Polymerization with Borane Chemistry. Tributylborane/p-Quinone System as a New Method of Reversible-Deactivation Radical Copolymerization for Styrene and Methyl Acrylate

Organoboron-mediated polymerizations

The scientific community has witnessed extensive developments and applications of organoboron compounds as synthetic elements and metal-free catalysts for the construction of small molecules, macromolecules, and functional materials over the last two decades. This review highlights the achievements of organoboron-mediated polymerizations in the past several decades alongside the mechanisms underlying these transformations from the standpoint of the polymerization mode. Emphasis is placed on free radical polymerization, Lewis pair polymerization, ionic (cationic and anionic) polymerization, and polyhomologation. Herein, alkylborane/O2 initiating systems mediate the radical polymerization under ambient conditions in a controlled/living manner by careful optimization of the alkylborane structure or additives; when combined with Lewis bases, the selected organoboron compounds can mediate the Lewis pair polymerization of polar monomers; the bicomponent organoboron-based Lewis pairs and bifunctional organoboron-onium catalysts catalyze ring opening (co)polymerization of cyclic monomers (with heteroallenes, such as epoxides, CO2, CO, COS, CS2, episulfides, anhydrides, and isocyanates) with well-defined structures and high reactivities; and organoboranes initiate the polyhomologation of sulfur ylides and arsonium ylides providing functional polyethylene with different topologies. The topological structures of the produced polymers via these organoboron-mediated polymerizations are also presented in this review mainly including linear polymers, block copolymers, cyclic polymers, and graft polymers. We hope the summary and understanding of how organoboron compounds mediate polymerizations can inspire chemists to apply these principles in the design of more advanced organoboron compounds, which may be beneficial for the polymer chemistry community and organometallics/organocatalysis community.

Grafting of Methyl Methacrylate onto Gelatin Initiated by Tri-Butylborane-2,5-Di-Tert-Butyl-p-Benzoquinone System

Graft gelatin and poly(methyl methacrylate) copolymers were synthesized in the presence of the tributylborane—2,5-di-tert-butyl-p-benzoquinone (2,5-DTBQ) system. The molecular weight parameters and morphology of the polymer indicate that it has a cross-linked structure. Obtained data confirm the simultaneous formation of a copolymer in two ways: “grafting from” and “grafting to”. It leads to the cross-linked structure of a copolymer. This structure was not obtained for copolymers synthesized in the presence of other initiating systems: azobisisobutyronitrile; tributylborane; azobisisobutyronitrile and tributylborane; azobisisobutyronitrile, tributylborane, and 2,5-di-tert-butyl-p-benzoquinone. In these cases, the possibility of the formation of the copolymer, simultaneously in two ways, was excluded. Graft gelatin and poly(methyl methacrylate) copolymers synthesized in the presence of the tributylborane—2,5-di-tert-butyl-p-benzoquinone system are promising in terms of their use in scaffold technologies due to the three-dimensional mesh structure, providing a high regenerative potential of materials.