Review on synthesis of polyether-co-polyester from copolymerization of epoxides and lactones

doi:10.11949/0438-1157.20200944

Abstract

Abstract:

As a high-performance, multi-purpose biodegradable material, aliphatic polyester is considered to be one of the attractive alternatives to petroleum-based polymers. However, they often suffer from drawbacks, such as hydrophobicity and brittleness due to their single structure nature, which limits its application in biomedical and pharmaceutical industries. Thus, the modification of polyester is of great theoretical significance and practical application, of which one efficient way is to incorporate the aliphatic polyethers segments into the main chain of polyesters. Herein, this review aims to describe the synthesis of polyester-polyether copolymers by the copolymerization of lactones and epoxides, including random, block, and alternating copolymers.

Key words: epoxide, lactone, polymerization, polyester-polyether copolymer, synthesis, catalysis

摘要：

脂肪族聚酯作为一种高性能、多用途的生物可降解材料，被认为是具有吸引力的石油基聚合物替代品之一。现有的脂肪族聚酯存在的结构单一、亲水性差以及脆性较强等缺点，限制了其在医药卫生等领域的应用。因此，高效地实现聚酯的改性具有重要的理论研究意义和实际应用价值。其中，将醚类官能团与酯链段相结合得到聚醚-聚酯共聚物是提高聚酯性能的一类行之有效的改性方法。本文综述了内酯和环氧烷烃共聚合成聚酯-聚醚共聚物的研究进展。以共聚物的主链序列分类，分别介绍了嵌段、无规以及交替共聚物的合成方法以及相应聚合物的性质和性能。

关键词: 环氧烷烃, 内酯, 聚合, 聚酯-聚醚共聚物, 合成, 催化

CLC Number:

TQ 317.3

GAO Hongjuan,REN Weimin. Review on synthesis of polyether-co-polyester from copolymerization of epoxides and lactones[J]. CIESC Journal, 2021, 72(1): 440-451.

高宏娟,任伟民. 内酯和环氧烷烃共聚合成聚酯-聚醚共聚物的研究进展[J]. 化工学报, 2021, 72(1): 440-451.

