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Four types of organic soluble polyimide (PI) resins with semi-cyclic structures were prepared by one-step high-temperature solution polycondensation using alicyclic dianhydride 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride (ccHPMDA) and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride (ctHPMDA) with two aromatic diamines 9,9-bis[(4-amino-3-methyl)benzene]fluorene (MFDA) and 2,2′-dimethylbenzidine (DMBZ), respectively. Four types of PI films were prepared by dissolving the above four resins in N,N-dimethylacetamide and baking at high temperature. The thermal, optical, and mechanical properties of the PI films were tested. The results show that functional groups including six-membered cyclohexane ring, bulky fluorene substituents, ortho methyl substituent, and rigid biphenyl units endow these PI films with excellent thermal stability. The glass transition temperature of the four films are all higher than 400℃ and the 5% thermal weight loss temperatures are higher than 500℃ in nitrogen. Meanwhile, the four PI films show good optical transparency, with transmittance at 450 nm all surpassing 84.8%, yellow-blue index ranging from 1.09 to 2.15, and haze value ranging from 0.16% to 1.21%. In addition, the DMBZ based PI films exhibit superior mechanical properties, with tensile strength and tensile modulus exceeding 118 MPa and 3.8 GPa, respectively.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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