scholarly journals A hybrid polymer gel with controlled rates of cross-link rupture and self-repair

2006 ◽  
Vol 4 (13) ◽  
pp. 373-380 ◽  
Author(s):  
Farrell R Kersey ◽  
David M Loveless ◽  
Stephen L Craig
Keyword(s):  
Single Molecule ◽  
Mechanical Response ◽  
Polymer Gel ◽  
Hybrid Polymer ◽  
Ligand Complex ◽  
Hybrid Gels ◽  
Cross Links ◽  
Modular Platform ◽  
The Individual ◽  
Metal Ligand

A family of hybrid polymer gels is described, in which covalent cross-links create a permanent, stiff scaffold onto which reversible metal–ligand coordinative cross-links are added. The reversible metal–ligand interactions are shown to bear mechanical stress within the hybrid gel, and relaxations in response to that applied stress are consistent with the stress-free kinetics of ligand exchange in systems that model the reversible cross-links. The stress-induced dissociation of a model metal–ligand complex is examined by a single-molecule force spectroscopy, and its mechanical response is compared with a previously studied complex. The mechanical response of the individual interactions is relevant to those found in the family of hybrid gels, and the modular platform is therefore suitable for the study of stress-induced molecular dissociations, and their subsequent repair, within a macroscopic material of fixed structure.

scholarly journals Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

2021 ◽  
Author(s):  
Jacopo Quaglierini ◽  
Alessandro Lucantonio ◽  
Antonio DeSimone
Keyword(s):  
Boundary Conditions ◽  
Elastic Properties ◽  
Central Region ◽  
Mechanical Response ◽  
Different Boundary Conditions ◽  
Kirchhoff Rods ◽  
Model Versus ◽  
The Individual ◽  
Opposite Chirality

Abstract Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.

scholarly journals Capable Cross-links: Polymersomes Reinforced with Catalytically Active Metal–Ligand Bonds

2015 ◽  
Vol 27 (13) ◽  
pp. 4808-4813 ◽  
Author(s):  
Ian M. Henderson ◽  
Hope A. Quintana ◽  
Julio A. Martinez ◽  
Walter F. Paxton
Keyword(s):  
Active Metal ◽  
Catalytically Active ◽  
Cross Links ◽  
Metal Ligand

Preparation and Characterization of Chitosan/Alginate Polyelectrolyte Complex Prepared by Using Calcium Tripolyphosphate Ionic Gelator

2016 ◽  
Vol 857 ◽  
pp. 447-451
Author(s):  
Nur Syairah Muhamad Rahim ◽  
Norlaily Ahmad ◽  
Dzaraini Kamarun
Keyword(s):  
Single Molecule ◽  
Polyelectrolyte Complex ◽  
Sodium Tripolyphosphate ◽  
Hybrid Compound ◽  
Polyelectrolyte Complexes ◽  
Sem Image ◽  
Degradation Temperature ◽  
Prepared Material ◽  
True Hybrid ◽  
The Individual

The formation of polyelectrolyte complexes (PECs) between chitosan and alginate has been widely investigated for many pharmaceutical and biomedical uses. Ionotropic gelation resulted from the crosslinking of polyelectrolytes (PEs) in the presence of ionic crosslinkers to form hydrogels. The most widely used ionic crosslinker for chitosan is sodium tripolyphosphate (NaTPP); and Ca2+ ions for alginates. The use of these cross-linkers to prepare PECs of chitosan and alginates resulted in hydrogels of similar moieties: chitosan-chitosan and alginate-alginate rather than the sought for hybrid chitosan-alginate PECs. Calcium tripolyphosphate (CaTPP) is a single molecule ionic gelator of chitosan and alginate that have the capability of producing the true hybrid compound of chitosan/alginate polyelectrolyte complex. This paper reported the synthesis of calcium tripolyphosphate and the preparation of a hybrid chitosan/alginate PECs using this newly identified ionic gelator. The newly-synthesized ionic gelator was characterized using ICP-OES; the PECs thereof prepared were characterized using TGA and SEM. The degradation temperature of the prepared PECs is higher than the degradation temperatures of the individual chitosan and alginates. SEM image of the prepared PECs showed rougher surfaces compared to the images of the individual chitosan and alginate compound. Both TGA and SEM revealed the possibility of the newly prepared material to be of the PECs sought for.

scholarly journals Morphology Control of Ni(II)-NTA-End-Functionalized Block Copolymer and Bio-Conjugation through Metal-Ligand Complex

