Step-growth polymerization enables future technologies and molecular design of diverse macromolecular architectures ranging from tailored long-chain branching to segmented block copolymers. Scientists and engineers continue to advance the traditional families of step-growth polymers with novel synthetic strategies, unique processing scenarios, and tailored interfaces. Many step-growth polymers impart sustainability into emerging technologies, including bio-derived monomers and biodegradable compositions. New reaction pathways including Michael addition reactions, ionene polyelectrolytes, and click modification strategies have reenergized this field. This chapter focuses on the structure–property–performance relationships that continue to advance macromolecular science and engineering.

ABSTRACT Polymeric porous media are fundamental to sensing, thermal management, and filtration, yet traditional stochastic fabrication often forces trade‐offs between permeability and mechanical integrity. This review examines the paradigm shift from intrinsic chemical synthesis to extrinsic architectural programming, where the topology of “negative space” is treated as a precise design variable via additive manufacturing. We analyze this transition through four pivotal patterning strategies: (1) surface patterning, transforming passive boundaries into active electromechanical zones; (2) directional anisotropy, replacing random dispersion with vector‐dependent properties; (3) topological periodicity, utilizing lattice geometries to program mechanical metamaterials; and (4) hierarchical integration, decoupling conflicting functionalities across length scales. By synthesizing advances in vat photopolymerization and extrusion‐based printing, we demonstrate how these deterministic architectures enhance performance in multimodal sensing, soft actuation, thermal insulation, and selective filtration. Ultimately, bridging monolithic chemistry with biomimetic design offers a scalable pathway to adaptive, multifunctional material systems essential for addressing next‐generation structural and energy challenges.

Additive manufacturing (AM), or 3D printing, has rapidly advanced due to its customization, speed, and precision manufacturing. Traditional vat photopolymerization (VPP) often produces densely cross-linked, brittle, and non-reprocessable materials, contributing to plastic waste generation. To address these issues, a UV-reactive latex formulation combining water-dispersed thermoplastics with a minimal amount of photocurable water-soluble additive yielding reprocessable pseudothermoplastic materials are proposed. The selection of the water-soluble additive is crucial not only to enable the printing of high molecular weight thermoplastics with exceptional resolution and tunable properties but more importantly also to retain the properties of the initial latex-containing polymer while tackling reprocessability issues in photoprinted materials. Reprocessability is demonstrated using traditional manufacturing techniques (e.g., injection, hot-pressing) as well as extrusion 3D printing. Furthermore, optimized photocurable latex resins are suitable for two-photon 3D laser printing, enabling the miniaturization of features using the materials reported herein. This innovation opens new pathways for creating reprocessable, high-performance 3D-printed materials with on-demand properties.

Photocurable ceramic suspensions used in vat photopolymerization (VP) to produce composite and ceramic parts suffer from reduced resolution due to light scattering by the particles. When irradiated, the scattered light causes a redistribution of the UV intensity, resulting in a reduction in cure depth and an increase in cure width. To predict the resulting exposure distribution and cure profile shape of ceramic-loaded resins, the authors develop a Monte Carlo ray-tracing (MCRT) simulation to predict light scattering and absorption of UV energy in particle-filled resins. The simulation incorporates volume-dependent light scattering physics of polydisperse particle sizes to accurately represent the scattering behavior of filled resins. Additionally, the simulation uses only experimentally acquired parameters, including refractive index, particle size distribution, the spatial intensity distribution of the light source, and critical exposure to cure to predict the photocured shape. With these parameters, the authors simulate cure profiles of a zinc oxide-filled polyester acrylate resin, which has a high refractive index of 2.2. Printed and simulated cure profiles are compared across varying ZnO loadings (1-5 vol%) to validate the simulation. The simulation demonstrates a high degree of accuracy in predicting the experimental cure profile shape with all cure depth predictions within 10% (20 µm) and cure widths within 30% (15 µm).

