Rodlike and Random‐Coil Behavior of Poly(n‐butyl Isocyanate) in Dilute Solution

1969 ◽  
Vol 51 (1) ◽  
pp. 406-420 ◽  
Author(s):  
Anthony J. Bur ◽  
Donald E. Roberts
Keyword(s):  
Random Coil ◽  
Dilute Solution

scholarly journals Triple Helix and Random Coil of Scleroglucan in Dilute Solution

1983 ◽  
Vol 15 (5) ◽  
pp. 389-396 ◽  
Author(s):  
Toshio Yanaki ◽  
Takashi Norisuye
Keyword(s):  
Triple Helix ◽  
Random Coil ◽  
Dilute Solution

Unperturbed Dimensions of Atactic Poly(phenylacetylene)

2005 ◽  
Vol 70 (11) ◽  
pp. 1787-1798 ◽  
Author(s):  
Dana Rédrová ◽  
Jan Sedláček ◽  
Majda Žigon ◽  
Jiří Vohlídal
Keyword(s):  
Molecular Weight ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Dilute Solution ◽  
Chain Branching ◽  
Unperturbed Dimensions ◽  
Molecular Weight Dependence ◽  
Atactic Polystyrene ◽  
Tetrahydrofuran Solution ◽  
Insight Into

Dilute solution characteristics of atactic (ca. 30% trans) poly(phenylacetylene), PPA, were determined by using the SEC/MALS technique in order to obtain a deeper insight into discrepancy between presumed rigidity of conjugated polyvinylene molecules and their random-coil behavior in solutions resulting from earlier viscometry measurements. PPA was found to exhibit the molecular-weight dependence of the radius of gyration in tetrahydrofuran solution similar to that of atactic polystyrene (saturated analogue of PPA); also unperturbed dimensions of these polymers are almost equal. This rather surprising observation is explained as a consequence of the increased π-π attraction between highly polarizable PPA segments with well-delocalized π-electrons, which compensates the effect of stiffening of these segments due to conjugation. Possible influence of chain branching is also discussed.

scholarly journals Contractility and Conformation

1967 ◽  
Vol 50 (6) ◽  
pp. 5-27 ◽  
Author(s):  
Harold A. Scheraga
Keyword(s):  
Partition Function ◽  
Mechanical Treatment ◽  
Random Coil ◽  
Dilute Solution ◽  
Factors Affecting ◽  
Macromolecular Conformation ◽  
Counting Procedure ◽  
Coil Transition ◽  
Statistical Mechanical ◽  
Α Helix

Contractility in fibers can arise from changes of macromolecular conformation caused by changes in some thermodynamic variable such as temperature, pH, or solvent composition. Illustrations are given of contractile processes in fibers and of changes in macromolecular conformation in dilute solution. These may involve order-disorder transitions, e.g. of the type exhibited by the helix-coil transition. A statistical mechanical treatment of the helix-coil transition involves the assignment of statistical weights to various states and the proper counting of these statistical weights in the formation and evaluation of the partition function; the thermodynamic properties of the system are derivable from the partition function. The counting procedure involved in the consideration of the α-helix and random coil is described. In addition, the factors affecting the relative stabilities of various helical conformations are discussed. These considerations of macromolecular conformation provide a basis for discussing contractile mechanisms in which changes of conformation are involved.

scholarly journals Salt effects on the dilute solution properties of bototo gum (Cochlospermum vitifolium)

2018 ◽  
Vol 3 (2) ◽  
pp. 49
Author(s):  
Maritza Coromoto Martínez ◽  
Juan Carlos Parra ◽  
Antonio José Vera
Keyword(s):  
Random Coil ◽  
Solution Properties ◽  
Dilute Solution ◽  
Salt Effects ◽  
Great Volume ◽  
Water Solvent ◽  
Intersection Model ◽  
Dilute Solution Properties ◽  
Ubbelohde Viscometer ◽  
Cation Charge

<p><span style="line-height: 113%; font-family: 'Times New Roman',serif; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 14.0pt; mso-contextual-alternates: yes; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">Salt effects on the dilute solution properties of bototo gum (<em>Cochlospermum vitifolium</em>) were investigated. There were measured the intrinsic viscosities of the polymer under study in water, in NaCl (at different concentrations) and in NaCl, CaCl<sub>2</sub> and AlCl<sub>3</sub>, at the same ionic strength (I = 1), using an Ubbelohde viscometer at 25°C. The Huggins intersection model (R<sup>2</sup>) is more appropriate to determine the intrinsic viscosity than the Kraemer's equation. This parameter tends to reduce with the increase in the salt concentration and the cation charge. The molecules of <em>C. vitifolium</em> gum exudate in water (solvent Φ) tend to adopt a “random coil” conformation, of great volume and radius, which exist in two regimes: diluted and semi-diluted; in the presence of salts, the coils exist only in a diluted regime where they are separate each other. The macromolecules in water have probably an extended ellipsoid shape but in presence of salts, they change to another more compact, probably spherical, with radii and smaller volumes. The knowledge of the behavior of <em>C. vitifolium</em> gum molecules in dilute solutions is an important criterion for its rational use in various industries</span></p>

Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts

1987 ◽  
Vol 45 ◽  
pp. 388-389
Author(s):  
P. Pradère ◽  
J.F. Revol ◽  
R. St. John Manley
Keyword(s):  
Low Dose ◽  
Polymer Concentration ◽  
Processing System ◽  
Limiting Factor ◽  
Dilute Solution ◽  
New Techniques ◽  
Dose Unit ◽  
Lattice Images ◽  
Dose Imaging ◽  
Imaging Conditions

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.

Two-stage self-seeding method for preparation of single crystals of poly(phenylene sulfide)

1989 ◽  
Vol 47 ◽  
pp. 368-369
Author(s):  
Sengshiu Chung ◽  
Peggy Cebe
Keyword(s):  
Single Crystals ◽  
High Performance ◽  
Dilute Solution ◽  
Two Stage ◽  
Annealing Behavior ◽  
High Performance Polymers ◽  
Seeding Method ◽  
Phenylene Sulfide

We are studying the crystallization and annealing behavior of high performance polymers, like poly(p-pheny1ene sulfide) PPS, and poly-(etheretherketone), PEEK. Our purpose is to determine whether PPS, which is similar in many ways to PEEK, undergoes reorganization during annealing. In an effort to address the issue of reorganization, we are studying solution grown single crystals of PPS as model materials.Observation of solution grown PPS crystals has been reported. Even from dilute solution, embrionic spherulites and aggregates were formed. We observe that these morphologies result when solutions containing uncrystallized polymer are cooled. To obtain samples of uniform single crystals, we have used two-stage self seeding and solution replacement techniques.

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