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Herein we report the use of a tetrazine-norbornene inverse electron demand Diels-Alder conjugation applied to polymer end-functionalization and polymer-polymer coupling. The reaction was found to be applicable to polymer-polymer coupling, as judged by SEC, DOSY NMR, and LCxSEC analyses, giving diblock copolymers by merely mixing the constituent homopolymers together under ambient conditions, using no catalyst, additive, or external stimulus.

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In most synthetic elastomers,c hanging the physical properties by monomer choice also results in ac hange to the crystallinity of the material, which manifests through alteration of its mechanicalperformance.Using organocatalyzed stereospecific additions of thiols to activated alkynes,h igh-molarmass elastomers were isolated via step-growth polymerization. The resulting controllable double-bond stereochemistry defines the crystallinity and the concomitant mechanical properties as well as enabling the synthesis of materials that retain their excellent mechanical properties through changing monomer composition. Using this approacht oe lastomer synthesis,f urther end group modification and toughening through vulcanization strategies are also possible.The organocatalytic control of stereochemistry opens the realm to an ew and easily scalable class of elastomers that will have unique chemical handles for functionalization and post synthetic processing.Nature has evolved the ability to create large and complex molecules in which the precise control over the spatial arrangement of the atoms is critical to their performance.The three-dimensional control over the arrangement of bonds is as important to the function and behavior of molecules as any other factor and is critical to the structure-function relationships that govern the role of arange of molecules.While the effect of stereochemistry on functionality is probably best known in the examples of small molecule drugs such as thalidomide (one enantiomer is effective against morning sickness,t he other is teratogenic) or naproxen (one enantiomer is used to treat arthritis pain, the other causes liver poisoning with no analgesic effect), it is less well-studied with respect to materials design.Elastomeric materials are applied widely to demanding applications on account of their inherent reversible deformation behavior. Many synthetic elastomer materials are tri-or multi-block copolymers that are based on the concept of an amorphous-crystalline or hard-soft phase-separated system in which organization of the hard and soft domains endows the strong but elastic properties upon the materials.[1] While these materials have found widespread application, changes to the monomers or stoichiometry designed to elicit ac hange in physical properties also alter the chain packing and hence the mechanical properties of the materials.I nterestingly,n atural rubber and gutta percha are homopolymers of poly(cisisoprene) and poly(trans-isoprene) respectively.W hile these materials differ by only the double bonds of the backbone,the superior elastomeric properties of natural rubber [2] are attributed to the enhanced chain packing afforded by its stereochemical orientation.[3] While the design principles to control crystallinity and the associated mechanical properties in these materials are clear,the inability to incorporate awide range of functional groups in ac ontrolled manner or rationally define the chain end functionality limits the applications of both these materials a...