Bottlebrush polymers, defined as polymers densely grafted with polymer side chains, have gained much attention for their unique mechanical properties. When cross-linked into a bottlebrush polymer network, these materials exhibit moduli in the kilopascal range, significantly softer than conventional linear polymer networks. The ability to access these "super-soft" materials creates exciting opportunities in fields requiring biointerfacing or highly compliant materials, such as tissue engineering, biomedical devices, and pressure sensors. Additive manufacturing (AM), specifically vat photopolymerization (VPP), provides a platform for the fabrication of a polymer network with precise and bespoke form factors. However, challenges such as high resin viscosity and slow curing rates are known obstacles for integrating bottlebrush polymer chemistry into VPP processes. This study introduces a synthetic approach leveraging acrylamide-terminated poly(dimethylsiloxane) (PDMS) macromonomers and cross-linkers for the VPP manufacturing of supersoft, solvent-free elastomers. These siloxane-based resins exhibit both low viscosity and rapid photocuring, making them ideal materials for VPP. The cross-link density can be directly controlled through formulation design, achieving storage moduli from 103 to 106 Pa, without necessitating solvent or plasticizer as in conventional systems. The elastomeric response of the photocured materials is evaluated with compression testing, reversibly accessing strains of up to 60%. The quality of the 3D-printed parts is confirmed via scanning electron microscopy. This work offers a practical synthetic route to 3D-printable PDMS-based supersoft elastomers, with modulus values on the order of soft tissue, for next-generation sensors and biointerfacing technologies.

Non-isocyanate polyureas offer a safer alternative to traditional polyureas with the avoidance of health and environmental hazards of isocyanate monomers. This manuscript presents a solvent-free melt polycondensation method that combines bio-sourceable urea with a linear primary diamine and an aromatic diamine, thereby bypassing isocyanate precursors. This approach allows direct incorporation of less nucleophilic aromatic diamines, previously challenging in earlier non-isocyanate routes. Adjusting the aromatic diamine content (5-20 wt%) created polyureas with excellent thermal stability (Td,5% > 318 degrees C) and widely varied mechanical properties. Most notably, Young's moduli spanned three orders-of-magnitude (3 MPa to 1.1 GPa), from soft elastomers to high modulus thermoplastics. Although atomic force microscopy and X-ray scattering studies revealed amorphous morphologies without distinct nanoscale phase separation, ductile films exhibited excellent mechanical performance due to the presence of the urea functionalities, i.e., associative bidentate hydrogen bonding serving as physical crosslinks. This report demonstrates the efficacy of synthesizing high-performance semi-aromatic polyureas in the presence of an organocatalyst with tunable properties using greener synthetic methods without sacrificing material performance.

This work presents the synthesis and characterization of poly (ethylene-co-1,2-octylene succinate) segmented polyethylene (PE) block copolymers synthesized via melt polycondensation of hydroxy-telechelic polyethylene (HTPE) macromonomers with 1,2-octane diol (12OD) and dimethyl succinate (DMS). Copolymers were synthesized with varying PE content (90, 75, 60, 50, and 25 wt%) and characterized for thermal, mechanical, and morphological properties. The introduction of 12OD disrupted crystallinity and effectively enhanced elongation at break, particularly for segmented copolymers with higher PE content. Increasing PE content improved mechanical properties, while higher polyester content reduced crystallinity and promoted the emergence of distinct polyester thermal transitions. These copolymers offer potential for chemical recycling with polyester segments serving as depolymerization points, thus contributing to sustainable material solutions and end of life (EOL) recycling strategies.

Vat photopolymerization (VPP) of highly aromatic polyurethanes (PUs) expands the library of additive manufacturing (AM) materials and enables a vast array of ductile thermoplastics, rigid and flexible thermosets, and elastomers. Aromatic diisocyanates and various diols enable printing of rigid, highly aromatic cross-linked parts, which offer high glass transition temperatures and tunable thermomechanical performance. The judicious control of molecular weight of the photo-reactive telechelic oligomers allows for a fundamental study of the influence of cross-link density in highly aromatic 3D PU printed objects. VPP AM produces objects with high resolution, smooth surface finish, and isotropic mechanical properties. Thermal post-processing is critical in maintaining excellent thermomechanical properties with semi-crystallinity as a function of cross-link density. Due to the presence of two ester carbonyls in the bis(2-hydroxyethyl) terephthalate chain extender, the printed parts are readily amenable to depolymerization with methanolysis to produce difunctional dimethyl dicarbamates under modest reaction conditions. Dimethyl dicarbamates serve as suitable monomers for subsequent polycondensation.

