1,721,039 research outputs found
Chemical Methods for Gelatin Crosslinking: A Review
No full textChemical methods so far experimentally investigated for gelatin crosslinking have been summarized with special emphasis on the reaction mechanisms. Advantages and disadvantages of all reactants have been reported in relation to the significant properties of the final applicative field
Understanding the Structural and Binding Properties of Collagen: a Theoretical Perspective
No full textThe change in the stability and conformational dynamics of a collagen-like microfibril segment (CMS),
23 amino acid residues long (around 5[3(GLY-X-Y)8]), as a result of the interaction with water, formaldehyde,
and gallic acid is studied by performing a series of nanosecond molecular dynamics simulations. Major changes
in the conformation of CMS occur when interacting with water while in the other solutions: (1) pure
formaldehyde, (2) 8.0% (v/v) formaldehyde/water, and (3) 1.4% (v/v) gallic acid/water; the variation is less
evident. Possible CMS/modifying agents’ binding sites are evidenced by the analysis of radial distribution
functions, coordination number, and H-bonding network. In particular, in the case of formaldehyde a high
preference for ARG, LYS, and GLN residues is found. Gallic acid molecules preferably bind to PRO and
HPR residues. The examination of average interaction energies per residue and their van der Waals and
electrostatic components confirms the results obtained with the structural analysis. Furthermore, both van der
Waals and electrostatic terms are important for the stabilization of the CMS. This is especially noted when
CMS interacts with gallic acid. A comparison between calculated and available experimental findings is
proposed. The agreement is very satisfactory, thus validating the computational approach to these systems
Uso di diazo derivati per l’innesto di gruppi funzionali sulla superficie di film di polietilene
No full textStudio della reazione della gelatina con esametilen-1,6-diisocianato
No full text1,6-hexamethylene diisocyanate and dimethylsolfoxide were exploited as crosslinker agent and reaction solvent, respectively in the crosslinking of gelatine. The effect of the diisocianate concentration on the crosslinking yield was studied by selective extraction with hot water of the treated gelatine. All produced materials were characterised by infrared spectroscopy, thermogravimetric analysis, electron dispersion analysis and electron microscopy investigation. High crosslinking yields and good thermal stability were found under all investigated conditions
Luminescent Bis-benzoxazolyl-stilbene as Molecular Probe for Polypropylene Films Deformation
No full textPoly(propylene) (PP) films containing different concentrations of bis(benzoxazolyl)stilbene (BBS) have been prepared by melt processing. We demonstrate that the emission characteristics of PP films depend on BBS concentration and polymer deformation. A well-defined excimer band is observed with more than 0.2 wt.-% of BBS, conferring to the film a green luminescence. During drawing (130 degrees C) the PP reorganisation breaks the BBS excimer-type arrangement, leading to the prevalence of the blue emission of the single molecules. We have efficiently applied the photophysics of this commercial stilbene derivative to the production of powerful tools acting as an internal probe for PP deformation
Preparation of gelatin/polyoxypropylene grafted copolymers by isocyanate promoted "grafting onto" reaction
No full textA "grafting onto" method for the synthesis of protein-based grafted copolymers is here described. Monofunctional oligo(oxypropylene) chains carrying a terminal isocyanate group were prepared and coupled with gelatin likely by reaction with hydroxyl or primary amino groups. A grafting yield higher than 85% was obtained by using an amount of isocyanate terminated oligo(oxypropylene) of 0.2 mmol per gram of gelatin. A tailored purification procedure based on fractionation with selective solvents was set up to remove homo-coupling products, affording water soluble gelatin-oligo(oxypropylene) graft copolymers having up to 19% wt of grafted oligo(oxypropylene) chains, as indicated by elemental analysis. The composition of all sample fractions were accomplished through NMR, FT-IR and elemental analysis. A negligible insoluble fraction and a water soluble gelatin fraction having a higher modification degree were obtained when the unreacted 1,6-diisocyanatehexane was removed by distillation from the intermediate reagents.The solid films of the graft copolymers showed single-phase morphology by scanning electron microscopy (SEM) observation, confirming the covalent bond formation between oligo(oxypropylene) and gelatin. Simple oligo(oxypropylene)/gelatin blends were prepared and characterized by SEM and stress-strain measurements for comparison. (C) 2012 Elsevier Ltd. All rights reserved
Sintesi e caratterizzazione ottica di amilosio modificato con gruppi spiropirano mediante reazione di “click”
No full textCon questo lavoro ci prefiggiamo l’obbiettivo di produrre rivestimenti innovativi a base di polimeri naturali, in grado di fornire risposte fotocromiche quando irraggiati con luce visibile. L’amilosio, un polimero lineare costituito da unità glucosidiche legate 1-4, è stato
scelto quale substrato di partenza poiché è uno dei componenti dell’amido e ne possiede quindi tutti i vantaggi. Esso è stato azidato selettivamente in C6 [1,2] e successivamente modificato con un gruppo responsivo tramite reazione di cicloaddizione di Huisgen azide-alchino, “click”. Il gruppo responsivo scelto è un derivato dello spiropirano avente una funzionalità alchinica (SPCC) [3]. Esso è in grado, mediante la modifica della propria struttura molecolare, di fornire variazioni cromatiche al variare delle condizioni ambientali nel quale il sistema è immerso [3,4]. Le variazioni ambientali includono l’irraggiato con luce UV/Vis, la polarità dell’intorno ed il pH [4].
Sono stati preparati tre derivati dell’amilosio a contenuto crescente di SPCC (DS 0.15, 0.40, 0.80). Essi sono stati caratterizzati mediante spettroscopia infrarossa, NMR ed analisi elementare e successivamente è stata studiata la loro risposta ottica in soluzione e/o dispersione mediante spettroscopia UV/Vis e fluorimetria. In particolare è stata indagata la stabilità delle dispersioni e la risposta al variare della polarità del solvente (solvatocromismo) sia prima che dopo irraggiamento con luce UV.
In fine, è stata valutata la possibilità di produrre coating utilizzando il derivato a contenuto intermedio di SPCC (Ds 0.4). A tale scopo sono stati preparati dei film per "solution casting" su vetro e per deep coating su carta. In tutti i casi il derivato dell’amilosio ha mostrato capacità di filmatura superiore all’amilosio tal quale. Tutti i film sono stati caratterizzati mediante misure di angolo di contatto e quelli su vetro anche mediante spettroscopia UV/Vis, prima e dopo irraggiamento. Il derivato contenente funzionalità spiropiraniche è risultato più idrofobo dell’amilosio di partenza. L’idrofilia viene parzialmente recuperata
irraggiando il film con luce UV/Vis. L’irraggiamento produce anche variaziani cromatiche nette dei coating (da giallo a viola) le quali sono stabili nel tempo a condizione ambiente, ma reversibili per irraggiamento con intensa luce verde
Catalizzatori di polimerizzazione mono- e multisito nella supportazione di metalloceni su zeoliti e silice
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