Using CO₂ polycarbonates as engineering thermoplastics has been limited by their mechanical performances, particularly their brittleness. Poly(cyclohexene carbonate) (PCHC) has a high tensile strength (40 MPa) but is very brittle (elongation at break <3%), which limits both its processing and applications. Here, well-defined, high molar mass CO₂ terpolymers are prepared from cyclohexene oxide (CHO), cyclopentene oxide (CPO), and CO₂ by using a Zn(II)Mg(II) catalyst. In the catalysis, CHO and CPO show reactivity ratios of 1.53 and 0.08 with CO₂, respectively; as such, the terpolymers have gradient structures. The poly(cyclohexene carbonate)-grad-poly(cyclopentene carbonate) (PCHC-grad-PCPC) have high molar masses (86 < M_n < 164 kg mol^–1, Đ_M < 1.22) and good thermal stability (T_d > 250 °C). All the polymers are amorphous with a single, high glass transition temperature (96 < T_g < 108 °C). The polymer entanglement molar masses, determined using dynamic mechanical analyses, range from 4 < M_e < 23 kg mol^–1 depending on the polymer composition (PCHC:PCPC). These polymers show superior mechanical performance to PCHC; specifically the lead material (PCHC_0.28-grad-PCPC_0.72) shows 25% greater tensile strength and 160% higher tensile toughness. These new plastics are recycled, using cycles of reprocessing by compression molding (150 °C, 1.2 ton m^–2, 60 min), four times without any loss in mechanical properties. They are also efficiently chemically recycled to selectively yield the two epoxide monomers, CHO and CPO, as well as carbon dioxide, with high activity (TOF = 270–1653 h^–1, 140 °C, 120 min). The isolated recycled monomers are repolymerized to form thermoplastic showing the same material properties. The findings highlight the benefits of the terpolymer strategy to deliver thermoplastics combining the beneficial low entanglement molar mass, high glass transition temperatures, and tensile strengths; PCHC properties are significantly improved by incorporating small quantities (23 mol %) of cyclopentene carbonate linkages. The general strategy of designing terpolymers to include chain segments of low entanglement molar mass may help to toughen other brittle and renewably sourced plastics.

中文翻译：

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受控二氧化碳三元聚合可提供增韧且可回收的热塑性塑料

使用CO ₂聚碳酸酯作为工程热塑性塑料受到其机械性能、特别是脆性的限制。聚环己烯碳酸酯（PCHC）具有高拉伸强度（40 MPa），但很脆（断裂伸长率<3%），这限制了其加工和应用。在此，通过使用Zn(II)Mg(II)催化剂，由环己烯氧化物(CHO)、环戊烯氧化物(CPO)和CO ₂制备明确的高摩尔质量CO ₂三元共聚物。在催化过程中，CHO和CPO与CO ₂的反应活性比分别为1.53和0.08；因此，三元共聚物具有梯度结构。聚(环己烯碳酸酯)-grad-聚(环戊烯碳酸酯) (PCHC- grad -PCPC) 具有高摩尔质量 (86 < M _n < 164 kg mol ^–1 , Đ _M < 1.22) 和良好的热稳定性 ( T _d > 250℃）。所有聚合物都是无定形的，具有单一的高玻璃化转变温度 (96 < T _g < 108 °C)。使用动态力学分析确定的聚合物缠结摩尔质量范围为 4 < Me < 23 kg mol ^–1 _，具体取决于聚合物成分 (PCHC:PCPC)。这些聚合物表现出优于 PCHC 的机械性能；特别是铅材料（PCHC _0.28 - grad -PCPC _0.72）的拉伸强度提高了 25%，拉伸韧性提高了 160%。这些新塑料通过压缩成型再加工循环（150 °C，1.2 吨米^–2，60分钟）进行四次回收，机械性能没有任何损失。它们还可以有效地进行化学回收，选择性地产生两种环氧化物单体：CHO 和 CPO，以及二氧化碳，具有高活性（TOF = 270–1653 h ^–1、140 °C、120 分钟）。分离出的回收单体重新聚合形成具有相同材料性能的热塑性塑料。研究结果强调了三元共聚物策略的优点，即提供结合了有益的低缠结摩尔质量、高玻璃化转变温度和拉伸强度的热塑性塑料；通过加入少量（23 mol%）的环戊烯碳酸酯键，PCHC 性能得到显着改善。设计三元共聚物以包含低缠结摩尔质量的链段的总体策略可能有助于增韧其他脆性和可再生来源的塑料。