Local segmental dynamics of polyisoprene in dilute solution: solvent and molecular weight effects

1989 ◽  
Vol 22 (3) ◽  
pp. 1345-1351 ◽  
Author(s):  
Dean A. Waldow ◽  
Brian S. Johnson ◽  
Patrick D. Hyde ◽  
M. D. Ediger ◽  
Toshiaki Kitano ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Dilute Solution ◽  
Segmental Dynamics

Molecular Weight Induced Conformational Change and Its Impact on β-Phase Formation of Polydiarylfluorene in Dilute Solution

2020 ◽  
Vol 124 (11) ◽  
pp. 6304-6310 ◽  
Author(s):  
Masaru Nagai ◽  
Jie Liu ◽  
Wei Huang ◽  
Moriya Kikuchi ◽  
Seigou Kawaguchi ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Conformational Change ◽  
Phase Formation ◽  
Dilute Solution ◽  
Β Phase

Synthesis and Properties of Regular Star Polybutadienes with 32 Arms

1992 ◽  
Vol 65 (2) ◽  
pp. 303-314 ◽  
Author(s):  
L-L. Zhou ◽  
N. Hadjichristidis ◽  
P. M. Toporowski ◽  
J. Roovers
Keyword(s):  
Molecular Weight ◽  
Coupling Agent ◽  
Hard Sphere ◽  
Star Polymers ◽  
Radius Of Gyration ◽  
Linear Polymers ◽  
Solution Properties ◽  
Mean Square ◽  
Dilute Solution ◽  
Dilute Solution Properties

Abstract A dendrimer carbosilane containing 32 Si—Cl bonds in the perimeter has been prepared and has been used as a coupling agent to prepare 32-arm star polybutadienes. The dilute-solution properties 〈RG2〉, A2, [η], and D0 have been measured in one good solvent and in one ¸ -solvent. The dimensions of the 32-arm star polymers are compared with those of linear polymers at constant molecular weight. It is shown that the 32-arm star polybutadiene has the characteristic properties of a hard-sphere molecule in dilute solution. The equivalent hard-sphere radii calculated from A2, D0 and [η] are identical and 1.29 times larger than the root mean-square radius of gyration. The Daoud—Cotton scaling model for stars is also tested.

Interpretation of long-chain structure from dilute solution properties of ultrahigh molecular weight polymers

1992 ◽  
Vol 27 (5) ◽  
pp. 571-575 ◽  
Author(s):  
Maria Bercea ◽  
Silvia Ioan ◽  
Bogdan C. Simionescu ◽  
Cristofor I. Simionescu
Keyword(s):  
Molecular Weight ◽  
Chain Structure ◽  
Solution Properties ◽  
Dilute Solution ◽  
Dilute Solution Properties ◽  
Ultrahigh Molecular Weight ◽  
Long Chain

Cryoscopy in molten pyridinium chloride

1967 ◽  
Vol 20 (12) ◽  
pp. 2583 ◽  
Author(s):  
H Bloom ◽  
VC Reinsborough
Keyword(s):  
Solid Solution ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Heat Of Fusion ◽  
Dilute Solution ◽  
Pyridinium Chloride ◽  
Cryoscopic Constant

The molal cryoscopic constant in molten pyridinium chloride (m.p. 146.0�) has been found to be 17.4� (subject to confirmation by calorimetry) and the cryoscopic heat of fusion, 2310�40 cal mole-1. In pyridinium chloride as a solvent, iodides appear to dissociate completely while bromides do not yield the expected depression possibly because of solid solution. Tetraalkylammonium and alkyl-pyridinium halides of high molecular weight are ideally dissociated in extremely dilute solution but with increasing concentration apparently form micelles.

