Synthesis and characterization of butyl rubber ionomers

丁基橡胶(异丁烯-异戊二烯橡胶，IIR)是一种具有特殊物理性能的材料，用于汽车、建筑和生物医学等不同领域。对于所有这些应用来说，良好的弹性(变形后的形状恢复)是必需的。对于IIR来说，这是可能的，因为除了异丁烯之外，聚合物链还含有低浓度(1-2%)的异戊二烯(不饱和)单元，从而允许链的共价(永久)交联成三维网络结构。共价键方法虽然提供了良好的尺寸稳定性，但仅允许对材料的机械性能进行有限的控制。另一方面，离子相互作用对改善橡胶和塑料的机械性能(如硬度、软化温度、抗撕裂性)非常有用，并已在商业产品中得到应用，例如用作泡罩包装的高抗撕裂材料的Surlyn®树脂。含有低浓度聚合物结合离子基团(离聚体)的聚合物的性能改善归因于离子部分的聚集，在中低温度下起到多价物理交联剂的作用。应用离聚体概念来改善丁基橡胶的力学性能几乎没有受到关注，这主要是因为传统的丁基橡胶合成中异戊二烯的含量很低(1-2%)。LANXESS Inc.最近开发的新工艺允许合成含有1)高达5-6%的异戊二烯单元或2)高达10%的对甲基苯乙烯单元的丁基橡胶。这将允许合成离子部分含量更高的离聚体，相应地，与传统的IIR相比，离聚体的机械性能范围更广。在拟议的项目中，将建立反应条件，通过不同的技术将高异戊二烯含量的IIR和对甲基苯乙烯改性的IIR衍生为新型离聚体，并将研究所得聚合物的力学性能，以使其结构与观察到的性能相关联。这些丁基橡胶离聚体是在汽车工业等领域应用的新兴材料。

Butyl rubber (isobutylene-isoprene rubber, IIR) is a material with unusual physical properties, useful in different areas including automotive, architectural, and biomedical applications. A good resilience (shape recovery upon deformation) is necessary for all these applications. This is possible for IIR because the polymer chains contain a low concentration (1-2%) of isoprene (unsaturated) units in addition to isobutylene, allowing covalent (permanent) cross-linking of the chains into a 3-dimensional network structure. The covalent bonding approach, while providing good dimensional stability, allows only limited control over the mechanical properties of the material. Ionic interactions, on the other hand, are known to be very useful to modify the mechanical properties (e.g. rigidity, softening temperature, tear resistance) of rubbers and plastics, and have found applications in commercial products such as the Surlyn® resins, used as highly tear-resistant materials for blister packaging. The improved properties of polymers containing a low concentration of polymer-bound ionic groups (ionomers) are attributed to the aggregation of the ionic moieties, acting as multivalent physical cross-links at low to moderate temperatures. The application of the ionomer concept to improve the mechanical properties of butyl rubber has received little attention, mainly due to the very low (1-2%) isoprene content achieved in the traditional butyl rubber synthesis. New processes developed recently at LANXESS Inc. allow the synthesis of butyl rubber containing 1) up to 5-6% of isoprene units, or 2) up to 10% of p-methylstyrene units. This would allow the synthesis of ionomers with higher ionic moieties contents, and correspondingly a much wider range of mechanical properties than for traditional IIR. In the proposed project, reaction conditions will be established for the derivatization of high isoprene content IIR and of p-methylstyrene-modified IIR to novel ionomers by different techniques, and the mechanical properties of the resulting polymers will be investigated to correlate their structure with the observed properties. These butyl rubber ionomers are emerging materials of interest for applications in areas including the automotive industry.