Preparation of a Certified Reference Material of Trifunctional Polypropylene Oxide

2011 ◽  
Vol 284-286 ◽  
pp. 1961-1968 ◽  
Author(s):  
Jing Xia Wang ◽  
Xiao Dong Fan ◽  
Wei Tian ◽  
Guang Wen Cheng ◽  
Juan Li Li
Keyword(s):  
Molecular Weight ◽  
Reference Material ◽  
Certified Reference Material ◽  
Storage Stability ◽  
Group Analysis ◽  
Size Exclusion ◽  
Distribution Model ◽  
Polypropylene Oxide ◽  
Exclusion Chromatography ◽  
End Group

Due to the lack of trifunctional polypropylene oxide (TPPO) certified reference material (CRM) with precise molecular weight on the market, it is therefore very important to prepare such CRM to calibrate the molecular weight testing equipments, and assure the quality in polyurethanes manufacture. In this paper, the certification of TPPO CRM was introduced based on the size-exclusion chromatography with a multi-angle laser light scattering (SEC-MALLS) method and end-group analysis method. First, TPPO was synthesized via controlled ring-opening polymerization of propylene oxide in the condition of both high temperature and pressure using double metal cyanide (DMC) complexes as catalyst, and TPPO oligomer as coinitiator. Then, the molecular weight homogeneity of TPPO CRM was evaluated by using the F-distribution model, and the storage stability of the molecular weight of TPPO CRM was assessed. All potential uncertainty factors for the certification of TPPO CRM were evaluated using cause-effect diagram. The results showed that the chemical structure of TPPO CRM was an anticipatory structure, which was confirmed by IR. The molecular weight homogeneity of TPPO CRM was qualified. The storage stability period of the final product was one year with respect to its molecular weight, and the certification results of TPPO CRM obtained by SEC-MALLS and end-group analysis were 4996±162 and 5025±146, respectively.

Characterisation of Persistent Anti-Xa Activity Following Administration of the Low Molecular Weight Heparin Enoxaparin Sodium (Clexane)

1994 ◽  
Vol 72 (02) ◽  
pp. 275-280 ◽  
Author(s):  
David Brieger ◽  
Joan Dawes
Keyword(s):  
Molecular Weight ◽  
Enoxaparin Sodium ◽  
Antithrombin Iii ◽  
Anticoagulant Activity ◽  
Active Material ◽  
Biologically Active ◽  
Size Exclusion ◽  
Low Molecular Weight ◽  
Exclusion Chromatography ◽  
Liver And Kidney

SummaryIt is widely reported that persistent anti-Xa activity follows administration of low molecular weight heparins. To identify the effectors of this activity we have injected 125I-labelled Enoxaparin sodium into rabbits and subsequently analysed the circulating radiolabelled material and anti-Xa activity by affinity and size exclusion chromatography. Antithrombin III-binding material derived from the injected drug was responsible for all the anti-Xa amidolytic activity. At early times after injection additional anticoagulant activity which was largely attributable to tissue factor pathway inhibitor was measured by the Heptest clotting assay after removal of glycosaminoglycans from plasma samples. Small radiolabelled fragments, including penta/hexasaccharide with affinity for antithrombin III, were detectable in the circulation 1 week later, and sulphated oligosaccharides persisted for 3-4 weeks. Significant quantities of radiolabel remained in the liver and kidney several weeks post-injection; these organs may sequester some of the injected drug and give rise to circulating biologically active material by degradation and secretion of catabolic products into the plasma.

A study on the kinetics and thermal properties of polystyrene/diatomite nanocomposites prepared via in situ ATRP

2018 ◽  
Vol 33 (2) ◽  
pp. 180-197 ◽  
Author(s):  
Khezrollah Khezri ◽  
Yousef Fazli
Keyword(s):  
Molecular Weight ◽  
In Situ Polymerization ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Linear Increase ◽  
Size Exclusion ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Exclusion Chromatography

Pristine mesoporous diatomite was employed to prepare polystyrene/diatomite composites. Diatomite platelets were used for in situ polymerization of styrene by atom transfer radical polymerization to synthesize tailor-made polystyrene nanocomposites. X-Ray fluorescence spectrometer analysis and thermogravimetric analysis (TGA) were employed for evaluating some inherent properties of pristine diatomite platelets. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the diatomite platelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Linear increase of ln ( M0/M) with time for all the samples shows that polymerization proceeds in a living manner. Addition of 3 wt% pristine mesoporous diatomite leads to an increase of conversion from 72% to 89%. Molecular weight of polystyrene chains increases from 11,326 g mol−1 to 14134 g mol−1 with the addition of 3 wt% pristine mesoporous diatomite; however, polydispersity index values increases from 1.13 to 1.38. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 81.9°C to 87.1°C by adding 3 wt% of mesoporous diatomite platelets.

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