Polymer InternationalVolume 73, Issue 2 p. 73-74 Editorial Simply stated, the world must consume less plastic! Timothy E. Long, Corresponding Author Timothy E. Long [email protected] Arizona State University, Biodesign Center for Sustainable Macromolecular Materials and Manufacturing (SM3), Tempe, AZ, USASearch for more papers by this author Timothy E. Long, Corresponding Author Timothy E. Long [email protected] Arizona State University, Biodesign Center for Sustainable Macromolecular Materials and Manufacturing (SM3), Tempe, AZ, USASearch for more papers by this author First published: 05 January 2024 https://doi.org/10.1002/pi.6602Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. REFERENCES 1Cencer MM, Moore JS and Assary RS, Polym. Int. 71: 537–542 (2022). 10.1002/pi.6345 CASWeb of Science®Google Scholar 2Caldera-Villalobos M, Ramos-Montañez DG, Cabrera-Munguía DA, Becerra-Rodriguez JJ, Rodríguez-Fuentes N and Claudio-Rizo JA, Polym. Int (2023). https://doi.org/10.1002/pi.6590 10.1002/pi.6590 Google Scholar 3Kubisa P, Polym Int 72: 681–686 (2023). 10.1002/pi.6532 CASWeb of Science®Google Scholar 4Rostami-Tapeh-Esmaeil E, Kazemi H, Ahmad H, Morin M and Rodrigue D, Polym. Int. 72: 1104–1111 (2023). 10.1002/pi.6559 CASGoogle Scholar 5Alharbi HY, Aljohani MS and Monier M, Polym. Int. 73: 50–60 (2023). 10.1002/pi.6570 Google Scholar 6Robertson M, Dunn CB and Qiang Z, Polym Int. 72: 1061–1069 (2023). 10.1002/pi.6562 CASGoogle Scholar 7Bean RH and Long TE, Polym. Int. 73: 5–8 (2023). 10.1002/pi.6584 Google Scholar 8Camani PH, da Silva Torin RF, de Souza CW, Zanata L and dos Santos Rosa D, Polym. Int. 70: 628–635 (2021). 10.1002/pi.6147 CASWeb of Science®Google Scholar 9Wilts EM, Herzberger J and Long TE, Polym. Int. 67: 799–814 (2018). 10.1002/pi.5569 CASWeb of Science®Google Scholar 10Nelson Esther EP, Venkatesan B, Sravankumar P and Ramasamy S, Polym. Int. 72: 1047–1054 (2023). 10.1002/pi.6554 CASWeb of Science®Google Scholar 11Peng H, Ji M, Li J, Shen S, Wang W, Chen M et al., Polym. Int. (2023). https://doi.org/10.1002/pi.6579 10.1002/pi.6579 Google Scholar 12Weyhrich CW and Long TE, Polym. Int. 71: 532–536 (2022). 10.1002/pi.6343 CASWeb of Science®Google Scholar Volume73, Issue2February 2024Pages 73-74 ReferencesRelatedInformation

Polyurethanes are remarkably versatile materials that offer exceptional control over structure-property relationships, making them the subject of extensive research and exploration across diverse applications. These materials have garnered significant attention due to their inherent chemical, mechanical, thermomechanical, biological and physical properties, further fueling interest in their potential uses. However, conventional processing methods, involving molds, high temperatures or solvents, impose limitations on geometric complexity, hindering their potential applications. Additive manufacturing, or 3D printing, has emerged as a transformative solution, enabling the fabrication of intricate geometries, unparalleled design flexibility, dematerialization and enhanced material properties. This mini-review explores recent advancements in additive manufacturing techniques applied to polyurethanes, focusing on three prominent 3D printing modalities: vat photopolymerization, direct ink write and fused filament fabrication. Examining the successful integration of polyurethanes with these cutting-edge 3D printing methods illuminates the remarkable progress achieved in tailoring part design, expanding the range of applications and unlocking novel material-object functionalities. This mini-review aims to provide valuable insight into the latest trends and development in 3D printing polyurethanes, paving the way for their future utilization in diverse industries. (c) 2023 Society of Chemical Industry. Polyurethanes are remarkably versatile materials that offer exceptional control over structure-property relationships; however, conventional processing methods impose limitations on geometric complexity, hindering their potential applications. This mini-review covers recent trends in the additive manufacturing of polyurethanes to address modern challenges in polymer processing and drive innovation.image

