苯并己内酯的开环聚合及其与环氧化合物共聚合研究

doi:10.6023/A25060226

摘要/Abstract

聚酯作为一类重要的高分子材料, 凭借其优异的性能在众多领域得到广泛应用, 并在全球塑料市场中占据约10%的份额, 对塑料经济的发展起到了关键作用. 然而, 废弃塑料所带来的日益严重的环境问题, 促使学术界和工业界将目光聚焦于开发具有闭环化学回收性能的新型聚酯材料. 以市售的α-四氢萘酮作为起始原料, 通过简单的Baeyer- Villiger氧化反应合成了一种芳香族苯并己内酯单体, 即4,5-二氢苯并[b]氧杂䓬-2(3H)-酮(DHBO). 利用1,5,7-三氮杂二环[4,4,0]癸-5-烯(TBD)为催化剂, 深入研究了不同聚合条件下DHBO的开环聚合行为, 制备了一种玻璃化转变温度T_g为4.8 ℃, 热分解温度T_d,5%为194 ℃的聚合物Poly(DHBO). 动力学实验表明在甲苯中聚合速率对单体浓度为一级反应. 该聚合物在无催化剂、110 ℃减压条件下能快速热降解为原始单体DHBO, 单体回收率高达97%, 纯度达到99%, 展现出优异的化学回收性能. 此外, 以双(三苯基正膦基)氯化铵(PPNCl)为催化剂, 采用本体熔融聚合方法, 使DHBO与多种环氧化合物[苯基缩水甘油醚(PGE)、烯丙基缩水甘油醚(AGE)、1,2-环氧丁烷(BO)、(R)-BO、(S)-BO、1,2-环氧己烷(HO)及环氧环己烷(CHO)]发生开环共聚反应, 成功制备了一系列聚(醚-酯)材料. 采用核磁共振氢谱(¹H NMR)、碳谱(¹³C NMR)、扩散排序谱(DOSY NMR)以及基质辅助激光解吸飞行时间质谱(MALDI-TOF MS)对代表性共聚合物进行表征, 证实所得聚(醚-酯)为含有醚键和酯基高度交替序列的共聚物. 通过对这些交替共聚物的形成机理进行深入探究, 进一步揭示了其独特的聚合反应机制.

关键词: 芳香族聚酯, 闭环化学回收, 开环聚合, 交替共聚物, 聚(醚-酯)

As an important type of polymer material, polyester is widely used due to its diverse properties and plays a significant role in the plastic economy, accounting for about 10% of the global plastic market. Facing the environmental problems caused by discarded plastics, the development of new types of polyesters with closed-loop chemical recycling properties has become the focus of attention in both academic and industrial research. In this work, benzo-fused caprolactone 4,5-dihydrobenzo[b]oxepin-2(3H)-one (DHBO) was synthesized from α-tetrahydronaphthone via Baeyer-Villiger oxidation reaction, and structurally characterized via NMR spectroscopy and single crystal X-ray diffraction. The ring-opening polymerization of DHBO under varied conditions was investigated using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, and the molecular weights of the resultant poly(DHBO) obtained via gel permeation chromatography are lower than theoretical values due to transesterification. The polymerization kinetics of DHBO in toluene with TBD/4-MeBnOH shows a first-order dependence on DHBO concentration. The poly(DHBO) is amorphous with a glass transition temperature T_g of 4.8 ℃, and a thermal decomposition temperature T_d (5% weight loss) of 194 ℃, which can be enhanced to 252 ℃ by capped the chain-end OH group with acetyl. In addition, the polyester can be rapidly thermally degraded into the initial monomer DHBO without any catalyst at 110 ℃ under reduced pressure, with a recovery rate of 97% and a monomer purity of 99%. Moreover, using bis(triphenylphosphine) iminium chloride (PPNCl) as the catalyst, DHBO can undergo ring-opening copolymerization with commercial epoxides, such as phenyl glycidyl ether (PGE), allyl glycidyl ether (AGE), 1,2-butylene oxide (BO), (R)-(BO), (S)-(BO), 1,2-hexene oxide (HO) and cyclohexene oxide (CHO) in bulk, producing poly(ether-ester) with highly alternating sequences. Representative copolymers were characterized with NMR spectroscopy (¹H, ¹³C, DOSY) and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). These poly(ether-ester)s showed good thermal stability with T_d over 290 ℃, where the poly((S)-BO-alt-DHBO) exhibited the highest T_d of 353 ℃. The structure of epoxides effected the T_gs of corresponding poly(ether-ester), and wide range of T_g from －19 ℃ to 43 ℃ can be regulated. Finally, the mechanism of the alternating poly(ether-ester) formation was investigated.

Key words: aromatic polyester, closed-loop chemical recycling, ring-opening polymerization, alternating polymer, poly(ether-ester)

引用此文

石力双, 戴雅男, 伍伟豪, 李世辉, 牟泽怀. 苯并己内酯的开环聚合及其与环氧化合物共聚合研究[J]. 化学学报, 2025, 83(12): 1488-1497.

