Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States.
J Am Chem Soc. 2011 Mar 23;133(11):4140-8. doi: 10.1021/ja111391z. Epub 2011 Feb 25.
Cyclic poly(5-hydroxy-1-cyclooctene) (PACOE) was synthesized by ring-expansion metathesis polymerization (REMP), and thiol-ene chemistry was used to cross-link the internal double bonds in the PACOE backbone. This created a novel network material (gels formed from cyclic polymers) with unique structural units, where the cyclic PACOE main chains, which serve as secondary topological cross-linkages, were connected by primary intermolecular chemical cross-linkages. The resulting properties were notably different from those of traditional chemically cross-linked linear PACOE gels, whose gel fraction (GF) and modulus (G) increased while the swelling ratio (Q) decreased with increasing initial polymer concentration in the gel precursor solution (C(0)). For the gels formed from cyclic polymers, however, the GF, Q, and G all simultaneously increased as C(0) increased at the higher range. Furthermore, at the same preparation state (same C(0)), the swelling ability and the maximum strain at break of the gels formed from cyclic polymers were always greater than those of the gels formed from linear polymers, and these differences became more pronounced as C(0) increased.
通过开环易位聚合（REMP）合成了环状聚（5-羟基-1-环辛烯）（PACOE），并用巯基-烯化学将 PACOE 主链中的内部双键交联。这创造了一种具有独特结构单元的新型网络材料（由环状聚合物形成的凝胶），其中环状 PACOE 主链作为二级拓扑交联点，通过初级分子间化学交联点连接。所得性能明显不同于传统化学交联的线性 PACOE 凝胶，随着凝胶前体溶液中初始聚合物浓度（C(0)）的增加，其凝胶分数（GF）和模量（G）增加，而溶胀比（Q）降低。然而，对于由环状聚合物形成的凝胶，GF、Q 和 G 均随着 C(0)在较高范围内的增加而同时增加。此外，在相同的制备状态（相同的 C(0)）下，由环状聚合物形成的凝胶的溶胀能力和断裂时的最大应变总是大于由线性聚合物形成的凝胶，并且随着 C(0)的增加，这些差异变得更加明显。
