School of Chemical Science and Engineering, Department of Fibre and Polymer Technology and ‡School of Electrical Engineering, Department of Electromagnetic Engineering, KTH Royal Institute of Technology , SE-100 44 Stockholm, Sweden.
ACS Appl Mater Interfaces. 2015 Nov 25;7(46):25669-78. doi: 10.1021/acsami.5b06427. Epub 2015 Nov 13.
Aluminum oxide nanoparticles (NPs) were surface-modified by poly(lauryl methacrylate) (PLMA) using surface-initiated atom-transfer radical polymerization (SI-ATRP) of lauryl methacrylate. Nanocomposites were obtained by mixing the grafted NPs in a low-density polyethylene (LDPE) matrix in different ratios. First, the NPs were silanized with different aminosilanes, (3-aminopropyl)triethoxysilane, and 3-aminopropyl(diethoxy)methylsilane (APDMS). Subsequently, α-BiB, an initiator for SI-ATRP, was attached to the amino groups, showing higher immobilization ratios for APDMS and confirming that fewer self-condensation reactions between silanes took place. In a third step SI-ATRP of LMA at different times was performed to render PLMA-grafted NPs (NP-PLMAs), showing good control of the polymerization. Reactions were conducted for 20 to 60 min, obtaining a range of molecular weights between 23 000 and 83 000 g/mol, as confirmed by size-exclusion chromoatography of the cleaved grafts. Nanocomposites of NP-PLMAs at low loadings in LDPE were prepared by extrusion. At low loadings, 0.5 wt % of inorganic content, the second yield point, storage, and loss moduli increased significantly, suggesting an improved interphase as an effect of the PLMA grafts. These observations were also confirmed by an increase in transparency of the nanocomposite films. At higher loadings, 1 wt % of inorganics, the increasing amount of PLMA gave rise to the formation of small aggregates, which may explain the loss of mechanical properties. Finally, dielectric measurements were performed, showing a decrease in tan δ values for LDPE-NP-PLMAs, as compared to the nanocomposites containing unmodified NP, thus indicating an improved interphase between the NPs and LDPE.
氧化铝纳米粒子 (NPs) 通过使用十二甲基丙烯酸酯 (PLMA) 的表面引发原子转移自由基聚合 (SI-ATRP) 对其表面进行修饰。将接枝 NPs 以不同比例混合到低密度聚乙烯 (LDPE) 基质中以获得纳米复合材料。首先，用不同的氨丙基硅烷对 NPs 进行硅烷化处理，（3-氨丙基）三乙氧基硅烷和 3-氨丙基 (二乙氧基) 甲基硅烷 (APDMS)。随后，将引发剂 α-BiB 连接到氨基上，显示出更高的接枝固定化率 APDMS，并证实硅烷之间发生的自缩合反应更少。在第三步中，在不同时间进行 LMA 的 SI-ATRP，以得到接枝 PLMA 的 NP（NP-PLMAs），显示出聚合的良好控制。反应进行了 20 到 60 分钟，得到了分子量在 23000 到 83000 克/摩尔之间的范围，这通过 cleaved grafts 的尺寸排除色谱法得到了证实。通过挤出制备了在 LDPE 中低负载的 NP-PLMA 纳米复合材料。在低负载下，无机含量为 0.5wt%时，第二屈服点、储能模量和损耗模量显著增加，这表明 PLMA 接枝的界面得到了改善。这些观察结果也得到了纳米复合材料薄膜透明度增加的证实。在更高的负载下，无机含量为 1wt%时，PLMA 的增加量导致了小团聚体的形成，这可能解释了力学性能的损失。最后，进行了介电测量，结果表明与含有未改性 NP 的纳米复合材料相比，LDPE-NP-PLMA 的 tan δ 值降低，这表明 NPs 和 LDPE 之间的界面得到了改善。
