“Click” Chemistry in Elastomers

Abstract

Click chemistry is an innovative approach to synthesizing new molecules by connecting two or more chemical entities having complementary “spring-loaded” reactive functional groups. Click reactions such as thiol–ene reactions, azide–alkyne reactions, Diels–Alder (DA) reactions, and retro Diels–Alder (rDA) reactions are useful in the synthesis of a single product with high yield and purity. Due to the high selectivity and good yield, these click reactions have become practical and reliable methods to develop new grades of polymer products with improved properties via post-synthetic structural modifications. Polyolefin elastomers having diversified structures and properties are widely used in various industries like the automotive, construction, medical, military and defense sectors. The major consumption of elastomers is mainly in tires, shoe soles, sports equipment, construction sealant, building materials, and toys. Due to the inhomogeneous structure and low functionality of the polymers used in elastomers, the tuning of properties and structural modifications are challenging. To overcome these challenges click reactions are considered as a simple and efficient way to tune the structure and achieve the desired properties by post-synthetic structural modification of the polymer chains. In this chapter, we will discuss the post-synthetic modifications of elastomers such as natural rubber (NR), polybutadiene rubber (PBR), styrene–butadiene rubber (SBR), isobutylene isoprene rubber (IIR), ethylene propylene diene monomer (EPDM), silicone rubber, and other specialty elastomers by various click reactions, including DA, rDA, azide–alkyne, and thiol–ene reactions, and the effect of such chemical modifications on the properties of the elastomers.