Vat photopolymerization (VPP) additive manufacturing (AM) produces complex geometries with micron-scale resolution and smooth surface finish from a wide range of photocrosslinkable polymeric precursors. However, mass transport limitations typically constrain VPP amenable precursors to viscosities less than 10 Pa & sdot;s. Reactive oligomers and monomers comprise the majority of VPP polymeric precursors, which result in highly crosslinked and brittle 3D objects upon printing. This work describes colloidal high molecular weight ABA triblock copolymers, or latex, as a feedstock for aqueous photoreactive compositions to enable AM of thermoplastic elastomers (TPE). Photorheological analysis determined 15 wt% aqueous reactive monomers and oligomers generated a structural scaffold that achieved sufficiently high modulus to maintain feature fidelity for iterative layer formation. Subsequent thermal post-processing removed water and promoted polymeric particle coalescence throughout the scaffold resulting in an interpenetrating network (IPN) that exhibited an isotropic dimensional shrinkage of 25 %. Small-angle X-ray scattering (SAXS) confirmed microphase-separated morphologies typical of triblock copolymers, revealing a characteristic length scale of 30 nm. Using commercially available VPP printers, ABA triblock copolymer poly(styrene-b-isoprene-b-styrene) latex yielded printed elastomers with precise feature fidelity and tensile extensibility exceeding 800 %.

Polymer InternationalVolume 72, Issue 2 p. 143-144 Editorial Nurturing a global choir of perspective Timothy E. Long, Timothy E. Long Arizona State University, Biodesign Center for Sustainable Macromolecular Materials and Manufacturing (SM3), Tempe, AZ, 85281 USASearch for more papers by this author Timothy E. Long, Timothy E. Long Arizona State University, Biodesign Center for Sustainable Macromolecular Materials and Manufacturing (SM3), Tempe, AZ, 85281 USASearch for more papers by this author First published: 10 January 2023 https://doi.org/10.1002/pi.6494Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. REFERENCES 1Douglas HR, Papegaaij A, Reuvers B, Buijsen P and Koning C, Polymer International. 70: 490– 498 (2021 May). 2Golling FE, Pires R, Hecking W, Richter D et al., Polymer International. 68: 848– 855 (2019 May). 3Wang LA and Han L, Polymer International. 69: 7– 17 (2020 January). 4Mautner., Polymer International. 69: 741– 751 (2020 September). 5Li X, Liu J, Zheng ZJ. Polymer International 2022 September. 6Ye Z, Lu H, Chai G, Wu C, Chen J and Leifeng L, Polymer International. 72: 27– 38 (2023 January). 7Ding L, Li D, Du F, Zhang Z and Wu T, Polymer International. 72: 61– 70 (2023 January). 8Lim J, Choi S and Kim HS, Polymer International. 72: 120– 125 (2023 January). 9Klayya, Tawichai, Intatha U, Zhang H, Bilotti, Soykeabkaew. Polymer International. 2022 October. 10Liu Y, Wang L, Huang Y, Hou C et al., Polymer International. 72: 166– 175 (2023). 11Mohanty D, Mohanty S and Kanny K, Polymer International. 72: 230– 242 (2023). Volume72, Issue2February 2023Pages 143-144 ReferencesRelatedInformation

Melt polycondensation of dimethyl 3,30 -bibenzoate (3,3'BB) with various linear and cycloaliphatic diols enabled the synthesis of a series of semi-aromatic polyesters. Size exclusion chromatography analysis confirmed high molecular weight (M-n > 20 kg mol(-1)). Compression molding resulted in ductile films and further established molecular weights desirable for mechanical performance. H-1 NMR spectroscopy confirmed polymer structure and retainment of the cis/trans ratios for the cyclohexyldimethylene-based polyesters before and after polymerization. Thermogravimetric analysis revealed high onset of weight loss temperatures for the novel semi-aromatic polymers (T-d,T-5% > 380 degrees C). Differential scanning calorimetry and dynamic mechanical analysis were used to determine glass transition temperatures and melting temperatures. Further evaluation of these thermal transitions against previously synthesized 4,4'BB, 3,4'BB, and isophthalate-based polymers elucidated the structure-property relationships of these systems. (c) 2023 Society of Industrial Chemistry.

