Method of Test for Cellulose Chain Length Uniformity by Fractional Precipitation of Cellulose Nitrate

10.1520/d1716 ◽  
1991 ◽  
Author(s):  
Keyword(s):  
Chain Length ◽  
Cellulose Nitrate ◽  
Fractional Precipitation ◽  
Cellulose Chain

scholarly journals FRACTIONAL PRECIPITATION OF CELLULOSE NITRATE

1955 ◽  
Vol 11 (1) ◽  
pp. 32-38
Author(s):  
Hiroshi Asaoka ◽  
Akira Suzuki
Keyword(s):  
Cellulose Nitrate ◽  
Fractional Precipitation

On the relationship between fibre length, cellulose chain length and pulp viscosity of a softwood sulfite pulp

Holzforschung ◽  
2006 ◽  
Vol 60 (4) ◽  
pp. 372-377 ◽  
Author(s):  
Luc Lapierre ◽  
Jean Bouchard ◽  
Richard Berry
Keyword(s):  
Chain Length ◽  
Fibre Length ◽  
Indirect Measurement ◽  
Pulp Mills ◽  
Cellulose Chain ◽  
Degree Of Polymerisation ◽  
Pulp Viscosity ◽  
Average Fibre ◽  
Sulfite Pulp ◽  
Pulp Strength

Abstract Many chemical pulp mills use pulp viscosity as an indicator of pulp strength, and some mill customers stipulate a particular viscosity threshold for the delivered product. Nevertheless, the value of the viscosity-strength relationship is often questioned, particularly as it varies with the wood species and the pulping process. To provide some insight, the viscosity, degree of polymerisation and fibre length were measured for a bleached softwood sulfite pulp segregated into different fractions with respect to fibre length using a Bauer-McNett fractionator. It was demonstrated that fractions with a longer average fibre length also had a higher degree of polymerisation and higher viscosity. The cellulose chain length in chemical pulps is approximately three orders of magnitude shorter than the fibre length, and thus a relationship between these two properties should not be expected. The possible causes of the correlation between fibre length and viscosity are discussed. In this work, viscosity appears to be an indirect measurement of the average fibre length of a pulp, which would be the direct contributor to the strength of that pulp.

Satiation in humans is modulated by fatty acid chain length

2001 ◽  
Vol 120 (5) ◽  
pp. A710-A710
Author(s):  
S LAL ◽  
J MCLAUGHLIN ◽  
O NIAZ ◽  
G DOCKRAY ◽  
A VARRO ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Chain Length ◽  
Fatty Acid Chain Length ◽  
Fatty Acid Chain

Cellulose Nitrate.

1958 ◽  
Vol 14 (3_4) ◽  
pp. 276-276
Author(s):  
G. V. Schulz
Keyword(s):  
Cellulose Nitrate

Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron-Electron Resonance

2019 ◽  
Author(s):  
Dennis Bücker ◽  
Annika Sickinger ◽  
Julian D. Ruiz Perez ◽  
Manuel Oestringer ◽  
Stefan Mecking ◽  
...  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Catalyst System ◽  
Chain Conformation ◽  
Controlled Polymerization ◽  
Chain Length Distribution ◽  
Electron Resonance ◽  
Double Electron ◽  
The Individual ◽  
Double Electron Electron Resonance

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Mechanisms of Drug Solubilization by Polar Lipids in Biorelevant Media

2020 ◽  
Author(s):  
Vladimir Katev ◽  
Zahari Vinarov ◽  
Slavka S. Tcholakova
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Polar Lipids ◽  
Superior Performance ◽  
Head Group ◽  
Formulation Development ◽  
Biorelevant Media ◽  
Drug Solubilization ◽  
Colloidal Aggregates ◽  
Class 1

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. We studied the effect of 26 polar lipids of the fatty acid, phospholipid or monoglyceride type on the solubilization of fenofibrate in a two-stage <i>in vitro</i> GI tract model. The main trends were checked also with progesterone and danazol.<br>Based on their fenofibrate solubilization efficiency, the polar lipids can be grouped in 3 main classes. Class 1 substances (n = 5) provide biggest enhancement of drug solubilization (>10-fold) and are composed only by unsaturated compounds. Class 2 materials (n = 10) have an intermediate effect (3-10 fold increase) and are composed primarily (80 %) of saturated compounds. Class 3 materials (n = 11) have very low or no effect on drug solubilization and are entirely composed of saturated compounds.<br>The observed behaviour of the polar lipids was rationalized by using two classical physicochemical parameters: the acyl chain phase transition temperature (<i>T</i><sub>m</sub>) and the critical micellar concentration (CMC). Hence, the superior performance of class 1 polar lipids was explained by the double bonds in their acyl chains, which: (1) significantly decrease <i>T</i><sub>m</sub>, allowing these C18 lipids to form colloidal aggregates and (2) prevent tight packing of the molecules in the aggregates, resulting in bigger volume available for drug solubilization. Long-chain (C18) saturated polar lipids had no significant effect on drug solubilization because their <i>T</i><sub>m</sub> was much higher than the temperature of the experiment (<i>T</i> = 37 C) and, therefore, their association in colloidal aggregates was limited. On the other end of the spectrum, the short chain octanoic acid manifested a high CMC (50 mM), which had to be exceeded in order to enhance drug solubilization. When these two parameters were satisfied (C > CMC, <i>T</i><sub>m</sub> < <i>T</i><sub>exp</sub>), the increase of the polar lipid chain length increased the drug solubilization capacity (similarly to classical surfactants), due to the decreased CMC and bigger volume available for solubilization.<br>The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order: choline phospholipids > monoglycerides > fatty acids.<br>As both the acyl chain length and the head group type are structural features of the polar lipids, and not of the solubilized drugs, the impact of <i>T</i><sub>m</sub> and CMC on solubilization by polar lipids should hold true for a wide variety of hydrophobic molecules. The obtained mechanistic insights can guide rational drug formulation development and thus support modern drug discovery pipelines.<br>

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