Browsing by Author "Dossi, Eleftheria"
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Item Open Access Chemical modification of β-cyclodextrins: balancing soft and rigid domains in complex structures(Wiley, 2019-09-19) Luppi, Federico; Mai, Nathalie; Kister, Guillaume; Gill, Philip P.; Gaulter, Sally; Stennett, Christopher; Dossi, EleftheriaCrystalline polymers such as β‐cyclodextrin (βCD) can be modified with polyethylene glycol (PEG) diglycidyl ether cross‐linkers (262, 394, 500 Da). Here we show that the quantity and length of the PEG soft segments influence the solubility and malleability of the products, which are water‐soluble and easily converted to nitrated analogues under standard reaction conditions. Inert and nitrated derivatives containing longer PEG segments showed the ability to self‐heal. The degree of cross‐linking and decomposition temperatures and energies depended on the quantity and length of the soft segment. Nitrated cross‐linked βCD containing longer PEG segments did not ignite following an electrostatic discharge of 4.5 J. The chemical stability of βCD/PEG binders was tested by heat flow calorimetry at 80 °C. We found that the balanced incorporation of soft PEG and rigid βCD segments improved the processability of cross‐linked βCDs and desensitised their nitrated derivatives, offering new solutions for inert and energetic binders.Item Open Access Chrysin directing an enhanced solubility through the formation of a supramolecular cyclodextrin–calixarene drug delivery system: a potential strategy in antifibrotic diabetes therapeutics(MDPI, 2024-01-12) Hermenean, Anca; Dossi, Eleftheria; Hamilton, Alex; Trotta, Maria Consiglia; Russo, Marina; Lepre, Caterina Claudia; Sajtos, Csilla; Rusznyák, Ágnes; Váradi, Judit; Bácskay, Ildikó; Budai, István; D’Amico, Michele; Fenyvesi, FerencCalixarene 0118 (OTX008) and chrysin (CHR) are promising molecules for the treatment of fibrosis and diabetes complications but require an effective delivery system to overcome their low solubility and bioavailability. Sulfobutylated β-cyclodextrin (SBECD) was evaluated for its ability to increase the solubility of CHR by forming a ternary complex with OTX008. The resulting increase in solubility and the mechanisms of complex formation were identified through phase-solubility studies, while dynamic light-scattering assessed the molecular associations within the CHR-OTX008-SBECD system. Nuclear magnetic resonance, differential scanning calorimetry, and computational studies elucidated the interactions at the molecular level, and cellular assays confirmed the system’s biocompatibility. Combining SBECD with OTX008 enhances CHR solubility more than using SBECD alone by forming water-soluble molecular associates in a ternary complex. This aids in the solubilization and delivery of CHR and OTX008. Structural investigations revealed non-covalent interactions essential to complex formation, which showed no cytotoxicity in hyperglycemic in vitro conditions. A new ternary complex has been formulated to deliver promising antifibrotic agents for diabetic complications, featuring OTX008 as a key structural and pharmacological component.Item Open Access Classification of colorimetric sensor data using time series(Society of Photo-Optical Instrumentation Engineers (SPIE), 2021-09-12) Francis, Deena P.; Laustsen, Milan; Babamoradi, Hamid; Mogensen, Jesper; Dossi, Eleftheria; Jakobsen, Mogens H.; Alstrøm, Tommy S.Colorimetric sensors are widely used as pH indicators, medical diagnostic devices and detection devices. The colorimetric sensor captures the color changes of a chromic chemical (dye) or array of chromic chemicals when exposed to a target substance (analyte). Sensing is typically carried out using the difference in dye color before and after exposure. This approach neglects the kinetic response, that is, the temporal evolution of the dye, which potentially contains additional information. We investigate the importance of the kinetic response by collecting a sequence of images over time. We applied end-to-end learning using three different convolution neural networks (CNN) and a recurrent network. We compared the performance to logistic regression, k-nearest-neighbor and random forest, where these methods only use the difference color from start to end as feature vector. We found that the CNNs were able to extract features from the kinetic response profiles that significantly improves the accuracy of the sensor. Thus, we conclude that the kinetic responses indeed improves the accuracy, which paves the way for new and better chemical sensors based on colorimetric responses.Item Open Access CRIM-TRACK: Sensor system for detection of criminal chemical substances(SPIE, 2015-10-21) Munk, Jens Kristian; Buus, Ole