Sparnacci Katia, Antonioli Diego, Gianotti Valentina, Laus Michele, Zuccheri Giampaolo, Ferrarese Lupi Federico, Giammaria Tommaso Jacopo, Seguini Gabriele, Ceresoli Monica, Perego Michele
Dipartimento di Scienze e Innovazione Tecnologica (DISIT), Università del Piemonte Orientale ''A. Avogadro'' , Viale T. Michel 11, 15121 Alessandria, Italy.
ACS Appl Mater Interfaces. 2015 Feb 25;7(7):3920-30. doi: 10.1021/am509088s. Epub 2015 Feb 17.
Two strategies are envisioned to improve the thermal stability of the grafted layer and to allow the processing of the random copolymer/block copolymer (RCP/BCP) system at high temperature. From one side, a high-temperature thermal treatment of a commercial α-hydroxyl ω-2,2,6,6-tetramethylpiperidinyloxy functional RCP, namely, TR58, leads to the formation of a stabilized layer able to induce the perpendicular orientation of a symmetric BCP to temperatures higher than 310 °C. On the other side, an α-hydroxyl ω-Br functional RCP, namely, BrR58, with the same molar mass and composition of TR58, was prepared by activator regenerated by electron transfer atom transfer radical polymerization. The resulting brush layer can sustain the self-assembly of the symmetric BCP for processing temperatures as high as 330 °C. In both systems, the disruption of the BCP film, deposited on the grafted RCP layer, occurs because of the formation of bubbles, due to a low-temperature evolution of monomers from the RCP layer. The extent of the low-temperature monomer evolution is higher for TR58 than it is for BrR58 and starts at lower temperatures. For both copolymers, the thermal treatment offsets the low-temperature monomer evolution while still maintaining surface characteristics suitable to induce the perpendicular orientation of the BCPs, thus ultimately extending the range of processing temperatures of the BCP film and consequently speeding the self-organization process.
设想了两种策略来提高接枝层的热稳定性，并允许在高温下加工无规共聚物/嵌段共聚物（RCP/BCP）体系。一方面，对市售的α-羟基ω-2,2,6,6-四甲基哌啶氧基官能化RCP（即TR58）进行高温热处理，会形成一个稳定层，该层能够使对称BCP在高于310°C的温度下实现垂直取向。另一方面，通过电子转移活化剂再生原子转移自由基聚合制备了与TR58具有相同摩尔质量和组成的α-羟基ω-溴官能化RCP，即BrR58。所得的刷状层能够在高达330°C的加工温度下维持对称BCP的自组装。在这两种体系中，沉积在接枝RCP层上的BCP膜的破坏是由于RCP层中单体的低温逸出形成气泡所致。TR58的低温单体逸出程度高于BrR58，且起始温度更低。对于这两种共聚物，热处理抵消了低温单体逸出，同时仍保持适合诱导BCP垂直取向的表面特性，从而最终扩展了BCP膜的加工温度范围，进而加速了自组装过程。
