Terpenes with olefin methyl branches and bifunctional hydroxyl groups were used as initiators in the ring-opening polymerization of ε-caprolactone (CL) catalyzed by ammonium decamolybdate (NH₄)₆[Mo₇O₂₄], resulting in α-hydroxyl-ω-olefin poly(ε-caprolactone) (PCL) (C_o–PCL–OH). The degree of polymerization was kept low (5 and 10) in all the species to increase the weight percent of the terminal group. Additionally, to compare the effects of the olefin terminal groups on PCLs, another family of PCL oligoesters with a linear alkyl terminal group α-hydroxyl-ω-alkyl PCL (C_a–PCL–OH) was synthesized under the same conditions. The olefin and alkyl terminal groups contained gradually increasing numbers of carbons (C₅, C₁₀, and C₁₅). Both families of PCL oligoesters were characterized by different analytical techniques such as GPC, NMR, MALDI-TOF, and FT-IR spectroscopy to corroborate the chemical nature of the oligoesters and their end groups. Thermal properties were analyzed by scanning differential calorimetry (DSC), which showed significant differences between olefin and alkyl terminal groups; this affected PCL crystalline domains, as evidenced by the crystallization temperatures (T_c), melting temperatures (T_m), and crystallinities (x_i) of the PCLs. In addition, computational studies using density functional theory indicated the differences in molar volume for the olefin and alkyl terminal groups.

Graphic abstract

中文翻译：

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萜烯与线性烷基取代基：端基对衍生自聚（ε-己内酯）的低聚物的影响

在癸酸铵 (NH ₄ ) ₆ [Mo ₇ O ₂₄ ]催化下，ε-己内酯 (CL) 的开环聚合反应中使用具有烯烃甲基支链和双官能羟基的萜烯作为引发剂，生成 α-羟基-ω-烯烃聚（ε-己内酯）（PCL）（C _o -PCL-OH）。所有种类的聚合度都保持在较低水平（5 和 10）以增加端基的重量百分比。此外，为了比较烯烃端基对 PCL 的影响，另一个家族的 PCL 低聚酯具有线性烷基端基 α-羟基-ω-烷基 PCL (C _a–PCL–OH) 在相同条件下合成。烯烃和烷基端基包含逐渐增加的碳数（C ₅、C ₁₀和C ₁₅）。这两个系列的 PCL 低聚酯均通过不同的分析技术（如 GPC、NMR、MALDI-TOF 和 FT-IR 光谱）进行表征，以证实低聚酯及其端基的化学性质。通过扫描差示量热法（DSC）分析热性能，显示烯烃端基和烷基端基之间存在显着差异；此受影响的PCL结晶域，就证明了结晶化温度（Ť _Ç），熔融温度（Ť_米），和结晶度（X_i ) 的 PCL。此外，使用密度泛函理论的计算研究表明烯烃和烷基端基的摩尔体积存在差异。

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