T.; Larsen, Jan; Dossi, Eleftheria; Tatlow, Sol; Lässig, Lina; Sandström, Lars; Jakobsen, Mogens H.Detection of illegal compounds requires a reliable, selective and sensitive detection device. The successful device features automated target acquisition, identification and signal processing. It is portable, fast, user friendly, sensitive, specific, and cost efficient. LEAs are in need of such technology. CRIM-TRACK is developing a sensing device based on these requirements. We engage highly skilled specialists from research institutions, industry, SMEs and LEAs and rely on a team of end users to benefit maximally from our prototypes. Currently we can detect minute quantities of drugs, explosives and precursors thereof in laboratory settings. Using colorimetric technology we have developed prototypes that employ disposable sensing chips. Ease of operation and intuitive sensor response are highly prioritized features that we implement as we gather data to feed into machine learning. With machine learning our ability to detect threat compounds amidst harmless substances improves. Different end users prefer their equipment optimized for their specific field. In an explosives-detecting scenario, the end user may prefer false positives over false negatives, while the opposite may be true in a drug-detecting scenario. Such decisions will be programmed to match user preference. Sensor output can be as detailed as the sensor allows. The user can be informed of the statistics behind the detection, identities of all detected substances, and quantities thereof. The response can also be simplified to “yes” vs. “no”. The technology under development in CRIM-TRACK will provide custom officers, police and other authorities with an effective tool to control trafficking of illegal drugs and drug precursors.Item Open Access Cross-linking of hydroxyl-terminated polyols with triethyleneglycol diglycidyl ether: an alternative to toxic isocyanates(Wiley, 2018-01-16) Dossi, Eleftheria; Akhavan, Jacqueline; Gaulter, Sally E.; Williams, Richard G.; Doe, William J.Isocyanates are highly reactive and toxic substances with severe health effects. Certain diisocyanates are restricted under REACH – The European Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals. Triethyleneglycol diglycidyl ether (TEGDGE) was used as an alternative to toxic isocyanates for the cross-linking of hydroxyl-terminated pre-polymers at 70oC. The effect of three curing accelerators was determined while following the reaction kinetics by 1H-NMR spectroscopy and differential scanning calorimetry (DSC). Polybutadiene (Poly BD R45HT-LO) and acrylic ester (HyTemp 4454) successfully cross-linked in 7–10 days to produce thermally stable networks with low glass transition temperatures, as observed by DSC. Pre-aging the polybutadiene resin promoted cross-linking with TEGDGE. Four energetic compositions were then prepared using cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN) as fillers, and polybutadiene (Poly BD R45HT-LO) and acrylic ester (HyTemp 4454) as binders. Both binders successfully cross-linked with TEGDGE in the presence of RDX and PETN, but only PETN was found to be chemically compatible with the cross-linked polymers. These results show that TEGDGE is suitable as a replacement for toxic isocyanates for the cross-linking of hydroxyl-terminated polyols.Item Open Access Cross-linking of γ-cyclodextrin using non-toxic polyethylene glycol spacer units(Wiley, 2021-08-16) Dossi, Eleftheria; Bolton, Morgan; Kister, Guillaume; Afsar, AshfaqThe crystalline cyclic oligosaccharide γ-cyclodextrin (γCD) is a natural, non-toxic and biodegradable precursor that can be used to prepare innovative polymers. We cross-linked γCD with variable quantities of non-toxic polyethylene glycol diglycidyl ether (PEGDGE) in aqueous NaOH to form 3D structures with tunable physicochemical properties. Mixtures with a 5:1 PEGDGE:γCD molar ratio produced a cross-linked material that was soluble in water and organic solvents, underwent glass transition at –23 °C. The properties of this material were further modified by additional curing with PEGDGE or nitration reaction. Curing produced an insoluble polymeric material with excellent swelling abilities (200% in water) and decreased glass transition temperature to –37 °C. The nitrated cross-linked γCD was soluble in common organic solvents and underwent glass transition at +19 °C, achieving thermal stability below 190 °C. These novel γCD polymers are promising materials for applications in the pharmaceutical and food industries and environmental remediation.Item Open Access Cure monitoring of CFRP composites by dynamic mechanical analyser(Elsevier, 2015-08-29) Kister, Guillaume; Dossi, EleftheriaThe cure characteristics of carbon/MTM44-1 