Tunable wettability of polyester fabrics functionalized by chitosan/poly(N-isopropylacrylamide-coacrylic acid) microgels

Functionalization of textiles has been the aim of many studies in the field of intelligent materials. Biomimesis (lotus, pinecone effect etc.), adapting informatics to textile production (integration of computer-controlled electronic sensors), creating new fibres either natural or synthetic (algae biocomposite, ferroelectric polymeric etc.) and convergence of opposites (e.g. hydrophilic with hydrophobic materials) are some of the approaches used for textile functionalization [1-5]. This research focuses on a novel approach for developing advanced textile materials with biopolymer-based functionalities: the use of a hydrophilic stimuli-responsive system based on polyelectrolyte hydrogels for the surface modification of hydrophobic polyester fabrics. The aim was to render textiles responsive to external stimuli such as pH and temperature changes, without affecting dramatically their good intrinsic properties (e.g. mechanical strength). This research involved the following tasks: preparation of surface modifying systems (hydrogels) based on specifically selected polymers; characterization of the surface functionalization; and study of the new functionalities imparted to the textile, expressed as pH/thermo-responsiveness of the material

Advanced microgel-functionalized polyester textiles adaptive to ambient conditions

A new approach toward textile-based multi-functional and stimuli-responsive materials is proposed. Polyelectrolyte microgel technology is combined with conventional functionalization methods of photo- and thermo-crosslinking to activate the surface of polyester textiles, making them interactive with their environment. The microgels consisted of pH/thermo-responsive poly(N-isopropylacrylamide-co-acrylic acid) (PNIAA) microparticles either alone or complexed with oppositely charged macromolecular chains of the pH-responsive natural polysaccharide chitosan. Microgel incorporation into polyester surface layers was achieved either through UV irradiation in the presence of the photoinitiator benzophenone or through low temperature treatment using the natural crosslinker genipin. The adaptivity of the functionalized textiles to\ud ambient conditions of pH, temperature and relative humidity was expressed by changes in the textile physicochemical and water management properties. These changes were found to occur within a physiological pH/temperature range of the human body (pH 4–8 and 20–40°C). More specifically, functionalized polyester textiles exhibited a shift in surface charge from positive to negative values at pH ranging from 5.0 to 6.6, following the trend of the incorporated microgels. Below the microgel Lower Critical Solution Temperature (36ºC), the chitosan-containing functionalized textiles exhibited improved water wettability compared with reference textiles. Above 36ºC, functionalized textiles had lower moisture regains and higher water vapor transmission rates than the reference textiles. Microgel incorporation was found to be sufficiently durable, in some cases even after 30 washing cycles. However, some of the textile advantageous properties (e.g. whiteness, crease recovery) deteriorated due to the functionalization process. Possible applications of the microgel-functionalized polyester textiles lie in the fields of biomedicine and protective clothing

Polyester textile functionalization through incorporation of pH/thermo-responsive microgels. Part II: polyester functionalization and characterization

A new approach to functionalize the surface of polyester textiles is described in this study. Functionalization was achieved by incorporating pH/temperature-responsive polyelectrolyte microgels into the textile surface layer using UV irradiation. The aim of functionalization was to regulate polyester wettability according to ambient conditions by imparting stimuli-responsiveness from the microgel to the textile itself. Microgels consisted of pH/thermo-responsive microparticles of poly(N-isopropylacrylamide-co-acrylic acid) either alone or complexed with the pH-responsive natural polysaccharide chitosan. Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, ζ-potential measurements, and topographical analysis were used for surface characterization. Wettability of polyester textiles was assessed by dynamic wetting, water vapor transfer, and moisture regain measurements. One of the main findings showed that the polyester surface was rendered pH-responsive, both in acidic and alkaline pH region, owing to the microgel incorporation. With a marked relaxation in their structure and an increase in their microporosity, the functionalized textiles exhibited higher water vapor transfer rates both at 20 and 40 °C, and 65% relative humidity compared with the reference polyester. Also, at 40 °C, i.e., above the microgel Lower Critical Solution Temperature, the functionalized polyester textiles had lower moisture regains than the reference. Finally, the type of the incorporated microgel affected significantly the polyester total absorption times, with an up to 300% increase in one case and an up to 80% decrease in another case. These findings are promising for the development of functional textile materials with possible applications in biotechnology, technical, and protective clothin

Fabrication of tailorable pH responsive cationic amphiphilic microgels on a microfluidic device for drug release

Cationic, amphiphilic microgels of differing compositions based on hydrophilic, pH, and thermoresponsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic, nonionic n-butyl acrylate (BuA) are synthesized using a lab-on-a-chip device. Hydrophobic oil-in-water (o/w) droplets are generated via a microfluidic platform, with the dispersed (droplet) phase containing the DMAEMA and BuA, alongside the hydrophobic cross-linker, ethylene glycol dimethacrylate, and a free radical initiator in an organic solvent. Finally, the hydrophobic droplets are photopolymerized via a UV light source as they traverse the microfluidic channel to produce the cationic amphiphilic microgels. This platform enables the rapid, automated, and in situ production of amphiphilic microgels, which do not match the core-shell structure of conventionally prepared microgels but are instead based on random amphiphilic copolymers of DMAEMA and BuA between the hydrophobic cross-links. The microgels are characterized in terms of their swelling and encapsulation abilities, which are found to be influenced by both the pH response and the hydrophobic content of the microgels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 59–66