Figures/Tables 21

References 70

1	Williams C K. Synthesis of functionalized biodegradable polyesters[J]. Chem. Soc. Rev., 2007, 36(10): 1573-1580.
2	Xu Y H, Zhou F Y, Zhou D M, et al. Degradation behaviors of biodegradable aliphatic polyesters and polycarbonates[J]. J. Biobased Mater. Bio., 2020, 14(2): 155-168.
3	Iman M, Ali F, Fariba D, et al. Biomedical applications of biodegradable polyesters[J]. Polymers, 2016, 8(1): 20.
4	丁良怡, 种刚刚, 潘江, 等. 生物转化脂肪酸合成ω-羟基酸和ω-氨基酸研究进展[J]. 化工学报, 2020, 71(9): 3919-3932.
	DING L Y, CHONG G G, PAN J, et al. Advances in biosynthesis of fatty acids to ω-hydroxyacids and ω-amino acids[J]. CIESC Journal, 2020, 71(9): 3919-3932.
5	Gross R A, Kalra B. Biodegradable polymers for the environment[J]. Science, 2002, 297(5582): 803-807.
6	丁颂东. 脂肪族聚酯的降解与稳定研究[D]. 成都, 四川大学, 2006.
	Ding S D. Degradation and stability of aliphatic polyesters[D]. Chengdu: Sichuan University, 2006.
7	王国利, 徐军, 郭宝华. 可生物降解聚丁二酸丁二醇酯及其共聚物的合成及改性研究进展[J]. 高分子通报, 2011, (4): 99-109.
	Wang G L, Xu J, Guo B H. Development in synthesis and modification of biodegradable poly(butylene succinate) and its copolymers[J]. Chin. Polym. Bull., 2011, (4): 99-109.
8	白桢慧, 苏婷婷, 王战勇. 可降解脂肪族聚酯的合成及酶解性能研究[J]. 化工新型材料, 2019, 47(3): 152-156.
	Bai Z H, Su T T, Wang Z Y. Study on the synthesis and enzymatic hydrolysis of biodegradable aliphatic polyester[J]. New Chem. Mater., 2019, 47(3): 152-156.
9	Tokiwa Y, Calabia B P. Biodegradability and biodegradation of poly(lactide)[J]. Appl. Microbiol. Biotechnol., 2006, 72(2): 244-251.
10	潘招银, 蔡培展. 聚乳酸: 让微生物降解塑料[J]. 广州化工, 2019, 47(5): 11-12.
	Pan Z Y, Cai P Z. Polylactic acid: allow microorganism degrade plastics[J]. Guangzhou Chem. Ind., 2019, 47(5): 11-12.
11	Nampoothiri K M, Nair N R, John R P. An overview of the recent developments in polylactide (PLA) research[J]. Bioresource Technol., 2010, 101(22): 8493-8501.
12	王身国, 贝建中. 生物降解高分子——一类重要的生物材料(2): 生物相容性及脂肪族聚酯的表面改性[J]. 高分子通报, 2017, (11): 1-14.
	Wang S G, Bei J Z. Biodegradable polymer——a kind important biomaterial(2): Biocompatibility and surface modification of aliphatic polyester[J]. Chin. Polym. Bull., 2017, (11): 1-4.
13	杜娟敏, 赵雄燕, 孙璐, 等. 功能化可降解脂肪族聚酯的研究进展[J]. 塑料, 2014, (1): 43-47.
	Du J M, Zhao X Y, Sun L, et al. Research progress in functionalized biodegradable aliphatic polyesters[J]. Plast., 2014, (1): 43-47.
14	王景昌, 杨昌盛, 万泽韬, 等. 生物医用脂肪族聚酯开环聚合的研究进展[J]. 高分子通报, 2018, 236(12): 34-39.
	Wang J C, Yang C S, Wan Z T, et al. Research progress of ring-opening polymerization for biomedical aliphatic polyester[J]. Chin. Polym. Bull., 2018, 236(12): 34-39.
15	Hoglund A, Hakkarainen M, Albertsson A C. Migration and hydrolysis of hydrophobic polylactide plasticizer[J]. Biomacromolecules. 2010, 11(1): 277-283.
16	李凯. 聚对苯二甲酸乙二醇酯(PET)的阻隔性研究[D]. 天津: 天津科技大学, 2014.
	Li K. Study on barrier properties of PET[D]. Tianjin: Tianjin University of Science and Technology, 2014.
17	Zhang X Y, Fevre M, Waymouth R M, et al. Catalysis as an enabling science for sustainable polymers[J]. Chem. Rev., 2018, 118(2): 839-885.
18	Zhang H B, Zheng W G, Yu Z Z, et al. Electrically conductive polyethylene terephthalate/graphene nanocomposites prepared by melt compounding[J]. Polymer, 2010, 51(5): 1191-1196.
19	Herzberger J, Niederer K, Frey H, et al. Polymerization of ethylene oxide, propylene oxide, and other alkylene oxides: synthesis, novel polymer architectures, and bioconjugation[J]. Chem. Rev., 2016, 116(4): 2170-2243.
20	Klein R, Wurm F R. Aliphatic polyethers: classical polymers for the 21st century[J]. Macromol. Rapid Commun., 2015, 36(12): 1147-1165.
21	Brocas A L, Mantzaridis C, Carlotti S, et al. Polyether synthesis: from activated or metal-free anionic ring-opening polymerization of epoxides to functionalization[J]. Prog. Polym. Sci., 2013, 38(6): 845-873.
22	安秋凤, 李歌, 杨刚. 聚醚型聚硅氧烷的研究进展及应用[J]. 化工进展, 2008, 27(9): 77-82.
	An Q F, Li G, Yang G. Research progress and application of polyether/polysiloxane[J]. Chem.Ind. Eng. Prog., 2008, 27(9): 77-82.
23	尹丹娜, 郑成, 张利萍, 等. 聚醚改性三硅氧烷表面活性剂的合成与表征[J]. 化工学报, 2010, 61(6): 1565-1570.
	Yi D N, Zheng C, Zhang L P, et al. Synthesis and characterization of polyether modified trisiloxanes[J]. CIESC Journal, 2010, 61(6): 1565-1570.
24	张敏, 夏青, 王昊, 等. 聚醚型与聚酯型聚氨酯弹性体的性能研究[J]. 塑料工业, 2013, 41(2): 87-89, 114.
	Zhang M, Xia Q, Wang H, et al. Study on properties of polyether and polyester polyurethane elastomer[J]. China Plast. Ind., 2013, 41(2): 87-89, 114.
25	Morris L S, Childers M I, Coates G W. Bimetallic chromium catalysts with chain transfer agents: a route to isotactic poly(propylene oxide)s with narrow dispersities[J]. Angew. Chem. Int. Ed., 2018, 57(20): 5731-5734.
