THE EFFECT OF ALTERNATING ELECTRICAL FIELDS ON THE POLYMERIZATION OF STYRENE

1950 ◽  
Vol 28b (4) ◽  
pp. 117-131
Author(s):  
C. A. Winkler ◽  
W. A. Bryce ◽  
C. A. Genge
Keyword(s):  
Molecular Weight ◽  
Benzoyl Peroxide ◽  
Chemical Reactions ◽  
Average Molecular Weight ◽  
Electrical Fields ◽  
Inhibiting Effect ◽  
Rate Of Polymerization ◽  
Field Strengths ◽  
Catalyzed Polymerization

Equipment for studying the effects of alternating fields on chemical reactions is described. The catalyzed polymerization of liquid styrene was investigated, with fields of frequencies ranging from 1.15 to 7.72 Mc. and with field strengths up to 4500 v. per cm. The rate of polymerization was reduced by the application of the fields, the inhibition increasing approximately as the square of the voltage. The fields appeared to have a greater inhibiting effect on the oxygen-catalyzed than on the benzoyl peroxide – catalyzed reaction. Varying the frequency over the above range had no effect on the amount of inhibition caused by the field. At all temperatures, catalyst concentrations, voltages, and frequencies, the fields had no significant effect on the viscosity-average molecular weight of the polymer.

THE DEGRADATION OF POLYSTYRENE: II. THE SYNTHESIS AND DEGRADATION OF POLYSTYRENE POSSESSING THE KUHN–SCHULZ CHAIN LENGTH DISTRIBUTION

1950 ◽  
Vol 28b (7) ◽  
pp. 416-428
Keyword(s):  
Molecular Weight ◽  
Benzoyl Peroxide ◽  
Chain Length ◽  
Average Molecular Weight ◽  
Length Distribution ◽  
Chain Scission ◽  
Limited Range ◽  
Number Average Molecular Weight ◽  
Chain Length Distribution ◽  
Synthesis And Degradation

By polymerizing styrene in emulsion it was possible to synthesize polystyrenes of known number average molecular weight, the chain length distributions of which corresponded closely to the Kuhn–Schulz relation Ny = N0py−1(1 − p)2. This enabled a relation between intrinsic viscosity and number average molecular weight to be established for polystyrenes with chain length distributions of this functional form. Assuming this form of chain length distribution to remain unaltered on degradation, it was possible to estimate the average number of scission points per structural unit from viscosimetric measurements. The extent of thermal scission of polystyrene after one week at 144 °C. was shown to be negligible while benzoyl peroxide caused appreciable chain scission at 80 °C. and 100 °C. The number of scission points estimated from viscosimetric measurements was directly proportional to the mass of benzoyl peroxide added to the system, and the scission appeared to be essentially random over the limited range investigated.

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

Phase-partitioning and chemical reactions of low molecular weight organic compounds in fog

Tellus B ◽  
1992 ◽  
Vol 44 (5) ◽  
pp. 533-544 ◽  
Author(s):  
M. C. Facchini ◽  
S. Fuzzi ◽  
J. A. Lind ◽  
H. Fierlinger-Oberlinninger ◽  
M. Kalina ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Compounds ◽  
Chemical Reactions ◽  
Low Molecular Weight ◽  
Phase Partitioning

Series of sequential polypeptides containing lysine or arginine: Preparation and characterization

1988 ◽  
Vol 53 (1) ◽  
pp. 145-156 ◽  
Author(s):  
Jana Pírková ◽  
Svetlana Churkina ◽  
Vladimír Gut ◽  
Ivo Frič ◽  
Karel Bláha
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Peptide Synthesis ◽  
Average Molecular Weight ◽  
Basic Amino Acid ◽  
Cd Spectra ◽  
Active Esters ◽  
Marked Tendency

The sequential polypeptides (Lys-Ala)n, (Lys-Ala-Ala)n, (Lys-Ala-Ala-Ala)n, (Lys-Leu-Ala)n, (Lys-Leu-Ala-Ala)n, (Lys-Leu-Ala-Ala-Ala)n, (Lys-Ala-Leu)n, (Lys-Ala-Leu-Ala)n, (Orn-Leu-Ala)n,(Arg-Ala-Ala)n, (Arg-Leu-Ala)n, (Arg-Leu-Ala-Ala)n, (Arg-Ala-Leu)n, and (Arg-Ala-Leu-Ala)n were synthesized by polymerization of active esters (1-succinimidyl or pentafluorophenyl) of the corresponding Nα-deblocked monomers. The monomers were prepared using the usual methods of peptide synthesis in solution. Upon dialysis, the average molecular weight of the polymer was 6 000-9 000 as determined by sedimentation in ultracentrifuge. Polypeptides, containing leucine in addition to the basic amino acid, showed a marked tendency to aggregation. CD spectra of the products were measured for characterization.

Metathesis Polymerization of Phenylacetylene by Tungsten Aryloxo Complexes

1995 ◽  
Vol 60 (3) ◽  
pp. 489-497 ◽  
Author(s):  
Hynek Balcar ◽  
Jan Sedláček ◽  
Marta Pacovská ◽  
Vratislav Blechta
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
Induction Period ◽  
Average Molecular Weight ◽  
Molar Fraction ◽  
Molar Ratio ◽  
Weight Average Molecular Weight ◽  
Polymer Yield ◽  
Positive Effect ◽  
Ligand Addition

Catalytic activity of the tungsten aryloxo complexes WCl5(OAr) and WOCl3(OAr), where Ar = 4-t-C4H9C6H4, 2,6-(t-C4H9)2C6H3, 2,6-Cl2C6H3, 2,4,6-Cl3C6H2, and 2,4,6-Br3C6H2 in polymerization of phenylacetylene (20 °C, monomer to catalyst molar ratio = 1 000) was studied. The activity of WCl5(OAr) as unicomponent catalysts increases with increasing electron withdrawing character of the -OAr ligand. Addition of two equivalents of organotin cocatalysts (Me4Sn, Bu4Sn, Ph4Sn, Bu3SnH) to WCl5(O-C6H2Cl3-2,4 ,6) has only slight positive effect (slightly higher polymer yield and/or molecular weight of poly(phenylacetylene)s was achieved). However, in the case of WOCl3(O-C6H3Cl2-2, 6) catalyst, it enhances the activity considerably by eliminating the induction period. Poly(phenylacetylene)s prepared with the catalysts studied have weight-average molecular weight ranging from 100 000 to 200 000. They are trans-prevailing and have relatively low molar fraction of monomer units comprised in cyclohexadiene sequences (about 6%).

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