Unsaturated polyurethanes degradable by conjugate substitution reactions with amines and carboxylate anions

Abstract

Methacrylate skeletons substituted with phenyl and carbamate groups at the allylic position are excellent decomposition points that induce selective and quantitative main chain scission with weak nucleophiles such as acetate anions.

Tailored Polyurethane Synthesis from AB-Type Monomers

“…Finally, the mechanical properties of a polyO2 film were evaluated by a tension test (Figure ). As a result, it showed fracture stress at 44 MPa with a low fracture strain value (3.3%), which was very different from conventional polyurethane elastomers known for their high toughness (fracture stress from around 0.01 to 70 MPa, strain ranges from 40 to 2800%). − ,− This significant difference would be attributed to the lower content of the soft component on polyO2 than the standard polyurethanes. Based on hard/soft segment chemistry in conventional polyurethanes, − the mechanical properties of the AB-type monomer-based polyurethane may be fine-tuned according to the intended use.…”

“…Controlling the primary polymer structure has been one of the most fundamental challenges in polymer synthesis because the primary structure sets most of the polymer properties. − To construct a well-defined polymer backbone structure, various approaches have been reported so far, e.g., via single monomer addition, specific catalyst preparation to control the repeating unit sequence, or using the intramolecular transformation reaction after one repeating unit addition. − Thanks to these efforts, a wide range of newly defined polymer structures have become accessible within the past decade, but major progress has only been made in chain polymerization systems such as vinyl polymer synthesis. Compared with the defined polymer synthesis on chain polymerization, sequence control on step polymerization has not progressed so far, probably because of the difficulty of controlling the latter. − Meanwhile, one of the most produced polymers in industries is polyurethane, which is typically prepared by step polymerization using a diol and a diisocyanate as monomers (Figure A). − Since the polymerization based on such AA plus BB-type monomers provides always a simple repeating pattern consisting of AA-BB repeating units, the idea of sequence does not make much sense. To implement a more sophisticated polyurethane backbone design, multiple approaches have been reported, such as ring-opening polymerization (ROP) of cyclic monomers or one-by-one monomer addition to synthesize oligomer species. − However, those methods often face inevitable limitations on their versatility caused by the taxing synthetic process, and highly defined structures have been achieved only for oligomers, not polymers.…”