26	Childers M I, Zimmerman P M, Coates G W, et al. Isospecific, chain shuttling polymerization of propylene oxide using a bimetallic chromium catalyst: a new route to semicrystalline polyols[J]. J. Am. Chem. Soc., 2017, 139(32): 11048-11054.
27	Ahmed S M, Coates G W, Cavallo L, et al. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: a mechanistic study[J]. J. Am. Chem. Soc., 2013, 135(50): 18901-18911.
28	Widger P C B, Ahmed S M, Coates G W, et al. Isospecific polymerization of racemic epoxides: a catalyst system for the synthesis of highly isotactic polyethers[J]. Chem. Commun., 2010, 46(17): 2935-2937.
29	Hirahata W, Thomas R M, Coates G W, et al. Enantioselective polymerization of epoxides: a highly active and selective catalyst for the preparation of stereoregular polyethers and enantiopure epoxides[J]. J. Am. Chem. Soc., 2008, 130(52): 17658-17659.
30	Thomas R M, Widger P C B, Coates G W, et al. Enantioselective epoxide polymerization using a bimetallic cobalt catalyst[J]. J. Am. Chem. Soc., 2010, 132(46): 16520-16525.
31	Widger P C B, Ahmed S M, Coates G W. Exploration of cocatalyst effects on a bimetallic cobalt catalyst system: enhanced activity and enantioselectivity in epoxide polymerization[J]. Macromolecules, 2011, 44(14): 5666-5670.
32	Wang B T, Zhang Y, Guo Z H, et al. Biodegradable aliphatic/aromatic copoly(ester-ether)s: the effect of poly(ethylene glycol) on physical properties and degradation behavior[J]. J. Polym. Res., 2011, 18(2): 187-196.
33	赵三平, 尹玥, 冯增国. PCL-PEG-PCL嵌段共聚物的合成与性能[J]. 功能高分子学报, 2002, 15(1): 67-71.
	Zhao S P, Yin Y, Feng Z Z. Synthesis and properties of PCL-PEG-PCL block copolymer[J]. Funct. Polym., 2002, 15(1): 67-71.
34	成澄, 杨瑞, 郑毅, 等. 两亲性多嵌段共聚物的合成及自组装[J]. 高分子材料科学与工程, 2019, 35(10): 43-48.
	Cheng C, Yang R, Zheng Y, et al. Synthesis and self-assembly of amphiphilic multi-block copolymers[J]. Polym. Master. Sci. Eng., 2019, 35(10): 43-48.
35	张文君, 王晴, 吴梦婷, 等. 聚合物PEG-PLGA在纳米给药系统中的应用研究进展[J]. 药学研究, 2019, 38(9): 532-538.
	Zhang W J, Wang Q, Wu M T, et al. Research progress on polymer PEG-PLGA in nano drug delivery system[J]. 2019, 38(9): 532-538.
36	张勇, 冯增国, 刘凤香, 等. 聚对苯二甲酸丁二醇酯-co-聚丁二酸丁二醇酯-b-聚乙二醇嵌段共聚物的合成及表征[J]. 化学学报, 2002, 60(12): 2225-2231.
	Zhang Y, Feng Z G, Liu F X, et al. Synthesis and Characterization of poly(butylene terephthalate)-co-poly(butylene succinate)-b-poly(ethylene glycol) segmented block copolymers[J]. Acta Chimica Sinica, 2002, 60(12): 2225-2231.
37	Tan C, Chen C. Emerging palladium and nickel catalysts for copolymerization of olefins with polar monomers[J]. Angew. Chemie., 2019, 131(22): 7268-7276.
38	Paul S, Zhu Y Q, Williams C K. Ring-opening copolymerization (ROCOP): synthesis and properties of polyesters and polycarbonates[J]. Chem. Commun., 2015, 51(30): 6459-6479.
39	Inoue S. Copolymerization of carbon dioxide and epoxide: functionality of the copolymer[J]. Journal of Macromol. Sci., Part A: Chem., 2006, 13(5): 651-664.
40	Ryu H K, Lee E, Son K, et al. Ring-opening copolymerization of cyclic epoxide and anhydride using a five-coordinate chromium complex with a sterically demanding amino triphenolate ligand[J]. Polym. Chem., 2020, 11(22): 3756-3761.
41	Cohn D, Younes H. Biodegradable PEO/PLA block copolymers[J]. J. Biomed. Mater. Res., 1988, 22(11): 993-1009.
42	Stevels W M, Ankone M J K, Dijkstra P J, et al. Stereocomplex formation in ABA triblock copolymers of poly(lactide) (A) and poly(ethylene glycol) (B)[J]. Macromol. Chem. Phys., 1995, 196(11): 3687-3694.
43	Kimura Y, Matsuzaki Y, Yamane H, et al. Preparation of block copoly(ester-ether) comprising poly(L-lactide) and poly(oxypropylene) and degradation of its fibre in vitro and in vivo[J]. Polymer, 1989, 30(7): 1342-1349.
44	Chen X H, Mccarthy S P, Gross R A. Synthesis and characterization of L-lactide-ethylene oxide multiblock copolymers[J]. Macromolecules, 1997, 30(15): 4295-4301.
45	Quan S M, Wang X K, Diaconescu P L, et al. Redox switchable copolymerization of cyclic esters and epoxides by a zirconium complex[J]. Macromolecules, 2016, 49(18): 6768-6778.
46	Biernesser A B, Delle Chiaie K R, Byers J A, et al. Block copolymerization of lactide and an epoxide facilitated by a redox switchable iron-based catalyst[J]. Angew. Chem. Int. Ed., 2016, 55(17): 5251-5254.
47	Qi M, Dong Q, Byers J A, et al. Electrochemically switchable ring-opening polymerization of lactide and cyclohexene oxide[J]. J. Am. Chem. Soc., 2018, 140(17): 5686-5690.
