This manuscript describes the versatility of highly directional, noncovalent interactions, i.e., quadruple hydrogen bonding (QHB), to afford novel polyurea segmented supramolecular polymers for melt extrusion three-dimensional (3D) printing processes. The molecular design of the polyurea elastomers features (1) flexible polyether segments and relatively weak urea hydrogen-bonding sites in the soft segments to provide elasticity and toughness, and (2) strong ureido-cytosine (UCyt) QHB in the hard segments to impart enhanced mechanical integrity. The resulting polyureas were readily compression-molded into mechanically-robust, transparent, and creasable films. Optimization of polyurea composition offered a rare combination of high tensile strength (95 MPa), tensile elongation (788% strain), and toughness (94 MJ/m3), which are superior to a commercially available Ninjaflex elastomer. The incorporation of QHB facilitated melt processability, where hydrogen bonding dissociation provided low viscosities at printing temperatures. During cooling, directional self-assembly of UCyt QHB facilitated the solidification process and contributed to part fidelity with the formation of a robust physical network. The printed objects displayed high layer fidelity, smooth surfaces, minimal warpage, and complex geometries. The presence of highly directional QHB effectively diminished mechanical anisotropy, and the printed samples exhibited comparable Young’s moduli along (x–y direction, 0°) and perpendicular to (z-direction, 90°) the layer direction. Remarkably, the printed samples exhibited ultimate tensile strains approaching 500% in the z-direction prior to failure, which was indicative of improved interlayer adhesion. Thus, this design paradigm, which is demonstrated for novel polyurea copolymers, suggests the potential of supramolecular polymers with enhanced mechanical performance, melt processability, recyclability, and improved interlayer adhesion for melt extrusion additive manufacturing processes.

This manuscript describes the structure–property–morphology relationships of doubly charged 1,4-diazabicyclo[2.2.2]­octane (DABCO) salt-containing ABA triblock ionomers. The triblock copolymers consist a soft poly­(n-butyl acrylate) (PnBA) central block and two external styrenic hard blocks bearing amphiphilic pendant C18-alkyl groups and doubly charged salt units. Surprisingly, the DABCO salt-containing ABA block copolymers preserved the thermomechanical integrity until degradation, which indicated the formation of a reinforcing physical network compared to the corresponding doubly charged random copolymers and singly charged block copolymer analogs. Small-angle X-ray scattering data revealed that the DABCO-based ABA block copolymers self-assembled into highly ordered hierarchical microstructures, in which the soft and hard domain of the block copolymers phase-separated into highly ordered lamellar morphologies. Moreover, a secondary structure that originated from the ordering of the amphiphilic pendant groups formed within the lamellar hard domain. The interesting thermal, thermomechanical, and morphological properties of doubly charged ionic block copolymers open promising avenues for the synthesis of novel thermoplastic elastomers.

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This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

Charged block copolymers (BCPs) find use in numerous applications spanning from gene delivery to electromechanical transducers. Recent advances in polymer synthesis have provided researchers with the necessary tools to study the properties of a wide variety of BCPs bearing cationic and anionic substituents. Controlling the architecture of these charged BCPs plays a key role in tailoring their performances in the desired application. Likewise, the polymer morphology significantly affects ion transport and thermomechanical properties of the charged BCP. This article aims to compare the structure–property relationships in charged BCPs across a variety of different polymer architectures including linear, branched, segmented, and multiply charged BCPs with a focus on tailoring properties for specific applications. Linear BCPs comprise of diblock, triblock, and multiblock copolymers. Diblocks frequently serve as micelles for drug delivery while triblocks, multiblocks, and segmented BCPs act as ion exchange membranes for transducers and fuel cells. The section on branched BCPs discusses polymer brushes, stars, micelles, and cross‐linked networks. The final section describes synthetic routes toward synthesizing multiply charged monomers and polymers while also emphasizing the challenges and benefits associated with these materials.