Screened intermolecular forces and covalent bond forces in polymer melts

1993 ◽  
Vol 98 (10) ◽  
pp. 8256-8261 ◽  
Author(s):  
J. Gao ◽  
J. H. Weiner
Keyword(s):  
Polymer Melts ◽  
Covalent Bond ◽  
Intermolecular Forces

scholarly journals A Review on Gelatin Based Hydrogels for Medical Textile Applications

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Seblewongel Petros ◽  
Tamrat Tesfaye ◽  
Million Ayele
Keyword(s):  
Biological Fluids ◽  
Low Cost ◽  
Polymer Networks ◽  
Covalent Bond ◽  
Cost Effective ◽  
Intermolecular Forces ◽  
Natural Polymers ◽  
Synthesis Mechanism ◽  
Sustainable Technologies ◽  
Drug Delivery Carrier

Hydrogels are hydrophilic polymer networks that absorb any kind of liquid including biological fluids. Natural polymers and their derivatives along with synthetic polymers are used to form the hydrogels. Networks that constitute the hydrogels are created by the crosslinking of either synthesized polymers starting from monomers or already developed polymers. Crosslinking can be developed either physically if secondary intermolecular forces are involved or chemically in which a covalent bond between polymeric chains is created. Gelatins are natural driven protein polymers. One of the main biopolymers used for producing hydrogels is gelatin. Gelatin has a very wide application other than hydrogels. In this review, hydrogels and their property and synthesis mechanism, as well as their application in biomedical along with gelatin chemistry and application, are reviewed. Due to its nonimmunogenicity, nontoxicity, low cost, and high availability gelatin-based hydrogels could find applications in drug delivery carrier, bioink, transdermal therapy, wound healing, and tissue repair. The beneficiation of gelatin can result in their sustainable conversion into high-value biomaterials on the proviso of the existence or development of cost-effective, sustainable technologies for converting this biopolymer into useful bioproducts.

Contribution of covalent bond force to pressure in polymer melts

1989 ◽  
Vol 91 (5) ◽  
pp. 3168-3173 ◽  
Author(s):  
J. Gao ◽  
J. H. Weiner
Keyword(s):  
Polymer Melts ◽  
Covalent Bond ◽  
Bond Force

scholarly journals Highly Stable Nanoparticle Supercrystals Formed by Aldol Reaction in Conjunction with Slow Solvent Evaporation

2020 ◽  
Author(s):  
Jiwhan Kim ◽  
Jahar Dey ◽  
Aminah Umar ◽  
Jae-Min Ha ◽  
Sang-Jo Lee ◽  
...  
Keyword(s):  
Structural Stability ◽  
Aldol Reaction ◽  
Three Dimensional ◽  
Covalent Bond ◽  
Intermolecular Forces ◽  
Particle Dispersion ◽  
Solvent Evaporation ◽  
Van Der Waals Interactions ◽  
Emergent Properties ◽  
Covalent Bonds

Abstract The nanoparticle supercrystals (NPSCs) have been of great interests for their collective emergent properties. While various NPSCs have been successfully fabricated using intermolecular forces, the limited structural stability of NPSCs due to the weak nature of the intermolecular forces still remains a major hurdle for practical applications. Herein, we report a new method to fabricate highly stable three-dimensional NPSCs by using aldol reaction, a model covalent bond forming reaction, in conjunction with slow solvent evaporation. Gold nanoparticles functionalized with thiol poly-ethylene glycol formyl are linked to each other by carbon-carbon covalent bonds formed by aldol reaction as the particle dispersion in aqueous NaOH solution is slowly evaporated, resulting in highly faceted three-dimensional NPSCs. As-synthesized NPSCs show excellent structural stability in solvents of different polartities as well as the dried condition and at temperature up to 160 °C, which is far superior to NPSCs stabilized by intermolecular forces such as hydrogen bonding and van der Waals interactions. The new covalent bonding appraoch opens up new opportunities in the synthesis of NPSCs and their applications.

