Smart and Functional Polymers

This book is based on the Special Issue of the journal Molecules on “Smart and Functional Polymers”. The collected research and review articles focus on the synthesis and characterization of advanced functional polymers, polymers with specific structures and performances, current improvements in advanced polymer-based materials for various applications, and the opportunities and challenges in the future. The topics cover the emerging synthesis and characterization technology of smart polymers, core?shell structure polymers, stimuli-responsive polymers, anhydrous electrorheological materials fabricated from conducting polymers, reversible polymerization systems, and biomedical polymers for drug delivery and disease theranostics. In summary, this book provides a comprehensive overview of the latest synthesis approaches, representative structures and performances, and various applications of smart and functional polymers. It will serve as a useful reference for all researchers and readers interested in polymer sciences and technologies

Peptide-Directed Supramolecular Self-Assembly of N-Substituted Perylene Imides

Synthetic peptides offer enormous potential to encode the assembly of molecular electronic components, provided that the complex range of interactions is distilled into simple design rules. Herein is reported a spectroscopic investigation of aggregation in an extensive series of peptide-perylene imide conjugates designed to interrogate the effect of structural variations. Throughout the course of this study, the self-assembly and photophysical properties of the compounds are explored to better understand the behavior and application of these materials. Three principal avenues of inquiry are applied: (1) the evaluation of structure-property relationships from a thermodynamic perspective, (2) the examination of peptide chiral effects upon properties and self-assembly, and (3) an application of the understanding gained from rationally designed systems to effectively utilize naturally optimized peptides in bio-organic electronics. By fitting different contributions to temperature-dependent optical absorption spectra, this study quantifies both the thermodynamics and the nature of aggregation for peptides with incrementally varying hydrophobicity, charge density, length, amphiphilic substitution with a hexyl chain, and stereocenter inversion. Coarse effects like hydrophobicity and hexyl substitution are seen to have the greatest impact on binding thermodynamics, which are evaluated separately as enthalpic and entropic contributions. Moreover, significant peptide packing effects are resolved via stereocenter inversion studies, particularly when examining the nature of aggregates formed and the coupling between π-electronic orbitals. Peptide chirality overall is seen to influence the self-assembly of the perylene imide cores into chiral nanofibers, and peptide stereogenic positions, stereochemical configurations, amphiphilic substitution, and perylene core modification are evaluated with respect to chiral assembly. Stereocenters in peptide residue positions proximal to the perylene core (1-5 units) are seen to impart helical chirality to the perylene core, while stereocenters in more distal residue positions do not exert a chiral influence. Diastereomers involving stereocenter inversions within the proximal residues consequently manifest spectroscopically as pseudo-enantiomers. Increased side-chain steric demand in the proximal positions gives a similar chiral influence but exhibits diminished Cotton Effect intensity with additional longer wavelength features attributed to interchain excimers. Amphiphilic substitution of a peptide with an alkyl chain disrupts chiral self-assembly, while an amphiphilic structure achieved through the modification of the perylene imide core with a bisester moiety prompts strongly exciton-coupled, chiral, solvent-responsive self-assembly into long nanofilaments. Informed by rationally designed sequences, and capitalizing upon the optimization seen in many natural systems, specific peptide sequences designed by inspection of protein-protein interfaces have been identified and used as tectons in hybrid functional materials. An 8-mer peptide derived from an interface of the peroxiredoxin family of self-assembling proteins is exploited to encode the assembly of perylene imide-based organic semiconductor building blocks. By augmenting the peptide with additional functionality to trigger aggregation and manipulate the directionality of peptide-semiconductor coupling, a series of hybrid materials based on the natural peptide interface is presented. Using spectroscopic probes, the mode of self-assembly and the electronic coupling between neighboring perylene units is shown to be strongly affected by the number of peptides attached, and by their backbone directionality. The disubstituted material with peptides extending in the N-C direction away from the perylene core exhibits strong coupling and long-range order, which are both attractive properties for electronic device applications. A bio-organic field-effect transistor is fabricated using this material, highlighting the possibilities of exploiting natural peptide tectons to encode self-assembly in other functional materials and devices. These results advance the development of a quantitative framework for establishing structure-function relationships that will underpin the design of self-assembling peptide electronic materials. The results further advance a model for adapting natural peptide sequences resident in β-continuous interfaces as tectons for bio-organic electronics

Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity

Non-covalent interactions are known to play a key role in biological compounds due to their stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings, such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl- 1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and aromatic interactions involving pyrimidine and phenyl rings in both complexes drives their self-assembly. Noncovalent interactions involving aromatic rings are key processes in both chemical and biological recognition, contributing to overall complex stability and forming recognition motifs. It is noteworthy that in Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between pairs of antiparallel triazolopyrimidine rings mimick basepair interactions physiologically occurring in DNA (Fig.1). M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a distorted octahedral structure, with C-Sn-C bond angles lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2 is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure. The compounds were screened for their in vitro antibacterial activity on a group of reference staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative pathogens [4] . We tested the biological activity of all the specimen against a group of staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P. aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also resulted active against methicillin resistant S. epidermidis RP62A

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry

The development of microfluidic based processes

Doctor of Science (DSc) thesis.Full version unavailable due to 3rd party copyright restrictions

DEFINITION OF AN ADVANCED PROCESS FOR THE PRODUCTION OF LOW ENVIRONMENTAL IMPACT CONTAINERS AS POTENTIAL ALTERNATIVE TO PLASTICS

For decades, petroleum-based synthetic polymers, commonly known as plastics, have become one of the most appealing materials used for a wide variety of applications. Nevertheless, currently, conventional petroleum-based plastics represent a serious problem for global pollution because remain for hundreds of years in the environment when discarded. In order to reduce dependence on fossil resources, bioplastic materials are being proposed as safer and more sustainable alternatives. Bioplastics are bio-based and/or biodegradable materials, typically derived from renewable sources. Among different resources, food waste is attracting more and more attention in the research field of bioplastics’ production. The sources of food waste include household, commercial, industrial and agricultural residues. In fact, every year, around one-third of all food resources produced for human consumption are lost or wasted. Although European Union guidelines stated that food waste should preferentially be used as animal feed, in some cases, it became illegal because of disease control concerns and other times its nutritional value is very poor. On the other hand, the production of bioplastics from food waste is a renewable, sustainable process, in which materials are fabricated from carbon neutral resources, thus aligning itself with the principles of the circular bioeconomy. However, the conversion of fruit and vegetable by-products into eco-friendly materials with mechanical and hydrodynamic performances comparable to those of fuel-based plastics still remains a challenge. In this thesis, different approaches have been investigated for the valorization of fruit and vegetable wastes to produce low environmental impact materials, as a potential alternative to plastics with application in the field of food packaging. In the first section, apple waste and tomato peel by-products have been used as fillers to fabricate starch-based biocomposites. The mechanical characterization of the samples showed their suitability for covering purposes, since a ductile and soft behaviour was exhibited. In the second section, an avocado by-product extract has been incorporated to an ethyl cellulose matrix for the production of impregnated paper with enhanced durability. Since fruit wastes can contain potential pathogens and physical and chemical contaminants which can be released when used as additive for active packaging, a preliminary untargeted metabolomic characterization of the extract was conducted by LC-ESI(-)-Q Exactive-Orbitrap- MS/MS. The lipid components detected in the extract proved to be useful additives to improve paper hydrophobicity, preventing food browning and moisture loss. In general, the addition of all tested wastes (apple waste, tomato peel and avocado by-products) has proved to be useful to increase the biodegradability of the fabricated biomaterials. Hence, the environmental benefits associated with their recovery are proposed as a driving force to expand their further use for these purposes. The upcycling of food waste through the production of value-added products is an ideal and practical end use, allowing to save huge economic and energy losses

Biomimetic Based Applications

The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions