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，可用于不同领域，包括汽车，建筑和生物医学应用。良好的弹性（变形后的形状恢复）对于所有这些应用都是必要的。这对于IIR是可能的，因为聚合物链除了异丁烯之外还含有低浓度（1-2%）的异戊二烯（不饱和）单元，允许链共价（永久）交联成三维网络结构。共价键合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，已知离子相互作用对于改变橡胶和塑料的机械性能（例如，刚性、软化温度、抗撕裂性）非常有用，并且已经在商业产品如Surlyn®树脂中发现了应用，其用作泡罩包装的高度抗撕裂材料。含有低浓度的聚合物结合的离子基团（离聚物）的聚合物的改进的性能归因于离子部分的聚集，在低温至中等温度下充当多价物理交联。应用离聚物概念来改善丁基橡胶的机械性能很少受到关注，这主要是由于在传统的丁基橡胶合成中获得的异戊二烯含量非常低（1-2%）。朗盛公司最近开发的新工艺允许合成含有1）至多5-6%的异戊二烯单元，或2）至多10%的对甲基苯乙烯单元的丁基橡胶。这将允许合成具有更高离子部分含量的离聚物，并且相应地具有比传统IIR宽得多的机械性能范围。在拟议的项目中，将建立反应条件的衍生化高异戊二烯含量的IIR和对甲基苯乙烯改性的IIR的新型离聚物通过不同的技术，和所得聚合物的机械性能将进行研究，以关联其结构与观察到的性能。这些丁基橡胶离聚物是在包括汽车工业在内的领域中应用的新兴材料。

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.