Periodic Reporting for period 3 - CoaExMatter (Bio-inspired Coacervate Extruded Materials)
Reporting period: 2023-09-01 to 2025-02-28
Summary of context and overall objective of the project:
Recently, biologists discovered that a crucial element in the processing of many natural materials (e.g. caddisfly silk and velvet worm slime) are coacervates, which are concentrated macromolecular phases that form upon liquid-liquid phase separation from the initial solution. An understanding is emerging that the liquid coacervate phases enable extrusion of the material and allow for conformational changes within the material before solidification. Thus, the coacervate nature is crucial for obtaining extraordinary property profiles in these natural materials. In this project we mimic this environmentally benign processing principle of Coacervate Extrusion (CoaEx) for the development of completely new synthetic and biopolymeric materials. Previously we developed bio-inspired synthetic coacervates with well-controlled architecture and composition, and various tools to study their structure and mechanics. Currently we take advantage of this expertise to develop unique material systems by extruding synthetic coacervates and using the induced mechanical stress to obtain alignment and conformational changes.
Analogous to the wide variety of materials found in natural systems that commence as a coacervate, this processing principle is applicable to a wide variety of synthetic material classes. In this project coacervate extrusion is used to produce fibers, rods or scaffolds composed of: polyelectrolyte complexes, liquid-crystal elastomers, peptide-polymers and proteins. This bio-inspired processing principle of coacervate extrusion will lead to materials with unexplored property profiles and holds great promise for the development of unprecedented high performance materials obtained by green processing.
Recently, biologists discovered that a crucial element in the processing of many natural materials (e.g. caddisfly silk and velvet worm slime) are coacervates, which are concentrated macromolecular phases that form upon liquid-liquid phase separation from the initial solution. An understanding is emerging that the liquid coacervate phases enable extrusion of the material and allow for conformational changes within the material before solidification. Thus, the coacervate nature is crucial for obtaining extraordinary property profiles in these natural materials. In this project we mimic this environmentally benign processing principle of Coacervate Extrusion (CoaEx) for the development of completely new synthetic and biopolymeric materials. Previously we developed bio-inspired synthetic coacervates with well-controlled architecture and composition, and various tools to study their structure and mechanics. Currently we take advantage of this expertise to develop unique material systems by extruding synthetic coacervates and using the induced mechanical stress to obtain alignment and conformational changes.
Analogous to the wide variety of materials found in natural systems that commence as a coacervate, this processing principle is applicable to a wide variety of synthetic material classes. In this project coacervate extrusion is used to produce fibers, rods or scaffolds composed of: polyelectrolyte complexes, liquid-crystal elastomers, peptide-polymers and proteins. This bio-inspired processing principle of coacervate extrusion will lead to materials with unexplored property profiles and holds great promise for the development of unprecedented high performance materials obtained by green processing.
Establishing CoaEx by extrusion and spinning of aligned polyelectrolyte fibers. Demonstration that, by using a combination of extrusion and spinning, aligned fibers can be produced from coacervate phases composed of oppositely charged polymers:
Schlenoff and coworkers introduced the concept of saloplastics, by extruding solid oppositely charged polyelectrolyte complexes using salt to plasticize the material. Perry and Schiffman showed in 2017 that fluid coacervates could be used for electrospinning and fibers were obtained consisting of oppositely charged polyelectrolytes. As stiffness and strength of a fiber can be greatly enhanced upon stretching of the polymeric chains, to establish CoaEx we go further: we spin and draw coacervates to produce aligned microfibers, due to reorganizing of electrostatic interactions, followed by dehydration. To obtain the fibers, we fed extruded material to the spinner and produced aligned and dehydrated fibers. As the viscoelasticity of coacervate-based materials is strongly dependent on salt concentration, spinning was optimized by adjusting the salt concentration.
Liquid, rubbery and rigid materials could be obtained from the same polyelectrolytes by just varying the amount of water and salt. Different oppositely charged polymer systems have been explored, e.g. the well-studied combinations poly(4-styrenesulfonic acid) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) and keratin.
