后磺化法精确可控制备磺化聚芳醚砜及其质子交换膜性能

doi:10.7503/cjcu20170842

摘要/Abstract

摘要：

以不同配比4,4'-二氟二苯砜、 4,4'-联苯二酚和4,4'-二羟基二苯砜为单体, 经共聚合得到具有不同高分子量的聚芳醚砜. 由于聚合物上联苯和苯砜片段的电子效应差异较大, 使磺化反应容易发生在电子云密度较高的联苯片段上. 因此采用简单温和的后磺化法, 使磺化聚芳醚砜中的磺酸基团精确接入到主链联苯片段中的醚键邻位上, 并且磺化度可预测. 研究结果表明, 制备的磺化聚芳醚砜(M-SPAES)中的磺酸基团被精确接入到主链上联苯片段中的醚键邻位, 其相对黏度均在1.2 dL/g以上. 质子交换膜(PEM)的离子交换容量(IEC)测定值与理论值完全一致. 膜的吸水率与尺寸变化率随IEC和温度的提高而显著增加, 并且膜平面方向的尺寸变化率小于膜厚方向. 热重分析显示, 所制备的磺化聚芳醚砜在280 ℃以上开始降解. 在20 ℃, 20%相对温度(RH)下, 膜的最大拉伸强度均大于50 MPa, 断裂伸长率在15%以上. PEM在Fenton’s试剂中的破碎时间随IEC的增加而缩短, 在20 ℃时, IEC较小的PEM的破碎时间可达到200 h以上. PEM的质子传导率(σ)随温度和IEC的增加而显著提高. 在H₂/O₂燃料电池性能测试中, 电池温度为60 ℃, 加湿度为80% RH, 背压为0.1 MPa时, 开路电压(OCV)为1.0 V以上, 最大功率可达0.54 W/cm².

关键词: 磺化聚芳醚砜, 质子交换膜, 后磺化法, 可控磺化度

Abstract:

A series of poly(arylene ether sulfone)s with high molecular weight was prepared from 4-fluorophenyl sulfone, 4,4'-biphenol and bis(4-hydroxyphenyl) sulfone with different mole ratio. Due to the large difference between the electronic effects of biphenyl fragment and phenyl sulfone fragment on the polymer, the sulfonation reaction is easily carried out on biphenyl fragments with higher electron cloud density. The sulfonic acid groups were introduced to ortho-position of the oxy ether group on the biphenyl and sulfonation degree were successfully predicted after post-sulfonation process. Sulfonated polylarylene ether sulfone(SPAES)-based proton exchange membranes(PEM) were prepared by solution casting method, of which relative viscosity, ion exchange capacity(IEC), water uptake and swell ratio, proton conductivity, oxidative stability, mechanical properties and cell performance were investigated. Relative viscosity of sulfonated copolymers was higher than 1.2 dL/g. The sulfonated copolymers showed that titration and ¹H nuclear magnetic resonance calculated value of IEC were accordingly to that of theoretical. Water uptake and swell ratio obviously increased with increasing of IEC and temperature, and the size change ratio of the thickness direction was larger than that of plane direction in the membranes. The thermal gravimetric analyse(TGA) results indicated that the PEMs have the decompose temperature at about 280 ℃. All the PEMs showed maximum tensile strength above 50 MPa, and the elongation at break over 15% at 20 ℃ and 20% RH. Free radical oxidative stability test showed the PEMs with low IEC become brittle in Fenton’s reagent over 200 h at 20 ℃. The proton conductivity of PEMs were increased rapidly with the increase of the IEC and temperature, for example, the conductivity of M2-SPAES(1.34 mmol/g) and M4-SPAES(1.60 mmol/g) were 68 and 89 mS/cm at 60 ℃ in water, and 99 and 129 mS/cm at 80 ℃ in water, respectively. H₂/O₂ Fuel cell performance showed that the open circuit voltage and maximum power output were higher than 1.0 V and 0.54 W/cm² under 60 ℃, 80% RH and 0.1 MPa back pressure, respectively.

Key words: Sulfonated poly(arylene ether sulfone), Proton exchange membrane, Post-sulfonation, Controlled sulfonated degree

中图分类号:

O631

TrendMD:

肖磊, 张晨, 何美玉, 陈康成. 后磺化法精确可控制备磺化聚芳醚砜及其质子交换膜性能. 高等学校化学学报, 2018, 39(6): 1281.

XIAO Lei, ZHANG Chen, HE Meiyu, CHEN Kangcheng. Precise Controllable Post-sulfonation for Preparation of Sulfonated Poly(arylene ether sulfone)s and Their Properties for Proton Exchange Membrane^†. Chem. J. Chinese Universities, 2018, 39(6): 1281.

图/表 10

Scheme 1 Synthetic routes of M-SPAES polymer

Fig.1 1H NMR spectra of DB, SDB before(A) and after sulfonation(B) in DMSO-d6

Fig.2 1H NMR spectra of copolymers in DMSO-d6a. M3-SAPES; b. M5-SAPES; c. M7-SAPES; d. M7-PAES.