Thermorheological and textural behaviour of gluten-free gels obtained from chestnut and rice flours

Nowadays, as celiac disease is becoming more common the consumers’ demand for gluten-free products with high nutritional and taste quality is increasing. This work deals with the study of the impact of four novelty gluten-free sources: chestnut flour (Cf), whole rice flour (Rw), Carolino rice flour (Rc) and Agulha rice flour (Ra). Textural, thermorheological and stability performance of gluten-free gels using different experimental techniques were evaluated. Mixed gels were also produced for comparison. Texture parameters were determined from the texture profile analysis using a texturometer. Thermorheological oscillatory measurements were conducted in a stresscontrolled rheometer in order to clarify the kinetics of gel formation and to characterise the structure of the matured gels. The stability of the gels was evaluated using transmittance profiling of the gels under gravitational fields (LUMiSizer®). Texture studies suggested that gels from mixtures of chestnut flour at 30 % and rice flour at 20 % showed the right texture to develop gel-based new desserts. Rheological results showed that the thermal profiles on heating of Cf gels were similar to those obtained for Rw and Ra, whereas Rc gels exhibited a particular pattern. Once the final gelatinisation temperature was achieved, no significant differences on the viscoelastic properties were noticed for all the tested gels. Stability tests showed that gels with Rc should present an industrial advantage over the other assayed formulations, since the stability of these gels is of the order of four times larger

ΜΕΤΑΒΙΒΑΣΗ ΦΟΡΤΙΟΥ ΣΕ ΚΥΚΛΙΚΕΣ ΚΑΡΒΥΝΕΣ ΜΕ ΙΣΧΥΡΗ ΔΕΣΜΕΥΣΗ

Η συγκεκριμένη πτυχιακή εργασία αφορά στη μελέτη του φαινομένου της μεταβίβασης φορτίου σε κυκλικές κουμουλενικές καρβύνες με το Πρότυπο Ισχυρής Δέσμευσης (Tight Binding Model). Οι κυκλικές κουμουλενικές καρβύνες αποτελούν νανοσύρματα άνθρακα, που εμφανίζουν sp-υβριδισμό, παρουσιάζουν ίσες αποστάσεις μεταξύ των ατόμων και διατάσσονται σε κυκλική (ακριβέστερα πολυγωνική) μορφή (καρβύνες-δαχτυλίδια). Εισάγοντας τεχνητά έναν φορέα (οπή ή ηλεκτρόνιο) σε μια θέση της κυκλικής αλυσίδας, εξετάζουμε την πιθανότητα εμφάνισής του σε καθένα από τα άτομα του μορίου. Η ανάλυση γίνεται χρησιμοποιώντας βασικές παραμέτρους, όπως την επιτόπιο ενέργεια των ατόμων και τα ολοκληρώματα αλληλεπίδρασης αυτών, με τα τελευταία να υπολογίζονται από τους τύπους του Harrison. Η αλληλεπίδραση περιορίζεται αποκλειστικά μεταξύ πρώτων γειτόνων. Εκτός από την ταλάντωση του φορτίου, κάποια ακόμα μεγέθη που μας απασχολούν και χαρακτηρίζονται απαραίτητα για τη διερεύνηση και κατανόηση του φαινομένου, είναι το ενεργειακό φάσμα, οι μέσες χρονικά πιθανότητες, ο καθαρός μέσος ρυθμός μεταβίβασης του φορέα, η ταλάντωση της διπολικής ροπής του μορίου και το συχνοτικό περιεχόμενο των πιθανοτήτων και της διπολικής ροπής. Σε γενικότερο πλαίσιο, η μελέτη της μεταβίβασης φορτίου σε καρβύνες διαμορφώνει ένα σημείο συνάντησης των επιστημών της Φυσικής και Χημείας, των Μαθηματικών και των Υπολογιστών, για την οποία είναι αναγκαία η επιστράτευση βασικών αρχών της Κβαντομηχανικής και της Φυσικής Στερεάς Κατάστασης, γνώσεων από τη Θεωρία Πινάκων και την Επίλυση Διαφορικών Εξισώσεων, από την Υπολογιστική Φυσική και την Στατιστική.This thesis concerns the investigation of the phenomenon of charge transfer in cyclic carbynes via the Tight Binding Model. Cyclic carbynes are in reality carbon nanowires, which exhibit sp-hybridization, display equal distances between the carbon atoms and are arranged in a cyclic (more accurately polygonal) geometry (carbynes-rings). By inserting artificially a charge carrier (hole or electron) on an atom in the cyclic chain, we calculate the probability of detecting it on any of the molecule’s atoms. We use some characteristic parameters, such as the atoms’ on-site energies and their interaction integrals, the latter being calculated using Harrison’s formula. The interactions are restricted exclusively between neighboring carbon atoms. Some more quantities, apart from the charge oscillation, which we analyze and are considered crucial for studying the phenomenon, are the energy spectrum, the mean over time probabilities, the pure mean transfer rate of the carrier, the dipole moment oscillation and the probabilities and dipole moment frequency content. In general, the analysis of the charge transfer in carbynes phenomenon forms a path in which the sciences of Physics and Chemistry, Maths and Computers meet together. Thus, fundamental principles of Quantum Mechanics and Solid State Physics and basic knowledge of Matrices and Differential Equations, Computational Physics and Statistics become required