Phase Equilibria in Cellulose Acetate-Acetone Solutions. The Effect of the Degree of Substitution and Molecular Weight on Upper and Lower Critical Solution Temperatures

1971 ◽  
Vol 4 (1) ◽  
pp. 57-61 ◽  
Author(s):  
J. M. G. Cowie ◽  
Ann Maconnachie ◽  
R. J. Ranson
Keyword(s):  
Molecular Weight ◽  
Phase Equilibria ◽  
Cellulose Acetate ◽  
Degree Of Substitution ◽  
Critical Solution Temperatures

HES 200/0.5 Is not HES 200/0.5

1995 ◽  
Vol 74 (06) ◽  
pp. 1452-1456 ◽  
Author(s):  
Johannes Treib ◽  
Anton Haass ◽  
Gerhard Pindur ◽  
Ulrich T Seyfert ◽  
Wolfgang Treib ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hydroxyethyl Starch ◽  
Clinical Relevance ◽  
Dilution Effect ◽  
Repeated Administration ◽  
Plasma Viscosity ◽  
Degree Of Substitution ◽  
Pronounced Increase ◽  
Large Molecules ◽  
Mean Molecular Weight

SummaryThe plasma clearance of hydroxyethyl starch (HES) depends on the initial molecular weight and the degree of substitution. So far, little attention has been paid to the clinical relevance of the C2/C6 substitution ratio of hydroxyethyl starch.10 patients with cerebrovascular circulatory disturbance received hemodilution therapy for 10 days, consisting of 10% HES 200/0.5 (mean molecular weight 200 kD, degree of substitution 0.5) with a C2/C6 ratio of 13.4. A second group of 10 patients received a starch solution with identical initial molecular weight and degree of substitution but with a C2/C6 ratio of 5.7.After the administration of a single dose, no significant differences between the two groups were observed. After repeated administration, significant differences could be detected in hemorheology, coagulation and elimination (p<0.01). The larger C2/C6 ratio led to a higher intravascular mean molecular weight (95 vs. 84 kD), which in turn led to a higher increase in serum concentration during the therapy (14.7 vs.8.6 mg/ml). Hematocrit was lowered more (-30,5 vs. -23,5%) and plasma viscosity was increased more. There was also a more pronounced increase in partial thromboplastin time (+30% vs. +13%) and a factor of 2 larger decrease of factor VIII/von Willebrand factor-complex (p <0.01), which exceeded the dilution effect.The higher C2/C6 ratio of HES 200/0.5/13.4 slows down enzymatic degradation. After repeated administration of this starch, large molecules accumulate which are inefficiently degraded. The same effect has been observed after therapy with highly-substituted HES. This accumulation of large molecules leads to a beneficial longer lasting volume effect. The disadvantages include an increase in plasma viscosity and coagulation disturbances, which cannot be explained with the respective dilution effect alone. For these reasons, the C2/C6 ratio is of clinical relevance and should be included in the product labeling in the future.

scholarly journals THE LOCATION OF THE XANTHATE GROUPS IN PARTLY SUBSTITUTED CELLULOSE XANTHATES

1957 ◽  
Vol 35 (12) ◽  
pp. 1522-1533 ◽  
Author(s):  
E. P. Swan ◽  
C. B. Purves
Keyword(s):  
Cellulose Acetate ◽  
Chlorine Dioxide ◽  
Methyl Esters ◽  
Lead Tetraacetate ◽  
Degree Of Substitution ◽  
Hydroxyl Groups ◽  
Primary Position ◽  
Standard Methods ◽  
The Third ◽  
Almost All

Cellulose sodium xanthates of degree of substitution (D.S.) 0.4 to 0.66 were methylated to xanthate S-methyl esters which were then acetylated completely, the final xanthate D.S. remaining close to the original value. Dexanthation with aqueous chlorine dioxide near pH 4.5 and −5° removed almost all of the S-methyl xanthate groups, but the loss of a few acetyl groups from, and the retention of 1 to 2% of sulphur in, the resulting cellulose acetate could not be avoided. The original xanthate groups were presumably represented in this acetate as unsubstituted hydroxyl groups, and these were located by standard methods involving tosylation–iodination, tritylation, and oxidations with lead tetraacetate. Xanthate groups appeared to occupy the third and sixth, but not the second, position in the cellulose, and 53 to 61% of the substituent was in the sixth or primary position; one sample of viscose was "ripened" before the cellulose sodium xanthate was isolated, and the value was 81%. The results were of a preliminary nature, because severe technical difficulties reduced their reliability.

scholarly journals Chitosan and Carboxymethyl Chitosan from Fish Scales of Labeo rohita

2013 ◽  
Vol 61 (1) ◽  
pp. 145-148 ◽  
Author(s):  
Tanvir Muslim ◽  
Mohammad Habibur Rahman ◽  
HOsne Ara Begum ◽  
Md. Azizur Rahman
Keyword(s):  
Molecular Weight ◽  
Spectral Analysis ◽  
Labeo Rohita ◽  
Carboxymethyl Chitosan ◽  
Degree Of Substitution ◽  
Monochloroacetic Acid ◽  
Fish Scales ◽  
Ft Ir

Chitin was extracted from the fish scales of Labeo rohita and chitosan was successfully prepared from it by deacetylation reaction. The prepared chtiosan was characterized by FT-IR spectral analysis and degree of decetylation was determined by pH-metric titration. The molecular weight of chitosan was estimated by viscometric method. Chitosan was converted into its carboxymethyl derivative using alkali and monochloroacetic acid. The prepared carboxymethyl chitosan was characterized by FT-IR spectral analysis and degree of substitution was estimated. Dhaka Univ. J. Sci. 61(1): 145-148, 2013 (January) DOI: http://dx.doi.org/10.3329/dujs.v61i1.15116

Effect of organoclay content and molecular weight on cellulose acetate nanocomposites properties

2012 ◽  
Vol 97 (10) ◽  
pp. 1996-2001 ◽  
Author(s):  
Francisco J. Rodríguez ◽  
Alejandro Coloma ◽  
María J. Galotto ◽  
Abel Guarda ◽  
Julio E. Bruna
Keyword(s):  
Molecular Weight ◽  
Cellulose Acetate
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