The importance of stereochemistry to the function of molecules is generally well understood. However, to date, control over stereochemistry and its potential to influence properties of the resulting polymers are, as yet, not fully realised. This review focuses on the state-of-the-art with respect to how stereochemistry in polymers has been used to influence and control their physical and mechanical properties as well as begin to control their function. A brief overview of the synthetic methodology by which to access these materials is included, with the main focus directed towards stereochemical control over properties such as mechanical, biodegradation and conductivity. Additionally, the advances being made towards enantioseparation, enantioselective catalyst supports and stereo-directed transitions are discussed. Finally, we also consider the opportunities that the rich stereochemistry of sustainably-sourced monomers could offer in this field. Where possible, parallels and general design principles are drawn together to identify opportunities and limitations that these approaches may present in their effects on materials properties, performance and function.

The remarkable elasticity and tensile strength found in natural elastomers are challenging to mimic. Synthetic elastomers typically feature covalently crosslinked networks (rubbers), but this hinders their reprocessability. Physical cross-linking via hydrogen bonding or ordered crystallite domains can afford reprocessable elastomers, but often at the cost of performance. Herein, we report the synthesis of ultra-tough, reprocessable elastomers based on linear alternating polymers. The incorporation of a rigid isohexide adjacent to urethane moieties affords elastomers with exceptional strain hardening, strain rate dependent behavior, and high optical clarity. Distinct differences were observed between isomannide and isosorbide-based elastomers where the latter displays superior tensile strength and strain recovery. These phenomena are attributed to the regiochemical irregularities in the polymers arising from their distinct stereochemistry and respective inter-chain hydrogen bonding.

Polypeptide nanoparticles were obtained by the miniemulsion polymerization of S-(o-nitrobenzyl)-L-cysteine (NBC) N-carboxyanhydride (NCA). Through process optimization, reaction conditions were identified that allowed the polymerization of the water sensitive NCA to yield nanoparticles of about 220 nm size. Subsequent UV-irradiation of the nanoparticle emulsions caused the in situ removal of the nitrobenzyl group and particle cross-linking through disulfide bond formation accompanied by the shrinkage of the particles.

Stereochemistry in polymers can be used as an effective tool to control the mechanical and physical properties of the resulting materials. Typically, though, in synthetic polymers, differences among polymer stereoisomers leads to incremental property variation, i.e., no changes to the baseline plastic or elastic behavior. Here we show that stereochemical differences in sugarbased monomers yield a family of nonsegmented, alternating polyurethanes that can be either strong amorphous thermoplastic elastomers with properties that exceed most cross-linked rubbers or robust, semicrystalline thermoplastics with properties comparable to commercial plastics. The stereochemical differences in the monomers direct distinct intra-and interchain supramolecular hydrogen-bonding interactions in the bulk materials to define their behavior. The chemical similarity among these isohexide-based polymers enables both statistical copolymerization and blending, which each afford independent control over degradability and mechanical properties. The modular molecular design of the polymers provides an opportunity to create a family of materials with divergent properties that possess inherently built degradability and outstanding mechanical performance.

Polymer crystallinity is known to be dependent upon backbone stereochemistry and this concept has emerged as an effective means of altering bulk material properties. Herein, we describe a simple, step-growth polymerization to synthesize unsaturated poly(ester-urethane)s using the thiol-Michael addition reaction. The absolute control of alkene stereochemistry (0−100 % trans content) in the polymer backbone was achieved by varying the cis/trans double bond content of the monomer feedstock. In turn, the crystallinity of the polymer was systematically varied which manifested in control over the resultant tensile properties such as Young's modulus, ultimate tensile strength and elongation at break. Generally, the crystallinity and tensile strength were positively correlated with increasing trans double bond content within the polymer.