epoxy composite prepreg and neat MTM44-1 epoxy resin are monitored using a dynamic mechanical analyser (DMA). This study also assesses whether the simple containment device recommended by the DMA manufacturer for powder and gel is suitable for prepregs. The device is a disposable 0.1-mm thick stainless steel pocket. The cure behaviour of the packaged materials is compared with that of the unpackaged prepreg. All the samples are cured following the manufacturer's 180°C-isothermal schedule with heating rates of 2 °C/min and 5 °C/min. The tests highlight that: (i) the cure of composite prepregs and resin can be monitored using a DMA; (ii) the stainless steel pocket does not influence the cure of the prepreg and resin; and (iii) the softening and melting of the uncured resin, the resin low viscosity state and the subsequent gelation-vitrification-solidification of the resin are detected with this method.Item Open Access Improved detection of chemical substances from colorimetric sensor data using probabilistic machine learning(SPIE, 2017-05) Mølgaard, Lasse L.; Buus, Ole T.; Larsen, Jan; Babamoradi, Hamid; Thygesen, Ida L.; Laustsen, Milan; Munk, Jens Kristian; Dossi, Eleftheria; O'Keeffe, Caroline; Lässig, Lina; Tatlow, Sol; Sandström, Lars; Jakobsen, Mogens H.We present a data-driven machine learning approach to detect drug- and explosives-precursors using colorimetric sensor technology for air-sampling. The sensing technology has been developed in the context of the CRIM-TRACK project. At present a fullyintegrated portable prototype for air sampling with disposable sensing chips and automated data acquisition has been developed. The prototype allows for fast, user-friendly sampling, which has made it possible to produce large datasets of colorimetric data for different target analytes in laboratory and simulated real-world application scenarios. To make use of the highly multi-variate data produced from the colorimetric chip a number of machine learning techniques are employed to provide reliable classification of target analytes from confounders found in the air streams. We demonstrate that a data-driven machine learning method using dimensionality reduction in combination with a probabilistic classifier makes it possible to produce informative features and a high detection rate of analytes. Furthermore, the probabilistic machine learning approach provides a means of automatically identifying unreliable measurements that could produce false predictions. The robustness of the colorimetric sensor has been evaluated in a series of experiments focusing on the amphetamine pre-cursor phenylacetone as well as the improvised explosives pre-cursor hydrogen peroxide. The analysis demonstrates that the system is able to detect analytes in clean air and mixed with substances that occur naturally in real-world sampling scenarios. The technology under development in CRIM-TRACK has the potential as an effective tool to control traf- ficking of illegal drugs, explosive detection, or in other law enforcement applications.Item Open Access Inert and nitrated cross-linked β-cyclodextrin binders for energetic applications(2019-03) Luppi, Federico; Dossi, EleftheriaThis PhD project focuses on the synthesis of new inert and nitrated cross-linked cyclodextrin systems as binders for energetic formulations. Three diglycidyl ethers with polyethylene glycol segments differing in length were used to crosslink β-cyclodextrin. The physicochemical properties of the compounds were investigated by proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. The polyethylene glycol chains linked to the rigid β-cyclodextrin conferred low glass transition temperatures (≥ –20 °C) on the inert binders and also on their nitrated derivatives (≥ –14 °C). This is the first time that nitrated βcyclodextrin derivatives have shown viscoelastic behaviour at temperatures below 0 °C. The viscoelasticity of both the inert and nitrated compounds increased with the amount of polyethylene glycol chains in the system. Inert binders with higher polyethylene glycol:β-cyclodextrin units ratios were softer and exhibited self-healing behaviour. The thermo-mechanical characterisation of these binders revealed that the system was exposed to mechanical stress below the glass transition temperature, and the stress was directly related to the proportion of the soft polyethylene glycol segments. The nitrated cross-linked derivatives were characterised by decomposition temperatures of ~200 °C and thermal degradation energies of 1400–2100 J g -1 strictly dependent on the degree of cross-linking and nitration. Self-healing properties were confirmed in nitrated products with a high polyethylene glycol segments content. Nitrated samples with polyethylene glycol segments:β-cyclodextrin