Michael-Thiol Addition cross-linked PDMS as a polar platform for improved dielectrics via protein integration
Pavle Ramah1
Supervisors: Anders Egede Daugaard1 and Anne Ladegaard Skov1
1 Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Thiol-maleimide conjugation is a well-established coupling method in biochemistry but has little reported use within silicone materials. A facile synthetic route of functionalised poly(dimethyl siloxane) (PDMS) to a prepolymer species capable of non-metal-catalysed cross-linking via Thia-Michael addition is presented. Two systems are compared: Maleimide (MI) terminated PDMS and its precursor, maleamic acid amide (MA) terminated PDMS. We argue that the increased relative concentration of polar groups and quadruple hydrogen bonding centres of the MA network matrix can be exploited for better electrical properties of self-healable dielectric elastomer actuators. This is highlighted by the MA networks self-healing capabilities, increased polarity, good electrical breakdown strength, and increased dielectric permittivity over both commercial and MI PDMS networks. Furthermore, exploiting the polar nature of such systems – and their bioconjugation reaction basis – allows for integration of low molecular weight protein, keratin hydrolysate. Integration of keratin and the effect of protein on dielectric properties and network structure is investigated.
Swelling of (silicone) elastomers in panorama view
Sofia Lindström1,2
Anders Egede Daugaard1, Anne Ladegaard Skov1
[1] Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
[2] Roxtec International AB, Rombvägen 2, 371 65 Lyckeby, Sweden
A fundamental difference between thermoplastic and thermosetting materials is their behaviour in solvents. Immersing a thermoplastic in a good solvent leads to the dissolution of it, while a thermoset, on the other hand, increases in size and volume to reach a so-called equilibrium swelling degree. The swelling kinetics as well as the final swelling degree are affected by multiple variables, e.g. the interactions between the solvent molecules and the polymer chains, and the crosslink density and filler content of the material.
Traditionally, swelling has been measured and reported as the weight or density difference before and after the immersion of a material in a solvent. In this work, we suggest a more refined approach where swelling is evaluated continuously by imaging the dimensional changes of a sample while it is being immersed in a solvent.
Synthetic Routes and Applications of Polyphenol-based Silicone Elastomers
Cagla Cinalioglu [1]
Supervisors: Cody B. Gale [1], Anne L. Skov [1], Michael A. Brook [2]
[1] Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
[2] Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada
Polyphenol-based silicone elastomers are emerging as sustainable materials, as they incorporate dynamic noncovalent interactions that enable reprocessability, recyclability, and tunable properties. These systems offer a promising alternative to conventional covalently cross-linked silicones, which are difficult to recycle [1].
In this work, aminopropyl-terminated PDMS was crosslinked with simple phenolics, including catechol, hydroquinone, and resorcinol, to prepare model elastomer systems which were utilized to understand reaction dynamics. These materials exhibited tunable properties arising from hydrogen bonding and ionic interactions. However, these materials suffered from slow cure times, ranging from 24-96 h which hindered mechanical testing. To overcome the slow curing times phenol functionalized silicones were synthesized including eugenol-and dopamine modified silicones. Eugenol silicones were synthesized cleanly while dopamine silicones were difficult to obtain without impurities from the polymerization of dopamine. These polymers are now under investigation for their potential in adhesives and reprocessable networks.
[1] Tamim, K., Gale, C. B., Silverthorne, K. E. C., Lu, G., Iao, C. H., & Brook, M. A. (2023). Antioxidant silicone elastomers without covalent cross-links. ACS Sustainable Chemistry & Engineering, 11(17), 7062–7071.
Improving hydrophobicity and mechanical properties of biopolymer composites
Eleftheria Gitsouli[1]
Anders Egede Daugaard[1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Biopolymers are naturally occurring polymers with appealing properties, like biodegradability, thermoformability, non-toxicity, and excellent film-forming abilities. However, the water affinity limits applications like food packaging. Several strategies have been reported for improving hydrophobicity, including the use of hydrophobic coatings, protein-polysaccharide interactions, or chemical modifications.
In this project, a novel method for sunflower oil incorporation into Soy Protein Isolate (SPI) via extrusion was investigated and optimized. While the addition of pure oil improved hydrophobicity, it negatively affected the mechanical properties. To overcome this limitation, a pickering oil-in-water emulsion was developed which enhanced the protein-oil interactions and resulted in superior mechanical properties, while keeping the material fully biobased and biodegradable. These findings broaden the spectrum to several pathways for tailoring biopolymer-based materials.