scholarly journals Chemical Bonding and Local Islamic Wisdom of Sasak Tribe, Lombok, West Nusa Tenggara

2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Adi Fadli
Keyword(s):  
Chemical Bonding ◽  
Social Values ◽  
Bond Formation ◽  
Covalent Bond ◽  
Negative Ions ◽  
Intermolecular Forces ◽  
Social Solidarity ◽  
Chemical Bond Formation ◽  
Electrostatic Stability ◽  
Theory Of Chemical Bond

A myriad of traditions underlie the local wisdom of Sasak tribe (the indigenous people in Lombok), namely tradisi merarik (wedding), nenarih (proposing), sorong serah ajikrame (dowry negotiation), langar, begawe (party) , banjar (the community body), begibung (eating together), berayan mangan (eating together), and nyongkolan (wedding parade). Such local customs in general entail the value of mutual concession or tolerance, compassion, dependency, social solidarity, sympathy, communal work for peace, and prosperity. The local wisdoms are strongly relevant to the theory of chemical bonding such as electrostatic stability and configuration, the positive and negative ions, theory of chemical bond formation, polar and nonpolar covalent, coordinate covalent bond, metal bonding, and intermolecular forces comprising hydrogen and Van der Waals bond. The interface and relevance of both are actualized in the religious and social values of Sasak Lombok tradition equivalent to the theory of chemical bonding. Therefore, this paper demonstrates that the theory of chemical bonding is strongly relevantly associated with the tradition of local Islamic wisdom of Sasak Lombok, West Nusa Tenggara.

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

Phase behavior of cationic and anionic surfactants at low concentrations

1992 ◽  
Vol 50 (1) ◽  
pp. 694-695
Author(s):  
E. Naranjo
Keyword(s):  
Phase Behavior ◽  
Structural Characterization ◽  
Dynamic Systems ◽  
Anionic Surfactants ◽  
Intermolecular Forces ◽  
Stable Form ◽  
Surfactant Mixtures ◽  
Low Concentrations ◽  
Cationic And Anionic Surfactants ◽  
General Method

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.

Structure of stacking faults in pyrite using TEM techniques

1992 ◽  
Vol 50 (1) ◽  
pp. 358-359
Author(s):  
Raja Subramanian ◽  
Kenneth S. Vecchio
Keyword(s):  
Lattice Structure ◽  
Stacking Faults ◽  
Covalent Bond ◽  
Group Symmetry ◽  
Iron Pyrite ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Contrast Analysis ◽  
Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

Effect of Integral Proteins on Frozen Membrane Fracture

1980 ◽  
Vol 38 ◽  
pp. 756-759 ◽  
Author(s):  
S. Kirchanski ◽  
D. Branton
Keyword(s):  
Lipid Bilayers ◽  
Freeze Fracture ◽  
Covalent Bond ◽  
Erythrocyte Membranes ◽  
Glycophorin A ◽  
Experimental Protocol ◽  
Transmembrane Glycoprotein ◽  
Bond Breakage ◽  
Human Erythrocyte Membranes ◽  
Integral Proteins

We have investigated the effect of integral membrane proteins upon the fracturing of frozen lipid bilayers. This investigation has been part of an effort to develop freeze fracture labeling techniques and to assess the possible breakage of covalent protein bonds during the freeze fracture process. We have developed an experimental protocol utilizing lectin affinity columns which should detect small amounts of covalent bond breakage during the fracture of liposomes containing purified (1) glycophorin (a transmembrane glycoprotein of human erythrocyte membranes). To fracture liposomes in bulk, frozen liposomes are ground repeatedly under liquid nitrogen. Failure to detect any significant covalent bond breakage (contrary to (2)) led us to question the effectiveness of our grinding procedure in fracturing and splitting lipid bilayers.

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