units ratios >3.8:1 were safer to handle in the laboratory as determined by small-scale hazard and compatibility tests with various energetic fillers. Additionally, preliminary Energetic Materials Testing Assessment Policy (EMTAP) tests confirmed the samples were not sensitive to electrostatic discharge up to 4.5 J but were sensitive to impact, with a figure of insensitiveness of 29. The nitrated samples were unstable at temperatures >80 °C. The materials developed during this PhD project could facilitate the manufacturing and storage of new binders and may offer a suitable replacement for nitrocellulose and other binders in ii energetic formulations. The stabilisation of the nitrated cross-linked binders should be prioritised in future workItem Open Access Machine learning methods for the detection of explosives, drugs and precursor chemicals gathered using a colorimetric sniffer sensor(Royal Society of Chemistry, 2023-04-18) Francis, Deena P.; Laustsen, Milan; Dossi, Eleftheria; Treiberg, Tuule; Hardy, Iona; Shiv, Shai Hvid; Hansen, Bo Svarrer; Mogensen, Jesper; Jakobsen, Mogens H.; Alstrøm, Tommy S.Colorimetric sensing technology for the detection of explosives, drugs, and their precursor chemicals is an important and effective approach. In this work, we use various machine learning models to detect these substances from colorimetric sensing experiments conducted in controlled environments. The detection experiments based on the response of a colorimetric chip containing 26 chemo-responsive dyes indicate that homemade explosives (HMEs) such as hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP), and methyl ethyl ketone peroxide (MEKP) used in improvised explosives devices are detected with true positive rate (TPR) of 70–75%, 73–90% and 60–82% respectively. Time series classifiers such as Convolutional Neural Networks (CNN) are explored, and the results indicate that improvements can be achieved with the use of kinetics of the chemical responses. The use of CNNs is limited, however, to scenarios where a large number of measurements, typically in the range of a few hundred, of each analyte are available. Feature selection of important dyes using the Group Lasso (GPLASSO) algorithm indicated that certain dyes are more important in discrimination of an analyte from ambient air. This information could be used for optimizing the colorimetric sensor and extend the detection to more analytes.Item Open Access Mechanical behavior of 3d printed poly(ethylene glycol) diacrylate hydrogels in hydrated conditions investigated using atomic force microscopy(American Chemical Society, 2023-04-05) Hakim Khalili, Mohammad; Panchal, Vishal; Dulebo, Alexander; Hawi, Sara; Zhang, Rujing; Wilson, Sandra; Dossi, Eleftheria; Goel, Saurav; Impey, Susan A.; Aria, Adrianus IndratThree-dimensional (3D) printed hydrogels fabricated using light processing techniques are poised to replace conventional processing methods used in tissue engineering and organ-on-chip devices. An intrinsic potential problem remains related to structural heterogeneity translated in the degree of cross-linking of the printed layers. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were used to fabricate both 3D printed multilayer and control monolithic samples, which were then analyzed using atomic force microscopy (AFM) to assess their nanomechanical properties. The fabrication of the hydrogel samples involved layer-by-layer (LbL) projection lithography and bulk cross-linking processes. We evaluated the nanomechanical properties of both hydrogel types in a hydrated environment using the elastic modulus (E) as a measure to gain insight into their mechanical properties. We observed that E increases by 4-fold from 2.8 to 11.9 kPa transitioning from bottom to the top of a single printed layer in a multilayer sample. Such variations could not be seen in control monolithic sample. The variation within the printed layers is ascribed to heterogeneities caused by the photo-cross-linking process. This behavior was rationalized by spatial variation of the polymer cross-link density related to variations of light absorption within the layers attributed to spatial decay of light intensity during the photo-cross-linking process. More importantly, we observed a significant 44% increase in E, from 9.1 to 13.1 kPa, as the indentation advanced from the bottom to the top of the multilayer sample. This finding implies that mechanical heterogeneity is present throughout the entire structure, rather than being limited to each layer individually. These findings are critical for design, fabrication, and application engineers intending to use 3D printed multilayer PEGDA hydrogels for in vitro tissue engineering and organ-on-chip devices.Item Open Access Nanoindentation