Post-processing was performed to improve mechanical stability, by means of rinsing to remove salts and by drawing. The mechanical properties were tested using dynamic mechanical analysis (DMA) and tensile testing. As the extent of hydration has a large influence on the mechanical properties, the extent of hydration in the different systems was measured using thermographimetric analysis (TGA) and related to the DMA data. In order to relate the morphology to the mechanical properties, the morphology of the materials was studied by scattering techniques (X-ray) and electron microscopy (scanning electron microscopy, SEM).
Since the tensile strength of a fiber is determined by intermolecular interactions, and electrostatic interactions can be very strong, this concept has resulted in strong high performance fibers using green processing.
Schlenoff and coworkers introduced the concept of saloplastics, by extruding solid oppositely charged polyelectrolyte complexes using salt to plasticize the material. Perry and Schiffman showed in 2017 that fluid coacervates could be used for electrospinning and fibers were obtained consisting of oppositely charged polyelectrolytes. As stiffness and strength of a fiber can be greatly enhanced upon stretching of the polymeric chains, to establish CoaEx we go further: we spin and draw coacervates to produce aligned microfibers, due to reorganizing of electrostatic interactions, followed by dehydration. To obtain the fibers, we fed extruded material to the spinner and produced aligned and dehydrated fibers. As the viscoelasticity of coacervate-based materials is strongly dependent on salt concentration, spinning was optimized by adjusting the salt concentration.
Liquid, rubbery and rigid materials could be obtained from the same polyelectrolytes by just varying the amount of water and salt. Different oppositely charged polymer systems have been explored, e.g. the well-studied combinations poly(4-styrenesulfonic acid) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) and keratin.
Post-processing was performed to improve mechanical stability, by means of rinsing to remove salts and by drawing. The mechanical properties were tested using dynamic mechanical analysis (DMA) and tensile testing. As the extent of hydration has a large influence on the mechanical properties, the extent of hydration in the different systems was measured using thermographimetric analysis (TGA) and related to the DMA data. In order to relate the morphology to the mechanical properties, the morphology of the materials was studied by scattering techniques (X-ray) and electron microscopy (scanning electron microscopy, SEM).
Since the tensile strength of a fiber is determined by intermolecular interactions, and electrostatic interactions can be very strong, this concept has resulted in strong high performance fibers using green processing.
Expected results by the end of this project:
• Established the CoaEx process as a versatile and sustainable processing tool to produce novel synthetic and biopolymeric materials and demonstrate its applicability to a wide variety of material systems.
Synthetic materials:
• Spinning of coacervates consisting of oppositely charged polyelectrolytes to produce highly oriented high performance fibers without the use of toxic solvents.
• Fabricated liquid crystal elastomers by CoaEx: Extrusion of oppositely charged polyelectrolytes with charged liquid crystalline moieties to induce macroscopic liquid-crystal order.
Biopolymer systems:
• CoaEx 3D printing of biopolymer coacervates.
• CoaEx of peptide-polyelectrolyte model systems: Synthesis and spinning of polyelectrolytes conjugated with structured peptides to study conformational changes upon mechanical drawing.
• CoaEx of proteins: 3D printing of protein-polymers to produce biomedically relevant scaffolds.
• Established the CoaEx process as a versatile and sustainable processing tool to produce novel synthetic and biopolymeric materials and demonstrate its applicability to a wide variety of material systems.
Synthetic materials:
• Spinning of coacervates consisting of oppositely charged polyelectrolytes to produce highly oriented high performance fibers without the use of toxic solvents.
• Fabricated liquid crystal elastomers by CoaEx: Extrusion of oppositely charged polyelectrolytes with charged liquid crystalline moieties to induce macroscopic liquid-crystal order.
Biopolymer systems:
• CoaEx 3D printing of biopolymer coacervates.
• CoaEx of peptide-polyelectrolyte model systems: Synthesis and spinning of polyelectrolytes conjugated with structured peptides to study conformational changes upon mechanical drawing.
• CoaEx of proteins: 3D printing of protein-polymers to produce biomedically relevant scaffolds.