48	Raynaud J, Gnanou Y, Taton D, et al. N-heterocyclic carbine-induced zwitterionic ring-opening polymerization of ethylene oxide and direct synthesis of α,ω-difunctionalized poly(ethylene oxide)s and poly(ethylene oxide)-b-poly(ε-caprolactone) block copolymers[J]. J. Am. Chem. Soc., 2009, 131(9): 3201-3209.
49	Zhao J, Pahovnik D, Hadjichristidis N, et al. Sequential polymerization of ethylene oxide, ε-caprolactone and L-lactide: a one-pot metal-free route to tri- and pentablock terpolymers[J]. Polym. Chem., 2014, 5(12): 3750-3753.
50	Liu Y Y, Li Z J, Guo K, et al. A switch from anionic to bifunctional H-bonding catalyzed ring-opening polymerizations towards polyether-polyester diblock copolymers[J]. Polym. Chem., 2018, 9(2): 154-159.
51	Liu S, Zhao J P, Ling J, et al. Biased lewis pairs: a general catalytic approach to ether-ester block copolymers with unlimited ordering of sequences[J]. Angew. Chem. Int. Ed., 2019, 58(43): 15478-15487.
52	Zhu K J, Lin X Z, Yang S L. Preparation and properties of D,L-lactide and ethylene oxide copolymer: A modifying biodegradable polymeric material[J]. J. Polym. Sci., Part C: Polym. Lett., 1986, 24(7): 331-337.
53	Xu J B, Yang J X, Pispas S, et al. Synthesis and properties of amphiphilic and biodegradable poly(ε-caprolactone-co-glycidol) copolymers[J]. J. Polym. Sci., Part A: Polym. Chem., 2015, 53(7): 846-853.
54	Chwatko M, Lynd N A. Statistical copolymerization of epoxides and lactones to high molecular weight[J]. Macromolecules, 2017, 50(7): 2714-2723.
55	Varghese J K, Gnanou Y, Feng X S, et al. Degradable poly(ethylene oxide) through metal-free copolymerization of ethylene oxide with L-lactide[J]. Polym. Chem., 2019, 10(27): 3764-3771.
56	Clayman N E, Waymouth R M, Coates G W, et al. Dual catalysis for the copolymerisation of epoxides and lactones[J]. Chem. Commun., 2019, 55(48): 6914-6917.
57	Ren W M, Wang R J, Ren B H, et al. Mechanism-inspired design of heterodinuclear catalysts for copolymerization of epoxide and lactone[J]. Chinese J. Polym. Sci., 2020.
58	Tadokoro A, Takata T, Endo T. Anionic ring-opening alternating copolymerization of a bicyclic bis(γ-lactone) with an epoxide: a novel ring-opening polymerization of a monomer containing a γ-lactone structure[J]. Macromolecules, 1993, 26(17): 4400-4406.
59	Takata T, Tadokoro A, Endo T, et al. Anionic ring-opening alternating copolymerizations of bicyclic and spirocyclic bis(γ-lactone)s with epoxides via a tandem double ring-opening isomerization of the bislactones [J]. Macromolecules, 1995, 28(5): 1340-1345.
60	Uenishi K, Sudo A, Endo T. Anionic alternating copolymerizability of epoxide and 3,4-dihydrocoumarin by imidazole[J]. Macromolecules, 2007, 40(18): 6535-6539.
61	Sudo A, Uenishi K, Endo T. Anionic copolymerization of epoxide with bifunctional aromatic lactone derived from 2-methylresorcinol[J]. J. Polym. Sci., Part A: Polym. Chem., 2008, 46(10): 3447-3451.
62	Uenishi K, Sudo A, Endo T. Anionic alternating copolymerization of 3,4-dihydrocoumarin and glycidyl ethers: a new approach to polyester synthesis[J]. J. Polym. Sci., Part A: Polym. Chem., 2008, 46(12): 4092-4102.
63	Sudo A, Uenishi K, Endo T. Anionic alternating copolymerization of epoxide and 3,4-dihydrocoumarin and its application to networked polymers[J]. Polym. Int., 2009, 58(9): 970-975.
64	Endo T, Sudo A. Development and application of novel ring-opening polymerizations to functional networked polymers[J]. J. Polym. Sci., Part A: Polym. Chem., 2009, 47(19): 4847-4858.
65	Uenishi K, Sudo A, Endo T. Anionic alternating copolymerization of a bifunctional six-membered lactone and glycidyl phenyl ether: Selective synthesis of a linear polyester having lactone moiety[J]. J. Polym. Sci., Part A: Polym. Chem., 2009, 47(6): 1661-1672.
66	Ohsawa S, Sudo A, Endo T, et al. Alternating copolymerization of bicyclic bis(γ-butyrolactone) and epoxide through zwitterion process by phosphines[J]. Macromolecules, 2010, 43(8): 3585-3588.
67	Sudo A, Zhang Y, Endo T. Anionic alternating copolymerization of epoxide and six-membered lactone bearing naphthyl moiety[J]. J. Polym. Sci., Part A: Polym. Chem., 2011, 49(3): 619-624.
68	Van Zee N J, Coates G W. Alternating copolymerization of dihydrocoumarin and epoxides catalyzed by chromium salen complexes: a new route to functional polyesters[J]. Chem. Commun., 2014, 50(48): 6322-6325.
69	Hu S Y, Dai G X, Zhao J P, et al. Ring-opening alternating copolymerization of epoxides and dihydrocoumarin catalyzed by a phosphazene superbase[J]. Macromolecules, 2016, 49(12): 4462-4472.
70	Zhang H X, Hu S Y, Zhao J, et al. Phosphazene-catalyzed alternating copolymerization of dihydrocoumarin and ethylene oxide: weaker is better[J]. Macromolecules, 2017, 50(11): 4198-4205.

