Tough and Thermally Recyclable Semiaromatic Polyesters by Ring-Opening Polymerization of Benzo-thia-caprolactones
2021; American Chemical Society; Volume: 54; Issue: 14 Linguagem: Inglês
10.1021/acs.macromol.1c00497
ISSN1520-5835
AutoresLi Linggao, Qiyuan Wang, Qiu-Yang Zheng, Fu‐Sheng Du, Zichen Li,
Tópico(s)Carbon dioxide utilization in catalysis
ResumoThermally recyclable semiaromatic polyesters with good mechanical properties are prepared by ring-opening polymerization (ROP) of benzene-fused caprolactones. Three constitutional isomers of benzo-thia-caprolactones (BOTO-I, BOTO-II, and BOTO-III) were synthesized. Their organocatalytic ROPs were systematically investigated and correlated with their structures. The diphenyl phosphate (DPP)-catalyzed ROP of BOTO-II is controllable and can reach high monomer conversion. BOTO-I has a high equilibrium monomer concentration ([M]e = 0.15 M) at 30 °C, whose ROP can only be achieved with 1,5,7-triazabicyclo[4.4.0] dec-5-ene (TBD) as the catalyst, but with poor control. BOTO-III can be polymerized with TBD or a binary catalytic system of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) and 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea (TU) with poor control. Polymers P(BOTO-I) and P(BOTO-II) are thermally stable up to 270 °C, but P(BOTO-III) starts to decompose at 180 °C. These three polymers are semicrystalline materials with slow crystallization rates. P(BOTO-I) displays the highest Tm of 146 °C and a Tg of 59 °C. The mechanical properties of these P(BOTO)s were examined by uniaxial tensile tests. Preliminary data indicates that P(BOTO-I) is a tough polymer with superior comprehensive material properties as compared to other reported thermally recyclable polyesters. Catalytic chemical recycling of P(BOTO)s in solution and bulk were examined. Depolymerization in solution is not selective, generating both monomers and oligomers, while the bulk thermal depolymerization selectively gives corresponding monomers in good yield and high purity. Given its good mechanical properties, excellent thermal recyclability, and repolymerizability of the recycled monomer, P(BOTO-I) can be considered as a new type of closed-loop recyclable plastic.
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