response of 3D printed PEGDA hydrogels in hydrated environment(American Chemical Society, 2023-01-20) Hakim Khalili, Mohammad; Williams, Craig J.; Micallef, Christian; Duarte-Martinez, Fabian; Afsar, Ashfaq; Zhang, Rujing; Wilson, Sandra; Dossi, Eleftheria; Impey, Susan A.; Goel, Saurav; Aria, Adrianus IndratHydrogels are commonly used materials in tissue engineering and organ-on-chip devices. This study investigated the nanomechanical properties of monolithic and multilayered poly(ethylene glycol) diacrylate (PEGDA) hydrogels manufactured using bulk polymerization and layer-by-layer projection lithography processes, respectively. An increase in the number of layers (or reduction in layer thickness) from 1 to 8 and further to 60 results in a reduction in the elastic modulus from 5.53 to 1.69 and further to 0.67 MPa, respectively. It was found that a decrease in the number of layers induces a lower creep index (CIT) in three-dimensional (3D) printed PEGDA hydrogels. This reduction is attributed to mesoscale imperfections that appear as pockets of voids at the interfaces of the multilayered hydrogels attributed to localized regions of unreacted prepolymers, resulting in variations in defect density in the samples examined. An increase in the degree of cross-linking introduced by a higher dosage of ultraviolet (UV) exposure leads to a higher elastic modulus. This implies that the elastic modulus and creep behavior of hydrogels are governed and influenced by the degree of cross-linking and defect density of the layers and interfaces. These findings can guide an optimal manufacturing pathway to obtain the desirable nanomechanical properties in 3D printed PEGDA hydrogels, critical for the performance of living cells and tissues, which can be engineered through control of the fabrication parameters.Item Open Access Nitrated cross-linked b-cyclodextrin binders exhibiting low glass transition tempratures(Wiley, 2018-09-04) Luppi, Federico; Cavaye, Hamish; Dossi, EleftheriaPolymeric binders such as β‐cyclodextrins (βCDs) are used to bind with other constituents of energetic formulations and to prevent accidental ignition. One of the advantages of βCDs is the ability to tune their properties by chemical modification. Here, we synthesised nitrated cross‐linked βCDs (βNCXCDs) to produce new binders for energetic formulations. The cross‐linking of βCD with non‐toxic triethylene glycol diglycidyl ether (TEGDGE, X=T) and poly(ethylene glycol) diglycidyl ethers (PEGDGE, X=P) yielded soft, water soluble oligomeric compounds (βCXCDs) which can improve the processability of energetic formulations and contribute to their desensitisation. When the PEGDGE cross‐linker was used, lower glass transition temperatures were achieved, which extended the operative range of the βCPCD binder to −20 °C. The analogous nitrated systems (βNCXCDs) were therefore synthesised using a 1 : 1 (v/v) ratio of 98 % sulfuric acid/100 % nitric acid or 100 % fuming nitric acid, increasing their solubility in acetone and tetrahydrofuran. The nitrated derivatives were characterised by decomposition temperatures (200 °C) and energies (up to 1750 J g−1) comparable to nitrocellulose. Moreover, the glass transition of the inert βCXCDs at low temperatures (<0 °C) was conserved in the corresponding nitrated βNCXCDs, ensuring the desensitisation of energetic compositions even at low temperatures. This is the first time that nitrated derivatives of βCD with glass transition temperatures below 0 °C have been reported, suggesting such derivatives could make suitable replacements for nitrocellulose and other binders in energetic formulations.Item Open Access Preformulation studies and bioavailability enhancement of curcumin with a ‘two in one’ PEG-β-cyclodextrin polymer(MDPI, 2021-10-16) Haimhoffer, Ádám; Dossi, Eleftheria; Béresová, Monika; Bácskay, Ildikó; Váradi, Judit; Afsar, Ashfaq; Rusznyák, Ágnes; Vasvári, Gábor; Fenyvesi, FerencDrug delivery systems are used to improve the biopharmaceutical properties of curcumin. Our aim was to investigate the effect of a water-soluble ‘two in one’ polymer containing covalently bonded PEG and βCD moieties (βCPCD) on the solubility and bioavailability of curcumin and compare it to a polymeric β-cyclodextrin (βCDP) cross-linked with epichlorohydrin. Phase-solubility and dynamic light scattering (DLS) experiments showed that the solubility of curcumin increased significantly in 10 m/m % βCPCD and βCDP solutions, but βCPCD–curcumin particles had higher hydrodynamic volume. The formation of the βCPCD–curcumin complex in solution and sedimented phase was confirmed by NMR spectroscopy. Biocompatibility and permeability experiments were performed on Caco-2 cells. Polymers did not show cytotoxicity up to 10 m/m % and βCPCD