scholarly journals Distribution of the Chemical Composition of Block and Graft Copolymers Assuming Gamma Distribution of Molecular Weights of the Precursor Blocks

1982 ◽  
Vol 14 (8) ◽  
pp. 603-627 ◽  
Author(s):  
Jaroslav Stejskal ◽  
Pavel Kratochvíl
Keyword(s):  
Chemical Composition ◽  
Gamma Distribution ◽  
Graft Copolymers ◽  
Molecular Weights

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

Synthesis and characterization of amphiphilic graft copolymers with hydrophobic poly(α-methylstyrene) backbone and hydrophilic poly(n-vinylpyrrolidone) side chains

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Fatima Zohra Sebba ◽  
Seghier Ould Kada ◽  
Mohamed Benaicha ◽  
Nerjesse Nemiche
Keyword(s):  
Graft Copolymer ◽  
Graft Copolymers ◽  
Radical Copolymerization ◽  
Side Chains ◽  
Free Radical Copolymerization ◽  
Good Efficiency ◽  
Molecular Weights ◽  
Grafting Reaction ◽  
Viscosity Variation ◽  
End Capping

AbstractIn this study, 2-oxopropylmethacrylate-terminated poly(N-vinyl-2- pyrrolidone) is produced by cationic polymerization using HClO4 as an initiator. Termination (end capping) step is accomplished using 2- hydroxypropylmethacrylate (2HPMA) and the polymer product has different chain lengths of molecular weight averages ranging from 672 to 3049 g/mol. The study also synthesised amphipathic graft copolymers having hydrophobic poly(α- methylstyrene) as a backbone chain and hydrophilic poly(N-vinyl-2-pyrrolidone) (PVP) as side chains of various lengths. The copolymer synthesis was accomplished by free radical copolymerization of ω-oxopropylmethacrylate PVP in the presence of α-methyl styrene initiated with benzoyl peroxide. Measurements of the dynamic viscosity of the polymer solution (20% weight of macromonomers in ethanol) show that the viscosity is proportional to the average molecular weights M̅n . However, a reverse behaviour of the viscosity variation with regard to M̅n is observed for graft copolymer samples. The viscosity variation with respect to the graft copolymer mass must be due to steric effects, which are strongly pronounced in grafted copolymer chains. Appearance of the number of side chains attached to poly(α-methylstyrene) backbone reveals that the grafting reaction has occurred with good efficiency.

First approach on transfection ability of novel amphiphilic water soluble degradable poly(ε-caprolactone)-g-poly(Llysine) copolymers

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Benjamin Nottelet ◽  
Julie Vendrell ◽  
Jean Coudane ◽  
Michel Vert
Keyword(s):  
Chemical Composition ◽  
Aqueous Solutions ◽  
Graft Copolymers ◽  
Water Soluble ◽  
Dna Transfection ◽  
Mcf 7

AbstractThe potential of novel amphiphilic water soluble and degradable poly(ε- caprolactone)-g-poly(L-lysine) as carriers for DNA transfection has been investigated. Two graft copolymers having the same proportion of lysine units but different structures have been synthesized following two grafting techniques. The chemical composition of these copolymers, their expected architectures and their behaviour in aqueous solutions have been studied. The benefits resulting from the use of these degradable polycationic structures as well as their ability to form polyplexes are discussed. Finally, preliminary transfection assays of MCF-7 cells by pRL-TK plasmid using poly(ε-caprolactone)-g-poly(L-lysine) copolymers as carriers are reported.

Molecular weights of backbones in graft copolymers

1975 ◽  
Vol 11 (3) ◽  
pp. 197-202 ◽  
Author(s):  
R. Collins ◽  
M.B. Huglin ◽  
R.W. Richards
Keyword(s):  
Graft Copolymers ◽  
Molecular Weights

scholarly journals Mitochondrial and cytoplasmic ribosomes from mammalian tissues. Further characterization of ribosomal subunits and validity of buoyant-density methods for determination of the chemical composition and partial specific volume of ribonucleoprotein particles

1977 ◽  
Vol 168 (2) ◽  
pp. 245-259 ◽  
Author(s):  
Ada Sacchi ◽  
Ugo Ferrini ◽  
Paola Londei ◽  
Piero Cammarano ◽  
Nadir Maraldi
Keyword(s):  
Chemical Composition ◽  
Specific Volume ◽  
Buoyant Density ◽  
Volume Ratio ◽  
Partial Specific Volume ◽  
Ribosomal Subunits ◽  
Molecular Weights ◽  
Mitochondrial Ribosomes ◽  
Density Methods ◽  
Cytoplasmic Ribosomes

