The paper is focused on investigation of layered double hydroxides (LDH) functionalized with ionic liquid (IL) as novel catalytic/initiating system for ring opening polymerization (ROP) of ε-caprolactone. Firstly, the Ca²⁺/Al³⁺ LDH nanoparticles were synthesized via a co-precipitation method followed by the anion exchange using phosphonium IL with decanoate anions producing the modified LDH with interlayered IL-anions. Then, the progress of microwave-assisted polymerization in the presence of the modified LDH was studied showing the anionic mechanism of ROP initiated by the water molecules, which were adsorbed on the LDH surface and intercalated in the LDH galleries. The whole polymerization was significantly accelerated by microwave energy, which induced molecular rotations of the intercalated IL-anions leading to LDH delamination and exfoliation into individual nanosheets, which made the catalytic sites (IL-anions) easily accessible for the εCL molecules. The kinetics of microwave-assisted ROP thus showed a 4.6-fold increase of the reaction rate compared to the polymerization performed under conventional heating. Activation enthalpy and entropy were calculated for the microwave-assisted polymerizations initiated by the modified LDH. The use of microwave-active catalytic-initiating LDH nanoparticles enables to synthesize the organometallic catalyst-free PCL or, at higher LDH loadings, the highly-exfoliated PCL/LDH nanocomposites, which are highly desirable for e.g. packaging materials.

中文翻译：

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离子液体官能化的LDH作为ε-己内酯的微波活化开环聚合的催化引发纳米粒子

本文着重研究用离子液体（IL）功能化的层状双氢氧化物（LDH），作为ε-己内酯开环聚合（ROP）的新型催化/引发体系。首先，通过以下方法合成了Ca ²⁺ / Al ³⁺ LDH纳米粒子一种共沉淀法，然后使用phospho离子与癸酸根阴离子进行阴离子交换，生成带有层间IL-阴离子的改性LDH。然后，研究了改性LDH存在下微波辅助聚合的进展，显示了由水分子引发的ROP的阴离子机理，水分子被吸附在LDH表面并嵌入LDH通道中。微波能量极大地促进了整个聚合反应，微波诱导了插入的IL阴离子的分子旋转，导致LDH分层和剥落成单个纳米片，这使得εCL分子易于接近催化位点（IL阴离子）。微波辅助ROP的动力学因此显示为4。与在常规加热下进行的聚合相比，反应速率提高了6倍。计算了改性LDH引发的微波辅助聚合反应的活化焓和熵。微波活性催化引发的LDH纳米颗粒的使用能够合成不含有机金属催化剂的PCL，或在较高的LDH负载下，高度剥离的PCL / LDH纳米复合材料，这对于例如包装材料。