Polymer colloids are complex materials that have the potential to be used in a vast array of applications. One of the main reasons for their continued growth in commercial use is the water-based emulsion polymerization process through which they are generally synthesized. This technique is not only highly efficient from an industrial point of view but also extremely versatile and permits the large-scale production of colloidal particles with controllable properties. In this perspective, we seek to highlight the central challenges in the synthesis and use of polymer colloids, with respect to both existing and emerging applications. We first address the challenges in the current production and application of polymer colloids, with a particular focus on the transition toward sustainable feedstocks and reduced environmental impact in their primary commercial applications. Later, we highlight the features that allow novel polymer colloids to be designed and applied in emerging application areas. Finally, we present recent approaches that have used the unique colloidal nature in unconventional processing techniques.

Vat photopolymerization (VP) and direct ink write (DIW) additive manufacturing (AM) provide complex geometries with precise spatial control employing a vast array of photo-reactive polymeric systems. Although VP is recognized for superior resolution and surface finish, DIW provides versatility for higher viscosity systems. However, each AM platform presents specific rheological requirements that are essential for successful 3D printing. First, viscosity requirements constrain VP polymeric materials to viscosities below 10 Pa s. Thus, this requirement presents a challenging paradox that must be overcome to attain the physical performance of high molecular weight polymers while maintaining suitable viscosities for VP polymeric materials. Second, the necessary rheological complexity that is required for DIW pastes requires additional rheological measurements to ensure desirable thixotropic behavior. This manuscript describes the importance of rheological measurements when designing polymeric latexes for AM. Latexes effectively decouple the dependency of viscosity on molecular weight, thus enabling high molecular weight polymers with low viscosities. Photo-crosslinking of water-soluble monomers and telechelic oligomeric diacrylates in the presence of the latex enables the fabrication of a scaffold, which is restricted to the continuous aqueous phase and effectively surrounds the latex nanoparticles enabling the printing of otherwise inaccessible high molecular weight polymers. Rheological testing, including both steady and oscillatory shear experiments, provides insights into system properties and provides predictability for successful printing. This perspective article aims to provide an understanding of both chemical functionality (photo- and thermal-reactivity) and rheological response and their importance for the successful design and evaluation of VP and DIW processable latex formulations.

Vat photopolymerization (VP) is an advanced additive manufacturing (AM) platform that enables production of intricate 3D monoliths that are unattainable with conventional manufacturing methods. In this work, modification of amorphous poly(arylene ether sulfone)s (PSU) allows for VP printing. Post-polymerization telechelic functionalization with acrylate functionality yielded photocrosslinkable PSUs across a molecular weight range. H-1 NMR spectroscopy confirms chemical composition and quantitative acrylate functionalization. Addition of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) photoinitiator to 30 wt% PSU solutions in NMP provides a photocurable composition. However, subsequent photorheological studies elucidate rapid photodegradation of the polysulfone main chain, which is especially apparent in high M-n (15 kg mol(-1)) PSU formulations. UV-light intensity and wavelength range are altered to reduce degradation while allowing for efficient crosslinking. The addition of 0.5 wt% of avobenzone photoblocker produces an ill-defined structure with 6 kg mol(-1) PSU. For higher molecular weights (>12 kg mol(-1)), solutions with a low molar mass reactive diluent, i.e., trimethylolpropane triacrylate, enable the printing of an organogel with a storage modulus (>10(5) Pa) sufficient for vat photopolymerization. Employing multicomponent solutions provide well-defined parts with complex geometries through vat photopolymerization.

AbstractCharged 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.

High-performance engineering polymers continually challenge existing boundaries of rapidly emerging research areas including electronics, transportation, energy, defense and aerospace. Significant research attention over the past decade highlights the exceptional performance of these polymers due to their superior thermomechanical properties and stability under extreme conditions. Unfortunately, inherent structure-property relationships of high-performance engineering polymers, which predict this unique complement of physical properties, also describe high-viscosity melts and high melting temperatures. These processing challenges have steered researchers towards advanced processing methods, such as additive manufacturing, that allow for unprecedented control over part geometry. In addition, additive manufacturing serves to advance application-cost relationships, as part optimization and 3D printing of previous monolithic components allow for less material consumption. Currently, the additive manufacturing materials toolbox only contains a fraction of commercially available high-performance polymers due to unique processing constraints. This review discusses recent efforts towards the successful additive manufacturing of three high-performance polymer families, i.e. polysulfones, poly(ether ether ketone)s and polyimides. (c) 2021 Society of Industrial Chemistry.