Enhanced ionic polymerization of styrene induced by radiation

1963 ◽  
Vol 273 (1354) ◽  
pp. 387-399 ◽  
Keyword(s):  
Molecular Weight ◽  
Radiation Intensity ◽  
Chain Transfer ◽  
Average Molecular Weight ◽  
Surface Adsorption ◽  
Silica Powder ◽  
Intensity Dependence ◽  
Radiation Induced

The radiation-induced ionic polymerization of styrene at — 78 °C has been studied, at various concentrations in diehloromethane solutions, in the presence of silica powder, and at various radiation intensities. Both yield of polymer, and average molecular weight were determined, allowing an estimate of G i for ionic polymerization to be made. The yield is greatly reduced by traces of water and this is ascribed to increased termination. On the assumption that chain transfer is small, Aerosil powder appears to cause an increase in initiation, rather than a reduction in termination. Evidence is presented for the view that the enhanced reaction occurs by the surface adsorption of styrene ions, so that the radiation intensity dependence changes from I 1.0 to I 0.5 . Energy absorbed in the solvent is also found to be capable of initiation.

Radiation-Induced Graft Polymerization of Maleic Anhydride onto Poly-β-Hydroxybutyrate

2005 ◽  
Vol 288-289 ◽  
pp. 477-480 ◽  
Author(s):  
Herong Ye ◽  
Dongzhi Yang ◽  
Ping Hu ◽  
Feng Bo Zhang ◽  
Qinglei Qi
Keyword(s):  
Molecular Weight ◽  
Maleic Anhydride ◽  
Graft Polymerization ◽  
Average Molecular Weight ◽  
Commercial Application ◽  
Radiation Induced

This paper focuses on an effective way to improve the thermostability of poly-β-hydroxybutyrate (PHB). Maleic anhydride (MA) is grafted onto PHB by 60Co γ of radiation. The spectra of both 1HNMR and 13CNMR were investigated following the radiation-induced polymerization. The results are consistent with successful grafting of the MA monomer onto the PHB, with a low graft degree. The graft degree and viscosity-average molecular weight Mηof the radiated samples were also investigated. The results observed through TGA demonstrate that thermostability has been measurably improved with the introduction of MA groups. These significant results suggest that wide commercial application of PHB may be possible.

scholarly journals Reversible Addition-Fragmentation Chain Transfer (RAFT) Polymerization of Poly(ethylmethacrylate) with Pendant Carbazole Groups

KIMIKA ◽  
2018 ◽  
Vol 29 (1) ◽  
pp. 41-50
Author(s):  
Shienna Marie Pontillas ◽  
Florentino C. Sumera ◽  
Rigoberto C. Advincula
Keyword(s):  
Molecular Weight ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Chain Extension ◽  
Conversion Characteristic ◽  
Reversible Addition ◽  
Ft Ir ◽  
Carbazole Group

Carbazole containing polymers have captured the interest of researchers for use in optoelectronics. For an important material to exhibit its optoelectronic properties intrinsic uniformity in the molecular level is required. Thus, a monomer of ethyl methacrylate with pendant carbazole group was synthesized and polymerized via Reversible Addition-Fragmentation Chain Transfer (RAFT) to produce polymers with controlled molecular weight distribution and narrow polydispersity index (PDI). This method of polymerization was compared with that of free radical polymerization by gel permeation chromatography (GPC). The RAFT’s polymerization kinetics was observed to follow a plot of number average molecular weight (Mn) versus % conversion, characteristic of living polymerization. It was also shown to possess polymer chain extension capability. The structure of the monomer and the polymers were characterized by Fourier-Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR).

Crosslink Density in Polybutadiene

1959 ◽  
Vol 32 (3) ◽  
pp. 706-717
Author(s):  
L. H. Howland ◽  
A. Nisonoff ◽  
L. E. Dannals ◽  
V. S. Chambers
Keyword(s):  
Molecular Weight ◽  
Crosslink Density ◽  
Chain Transfer ◽  
Average Molecular Weight ◽  
Weight Fraction ◽  
Side Reactions ◽  
Polymerization Temperature ◽  
Low Molecular Weight ◽  
High Molecular Weight Fraction ◽  
Rate Of Increase

Abstract 1. A method has been developed for the measurement of crosslink density of diene polymers. This method, which involves the use of radioactive chain transfer agents, is applicable to ungelled polymer prepared under a wide variety of conditions so that any polymerization variable can be studied independently. 2. The crosslink density in polybutadiene decreases with decreasing polymerization temperature. At low molecular weight of polymers, the amount of crosslinking varies linearly with the polymerization temperature. 3. The crosslink density of polybutadiene increases with increasing number-average polymer molecular weight. The rate of increase is less for polymer prepared at −18° C than for that polymerized at 5° to 50° C. This means that, in a polymerization, as the average molecular weight increases with conversion the crosslink density increases. However, when the molecular weight is kept constant, by changes in the modifier loading, the crosslink density of polybutadiene appears to be independent of the degree of conversion attained within the range of 0.12–0.48. 4. The crosslink density of a high molecular weight fraction of polybutadiene was not significantly different from that of the whole polymer (from which about 3% of low molecular weight material had been removed). 5. The kind of initiator system does not affect the crosslink density of polybutadiene, providing the initiator loading is not too high. However, if large amounts of initiator are used in the polymerization, 10% or more of the polymer molecules may not contain mercaptan modifier. 6. Tertiary alkyl mercaptans are necessary for the crosslinking studies because they do not appear to give side reactions. Primary dodecylmercaptan and diisopropyl xanthogen disulfide are unsatisfactory for determinations because they appear to add to the double bonds of the polymer molecule in addition to the usual chain transfer reactions. 7. Incomplete emulsification of monomers in some 5° C recipes apparently increased the crosslink density of polybutadiene by retarding the diffusion of monomer into the monomer-polymer particles.

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.

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.

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