Reprocessable Covalent Adaptable Networks via Free-Radical Polymerization with an Aromatic Disulfide Cross-Linker

ACS Applied Polymer Materials, Journal Year: 2024, Volume and Issue: 6(15), P. 9209 - 9218

Published: July 22, 2024

Aromatic disulfides have seen widespread use in covalent adaptable networks (CANs), though previous studies exclusively used step-growth methods to integrate them into CANs. Here, we describe a case which an aromatic disulfide-based cross-linker, bis(4-methacryloyloxyphenyl) disulfide, also called BiPheS methacrylate or BPMA, is incorporated CAN by nonstep-growth polymerization. Free-radical copolymerization of n-hexyl with 5 mol % BPMA results exhibits full recovery cross-link density and thermomechanical properties across multiple reprocessing cycles. The rubbery-plateau storage modulus directly proportional absolute temperature, characteristic constant density, even at temperatures where the reprocessable. Indeed, BPMA-based thus associative dynamic character, up least 200 °C, enabling it be elevated-temperature applications without risk loss network character. Under 3.0 kPa shear stress, almost total arrest creep 180 °C major suppression its temperature overcoming potential Achilles' heel associated Thus, integration CANs free-radical polymerization provides facile route produce recyclable that maintain character very high contributing polymer sustainability. Finally, determined Arrhenius apparent activation energy ∼100 kJ/mol for stress relaxation viscosity. This value differs substantially from bond dissociation but agrees alpha-relaxation poly(n-hexyl methacrylate) (PHMA). indicates dependence these viscoelastic responses our associative-type defined cooperative segmental mobility PHMA, makes 95 CAN.

Language: Английский

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Rapidly Self‐Healable and Melt‐Extrudable Polyethylene Reprocessable Network Enabled with Dialkylamino Disulfide Dynamic Chemistry

Macromolecular Rapid Communications, Journal Year: 2024, Volume and Issue: 45(22)

Published: July 24, 2024

Abstract Catalyst‐free, radical‐based reactive processing is used to transform low‐density polyethylene (LDPE) into covalent adaptable networks (PE CANs) using a dialkylamino disulfide crosslinker, BiTEMPS methacrylate (BTMA). Two versions of BTMA are used, BTMA‐S 2 , with nearly exclusively bridges, and n mixture oligosulfide produce S PE CAN CAN, respectively. The two CANs exhibit identical crosslink densities, but the manifests faster stress relaxation, average relaxation times ∼4.5 shorter than those over 130 160 °C temperature range. more rapid dynamics translate compression‐molding reprocessing time at only 5 min (vs 30 for CAN) achieve full recovery density. Both melt‐extrudable within experimental uncertainty density after extrusion. self‐healable, crack fully repaired original tensile properties restored or 60 slightly above LDPE melting point without assistance external forces.

Language: Английский

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Extrudable and Highly Creep-Resistant Covalent Adaptable Networks Made from Polyethylene and Ethylene/1-Octene Copolymers by Reactive Processing with Aromatic Disulfide Cross-Links

ACS Applied Polymer Materials, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 3, 2024

Polyolefins like polyethylene (PE) and ethylene-based copolymers are widely used in consumer industrial applications due to their versatility, the diversity tunability of properties, theoretical recyclability at elevated temperatures. However, recycling rates markedly low, and, though cross-linking PE enhances its properties through creation a networked architecture, resulting thermoset known as PEX is rendered completely unrecyclable. Incorporating associative or dissociative dynamic covalent bonds cross-links into plastics promising route both make use spent (via "upcycling" them) generate recyclable alternatives unrecyclable thermosets PEX. Such materials adaptable networks CANs (also called vitrimers if exclusively associative). Here, we present method for imbuing polymers with aromatic disulfide cross-links, robust, reprocessable CANs. Radical-based reactive processing ethylene/1-octene-based 1 wt % dicumyl peroxide 5 bis(4-methacryloyloxyphenyl) (BiPheS methacrylate BPMA) successfully resulted which fully recovered cross-link densities associated thermomechanical after multiple reprocessing cycles. These demonstrate remarkable elevated-temperature creep resistance high-temperature thermal stability high temperatures required exchanges BiPheS-based cross-links. copolymer also enable (re)processability via extrusion temperatures, property recovery demonstrated 260 °C, thereby indicating feasibility extending our approach scales processes well other rigorous applications.

Language: Английский

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Covalent Adaptable Networks with Associative Siloxane Exchange Enabled by Amide‐Based Internal Catalysis: Designing for Reprocessability and Extrudability by Increasing the Cross‐Link Density

Advanced Functional Materials, Journal Year: 2025, Volume and Issue: unknown

Published: May 9, 2025

Abstract Replacing non‐recyclable thermosets with covalent adaptable networks (CANs) that recover cross‐link density after reprocessing will reduce waste and contribute to a circular polymer economy. Many CANs undergoing associative dynamic exchange require catalysis. External catalysis often leads harmful effects, e.g., increased creep, accelerated material aging, catalyst leaching. Herein, internally catalyzed siloxane chemistry is demonstrated resulting from amides covalently linked through alkyl chains siloxanes. Small‐molecule studies show the formation of products reaction two amide‐containing molecules. From rubbery plateau modulus, each siloxane‐exchange‐based CAN exhibits temperature‐invariant, or nearly so, characteristic CANs. The length in siloxane‐containing monomer tunes network density. Cross‐link recovery achieved, required time temperature decreasing increasing Stress relaxation also faster dynamics reprocessability arise because second order (i.e., cross‐linker) concentration. Capitalizing on this, melt extrusion highest demonstrated, achieving same extruded compression‐molded Using identical conditions, next‐highest not extrudable.

Language: Английский

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Reprocessable Polymer Networks Containing Sulfur‐Based, Percolated Dynamic Covalent Cross‐Links and Percolated or Non‐Percolated, Static Cross‐Links

Macromolecular Rapid Communications, Journal Year: 2024, Volume and Issue: unknown

Published: July 11, 2024

Abstract One method to improve the properties of covalent adaptable networks (CANs) is reinforce them with a fraction permanent cross‐links without sacrificing their (re)processability. Here, simple synthesize poly( n ‐hexyl methacrylate) (PHMA) and ‐lauryl (PLMA) containing static dialkyl disulfide (utilizing bis(2‐methacryloyl)oxyethyl disulfide, or DSDMA, as cross‐linker) dynamic dialkylamino sulfur‐sulfur BiTEMPS methacrylate dissociative presented. The robustness (re)processability CANs are demonstrated, including full recovery cross‐link density after recycling. authors also investigate effect content on stress relaxation responses percolated, cross‐links. As PHMA PLMA have very different activation energies respective cooperative segmental mobilities, it shown that dominated by dissociation rather than relaxations backbone segments, i.e., alpha relaxation. In cross‐links, side chains, beta relaxation, critical in allowing for large‐scale governs

Language: Английский

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Chemical Innovations in Polymer Upcycling: Beyond Traditional Recycling

Advances in sustainability science and technology, Journal Year: 2024, Volume and Issue: unknown, P. 171 - 183

Published: Dec. 18, 2024

Language: Английский

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