Tuning Compositional Drift in the Anionic Copolymerization of Styrene and Isoprene

Abstract

The properties of polymer materials are largely a result of the local and long-range order of polymer chains and systems of polymer chains. The ability to tune polymer chain architecture at the monomer and chain levels through controlled synthesis is therefore a powerful tool for manipulating its properties. Perhaps, the most widely used synthetic means to manipulate polymer properties is copolymerization, where more than one monomer is simultaneously polymerized. For living anionic copolymerization, the statistics of comonomer incorporation have long been known to be dependent on the solvent, temperature, and initiator. Here, we leverage solvent dependence in the anionic copolymerization of styrene and isoprene to tailor the compositional profile along the polymer chain. Copolymerization of styrene and isoprene is conducted with varied quantities of a polar modifier (triethylamine), and the conversion is monitored by in situ attenuated total reflectance Fourier transform infrared spectroscopy. Monomer conversion profiles are used to extract reactivity ratios as a metric for examining the change in the compositional drift as the solvent composition is varied. Increasing triethylamine content leads to a continuous flattening of the compositional profile from the extreme nearly pure diblock structure for synthesis in cyclohexane to an essentially flat compositional profile in 50/50 (vol./vol.) cyclohexane/triethylamine. The ability to continuously tune compositional drift, as shown here, between these two extremes is a powerful synthetic tool for preparing copolymers and block copolymers with tunable properties.

Evolution of the Nanostructure and Viscoelastic Properties of Nitrile Rubber upon Mechanical Rejuvenation and Physical Aging

“…Interestingly, this evolution of NBR into a more nanostructured solid-like material can be accelerated by casting from a solvent and lowering the energy barrier for polymer self-diffusion. NBR was industrially developed in the 1930s but has a monomer chain distribution, thermodynamics of self-assembly, and polymer chain dynamics similar to that of recently developed tapered block copolymers ,,, or more conventional thermoplastic elastomers . Its synthesis by emulsion polymerization, thermal and solvent processability, self-healing capability, linear and nonlinear mechanical properties, and outstanding oil resistance still make it, almost a century later, a high-performance material for a range of engineering applications.…”

Investigation of eight-arm tapered star copolymers prepared by anionic copolymerization and coupling reaction

“…The enrichment of compatibilizing groups in the gradient structure can enhance interface mixing and broaden the interface width. To date, several approaches have been proposed to control the gradient composition in tapered copolymers depending on the reactivity ratios of monomers: (i) the addition of polar additives, 20,21 (ii) the injection of monomers with automated syringe pumps, 22 (iii) sequential addition of pure monomers or monomer mixtures, 23 and (iv) the use of substituted monomers. 15,[24][25][26][27] However, at present, the tapered copolymers under study are mostly linear.…”

Degradation of Polydienes Induced by Alkyllithium: Characterization and Reaction Mechanism

“…Since their introduction, many studies have been carried out yearly based on these techniques. In these works, researchers have focused on the polymer topology, − polymer microstructure, − functional monomers, − and novel catalysts for anion modification or polymerization . The products obtained by anionic methods are widely applied as functional polymer materials, such as self-healing rubbers, stimulus-responsive materials, , superhydrophobic materials, special nanoparticles, − and field-effect transistors (FETs) .…”