Comb Polyurethanes Consisting of Hard Segment Backbones and Dangling Soft Segments for Tailoring Mechanical Properties of Thermoplastics

Abstract

Graft polymers, including comb and bottlebrush polymers, have emerged as a topological molecular design for tailoring elastic material properties, relying on structural parameters. Yet, in stiffer materials, particularly thermoplastics, the inherent chemical nature of polymers often eclipses this topological design of mechanical properties. Here, we present comb polyurethanes (PUs) with hard segments in the backbone and soft segments in the side chains, with varying structural parameters, side chain spacing, and length. A series of comb PUs were synthesized by combining 4,4′-methylenebis(cyclohexylisocyanate), ethylene glycol, and two types of α-methyl, ω-diol-terminated polyether macromonomers in a polyaddition procedure. These macromonomers with a controlled average molecular mass were synthesized through end group modification of methyl-terminated polyethylene glycol and cationic ring-opening polymerization of THF. Interestingly, the comb PUs displayed a linear correlation between various mechanical properties and backbone volume fraction (φ HS ), including Young's modulus, tensile strength, yielding strength, and elongation at break. FT-IR and rheological measurements indicated that the backbones approach each other more freely than scaling analysis predicted. We hypothesized that comb PU has a network structure composed of hard segments diluted by viscoelastic soft segment side chains. Overall, this work highlights the unique mechanical properties of the comb PUs with hydrogen bonds in the backbone in topological designs for thermoplastic mechanical properties.

Tunable multicolor fluorescence of polyurethane derivatives controlled by molecular weight

“…29 The soft segments offer flexibility and elasticity, while the latter contribute to high strength, rigidity, and wear resistance. 30–32…”