Rice scientists probing the interfacial interactions of polymer (blue) and cement (yellow) discovered the right mix of hydrogen bonds is critical to making strong, tough and ductile composite materials for infrastructure. Computer simulations like that in the illustration measured the strength of the bonds as hard cement slides past the soft polymer in a layered composite, which mimics the structure nacre, seen in the background. Image credit: Illustration by Probhas Hundi/Multiscale Materials Laboratory
The right mix of hydrogen bonds in polymer and cement composites is critical to making strong, tough and ductile infrastructure material, according to Rice University scientists who want to mimic the mechanics of mother-of-pearl and similar natural composites with synthetic materials.
Seashells made of珍珠母，又名nacre，从重叠的微米大小的矿化板中获得其出色的特性，由软基质固定在一起。民间和环境工程助理教授Rouzbeh Shahsavari表示，可以通过水泥和聚合物复合材料来接近这种结构。
赖斯实验室进行了20多次计算机模拟，以了解聚合物和水泥分子如何在纳米级融合在一起以及什么驱动其粘附。研究人员表明，氧和氢原子的接近性是形成连接软层的弱氢键网络的关键因素。常见的聚丙烯酸（PAA）在结合水泥晶体的重叠层的最佳重叠约15纳米方面被证明是最好的。
“这项信息对于制造最好的合成复合材料很重要，”与赖斯研究生Navid Sakhavand一起进行该项目的Shahsavari说。“这些材料的现代工程方法将对社会产生重大影响，尤其是当我们建立新的和取代老化的基础设施时。”
The lab’s results appear inApplied Physical Letters。
Shahsavari说，虽然工程师知道添加聚合物通过阻止侵入毛孔的“侵略性”离子的破坏作用来改善水泥，但有关材料如何在分子尺度相互作用的细节仍然未知。为了发现，研究人员对使用PAA和聚乙烯醇（PVA）建模了复合材料，这两种软基质材料都用于改善水泥。
They discovered that the two different oxygen atoms in PAA (as opposed to one in PVA) allowed it toreceive and donate ions当它在晶体中与氢键结合tobermoritecement. Oxygen in PAA had eight ways to bond with hydrogen (six for PVA) and could also participate insalt bridgingbetween the polymer and cement, which makes the bonding network even more complex.
研究人员通过滑动聚合物和水泥相互对抗来测试其模拟结构，发现复杂性使PAA和水泥之间的键在材料受到压力时更频繁地破裂和重新连接，从而大大增加了其。韧性, the ability to deform without fracturing. This allowed the researchers to determine the optimum overlap between cement crystals.
Shahsavari说：“与常见的直觉相反，当氢键的合适数量（最佳重叠）合作时，它们在复合材料中提供了足够的连通性，以赋予高强度和高韧性。”“从实验的角度来看，这可以通过在控制水泥矿物质形成的同时仔细调整和控制右分子量的聚合物来完成。确实，最近experimental paper我们的同事们向这种策略展示了概念证明。”
国家科学基金会（NSF）支持这项研究。超级计算资源由Rice的NSF支持的Davinci超级计算机提供研究计算中心并与赖斯合作采购肯·肯尼迪信息技术研究所。
提交以下：Materials • advanced
