	0.46	1777,1715,750	3.98
PI-2	75	25	76	0.35	1775,1718,740	4.30
PI-3	50	50	75	0.33	1778,1715,730	3.88
PI-4	25	75	74	0.32	1780,1715,740	4.32
PI-5	–	100	74	0.30	1775,1720,730	4.56

^a Measured with 0.5 g/dL at room temperature in DMSO.

Figure 4. ¹H-NMR spectrum of PI-1.

Figure 5. ¹H-NMR spectrum of PI-5.

Table 2. Solubility characteristics of PIs and co-PIs.

PIs and co-PIs	NMP DMSO	DMF DMAc	Pyridine	THF	o-cresol	CHCl3 methanol	Conc. H2SO4
PI-1	SS	SS	SS	I	SS	I	SS
PI-2	SS	S	S	I	I	I	SS
PI-3	SS	Sw	S	Sw	Sw	I	SS
PI-4	SS	S	I	I	I	I	SS
PI-5	SS	S	I	I	I	I	SS

Notes:

SS = soluble at RT, S = soluble on heating, I = insoluble, S_w = swelling.

Figure 6. Molecular modeling of PI-1.

Figure 7. Molecular modeling of PI-5.

Figure 8. TG and DTA curves of polyimide PI-1.

Table 3. Thermal properties of PIs and co-PIs.

PIs and co-PIs	T10^a	T20^a	Tmax^b	CR (%)^c	Tg^d	LOI^e
PI-1	390	463	475	57	228	40.3
PI-2	390	490	480	62	–	42.3
PI-3	405	491	480	51	–	37.9
PI-4	426	524	495	48	270	36.7
PI-5	452	534	550	62	280	42.3

^a T₁₀ and T₂₀, temperature at 10 or 20% weight loss in N₂ atmosphere.

^b T_max, temperature at the maximum degradation.

^c Percentage char yield at 800 °C.

^d T_g measured by DSC at a heating rate of 10 °C/min in N₂ atmosphere.

^e Limited oxygen index.

Figure 9. DSC curves of polyimides PI-1.

Figure 10. X-ray diffractograms of PIs and co-PIs.

Scheme 1. Synthesis of monomer.

Scheme 2. Synthesis of polyimides and co-polyimides.