Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Am Chem Soc. 2013 Aug 28;135(34):12755-61. doi: 10.1021/ja405628g. Epub 2013 Aug 20.
End-capped poly(phthalaldehyde) (PPA) synthesized by anionic polymerization has garnered significant interest due to its ease of synthesis and rapid depolymerization. However, alternative ionic polymerizations to produce PPA have been largely unexplored. In this report, we demonstrate that a cationic polymerization of o-phthalaldehyde initiated by boron trifluoride results in cyclic PPA in high yield, with high molecular weight, and with extremely high cyclic purity. The cyclic structure is confirmed by NMR spectroscopy, MALDI-TOF mass spectrometry, and triple-detection GPC. The cyclic polymers are reversibly opened and closed under the polymerization conditions. Owing to PPA's low ceiling temperature, cyclic PPA is capable of chain extension to larger molecular weights, controlled depolymerization to smaller molecular weights, or dynamic intermixing with other polymer chains, both cyclics and end-capped linears. These unusual properties endow the system with great flexibility in the synthesis and isolation of pure cyclic polymers of high molecular weight. Further, we speculate that the absence of end groups enhances the stability of cyclic PPA and makes it an attractive candidate for lithographic applications.
端封聚邻苯二甲醛（PPA）通过阴离子聚合合成，因其易于合成和快速解聚而受到广泛关注。然而，用于生产 PPA 的其他离子聚合方法在很大程度上尚未得到探索。在本报告中，我们证明邻苯二甲醛的阳离子聚合由三氟化硼引发，可高产率、高分子量和极高的环状纯度得到环状 PPA。环状结构通过 NMR 光谱、MALDI-TOF 质谱和三重检测 GPC 得到证实。环状聚合物在聚合条件下可可逆地开环和闭环。由于 PPA 的上限温度低，环状 PPA 能够进行链延伸以获得更大的分子量、可控解聚以获得更小的分子量，或与其他聚合物链（环状和端封线性）进行动态混合。这些不寻常的性质赋予了该系统在合成和分离高分子量纯环状聚合物方面的极大灵活性。此外，我们推测末端基团的缺失提高了环状 PPA 的稳定性，使其成为光刻应用的有吸引力的候选材料。