1. At 0–4°C mitochondrial ribosomes (55S) dissociate into 39S and 29S subunits after exposure to 300mm-K+ in the presence of 3.0mm-Mg2+. When these subunits are placed in a medium containing a lower concentration of K+ ions (25mm), approx. 75% of the subparticles recombine giving 55S monomers. 2. After negative staining the large subunits (20.3nm width) usually show a roundish profile, whereas the small subunits (12nm width) show an elongated, often bipartite, profile. The dimensions of the 55S ribosomes are 25.5nm×20.0nm×21.0nm, indicating a volume ratio of mitochondrial to cytosol ribosomes of 1:1.5. 3. The 39S and 29S subunits obtained in high-salt media at 0–4°C have a buoyant density of 1.45g/cm3; from the rRNA content calculated from buoyant density and from the rRNA molecular weights it is confirmed that the two subparticles have weights of 2.0×106 daltons and 1.20×106 daltons; the weights of the two subunits of cytosol ribosomes are 2.67×106 and 1.30×106 daltons. 4. The validity of the isodensity-equilibrium-centrifugation methods used to calculate the chemical composition of ribosomes was reinvestigated; it is confirmed that (a) reaction of ribosomal subunits with 6.0% (v/v) formaldehyde at 0°C is sufficient to fix the particles, so that they remain essentially stable after exposure to dodecyl sulphate or centrifugation in CsCl, and (b) the partial specific volume of ribosomal subunits is a simple additive function of the partial specific volumes of RNA and protein. The RNA content is linearly related to buoyant density by the equation RNA (% by wt.)=349.5−(471.2×1/ρCsCl), where 1/ρCsCl=[unk]RNP (partial specific volume of ribonucleoprotein). 5. The nucleotide compositions of the two subunit rRNA species of mitochondrial ribosomes from rodents (42% and 43% G+C) are distinctly different from those of cytoplasmic ribosomes.

scholarly journals Nanofibers for drug delivery – incorporation and release of model molecules, influence of molecular weight and polymer structure

2015 ◽  
Vol 6 ◽  
pp. 1939-1945 ◽  
Author(s):  
Jakub Hrib ◽  
Jakub Sirc ◽  
Radka Hobzova ◽  
Zuzana Hampejsova ◽  
Zuzana Bosakova ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Polyvinyl Alcohol ◽  
Polymer Structure ◽  
Release Profile ◽  
Polyethylene Glycols ◽  
Aqueous Environment ◽  
Molecular Weights ◽  
Molecular Length ◽  
Pharmacologically Active ◽  
Pharmacologically Active Compounds

Nanofibers were prepared from polycaprolactone, polylactide and polyvinyl alcohol using NanospiderTM technology. Polyethylene glycols with molecular weights of 2 000, 6 000, 10 000 and 20 000 g/mol, which can be used to moderate the release profile of incorporated pharmacologically active compounds, served as model molecules. They were terminated by aromatic isocyanate and incorporated into the nanofibers. The release of these molecules into an aqueous environment was investigated. The influences of the molecular length and chemical composition of the nanofibers on the release rate and the amount of released polyethylene glycols were evaluated. Longer molecules released faster, as evidenced by a significantly higher amount of released molecules after 72 hours. However, the influence of the chemical composition of nanofibers was even more distinct – the highest amount of polyethylene glycol molecules released from polyvinyl alcohol nanofibers, the lowest amount from polylactide nanofibers.

ALBERTA BITUMEN: I. THE COMPOSITION OF BLOWN ALBERTA BITUMEN

1934 ◽  
Vol 10 (4) ◽  
pp. 435-451 ◽  
Author(s):  
Morris Katz
Keyword(s):  
Molecular Weight ◽  
Chemical Composition ◽  
Physical Properties ◽  
Pronounced Increase ◽  
Molecular Weights ◽  
Asphaltene Content

The relation between the physical consistency and chemical composition of a series of blown asphalts from Alberta bitumen has been studied. The amounts of asphaltous acids and anhydrides decrease on blowing, with rise in fusing point of the bitumen. The amounts of oily constituents and resins also decrease but the asphaltene content increases. The molecular weights of the resins increase from 733 to 1012 during blowing. The asphaltenes also show a pronounced increase in molecular weight from 2219 to 4690 Only traces of oxygen are found in the products blown for 6 to 8. 5 hr. at 270 °C; the amount however increases in the later stages of blowing to a maximum of 1.88%. The oily constituents do not contain oxygen, which is distributed mainly in the resin fractions, with smaller amounts occurring in the asphaltene fractions. The sulphur and nitrogen in the bitumen are distributed principally among the resins and asphaltenes. The essential process in blowing bitumen with air is one of condensation by removal of some hydrogen to form water, followed by polymerization, assisted by the sulphur in the bitumen, to products of higher molecular weight. Products similar in composition and physical properties to commercial grades of mineral rubber have been prepared from Alberta bitumen by blowing.

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