ABAC-type periodic poly(cyclic acetal)s were synthesized via a two-step method consisting of the synthesis of a sequence-programmed cyclic trimers from one vinyl monomer and two bifunctional aldehydes (isophthalaldehyde or terephthalaldehyde) and the successive cyclotrimerization of the cyclic trimer with another vinyl monomer. The use of 1,1-diphenylethylene (DPE) was important for synthesizing the cyclic trimer in high yield because the successive cyclotrimerization and other side reactions were suppressed due to the steric hindrance of DPE. The ABA-type sequence-programmed cyclic trimer consisting of one DPE molecule (unit B) and two dialdehydes (unit A) possesses two unreacted aldehyde moieties; hence, the cyclic trimer successfully underwent successive cyclotrimerization with vinyl ethers (VEs) (unit C), such as 2-chloroethyl VE (CEVE) and ethyl 2-methyl-1-propenyl ether (EMPE). As a result, ABAC-type periodic poly(cyclic acetal)s with alternately arranged two phenyl rings and VE-derived side chains were produced. The two types of cyclic acetal structures in the main chain exhibited different acid degradability. Indeed, the CEVE-derived cyclic acetal structures were selectively degraded under acidic conditions at 60 °C for 15 min, which was followed by the subsequent degradation of the DPE-derived cyclic acetal structures in 24 h. In addition, the ABAC-type periodic polymers exhibited good thermal properties, which were attributed to the cyclic acetal structures.

ABAC 型周期性聚（环状缩醛）通过两步法合成，包括从一个乙烯基单体和两个双功能醛（间苯二甲醛或对苯二甲醛）合成顺序编程的环状三聚体和环状三聚体的连续环三聚化与另一种乙烯基单体。使用 1,1-二苯基乙烯 (DPE) 对于以高产率合成环状三聚体非常重要，因为由于 DPE 的空间位阻，连续的环三聚反应和其他副反应被抑制。由一个 DPE 分子（单元 B）和两个二醛（单元 A）组成的 ABA 型序列编程环状三聚体具有两个未反应的醛部分；因此，环状三聚体成功地经历了与乙烯基醚（VE）（单元C）的连续环三聚，例如2-氯乙基VE（CEVE）和乙基2-甲基-1-丙烯基醚（EMPE）。结果，产生了具有交替排列的两个苯环和 VE 衍生侧链的 ABAC 型周期性聚（环状缩醛）。主链中的两种环状缩醛结构表现出不同的酸降解性。事实上，CEVE 衍生的环状缩醛结构在 60 °C 的酸性条件下选择性降解 15 分钟，随后 DPE 衍生的环状缩醛结构在 24 小时内发生降解。此外，ABAC 型周期性聚合物表现出良好的热性能，这归因于环状缩醛结构。主链中的两种环状缩醛结构表现出不同的酸降解能力。事实上，CEVE 衍生的环状缩醛结构在 60 °C 的酸性条件下选择性降解 15 分钟，随后 DPE 衍生的环状缩醛结构在 24 小时内发生降解。此外，ABAC 型周期性聚合物表现出良好的热性能，这归因于环状缩醛结构。主链中的两种环状缩醛结构表现出不同的酸降解性。事实上，CEVE 衍生的环状缩醛结构在 60 °C 的酸性条件下选择性降解 15 分钟，随后 DPE 衍生的环状缩醛结构在 24 小时内发生降解。此外，ABAC 型周期性聚合物表现出良好的热性能，这归因于环状缩醛结构。