THE VISCOSITY – MOLECULAR WEIGHT RELATION FOR POLY-levo-2,3-BUTANEDIYL o-PHTHALATE

1948 ◽  
Vol 26b (12) ◽  
pp. 783-797
Author(s):  
R. W. Watson ◽  
N. H. Grace
Keyword(s):  
Molecular Weight ◽  
High Purity ◽  
Molecular Orientation ◽  
Degree Of Polymerization ◽  
Solution Viscosity ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Complex Relation ◽  
End Group ◽  
Long Chain

The inherent viscosities of dilute solutions of acidic polyesters of high purity have been compared with number average molecular weights accurately determined by end-group titration. For unfractionated resins with a degree of polymerization from 2 to 11 [Formula: see text] the viscosity – molecular weight relation is linear in chloroform at 25 °C. Where [Formula: see text], K = 1.923 × 10−5 and β = 0.0176. For fractionated polyesters from DP 5 to 8, K = 1.959 × 10−6 and β = 0.0161. For unfractionated resins with a DP > 11, molecular weights increase more rapidly than inherent viscosities. Above [Formula: see text] for fractionated resins linearity is resumed, and the slope increases. Several attempts have been made to explain this complex relation. Apparently the short chains remain linear, and the formation of anisotropic fibers at a DP close to 100 establishes a degree of molecular orientation in the long-chain superpolyesters. Isomerization of levo-diol to the diastereoisomer during polycondensation is without effect on the dilute solution viscosity of the resulting resin. Preferential degradation of the longer chains is assumed to be partially responsible for the decreasing slope from DP 11 to 65. As yet it has not been possible to assess the roles played by changes in size distribution, and variation in solvation with increasing chain length, but the data point to a curved viscosity – molecular weight relation in chloroform at 25 °C.

Characteristic Ratio and Plateau Modulus of 1,2-Polybutadiene. A Comparison with Other Rubbers

1990 ◽  
Vol 63 (5) ◽  
pp. 734-746 ◽  
Author(s):  
Jacques Roovers ◽  
Paul M. Toporowski
Keyword(s):  
Molecular Weight ◽  
Star Polymer ◽  
Dilute Solution ◽  
Plateau Modulus ◽  
Characteristic Ratio ◽  
Polymer Systems ◽  
Dilute Solution Properties ◽  
Linear Viscoelastic ◽  
Low Levels

Abstract In the course of work on linear and ring polybutadienes with 62% 1,2 units, a number of discrepancies were noted with data on polybutadienes of various microstructure available in the literature. For example, GNο=870 kPa for our 62% 1,2-polybutadiene. This is larger than GNο=730 kPa for a 56% 1,2-polybutadiene and GNο=550 kPa for a 78% 1,2-polybutadiene sample. The cis : trans ratio of our 62% 1,2-polybutadiene, prepared with potassium counterion, is 1 : 4, On the other hand, the cis : trans ratio of 62% 1,2-polybutadiene prepared with a modified Li catalyst is estimated to be 1 : 2. It is conceivable that the different cis : trans ratio leads to different properties at constant 1,2 content. Nevertheless, the low levels of both the cis and the trans units are not expected to cause more than minor differences in the properties of the polybutadienes. Correct values for GNο of model polymers are important for the study of the influence of the chemical structure on the melt characteristics of a polymer. For this reason, it was thought useful to reinvestigate 1,2-polybutadiene itself in some detail. The synthesis of narrow molecular-weight distribution 1,2-polybutadiene by anionic polymerization techniques has been described recently. The dilute-solution properties of 1,2-polybutadiene has been investigated. The melt rheology of two 1,2-polybutadiene samples have been studied, but no systematic study of the molecular-weight dependence of the melt properties was made. 1,2-Polybutadiene has been used as a component in block copolymers with 1,4-polybutadiene. These studies have permitted an investigation of the phase behavior of two rubbery blocks at room temperature. Poly(l,4-butadiene-graft-l,2-butadiene)s with well-defined composition and architecture have also been prepared. Hydrosilylated 1,2-polybutadiene has found use as the coupling agent for multiarm star polymer, and this method can easily be extended to the preparation of poly( l,2-butadiene-graft-l,4-butadiene). Hydrogenated 1,2-polybutadienes are prepared as model polymers for poly(l-butene). The synthesis and characterization of a series of 1,2-polybutadienes are described here. Special attention is given to low-molecular-weight polymers. The linear viscoelastic properties of the melts are also described. In the discussion, the relation between the characteristic ratio, C∞, and the plateau modulus, GNο, of a number of model polymer systems is explored.

Sign in / Sign up

Export Citation Format

Share Document