Lishuang Shi, Yanan Dai, Weihao Wu, Shihui Li, Zehuai Mou. Ring-opening Polymerization of Benzo-fused Caprolactone and its Copolymerization with Epoxides[J]. Acta Chimica Sinica, 2025, 83(12): 1488-1497.

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图/表 13

图1. 代表性的芳香族内酯单体

Figure 1. Representative aromatic lactone

图式1. 单体DHBO的合成

Scheme 1. Synthesis of DHBO

图2. 单体DHBO的单晶结构

Figure 2. X-ray crystal structure of DHBO Thermal ellipsoids are drawn at the 30% probability level. Selected bond lengths (nm) and angles (°): C(1)—O(1) 0.1364(2), C(1)—O(2) 0.11993(19), C(10)—O(1) 0.14052(18), O(1)—C(1)—O(2) 117.57(14), C(2)—C(1)—O(2) 117.29(13), C(1)—O(1)—C(10) 120.60(11)

Entry	[M]₀/[Cat.]/[ROH]	Solvent	[M]₀/(mol•L^－1)	t/h	T/℃	Conv.^b/%	M_n,_GPC^c/(kg•mol^－1)	Ð^c
1	100/1/1	toluene	1	5	r.t.	73	4.79	1.88
2	100/1/1	toluene	2	5	r.t.	85	7.17	1.86
3	100/1/1	toluene	4	5	r.t.	93	6.06	1.62
4	100/1/1	THF	2	5	r.t.	77	6.03	1.62
5	100/1/1	DMF	2	5	r.t.	36	1.36	1.89
6	100/1/1	DCM	2	5	r.t.	48	3.00	1.24
7	100/1/1	DCM	2	24	r.t.	55	8.75	2.15
8	100/1/1	—	—	10 min	90	90	7.49	2.09
9	100/1/1	—	—	10 min	110	92	6.21	1.93
10	300/1/1	—	—	0.5	90	84	9.00	1.89
11	500/1/1	—	—	0.5	90	80	10.20	2.00

表1. TBD催化DHBO的均聚合a

Table 1. Homopolymerization of DHBO mediated with TBD

图3. DHBO聚合动力学

Figure 3. Semilogarithmic plots of DHBO conversion versus the reaction time Conditions: [DHBO]/[TBD]/[4-MeBnOH]=100/1/1, [DHBO]0=1.0 mol/L in toluene

图4. 具有不同链末端的Poly(DHBO)s的热重分析

Figure 4. TGA curves of Poly(DHBO)s with different chain-ends

图5. Poly(DHBO)减压条件下的热降解以及原始DHBO、poly(DHBO)和回收DHBO的核磁共振氢谱(CDCl3, 400 MHz)

Figure 5. Thermal depolymerization of Poly(DHBO) under reduced pressure and the stacked 1H NMR spectra of starting DHBO, poly(DHBO) and recycled DHBO (CDCl3, 400 MHz)

Entry	[Epoxide]₀/[M]₀/[PPNCl]₀	Epoxide	T/℃	Conv.^b/%	Alternating^c/%	Regioselectivity^c/%	M_n^d/kDa	Ð^d
1	—/100/1	—	110	0			—	—
2	20/—/1	PGE	110	16			—	—
3	200/100/1	PGE	110	>99	98	99	14.4	1.45
4	200/100/1	PGE	90	95	98	98	15.0	1.47
5	200/100/1	PGE	60	75	96	94	4.75	1.31
6	200/100/1	AGE	110	>99	96	97	16.1	1.38
7	200/100/1	BO	110	>99	97	97	13.0	1.37
8^e	200/100/1	R-BO	110	>99	98	97	8.9	1.67
9^e	200/100/1	S-BO	110	>99	98	97	6.6	1.62
10	200/100/1	HO	110	>99	96	98	8.8	1.34
11	200/100/1	CHO	110	>99	95	—	11.3	1.39

表2. PPNCl催化DHBO和环氧化合物的共聚合a

Table 2. Copolymerization of DHBO with epoxides using PPNCl

图6. Poly(PGE-alt-DHBO)中酯基的1H NMR谱(CDCl3, 400 MHz)和羰基区域的13C NMR谱(CDCl3, 100 MHz)

Figure 6. 1H NMR spectrum (CDCl3, 400 MHz) of ester group region and 13C NMR spectrum (CDCl3, 100 MHz) of carbonyl region

图7. Poly(PGE-alt-DHBO)中酯基和醚键区域的1H NMR谱 (CDCl3, 400 MHz)

Figure 7. 1H NMR spectrum of obtained Poly(PGE-alt-DHBO) in CDCl3, only phenol ether and ester were shown for regioselective analyses (CDCl3, 400 MHz)

图8. 交替共聚物Poly(epoxide-alt-DHBO)的热重分析

Figure 8. TGA curves of Poly(epoxide-alt-DHBO)

图9. 交替共聚物poly(epoxide-alt-DHBO)的差示扫描量热第二次升温曲线(10 ℃/min)

Figure 9. DSC second heating curves of poly(epoxide-alt-DHBO) (10 ℃/min)

图式2. 交替聚(醚-酯)的形成机理

Scheme 2. Proposed mechanism of the alternating poly(ether-ester) formation

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