图3中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/h	温度/℃	转化率^①/%		分子量^②	分子量分布^②	文献
图3中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/h	温度/℃	内酯	环氧化物	分子量^②	分子量分布^②	文献
1	LA/EO	0.5	22	60	—	—	26100	6.2	[44]
2	LA/EO	0.5	22	60	—	—	17600	3.2	[44]
3	LA/CHO	1.0	—	—	45	75	7600	1.29	[45]
4	LA/CHO	1.0	3	24	98	69	37500	1.5	[46]
5	CL/EO	1.8	—	50	50	—	10400	1.08	[48]
6	CL/LA/EO	—	—	—	—	70	3500	1.12	[49]
7/8	LA/GPE	0.5	0.75	25	—	98	4600	1.13	[50]

图3中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/h	温度/℃	转化率^①/%		分子量^②	分子量分布^②	文献
图3中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/h	温度/℃	内酯	环氧化物	分子量^②	分子量分布^②	文献
1	LA/EO	0.5	22	60	—	—	26100	6.2	[44]
2	LA/EO	0.5	22	60	—	—	17600	3.2	[44]
3	LA/CHO	1.0	—	—	45	75	7600	1.29	[45]
4	LA/CHO	1.0	3	24	98	69	37500	1.5	[46]
5	CL/EO	1.8	—	50	50	—	10400	1.08	[48]
6	CL/LA/EO	—	—	—	—	70	3500	1.12	[49]
7/8	LA/GPE	0.5	0.75	25	—	98	4600	1.13	[50]