Polylactide Based Networks for Sustainable Thermostable Capacitors
Neha Mulchandani [1]
Bartosz M. Gackowski [2], Luciana Tavares [2] William Greenbank [2], Thomas Ebel [2], Anne L. Skov [1], Anders E. Daugaard [1]
[1]Danish Polymer Centre, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
[2]Centre for Industrial Electronics, University of Southern Denmark, Alsion 2, Sønderborg DK-6400, Denmark
Biaxially oriented polypropylene (BOPP) is a state-of-the-art dielectric material used in capacitors due to its inherent self-healability and high breakdown strength. However, the petroleum-derived polymer can withstand a maximum of 105°C, whereas the hotspot temperatures around capacitors could be significantly higher, questioning their service life.
This work endeavors to develop sustainable and thermostable capacitors from polylactide (PLA), a bio-based and biodegradable polymer having high thermal stability. Careful synthesis of PLA is an approach to designing polymers with different backbone architectures, tailored to meet specific thermal properties. We exploited this characteristic of PLA to design physical and chemically crosslinked networks- responsible for thermostability. Hybrid PLA networks containing free mobile PLA were fabricated into capacitors, which resulted in self-healable materials that can tolerate temperatures up to 90°C higher than commercial BOPP capacitors.
Soft Silicone Elastomer: Promising Alternatives to Current Breast Implants
Herenia Espitia Armenta, [1] Uzair S Hashmi, [1] Elias Kjær-Westermann, [1] Michelle M. T.Jansman [2], Leticia H. Rigau [2],
Anne L. Skov [1]
[1] Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs, Lyngby, Denmark
[2] Center for Nanomedicine and Theranostics, Department of Health Technology, Technical University of Denmark, Nils Koppels Allé, Building 423, 2800 Kgs. Lyngby, Denmark
Silicone breast implants are widely used in both reconstructive and cosmetic surgery. Concerns persist regarding the long-term safety, mechanical integrity, and biocompatibility of implants, with capsular contracture remaining a common complication linked to rupture, silicone leakage, and mechanical incompatibility.
Bottle brush polymers have shown high biocompatibility and a low elastic modulus in the kPa region, similar to biological tissue. This study focused on making soft silicone bottle brush elastomers with a Young’s modulus ranging from 0.3 kPa to 2 kPa, comparable to breast tissue. Our silicone elastomers were composed of a bottlebrush that had grafted vinyl polydimethylsiloxane (PDMS) onto methylhydrosiloxane copolymers via hydrosilylation. The reacting groups, hydride to vinyl, were varied to make a tunable material. The silicone bottle brush elastomers' mechanical and cohesive properties, along with biocompatibility and silicone leakage, were assessed to determine their suitability as breast implant material.
RubBatts: A Rubber-based Approach to Sustainable Energy Storage
Saul Ismael Utrera Barrios [1]
Christopher Daniel Wooldridge [1]
Anne Ladegaard Skov [1]
[1 ]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Abstract text, 80-140 words
When stretched, silicone rubbers can store mechanical energy. Upon release, the elastically restored energy can be harvested and converted into electricity through an electromechanical transduction mechanism (e.g., using an induction motor with a gearbox). However, the viscoelastic nature of silicone rubbers introduces significant energy losses, causing the loading and unloading stress-strain curves to deviate. As a result, the usable energy released during unloading is considerably lower than the energy applied during loading. These viscous losses must be carefully balanced against the required network elasticity and fatigue resistance to maximize energy output. We will present results on the influence of material selection on viscous losses, energy output measurements, and efficiency calculations. Our findings demonstrate how silicone-based elastomers can be effectively used for energy storage applications, potentially serving as backup systems in regions with fluctuating energy production.
Development of sustainable films from citrus fibers for edible packaging applications
Matina Terzi [1]
Anders Egede Daugaard [1] Mohammadamin Mohammadifar [2]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
[2]National Food Institute, Research Group for Food Production Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
The modern food packaging industry faces the challenges of meeting growing consumer demands while minimizing environmental impact. However, it remains heavily reliant on fossil-based plastics, raising critical concerns regarding their end-of-life disposal and long-term environmental impact. As regulations are becoming stricter and consumer awareness increases, the search for sustainable, functional, and cost-effective alternatives in food packaging has become a priority. Biopolymer-based materials, and in particular edible films, emerge as solutions that align with circular economy principles by reducing or even eliminating waste after use. The present research focuses on the development of edible films from citrus fibers and biopolymers for food packaging applications. By hot-processing citrus fibers and biopolymers with edible plasticizers and additives, thin films can be produced that combine the required mechanical strength, barrier properties, and shelf-life performance, while remaining fully consumable, offering a truly sustainable alternative to conventional plastics.