Anionic Polymerization of Isoprene

1965 ◽  
Vol 38 (3) ◽  
pp. 627-635 ◽  
Author(s):  
D. J. Worsfold ◽  
S. Bywater
Keyword(s):  
Light Scattering ◽  
Anionic Polymerization ◽  
Great Increase ◽  
Major Effect ◽  
Dilute Solution ◽  
Initiation Rate ◽  
Kinetic Order ◽  
Scattering Measurements ◽  
Initiation Reaction

Abstract Polymerization of isoprene with butyllithium in cyclohexane has been studied. The initiation reaction was found to be complex; plots of conversion of butyllithium against time are sigmoidal. The order with respect to the initiator was found to be between one-half and one. The order of the isolated propagation reaction in polyisoprenyllithium was found to be one-quarter and was correlated with a fourfold association of active chain ends determined by dilute solution light-scattering measurements. The major effect of tetrahydrofuran on the reaction was the great increase of the initiation rate. The kinetic order changes slowly with the addition of small amounts of tetrahydrofuran, suggesting that the aggregates are broken down with difficulty. The microstructure of the polymer has been determined by NMR measurements and shows a steady transition from a largely 1:4 to a largely 3:4 structure as the polarity of the solvent is increased by the addition of tetrahydrofuran.

ANIONIC POLYMERIZATION OF ISOPRENE

1964 ◽  
Vol 42 (12) ◽  
pp. 2884-2892 ◽  
Author(s):  
D. J. Worsfold ◽  
S. Bywater
Keyword(s):  
Light Scattering ◽  
Anionic Polymerization ◽  
Great Increase ◽  
Major Effect ◽  
Dilute Solution ◽  
Initiation Rate ◽  
Kinetic Order ◽  
Initiation Reaction

The polymerization of isoprene with butyllithium in cyclohexane has been studied. The initiation reaction was found to be complex; plots of conversion of butyllithium against time are sigmoidal. The order with respect to the initiator was found to be between one-half and one. The order of the isolated propagation reaction in polyisoprenyllithium was found to be one-quarter and was correlated with a fourfold association of active chain ends determined by dilute solution light-scattering measurements.The major effect of tetrahydrofuran on the reaction was the great increase of the initiation rate. The kinetic order changes slowly with the addition of small amounts of tetrahydrofuran, suggesting that the aggregates are broken down with difficulty. The microstructure of the polymer has been determined by n.m.r. measurements and shows a steady transition from a largely 1:4 to a largely 3:4 structure as the polarity of the solvent is increased by the addition of tetrahydrofuran.

Light Scattering Study of [60] Fullerenol-Based Poly(Urethane-Ether) Star-Shaped Polymers

1994 ◽  
Vol 359 ◽  
Author(s):  
Lee Y. Wang ◽  
Long Y. Chiang
Keyword(s):  
Light Scattering ◽  
Diffusion Coefficients ◽  
Gaussian Model ◽  
Polymer Chains ◽  
Star Polymer ◽  
Dilute Solution ◽  
Analog Model ◽  
Scattering Measurements ◽  
Star Shaped Polymer ◽  
Scattering Study

ABSTRACTThe dynamic behavior of the fullerenol-based polyurethane star-shaped polymer and its analog model stars, containing three or four polymer arms, was investigated in toluene solution by dynamic light scattering measurements. In these systems, the diffusion coefficients clearly showed no angular dependence. In the case of study in dilute solution, all three star polyurethanes were found to possess higher mobility than that of the corresponding linear polyurethane with a similar molecular weight. Furthermore, the conformation of anchoring polymer chains was characterized by the hydrodynamic shrinking factor and compared with the Gaussian model. Results suggested that the polymer arms in the fullerenebased star-polymer were uniformly distributed around the central C60 cage.

Scattering Rings in Birefringent Porous Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
Claudio J. Oton ◽  
Zeno Gaburro ◽  
Mher Ghulinyan ◽  
Nicola Daldosso ◽  
Lucio Pancheri ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Light Scattering ◽  
Porous Silicon ◽  
Direct Measurement ◽  
Optical Anisotropy ◽  
Oblique Incidence ◽  
Laser Light ◽  
Anisotropic Scattering ◽  
Scattering Measurements

AbstractWe report the observation of strongly anisotropic scattering of laser light at oblique incidence on (100)-oriented porous silicon layers. We performed angle-resolved light scattering measurements and three concentric rings were observed. Modeling porous silicon by means of nanometric columnar air pores and an effective anisotropic uniaxial dielectric constant explains the observed phenomenon, and besides, the observation of the angle aperture of these rings allows a direct measurement of relative birefringence. We finally study the changes of optical anisotropy after different modifications of the structure.

A STUDY OF A WATER-SOLUBLE COMPLEX OF PRODIGIOSIN PRODUCED BY A STRAIN OF SERRATIA MARCESCENS

1962 ◽  
Vol 40 (1) ◽  
pp. 1019-1024 ◽  
Author(s):  
Seiichi Yoshida
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Serratia Marcescens ◽  
Average Molecular Weight ◽  
Electrophoretic Analysis ◽  
Water Soluble ◽  
Soluble Complex ◽  
Ph Values ◽  
Scattering Measurements ◽  
Water Soluble Complex

A water-soluble pigment excreted from Serratia marcescens has been purified by precipitation with ammonium sulphate, dialysis, and ultracentrifugation at different pH values. The purified pigment showed a single band in the ultracentrifuge and by electrophoretic analysis at several pH values. An average molecular weight of 5 × 106 was calculated from light-scattering measurements. This pigment is composed of carbohydrate and protein combined with prodigiosin, and several properties of the complex are described.

Light scattering measurements on microemulsions: Estimation of droplet sizes

2006 ◽  
Vol 312 (1-2) ◽  
pp. 187-195 ◽  
Author(s):  
C. Goddeeris ◽  
F. Cuppo ◽  
H. Reynaers ◽  
W.G. Bouwman ◽  
G. Van den Mooter
Keyword(s):  
Light Scattering ◽  
Scattering Measurements ◽  
Droplet Sizes

Light Scattering and Flow Dichroism Studies on DNA After the Photoreaction with Psoralen

1972 ◽  
Vol 27 (2) ◽  
pp. 196-200 ◽  
Author(s):  
S. Marciani ◽  
M. Terbojevic ◽  
F. Dall’Acqua
Keyword(s):  
Heat Treatment ◽  
Molecular Weight ◽  
Light Scattering ◽  
Double Helix ◽  
Heat Denaturation ◽  
Scattering Measurements ◽  
Helix Structure ◽  
Double Helix Structure

Light scattering measurements performed on DNA after irradiation in the presence of psoralen clearly show that inter strand cross linkings are present in the macromolecule. In fact after heat denaturation and successive cooling irradiated macromolecule shows a molecular weight practically unchanged while a DNA sample after the same treatment shows a molecular weight half of the intact native DNA. Also the general conformation of irradiated DNA undergoes practically to no modifications after the same heat treatment while native DNA shows itself to have been strongly modified. Moreover, on the basis of flow dichroism determinations, DNA cross-linked by psoralen after heat denaturation showed to be able to restore its ordered double helix structure, during the successive cooling.

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