图6、图8~图10、图12~图13中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/ h	温度/ ℃	转化率^①/%	含量^②/%		分子量^③	分子量分布^③	T_g^④/℃	文献
图6、图8~图10、图12~图13中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/ h	温度/ ℃	转化率^①/%	内酯	环氧烷烃	分子量^③	分子量分布^③	T_g^④/℃	文献
9	LA/EO	0.15	2	25	—	3.6	—	11100	1.14	—	[55]
10	LA/EO	1.0	5	90	—	—	—	20000	1.5	11	[52]
11	CL/BGE	2.33	—	80	—	—	28	18000	1.4	–54	[53]
12	LA/BO	1.0	24	45	—	0.25	—	29000	11.2	26	[54]
12	LA/PO	2.0	24	45	—	0.34	—	80000	6.5	18	[54]
12	CL/PO	2.0	24	45	—	0.51	—	45000	8.3	—	[54]
12	LA/ECH	2.0	24	45	—	0.22	—	16840000	1.5	–33	[54]
13/14	VL/PO	1.0	6	23	25	—	—	11100	1.2	—	[56]
15	CL/PO	1.0	4	50	33	—	—	14300	1.36	—	[57]

图6、图8~图10、图12~图13中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/ h	温度/ ℃	转化率^①/%	含量^②/%		分子量^③	分子量分布^③	T_g^④/℃	文献
图6、图8~图10、图12~图13中催化剂	单体	投料摩尔比 (内酯/环氧烷烃)	时间/ h	温度/ ℃	转化率^①/%	内酯	环氧烷烃	分子量^③	分子量分布^③	T_g^④/℃	文献
9	LA/EO	0.15	2	25	—	3.6	—	11100	1.14	—	[55]
10	LA/EO	1.0	5	90	—	—	—	20000	1.5	11	[52]
11	CL/BGE	2.33	—	80	—	—	28	18000	1.4	–54	[53]
12	LA/BO	1.0	24	45	—	0.25	—	29000	11.2	26	[54]
12	LA/PO	2.0	24	45	—	0.34	—	80000	6.5	18	[54]
12	CL/PO	2.0	24	45	—	0.51	—	45000	8.3	—	[54]
12	LA/ECH	2.0	24	45	—	0.22	—	16840000	1.5	–33	[54]
13/14	VL/PO	1.0	6	23	25	—	—	11100	1.2	—	[56]
15	CL/PO	1.0	4	50	33	—	—	14300	1.36	—	[57]

图3、图9、图15~图18中催化剂	单体	投料摩尔比内酯/环氧烷烃	时间/ h	温度/ ℃	转化率^①/ %	分子量^②	分子量分布^②	文献
16	A^③/GPE	1.0	74	120	91	6600	1.6	[59]
17	DHNP/GPE	1.0	3	120	93	2400	1.9	[67]
18	DHCM/PO	0.5	6	—	88	15000	1.3	[68]
18	DHCM/CPO	0.5	24	—	70	18000	1.5	[68]
18	DHCM/CHO	0.5	6	—	58	7000	1.4	[68]
11	DHCM/EO	0.2	72	50	25	2500	1.29	[69]
6	DHCM/EO	0.8	22	60	＞99	2100	1.07	[70]
19	DHCM/EO	0.5	72	60	＞99	7500	1.09	[70]