Synthesis of High Performance Carboxyl-terminated Liquid Fluoroelastomers Based on Fluorination Addition Reaction

doi:10.11901/1005.3093.2024.108

Chinese Journal of Materials Research

2025, Vol. 39

Issue (1): 11-20 DOI: 10.11901/1005.3093.2024.108

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Synthesis of High Performance Carboxyl-terminated Liquid Fluoroelastomers Based on Fluorination Addition Reaction

JIANG Fan¹^,², LI Wantong¹^,², ZHAO Shufa³, SHI Ning¹, ZHANG Mengxia¹, FANG Qinghong¹^,², LI Donghan¹^,²(

)

1 College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142, China
2 Liaoning Provincial Key Laboratory of Rubber & Elastomer, Shenyang University of Chemical Technology, Shenyang 110142, China
3 Shenyang Guide Rubber Products Co. Ltd., Shenyang 110141, China

Cite this article:

JIANG Fan, LI Wantong, ZHAO Shufa, SHI Ning, ZHANG Mengxia, FANG Qinghong, LI Donghan. Synthesis of High Performance Carboxyl-terminated Liquid Fluoroelastomers Based on Fluorination Addition Reaction. Chinese Journal of Materials Research, 2025, 39(1): 11-20.

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Abstract

A high-performance carboxyl-terminated liquid fuoroelastomers (SCTLF) was synthesized by a one-pot oxidative degradation/fluorination addition synergistic reaction for the first time, with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate)(Selectflour) as fluorination reagent, tetrabutylammonium fluoride (TBAF) as nucleophilic reagent, and N-bromosuccinimide (NBS) as electrophilic reagent. This reaction system can simultaneously eliminate the fluorinated double bonds (C=C), increase the fluorine content, enhance their thermal stability, and thereby achieve high performance of the products. The molecular chain structure of the synthesized SCTLF was characterized by using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H-NMR), and fluorine nuclear magnetic resonance (¹⁹F-NMR). Besides, its molecular weight and terminal group content was determined by means of gel permeation chromatography (GPC) and chemical titration method. After the fluorination addition reaction, SCTLF had average molecular weight of 2410, carboxyl content of 2.30%, and C=C content decreased from 0.30 mmol/g to 0.08 mmol/g. The fluorinated C=C conforming to Zaitsev's rule showed high reactivity and complete reaction, while those conforming to Hofmann's rule had some residuals, with a calculated fluorine content of 65.47%. The glass transition temperature (T_g) of SCTLF was -34 ^oC, and its initial thermal decomposition temperature (T_d) significantly increased to 270 ^oC. At 20 ^oC, its dynamic viscosity was 46 Pa·s. The curing of SCTLF with HDI trimer resulted in a cured product with excellent mechanical properties and chemical stability.

Key words: organic polymer materials fluorination addition reaction liquid fluoroelastomers one-pot method

Received: 07 March 2024

ZTFLH:

TQ333.93

Fund: National Natural Science Foundation Youth Fund of China(52003165);Youth Talent Support Program of Liaoning Province(XLYC2203101);Educational Department Foundation of Liaoning Province(LJKMZ20220769);Natural Science Foundation of Liaoning Province(2023-MSLH272);Program for Young & Middle-aged Scientific and Technological Innovative Talents of Shenyang(RC210195);National Science Foundation Training Project for Excellent Young Scholars of SYUCT(2022YQ001)

Corresponding Authors: LI Donghan, Tel: 15904024628, E-mail: lidonghansyuct@126.com

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	JIANG Fan
	LI Wantong
	ZHAO Shufa
	SHI Ning
	ZHANG Mengxia
	FANG Qinghong
	LI Donghan

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https://www.cjmr.org/EN/10.11901/1005.3093.2024.108 OR https://www.cjmr.org/EN/Y2025/V39/I1/11

Temperature / ^oC	$M n ¯$	PDI	COOH / %	C=C / mmol·g^-1
-	2620	1.80	2.45	0.30
10	2510	1.88	1.94	0.26
20	2460	1.93	2.23	0.18
30	2410	1.92	2.25	0.10
40	2430	1.92	2.23	0.12
50	2450	1.92	2.22	0.13
60	2380	2.05	2.21	0.11

Table 1 Effect of reaction temperature on the product structure

Time / h	$M n ¯$	PDI	COOH / %	C=C / mmol·g^-1
-	2620	1.80	2.45	0.30
2	2510	1.88	2.38	0.26
4	2470	1.93	2.33	0.18
6	2480	1.95	2.30	0.14
8	2430	1.93	2.27	0.12
10	2410	1.92	2.25	0.10
12	2450	2.11	2.12	0.10

Table 2 Effect of reaction time on the product structure

[Selectfluor]: [C=C]	$M n ¯$	PDI	COOH / %	C=C / mmol·g^-1
-	2620	1.80	2.45	0.30
1.0:1.0	2430	1.88	2.38	0.14
2.0:1.0	2410	1.85	2.30	0.08
3.0:1.0	2420	1.90	2.30	0.11
4.0:1.0	2490	1.95	2.27	0.13
5.0:1.0	2440	1.92	2.23	0.11

Table 3 Effect of amount of Selectflour on the product structure

[TBAF]: [C=C]	$M n ¯$	PDI	COOH / %	C=C / mmol·g^-1
-	2620	1.80	2.45	0.30
0.5:1.0	2420	1.82	2.36	0.12
1.0:1.0	2410	1.85	2.30	0.08
1.5:1.0	2380	1.93	2.11	0.11
2.0:1.0	2420	2.01	1.98	0.13
2.5:1.0	2480	2.40	1.86	0.13

Table 4 Effect of amount of TBAF on the product structure

[NBS]: [C=C]	$M n ¯$	PDI	COOH / %	C=C / mmol·g^-1
-	2620	1.80	2.45	0.30
0.5/1.0	2410	1.85	2.30	0.08
1.0/1.0	2420	1.82	2.23	0.11
1.5/1.0	2300	1.93	2.20	0.14
2.0/1.0	2440	1.88	2.09	0.12
2.5/1.0	2490	2.07	2.02	0.13

Table 5 Effect of amount of NBS on the product structure

Fig.1 FT-IR spectra of CTLF and SCTLF

Fig.2 ¹H-NMR spectra of CTLF and SCTLF

Fig.3 ¹⁹F-NMR spectra of CTLF and SCTLF

Table 6 Assignments of ¹⁹F-NMR peaks in CTLF and SCTF

Fig.4 GPC spectra of CTLF and SCTLF

Type	$M n ¯$	PDI
CTLF	2620	1.80
SCTLF	2410	1.85

Table 7 Molecular weight and molecular weight distribution of CTLF and SCTLF

Fig.5 Mechanism of fluorination addition reaction

Fig.6 DSC curves of CTLF and SCTLF

Fig.7 TGA (a) and DTG (b) thermograms of CTLF and SCTLF

Fig.8 Dynamic viscosity of CTLF and SCTLF

Fig.9 FT-IR spectra of SCTLF, HDI trimer and cured SCTLF

Fig.10 Curing mechanism of SCTLF

Fig.11 Mechanical properties of cured CTLF and cured SCTLF

Fig.12 Aircraft oil, acid and alkali resistance of cured CTLF and cured SCTLF

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