Molecular structure of polyethylene. XIII. An improved cryoscopic method for determining number-average molecular weight of polyethylene

1966 ◽  
Vol 4 (5) ◽  
pp. 705-714 ◽  
Author(s):  
E. J. Newitt ◽  
V. Kokle
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight

Chemistry and Properties of Imide Oligomers from Phenylethynyl-Containing Diamines

2000 ◽  
Vol 12 (1) ◽  
pp. 213-223 ◽  
Author(s):  
J G Smith ◽  
J W Connell
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Research Effort ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Similar Composition ◽  
Imide Oligomers ◽  
Calculated Number

As an extension of work on pendent phenylethynyl-containing imide oligomers, three new diamines containing pendent phenylethynyl groups were prepared and characterized. These diamines were used to prepare pendent and pendent and terminal phenylethynyl imide oligomers via the amide acid route in N-methyl-2-pyrrolidinone at a calculated number average molecular weight of 5000 g mol−1. The pendent phenylethynyl groups were randomly distributed along the oligomer backbone and provided a means of controlling the distance between reactive sites. The imide oligomers were characterized and thermally cured, and the cured polymers evaluated as thin films and compared with materials of similar composition prepared from 3,5-diamino-4′-phenylethynylbenzophenone. This work was performed as part of a continuing research effort to develop structural resins for potential aeronautical applications.

Alternating poly(ester amide)s from glutaric anhydride and α,ω-aminoalcohols: synthesis and thermal properties

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Thomas Fey ◽  
Helmut Keul ◽  
Hartwig Höcker
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Homologous Series ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Melting Points ◽  
Glutaric Anhydride ◽  
H Nmr ◽  
Activating Agent ◽  
Dimethylformamide Solution

Abstract Alternating poly(ester amide)s 6a - e were prepared by polycondensation of α-carboxyl-ω-hydroxyamides 3a - e which were obtained by aminolysis of glutaric anhydride (1) and α,ω-aminoalcohols, H2N-(CH2)x-OH (x = 2 - 6) 2a - e. The polycondensation was performed in dimethylformamide solution using a carbodiimide as activating agent, or in bulk with Bu2Sn(OMe)2, Ti(OBu)4 and Sn(octoate)2 as a catalyst. For the polycondensation in bulk, the influence of catalyst and of temperature on the number-average molecular weight was studied. 1H NMR analyses of the poly(ester amide)s clearly show the alternating microstructure. The poly(ester amide)s from glutaric anhydride and the homologous series of α,ω-aminoalcohols are semicrystalline materials; their melting points show the odd/even effect observed for other poly(ester amide)s.

Study on the Reaction of TDI and PPG with Organo-Tin Mixed Catalyst

2011 ◽  
Vol 418-420 ◽  
pp. 13-17
Author(s):  
Su Ran Liao ◽  
Yuan Wei ◽  
Yu Qi Zhang ◽  
Meng Zhang ◽  
Gao Fei Feng
Keyword(s):  
Molecular Weight ◽  
Hydrogen Bonding ◽  
Average Molecular Weight ◽  
Polypropylene Glycol ◽  
Number Average Molecular Weight ◽  
Mixed Catalyst ◽  
Back Titration ◽  
Step Growth ◽  
Step Growth Polymerization ◽  
Polymerization Conditions

The study of polyurethanes are of continuing interest due to their excellent physical properties. In this study, the reaction kinetics and polymerization conditions in two-step process of toluene diisocyante (TDI) and polypropylene glycol (PPG) with organo-tin mixed catalyst were investigated by di-n-butylamine back-titration. It was showed that the reaction obeyed the second-order equation of step-growth polymerization, the rate constants of TDI and PPG reaction at 50, 60 and 70°C were 0.0922, 0.3373 and 0.5828 kg•mol-1•min-1，respectively. The activation energy obtained from the result was 71.63 kJ•mol-1. The number average molecular weight (Mn) and molecular-weight distribution (Mw/Mn) of the polyurethane were 45175 and 1.53, respectively, and the content of hydrogen bonding in the N-H group from Fourier transform infrared spectrum (FTIR) was 80.75%, which manifested that the large amount of N-H were present in hydrogen bonding.

scholarly journals The presence of a high-molecular-weight (guanine-plus-cytosine)-rich segment at the 3' end of rabbit 28S ribosomal ribonucleic acid.

1975 ◽  
Vol 147 (3) ◽  
pp. 625-628 ◽  
Author(s):  
A A Hadjiolov ◽  
R A Cox ◽  
P Huvos
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Ribonucleic Acid ◽  
Average Molecular Weight ◽  
28S Rrna ◽  
Number Average Molecular Weight ◽  
Ribonuclease T1 ◽  
Naphthoic Acid ◽  
Rrna Molecule ◽  
Ribosomal Ribonucleic Acid

The 3′ hydroxyl end of 28S L-rRNA (major RNA species of the larger subribosomal particle) was labelled by coupling its 2-hydroxy-3-naphthoic acid hydrazine with diazotized [3H]aniline. The RNA was hydrolysed partially with ribonuclease T1 and fractionated on Sephadex G-200. The results show that a highly structured segment with 78% G+C content and a number-average molecular weight of at least 1.0×10(5)-1.8×10(5) is located at the 3′ hydroxyl end of the 28S rRNA molecule.

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