Simple method for determining the critical molecular weight from the loss modulus

2004 ◽  
Vol 42 (14) ◽  
pp. 2724-2729 ◽  
Author(s):  
Kwang Soo Cho ◽  
Kyung Hyun Ahn ◽  
Seung Jong Lee
Keyword(s):  
Molecular Weight ◽  
Loss Modulus ◽  
Simple Method ◽  
Critical Molecular Weight

scholarly journals Certain Rheological Aspects of Functionalized Guar Gum

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Meenu Kapoor ◽  
Dhriti Khandal ◽  
Ruchi Gupta ◽  
Pinklesh Arora ◽  
Geetha Seshadri ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Guar Gum ◽  
Loss Modulus ◽  
Industrial Applications ◽  
Green Technology ◽  
Low Molecular Weight ◽  
Radiation Processing ◽  
Industrial Sectors ◽  
Wide Acceptance

Guar gum and its derivatives are highly important industrial hydrocolloids as they find applications in various industrial sectors. Guar is a polymer of high molecular weight and its aqueous solutions exhibit unique rheological properties, which has led to its wide acceptance by the industry. In certain industrial applications low molecular weight guar and its derivatives are needed, and conventionally chemical depolymerisation of guar is carried out for this purpose. Radiation processing is a novel and green technology for carrying out depolymerization and can be an ideal substitute for chemical depolymerisation technique. In order to study the effect of radiation on guar derivatives, three types of derivatives have been taken in the present study: carboxymethyl, hydroxyethyl, and methyl guar. The effect of 1–50 KGy radiation dose on the rheological behavior of these derivatives has been studied, and the results have been described in the present paper. The effect on storage and loss modulus with respect to frequency and effect on viscosity with respect to shear rate have been discussed in detail.

scholarly journals Melt Blending Modification of Commercial Polystyrene with Its Half Critical Molecular Weight, High Ion Content Ionomer, Poly(styrene–ran–cinnamic Acid) Zn Salt, toward Heat Resistance Improvement

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 584
Author(s):  
Zixin Yu ◽  
Jie Wang ◽  
Peihua Li ◽  
Dachuan Ding ◽  
Xuan Zheng ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Heat Resistance ◽  
Cinnamic Acid ◽  
Average Molecular Weight ◽  
Softening Temperature ◽  
Melt Blending ◽  
Ion Content ◽  
Critical Weight ◽  
Critical Molecular Weight ◽  
Cross Links

A half-critical weight-average molecular weight ( M ¯ w ) (approximately 21,000 g mol−1), high-ion-content Zn-salt poly(styrene–ran–cinnamic-acid) (SCA–Zn) ionomer was successfully synthesized by styrene–cinnamic-acid (10.8 mol %) copolymerization followed by excess-ZnO melt neutralization. At 220 °C, the SCA–Zn’s viscosity was only approximately 1.5 magnitude orders higher than that of commercial polystyrene (PS) at 102 s−1, and the PS/SCA–Zn (5–40 wt %) melt blends showed apparently fine, two-phased morphologies with blurred interfaces, of which the 95/5 and 90/10 demonstrated Han plots suggesting their near miscibility. These indicate that any PS–(SCA–Zn) processability mismatch was minimized by the SCA–Zn’s half-critical M ¯ w despite its dense ionic cross-links. Meanwhile, the SCA–Zn’s Vicat softening temperature (VST) was maximized by its cross-linking toward 153.1 °C, from that (97.7 °C) of PS, based on its half-critical M ¯ w at which the ultimate glass-transition temperature was approximated. Below approximately 110 °C, the PS/SCA–Zn (0–20 wt %) were seemingly miscible when their VST increased linearly yet slightly with the SCA–Zn fraction due to the dissolution of the SCA–Zn’s cross-links. Nevertheless, the 60/40 blend’s VST significantly diverged positively from the linearity until 111.1 °C, revealing its phase-separated morphology that effectively enhanced the heat resistance by the highly cross-linked SCA–Zn. This work proposes a methodology of improving PS heat resistance by melt blending with its half-critical M ¯ w , high-ion-content ionomer.

scholarly journals SIMPLE METHOD FOR OPTIMIZATION OF HEPARIN AND ENOXAPARIN DETECTION USING AGAROSE GEL ELECTROPHORESIS

2019 ◽  
pp. 12-15
Author(s):  
Ahmad Abdulrahman Almeman
Keyword(s):  
Molecular Weight ◽  
Toluidine Blue ◽  
Gel Electrophoresis ◽  
Optimization Procedure ◽  
Solvent Mixture ◽  
Acid Mixture ◽  
Low Molecular Weight ◽  
Simple Method ◽  
Electrophoresis Method ◽  
Tools And Techniques

Objective: A simple gel electrophoresis method for low-molecular-weight heparins (LMWH) is required for use in a variety of laboratories to allow further identification and purification. This study aimed to optimize the detection of heparin and enoxaparin (low-molecular-weight heparin by gel electrophoresis. Methods: Several gel electrophoresis conditions were tested to optimize the detection of enoxaparin by using a simple method with a modified Volpi’s approach. Multiple gel thicknesses, voltage settings, and enoxaparin concentrations were tested in the optimization procedure. Enoxaparin was purchased from a local supplier as pre-filled pharmaceutical injections. Highly purified 0.5% and 1.0% agarose gels were prepared and a series of enoxaparin concentrations was added to both gels for comparison and optimization. The 0.2% toluidine blue stain was prepared by the addition of 1 ml in an ethanol-water-acetic acid mixture (50:49:1; v/v/w). The staining process comprised two steps: first, toluidine blue was added for 30 min and destained overnight in the solvent mixture. Subsequently, the following morning, the second step was conducted, in which the gel was restained for 30 min with the same concentration of toluidine blue. We continued to stain the gel until the bands were visible. Results: The gel electrophoresis results showed that clearest and sharpest bands were obtained using 65–75 mAh and 85 V settings. At 95 mAh, the bands were slightly washed out. Conclusion: This study successfully facilitated the detection of enoxaparin, a LMWH, and heparin in the laboratory by using simple tools and techniques available in most laboratories.

scholarly journals A simple method for the production of low molecular weight hyaluronan by in situ degradation in fermentation broth

e-Polymers ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 477-481
Author(s):  
Jianfeng Mei ◽  
Zhihong Dong ◽  
Yu Yi ◽  
Yanlu Zhang ◽  
Guoqing Ying
Keyword(s):  
Molecular Weight ◽  
Enzymatic Degradation ◽  
Fermentation Broth ◽  
Low Molecular Weight ◽  
Streptococcus Zooepidemicus ◽  
Medium Ph ◽  
Simple Method ◽  
Suitable Temperature ◽  
In Situ Degradation

AbstractFermentation of hyaluronan (HA) by Streptococcus zooepidemicus was carried out in a 10-L fermentor. When the medium pH was controlled at 7.0 and the temperature was maintained at 38°C for 12 h followed by 35°C for 8 h, the yield of HA was 4.83 g/L with a molecular weight of 1,890 kDa. After the cells were removed by centrifugation from the fermentation broth, HA was slowly degraded to low molecular weight HA by hyaluronidase at a suitable temperature without a decrease in HA concentration. If the time and temperature for enzymatic degradation were controlled, the desired low molecular weight HA could be obtained by in situ degradation in the fermentation broth. The method does not require the addition of exogenous hyaluronidase, and is a simple way to produce low molecular weight HA.

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