几种自组装拉胀分子网络的分子模拟

报道了几种蜈蚣形、双足蜈蚣形聚合物 ,以及单箭头、双箭头形小分子通过氢键自组装形成拉胀分子网络的分子设计 .分子力学计算结果表明这些自组装分子网络靠氢键相互作用规则排列 ,具有类似倒插蜂窝网络结构 ,所设计的聚合物、小分子的合成较之以往报道的二维网络结构的合成简便易行 ,为真正分子水平意义上的拉胀结构的实现提供了新的思路和指导

MOLECULAR DESIGN OF SEVERAL TYPES OF SELF-ASSEMBLY AUXETIC NETWORKS

Most materials will shrink or expand laterally when stretched or compressed,i.e.they have positive Poisson ratios,but materials with negative Poisson ratios will undergo lateral expansion when stretched longitudinally and become thinner when compressed.And materials exhibiting this novel and counterintuitive behavior,now known as auxetic materials,have been successfully fabricated with many new applications.Currently,molecular auxetics,namely auxetic materials at the molecular level,have become the most exciting endeavor in the development of auxetic materials.In this paper,as new alternatives to the making of molecular auxetics,several types of centipede-like linear polymers both with single and double legs on the side chain,single-arrow-like,double-arrow-like organic compounds were designed as building blocks for self-assembling into auxetic network structures through hydrogen bonds.The second derivative method is used to calculate Poisson ratios after doing molecular mechanics (MM) optimization.The results show that all these self-assembly networks can be arranged as inverted honey-comb like structures and their Poisson's ratios in at least one plane are negative and even the self assembly of small molecules with special architecture may achieve auxeticity in some cases.Compared with many approaches proposed so far,that of the self-assembly of both single polymers and single small molecules into molecular auxetics reported here is quite novel.It provides a new route to synthesize molecular auxetics,which should be much easier than that for synthesizing two-dimensional cross-linked auxetic networks.Yet its successful realization requires great experimental efforts.