significantly increased the permeability of curcumin. DLS measurements revealed that among the interaction of polymers with mucin, βCPCD formed bigger aggregates compared to βCDP. Curcumin complexes were lyophilized into capsules and structurally characterized by micro-CT spectroscopy. Drug release was tested in a pH 1.2 medium. Lyophilized complexes had a solid porous matrix and both βCPCD and βCDP showed rapid drug release. βCPCD provides an opportunity to create a swellable, mucoadhesive matrix system for oral drug delivery.Item Open Access Shaping the structure and properties of HyTemp using polyethylene glycol diglycidyl ether cross-linkers(Wiley, 2024-06-03) Dossi, Eleftheria; Mutele-Nkuna, Khuthadzo Lourate; Wilkinson, Peter; Kister, Guillaume; Patrick, Hugh; Khalili, Mohammad Hakim; Hawi, SaraNovel elastomers are made by reaction of hydroxyl-terminated polyacrylic ester (HyTemp) with polyethylene glycol (PEG, number of ethylene glycol units 1, 3, 6, 9) based cross-linkers. The influence of the cross-linker length, the HyTemp/cross-linker (w/w) ratio and the cross-linking accelerator trifluoromethanesulfonate scandium salt (ScTFMS) on the structure and the properties of the materials are studied. The cross-linker length has not influence on the glass transition (Tg) of the products because of the presence of the flexible PEG units that cancels out the cross-linking effect associated to a shift to higher Tg. A two-domain structure is seen by the presence of a dual Tg in samples cured with ScTFMS. Mathematical analysis of the modulated differential scanning calorimetry curves offers for the first time the possibility to identify/confirm structural differences in complex three-dimensional polymeric structures. Scanning electron microscopy and swelling experiments in ethyl acetate respectively reveal an increase in the pore size (1.13 to 5.48 nm) and in the absorption ability of the elastomers cured with different types and quantities of PEG cross-linker. The new elastomeric materials are exhibiting a rubbery state over a wide temperature range and absorptivity for the potential recovery of pollutants in soil and/or water.Item Open Access Synthesis, structure characterization, Hirshfeld surface analysis, and computational studies of 3-nitro-1,2,4-triazol-5-one (NTO):acridine(Springer, 2024-04-30) Şen, Nilgün; Pons, Jean-François; Zorlu, Yunus; Dossi, Eleftheria; Persico, Federica; Temple, Tracey; Aslan, Nazife; Khumsri, AkachaiTo modify the physical features and extend applications of the 3-nitro-1,2,4-triazol-5-one (NTO), we synthesized NTO with acridine (ACR) at a molar ratio of 1:1, a neutralization reaction. Through altering the chemical composition, it was possible to alter physical properties such as thermal stability, free space (voids), packing coefficient, crystal density, difference in pKa of co-formers, morphology, solubility, and impact sensitivity, and detonation parameters . It appears that physical attributes could be entirely altered. Single-crystal and powder X-ray diffraction methods, infrared spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR), and thermal analysis were utilized to comprehensively characterize and confirm the formation of the structure of NTO:ACR. The substantial hydrogen bond interactions and planar layered structures observed between the cations and anions generated a complex 3D network, providing insight into the structure–property interrelationship. One intriguing feature discovered is the layered structure present in NTO:ACR, which may be responsible for the low impact sensitivity. According to the experimental results, NTO:ACR showed good thermal stability (Td = 229 °C) and outstanding impact sensitivity (IS = 100 J). Detonation velocity and pressure were calculated using the EXPLO5 software program and found to be 7006 m·s−1 and 20.02 GPa, respectively.Item Open Access Thermal response of multi-layer UV crosslinked PEGDA hydrogels(Elsevier, 2022-01-07) Khalili, Mohammad Hakim; Afsar, Ashfaq; Zhang, Rujing; Wilson, Sandra; Dossi, Eleftheria; Goel, Saurav; Impey, Susan A.; Aria, Adrianus IndratPoly(ethylene glycol) diacrylate (PEGDA) hydrogels are ubiquitously used in a wide variety of applications in tissue engineering. In this study, the thermal response of multi-layered PEGDA hydrogels was investigated under various conditions of the temperature-controlled environments (8, 20, 37, and 45 °C) through gravimetric and volumetric methods. These multi-layered hydrogels were produced using a computer-controlled projection lithography and compared to the monolithic hydrogels fabricated through bulk photo-crosslinking. It was observed that the volume of multi-layered PEGDA hydrogels increased to about 10% at a temperature of 8 °C, while their volume decreased by 8% and 