Table 1 Physical properties of polymers and membranes

Polymer	IEC/(mmol·g^-1)			Water uptake(%)			Swell ratio(%)				η_r ^f	λ^g
	Theo.^a	Titr.^b	NMR^c	30 ℃	60 ℃	80 ℃	30 ℃		60 ℃
	Theo.^a	Titr.^b	NMR^c	30 ℃	60 ℃	80 ℃	Δ $l d c$	Δ $l e c$	Δ $l d c$	Δ $l e c$
M1-SPAES	1.09	1.03	1.05	32	39	42	4	20	7	25	1.16	17
M2-SPAES	1.34	1.26	1.31	44	57	67	5	25	11	28	1.49	18
M3-SPAES	1.50	1.44	1.49	60	81	128	9	26	11	29	1.52	22
M4-SPAES	1.60	1.54	1.57	65	84	133	10	28	15	35	1.70	23
M5-SPAES	1.70	1.63	1.65	70	121	163	15	31	23	39	1.85	23
M6-SPAES	1.83	1.80	1.89	78	133	188	16	34	28	44	1.95	24
M7-SPAES	1.95	1.94	1.95	106	249	467	25	36	29	45	2.10	30
M8-SPAES	2.30	2.23	2.28	170	—	—	31	40	—	—	2.67	41
R1-SPAES	1.56	1.41	—	27	37	42	11	10	—	—	1.51	17
R2-SPAES	1.80	1.63	—	37	50	61	13	14	—	—	1.55	21

Table 1 Physical properties of polymers and membranes

Polymer	IEC/(mmol·g^-1)			Water uptake(%)			Swell ratio(%)				η_r ^f	λ^g
	Theo.^a	Titr.^b	NMR^c	30 ℃	60 ℃	80 ℃	30 ℃		60 ℃
	Theo.^a	Titr.^b	NMR^c	30 ℃	60 ℃	80 ℃	Δ $l d c$	Δ $l e c$	Δ $l d c$	Δ $l e c$
M1-SPAES	1.09	1.03	1.05	32	39	42	4	20	7	25	1.16	17
M2-SPAES	1.34	1.26	1.31	44	57	67	5	25	11	28	1.49	18
M3-SPAES	1.50	1.44	1.49	60	81	128	9	26	11	29	1.52	22
M4-SPAES	1.60	1.54	1.57	65	84	133	10	28	15	35	1.70	23
M5-SPAES	1.70	1.63	1.65	70	121	163	15	31	23	39	1.85	23
M6-SPAES	1.83	1.80	1.89	78	133	188	16	34	28	44	1.95	24
M7-SPAES	1.95	1.94	1.95	106	249	467	25	36	29	45	2.10	30
M8-SPAES	2.30	2.23	2.28	170	—	—	31	40	—	—	2.67	41
R1-SPAES	1.56	1.41	—	27	37	42	11	10	—	—	1.51	17
R2-SPAES	1.80	1.63	—	37	50	61	13	14	—	—	1.55	21

Fig.3 FTIR spectra of un-sulfonated and sulfonated copolymersa. M3-SAPES; b. M5-SAPES; c. M7-SAPES; d. M7-PAES.

Fig.4 TGA curves of the membranesa. M1-SPAES; b. M3-SPAES; c. M5-SPAES; d. M7-SPAES.

Table 2 TGA and proton conductivity of PEMs

Polymer	IEC/(mmol·g^-1)	TGA		σ/(mS·cm^-1)			E_a/(kJ·mol^-1)
Polymer	IEC/(mmol·g^-1)	T_d1/℃	T_d2/℃	40 ℃	60 ℃	80 ℃	E_a/(kJ·mol^-1)
M1-SPAES	1.09	298	494	31	57	94	26.7
M2-SPAES	1.34	290	463	44	68	99	19.1
M3-SPAES	1.50	293	506	48	74	110	18.9
M4-SPAES	1.60	287	488	57	89	129	19.5
M5-SPAES	1.70	286	499	87	129	175	17.2
M6-SPAES	1.83	283	491	102	142	184	14.5
M7-SPAES	1.95	306	483	108	161	188	17.5
M8-SPAES	2.30	311	496	126	178	211	15.1
R1-SPAES	1.56	—	—	68	85	117	14.0
R2-SPAES	1.80	—	—	107	133	158	9.6
SPAES40^[10]	1.51	—	—	71	83	127	6.8
SPES-20^[28]	1.61	—	—	100	111	142	4.6
Nafion	0.91	—	—	104	142	179	12.6

Table 3 Mechanical properties and oxidative stability of PEMs

Polymer	IEC/(mmol·g^-1)	Y^a/GPa	S^b/MPa	E^c(%)	Oxidative stability^d
Polymer	IEC/(mmol·g^-1)	Y^a/GPa	S^b/MPa	E^c(%)	t/h(20 ℃)	t/min(80 ℃)
M1-SPAES	1.09	1.19	56	15	216	84
M2-SPAES	1.34	1.32	61	28	209	65
M3-SPAES	1.50	1.26	60	15	198	57
M4-SPAES	1.60	1.25	57	26	183	43
M5-SPAES	1.70	1.36	52	18	175	24
M6-SPAES	1.83	1.23	58	28	167	17
M7-SPAES	1.95	1.29	54	24	167	9
M8-SPAES	2.23	1.34	51	16	112	5
R1-SPAES	1.56	0.91	50	15	—	—
R2-SPAES	1.80	0.96	54	11	—	—

Fig.5 Temperature dependence of proton conductivity of membranesa. M2-SPAES; b. M3-SPAES; c. M4-SPAES; d. M6-SPAES; e. R1-SPAES; f. R2-SPAES; g. Nafion.

Fig.6 PEMFC performances for M2-SPAES(●, ○) and M4-SPAES(▲, △) membranes at 60 ℃, 80% RH and 0.1 MPa back pressure

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