Bead‐and‐Spring Model for Solution Dynamics of Short‐Chain Polymer Molecules

1968 ◽  
Vol 49 (6) ◽  
pp. 2875-2876 ◽  
Author(s):  
Chong Wha Pyun
Keyword(s):  
Short Chain ◽  
Spring Model ◽  
Chain Polymer ◽  
Polymer Molecules ◽  
Solution Dynamics

Statistical thermodynamics of semi-flexible chain molecules

1956 ◽  
Vol 234 (1196) ◽  
pp. 60-73 ◽  
Keyword(s):  
Dominant Factor ◽  
Cellulose Derivatives ◽  
Chain Polymer ◽  
Configurational Energy ◽  
Chain Molecules ◽  
Polymer Molecules ◽  
Disordered Phase ◽  
Intermolecular Energy ◽  
Free Energy Of Solution ◽  
Intramolecular Forces

Long-chain polymer molecules are approximated by a model consisting of isodimensional segments which tend to arrange themselves in co-linear succession. A fraction f of the bonds is assumed to be ‘bent’ out of the co-linear direction of preceding segments. The fact that the free energy of solution derived using the lattice model separates into (a) a mixing term dependent only on the concentration, and (b) a disorientation term depending on f but not on the concentration, leads to the concept of an equilibrium ‘flexibility’ f which is characteristic of the polymer chain at a given temperature. This f must exceed a specified critical value, which decreases with dilution, if the disordered phase usually considered to occur is to be more stable than an ordered one in which the chains assume their preferred rod-like form and lie parallel to one another. Transition between the two states should be co-operative, and should involve a latent heat (owing to the change in intramolecular configurational energy) even in the absence of a change in the intermolecular energy. The concept of a phase transition due solely to intramolecular forces thus arises. Configurational dimensions of various polymers are such as to suggest that inflexibility may be a dominant factor in causing them to crystallize. This is certainly true for cellulose derivatives, probably also for polytetrafluoroethylene, and possible for polymethylene as well. Intramolecular forces favouring the rod-like form are, doubtless of major importance also in bringing about crystallization of proteins in the α-form.

Effect of HCl Concentration and Acetone Washing on the Dielectric and Conduction Properties of Polyaniline Salts

2021 ◽  
Vol 14 ◽  
Author(s):  
Jayashree Mohanty ◽  
S.R. Mishra ◽  
Tanmaya Badapanda ◽  
S. Anwar
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Acid Concentration ◽  
Charge Carriers ◽  
Short Chain ◽  
Water Medium ◽  
Distilled Water ◽  
Chain Polymer ◽  
Pani Salt ◽  
Long Chain

Aims: The aim of the work is to study the effect of acid concentration and acetone washing on electrical properties of Polyaniline (PANI) salts prepared through chemically oxidative polymerization. Background: The frequency dependent conductivity and dielectric permittivity provide important information on the electrical properties of conducting polymers which gives information regarding their utility in electronic applications. Objective: Hence, the present study is based on the comparative the electrical properties study (dielectric and electrical conductivity) of PANI salts prepared in two different media like water and 1M HCl along with study regarding effect acetone washing on the said electrical properties of the polymer samples. Methods: PANI salts are synthesized through chemical oxidative polymerisation of aniline hydrochloride with the oxidant ammonium persulphate in two different media like water and 1M HCl. One part of the PANI salt samples were washed with distilled water after synthesis and another part of the polymer samples were washed with distilled water followed by acetone to study the effect of acetone washing on the electrical properties of polymer samples. Results: Non-acetone washed PANI salt prepared in water medium shows the highest dielectric as well as electrical conductivity due to the increased charge carriers provided both by long chain polymer as well as short chain oligomers. When the acid concentration is increased to 1M there may be loss of protons accompanied by pairing of free radicals to form quinoimine units that leads to the loss of charge carriers consequently decreasing the dielectric constant and electrical conductivity. Conclusion : PANI salt prepared in water shows the highest dielectric as well as conductivity due to the increased charge carriers provided both by long chain polymer as well as short chain oligomers.

Simulation of short-chain polymer collapse with an explicit solvent

2002 ◽  
Vol 116 (16) ◽  
pp. 7244-7254 ◽  
Author(s):  
James M. Polson ◽  
Martin J. Zuckermann
Keyword(s):  
Short Chain ◽  
Chain Polymer ◽  
Polymer Collapse ◽  
Explicit Solvent

Salt Effects in Mucin Lubrication

1969 ◽  
Vol 91 (3) ◽  
pp. 371-373 ◽  
Author(s):  
C. W. McCutchen ◽  
J. F. Wilkins
Keyword(s):  
Salt Concentration ◽  
Entire Range ◽  
Good Evidence ◽  
Joint Fluid ◽  
Chain Polymer ◽  
Polymer Molecules ◽  
Lubricating Film ◽  
Joint Load ◽  
Long Chain ◽  
Physiological Salt Concentration

Animal joints are lubricated by two complementary mechanisms. Weeping lubrication carries most of the joint load hydrostatically, leaving only a small fraction of the total to be carried by rubbing of the solid “skeletons” of the two cartilages. This rubbing is, in turn, lubricated by the synovial mucin; i.e., by long chain polymer molecules dissolved in the joint fluid. There is good evidence that the mucin molecules adsorb to the surfaces and provide boundary lubrication. In this paper we examine further this adsorption processs using a bearing whose two surfaces are rubber and glass, respectively. It is found that the lubricating ability of the mucin is good if it is applied to the bearing in a solution with about physiological salt concentration. At higher salt concentrations the lubrication is comparatively poor, while at zero salt concentration it is very bad indeed. If, on the other hand, the mucin is applied at physiological salt concentration, and then the salt and unadsorbed mucin are washed away with distilled water the lubrication remains good, and has, on occasion, even improved. Once the mucin has been adsorbed the entire range of salt concentration can be explored, with the lubrication becoming worse at high salt concentration and then recovering in greater or lesser degree when the salt is washed off. It seems, then, that the salt concentration affects lubrication in two ways. It can upset the adsorption of the lubricating film, and it can change the lubricating effectiveness of the film once it is adsorbed.

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