Polymers ◽  
2017 ◽  
Vol 9 (12) ◽  
pp. 144 ◽  
Author(s):  
Dasom Park ◽  
Chaeyeon Lee ◽  
Minsu Chae ◽  
Mohammad Kadir ◽  
Ji Choi ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Morphology Control ◽  
Ligand Complex ◽  
Metal Ligand

scholarly journals Structure and mechanics of aegagropilae fiber network

2017 ◽  
Vol 114 (18) ◽  
pp. 4607-4612 ◽  
Author(s):  
Gautier Verhille ◽  
Sébastien Moulinet ◽  
Nicolas Vandenberghe ◽  
Mokhtar Adda-Bedia ◽  
Patrice Le Gal
Keyword(s):  
Mechanical Response ◽  
Posidonia Oceanica ◽  
Biological Tissues ◽  
Individual Response ◽  
Fiber Network ◽  
Friction Forces ◽  
Fiber Clustering ◽  
Wide Range ◽  
Natural Aggregates ◽  
The Individual

Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal behavior of these complex structures depends on both the individual response of the constituent fibers and the density and degree of entanglement of the network. A question of paramount importance is how to control the formation of a given fiber network to optimize a desired function. The study of fiber clustering of natural flocs could be useful for improving fabrication processes, such as in the paper and textile industries. Here, we use the example of aegagropilae that are the remains of a seagrass (Posidonia oceanica) found on Mediterranean beaches. First, we characterize different aspects of their structure and mechanical response, and second, we draw conclusions on their formation process. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers held together by friction forces. Although formed in a natural environment, thus under relatively unconstrained conditions, the geometrical and mechanical properties of the resulting fiber aggregates are quite robust. This study opens perspectives for manufacturing complex fiber network materials.

Non-linearity with metal-metal ligand complex reactions in flow injection systems. Metal-thiocyanate reactions

1997 ◽  
Vol 350 (1-2) ◽  
pp. 37-50 ◽  
Author(s):  
J.F. van Staden ◽  
C. Saling ◽  
D. Malan ◽  
R.E. Taljaard
Keyword(s):  
Flow Injection ◽  
Ligand Complex ◽  
Metal Metal ◽  
Metal Ligand

scholarly journals Function of the CysD domain of the gel-forming MUC2 mucin

2011 ◽  
Vol 436 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Daniel Ambort ◽  
Sjoerd van der Post ◽  
Malin E. V. Johansson ◽  
Jenny MacKenzie ◽  
Elisabeth Thomsson ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Disulfide Bonds ◽  
Tandem Repeats ◽  
Gel Filtration ◽  
Middle Part ◽  
Domain Of Unknown Function ◽  
Cross Links ◽  
Native Gel ◽  
The Individual ◽  
Covalent Nature

The colonic human MUC2 mucin forms a polymeric gel by covalent disulfide bonds in its N- and C-termini. The middle part of MUC2 is largely composed of two highly O-glycosylated mucin domains that are interrupted by a CysD domain of unknown function. We studied its function as recombinant proteins fused to a removable immunoglobulin Fc domain. Analysis of affinity-purified fusion proteins by native gel electrophoresis and gel filtration showed that they formed oligomeric complexes. Analysis of the individual isolated CysD parts showed that they formed dimers both when flanked by two MUC2 tandem repeats and without these. Cleavages of the two non-reduced CysD fusion proteins and analysis by MS revealed the localization of all five CysD disulfide bonds and that the predicted C-mannosylated site was not glycosylated. All disulfide bonds were within individual peptides showing that the domain was stabilized by intramolecular disulfide bonds and that CysD dimers were of non-covalent nature. These observations suggest that CysD domains act as non-covalent cross-links in the MUC2 gel, thereby determining the pore sizes of the mucus.

Skeletal and Lattice Vibrations of Crystals of Dihalogenobis(pyridine)zinc(II)

1974 ◽  
Vol 52 (11) ◽  
pp. 2005-2015 ◽  
Author(s):  
P. T. T. Wong
Keyword(s):  
Single Molecule ◽  
Room Temperature ◽  
Normal Modes ◽  
Low Frequency ◽  
Far Infrared ◽  
Liquid Nitrogen Temperature ◽  
Lattice Vibrations ◽  
Individual Molecule ◽  
Stretching Vibrations ◽  
The Individual

Detailed measurements of the low-frequency Raman spectra of the crystals of [ZnPy2Cl2] and [ZnPy2Br2] at room temperature, where Py is the pyridine molecule, and the far-infrared spectrum of the crystal of [ZnPy2Cl2] at liquid nitrogen temperature have been made. The vibrational frequencies for the single molecule and for the complete crystal of these two complexes have been calculated and compared with the observed spectra, and the distribution of the potential energy of the normal modes has also been calculated to assist the refinement of the calculation and the interpretation of the spectra. Apparently, the skeletal Zn–ligand vibrations of the individual molecule couple with the lattice vibrations in the crystal, except for the normal modes at 326 cm−1 for [ZnPy2Cl2] and at 250 cm−1 for [ZnPy2Br2] which are dominated by the Zn–halogen stretching vibrations. Reasonably good Zn–ligand stretching force constants were obtained. The nature of the coordination bonds of these complexes has been discussed.

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