12% when stored at 37 °C and 45 °C, respectively. PEGDA hydrogel also showed an anisotropic characteristic where the axial dimensional change was about 43% higher than the lateral dimension. This finding is critical to inform the design and fabrication of PEGDA hydrogels to compensate for the axial and lateral volume changes during the application at different temperatures.Item Open Access Thermomechanical characterisation of cross-linked β-cyclodextrin polyether binders(Elsevier, 2018-11-26) Luppi, Federico; Kister, Guillaume; Carpenter, Mark; Dossi, EleftheriaCyclodextrins are promising building blocks for the synthesis of industrial binders. A new binder was prepared by cross-linking β-cyclodextrin with variable amounts of polyethylene glycol diglycidyl ether (40–60% w/w) to produce a soft polyether network that was soluble in water and alcohol, and the thermomechanical properties of the binder were determined. Increasing the amount of cross-linker reduced the glass transition temperature of the binder, as determined by differential scanning calorimetry and dynamic mechanical analysis. Cooling experiments revealed sudden stress relief below the glass transition temperature, reflecting the de-bonding of the polymer from the metallic supports. This was prevented by contact with polytetrafluoroethylene tape. Optical microscopy confirmed the stress relief in the form of cracking, and revealed self-healing by reptation, promoted by a higher cross-linker content and temperature. The information gained on the influence of the support medium on the thermomechanical properties of the cross-linked β-cyclodextrins can be used by industry for optimising manufacture and storage methods for new binders.Item Open Access Understanding and controlling the glass transition of HTPB oligomers(Royal Society of Chemistry, 2021-04-07) Dossi, Eleftheria; Earnshaw, Jacob; Ellison, Laurence; Rabello dos Santos, Gabriella; Cavaye, Hamish; Cleaver, Douglas J.In this paper, we use a combination of experiment and simulation to achieve enhanced levels of synthetic control on the microstructure of the much-used binder material hydroxyl terminated polybutadiene (HTPB). Specifically, we determine the appropriate combination of initiator, temperature and solvent required to dial in the relative contents of trans, cis and vinyl monomeric units. When an alkylithium initiator (TBDMSPLi) is used, the vinyl content increases from 18% to >90% as the polymerization solvent is switched from non-polar to polar. Further, in non-polar solvents, the vinyl content increases from 18% to 40% with decreasing polymerization temperature. The glass transition temperature, Tg, is shown to be strongly affected by the microstructure, covering the very wide range of −95 °C to −25 °C. The Tg values of HTPB oligomers with high vinyl content are exceptionally high (−25 °C) and can be associated with their aliphatic backbones with pendant side-groups structures. The experimental indications that intramolecular degrees of freedom have a dominant effect on Tg are confirmed by Molecular Dynamics simulations. These simulations identify crankshaft flips of main-chain sub-sections as the key mechanism and relate this to the vinyl content; the frequency of these rotations increases by an order of magnitude, as the vinyl content is reduced from 90% to 20%. The generic mechanistic understanding gained here into what constitutes a “good binder” material is readily transferrable to the potential identification of future candidate systems with very different chemistries.Item Open Access Validation of data from an artificial sniffer dog by common analytical techniques(SETCOR, 2021-10-22) Hardy, Iona; Jakobsen, Mogens Havsteen; Treiberg, Tuule; Gotfredsen, Charlotte Held; Dossi, EleftheriaCRIM-TRACK, an artificial sniffer dog, employs a colourimetric sensor system to monitor the colour change of chromic dyes when in contact with the vapours of illicit molecules (analytes) for detection and identification of substances. Within, the interaction of illicit chemicals and chromic dyes have been studied in solution using Proton Nuclear Magnetic Resonance ( 1 H NMR) spectroscopy and Ultraviolet-Visible (UV-Vis) spectrophotometry, to validate data generated from detection experiments using CRIM-TRACK sniffer. 1 H-NMR revealed the colour change mechanism induced by benzyl methyl ketone (BMK), a precursor chemical of methamphetamines, was hydrogen bonding between the BMK and specific dye molecules. It also revealed that hexamine (HEX), an explosives precursor, induced a colour change by formation of ion pairs with the specific dye molecules. The colour changes detected by CRIM-TRACK were confirmed by UV-Vis where a shift in absorption wavelength and/or a change in absorbance occurred.