scholarly journals PROCEDURE FOR DETERMINATION OF THE MOLECULAR WEIGHT OF CHITOSAN BY VISCOMETRY

2018 ◽  
Vol XXIII ◽  
pp. 45-54 ◽  
Author(s):  
Renata Czechowska-Biskup ◽  
Radosław A. Wach ◽  
Janusz M. Rosiak ◽  
Piotr Ulański
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Accurate Determination ◽  
Low Molecular Weight ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Experimental Procedure ◽  
Initial Concentration ◽  
Analytical Instruments

The aim of this publication is to facilitate the estimation of chitosan molecular weight (MW) in laboratories with no access to sophisticated analytical instruments, by applying the easily accessible and economical capillary viscometry. The procedure of viscosity-average molecular weight (Mv) determination is described in details. The examples provided encompass testing of the experimental procedure for determination of the Mv of chitosan with a low-molecular weight of 7.7 kDa and 88 kDa, after verification with a high-molecular weight polymer (477 kDa). The experimental work demonstrated the importance of the initial concentration of low-MW chitosan for the accurate determination of intrinsic viscosity and, as a consequence, the viscosity-average molecular weight.

Ozonolytic Degradation of Interpolymers of Natural Rubber with Methyl Methacrylate and Styrene

1958 ◽  
Vol 31 (1) ◽  
pp. 82-85
Author(s):  
D. Barnard
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Natural Rubber ◽  
Accurate Determination ◽  
Synthetic Polymers ◽  
Polymer Chains ◽  
Low Molecular Weight ◽  
Rubber Content ◽  
Tert Butyl Hydroperoxide

Abstract The preparation of graft and block interpolymers of natural rubber and synthetic polymers has made it desirable that the number and size of polymer chains attached to rubber be readily determinate. The degradation of unsaturated polymers with tert-butyl hydroperoxide in the presence of osmium tet oxide has been used for the determination of free polystyrene in SBR and carbon black in several elastomers, and has recently been applied to the present problem. The accurate determination of the rubber content of interpolymers by quantitative ozonolysis essentially according to the method of Boer and Kooyman suggested that this might be made the basis of isolation of the attached polymer, the rubber being degraded into fragments of low molecular weight, from which the polymer could be separated by conventional techniques. The method should be applicable to any interpolymer, or mixture, of a polyunsaturated and a saturated polymer and is illustrated with reference to interpolymers of natural rubber (NR)-polymethyl methacrylate (PMM) and NR-polystyrene (PS).

scholarly journals Preparation, Characterization, and In Vivo Evaluation of Olanzapine Poly(D,L-lactide-co-glycolide) Microspheres

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Susan D’Souza ◽  
Jabar A. Faraj ◽  
Stefano Giovagnoli ◽  
Patrick P. DeLuca
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Copolymer Composition ◽  
Low Molecular Weight ◽  
Multiple Dosing ◽  
In Vivo Evaluation ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Steady State Levels

The aim of this study was to prepare injectable depot formulations of Olanzapine using four poly(D,L-lactide-co-glycolide) (PLGA) polymers of varying molecular weight and copolymer composition, and evaluate in vivo performance in rats. In vivo release profiles from the formulations were governed chiefly by polymer molecular weight and to a lesser extent, copolymer composition. Formulations A and B, manufactured using low molecular weight PLGA and administered at 10 mg/kg dose, released drug within 15 days. Formulation C, prepared from intermediate molecular weight PLGA and administered at 20 mg/kg dose, released drug in 30 days, while Formulation D, manufactured using a high molecular weight polymer and administered at 20 mg/kg dose, released drug in 45 days. A simulation of multiple dosing at 7- and 10-day intervals for Formulations A and B revealed that steady state was achieved within 7–21 days and 10–30 days, respectively. Similarly, simulations at 15-day intervals for Formulations C and D indicated that steady state levels were reached during days 15–45. Overall, steady state levels for 7-, 10-, or 15-day dosing ranged between 45 and 65 ng/mL for all the formulations, implying that Olanzapine PLGA microspheres can be tailored to treat patients with varying clinical needs.

Experimental Study on Flow-Front Fingering Instabilities in Injection Molding of Polymer Solutions and Melts

2004 ◽  
Author(s):  
Kalonji K. Kabanemi ◽  
Jean-Franc¸ois He´tu ◽  
Samira H. Sammoun
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polymer Solutions ◽  
Low Molecular Weight ◽  
Flow Front ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Polymer Molecules ◽  
Molecular Weights ◽  
Solvent Molecules

An experimental investigation of the flow behavior of dilute, semi-dilute and concentrated polymer solutions has been carried out to gain a better understanding of the underlying mechanisms leading to the occurrence of instabilities at the advancing flow front during the filling of a mold cavity. Experiments were performed using various mass concentrations of low and high molecular weight polyacrylamide polymers in corn syrup and water. This paper reports a new type of elastic fingering instabilities at the advancing flow front that has been observed only in semi-dilute polymer solutions of high molecular weight polymers. These flow front elastic instabilities seem to arise as a result of a mixture of widely separated high molecular weight polymer molecules and low molecular weight solvent molecules, which gives rise to a largely non-uniform polydisperse solution, with respect to all the kinds of molecules in the resulting mixture (solvent molecules and polymer molecules). The occurrence of these instabilities appears to be independent of the injection flow rate and the cavity thickness. Moreover, these instabilities do not manifest themselves in dilute or concentrated regimes, where respectively, polymer molecules and solvent molecules are minor perturbation of the resulting solution. In those regimes, smooth flow fronts are confirmed from our experiments. Based on these findings, the experimental investigations have been extended to polymer melts. Different mixtures of polycarbonate melts of widely separated molecular weights (low and high molecular weights) were first prepared. The effect of the large polydispersity of the resulting mixtures on the flow front behavior was subsequently studied. The same instabilities at the flow front were observed only in the experiments where a very small amount of high molecular weight polycarbonate polymer has been mixed to a low molecular weight polycarbonate melt (oligomers).

Determination of the Phase Boundary of High Molecular Weight Polymer Blends

2002 ◽  
Vol 35 (20) ◽  
pp. 7758-7764 ◽  
Author(s):  
A. A. Lefebvre ◽  
N. P. Balsara ◽  
J. H. Lee ◽  
C. Vaidyanathan
Keyword(s):  
Molecular Weight ◽  
Polymer Blends ◽  
Phase Boundary ◽  
High Molecular Weight ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer

scholarly journals THE NON-VIRUS PROTEINS ASSOCIATED WITH TOBACCO MOSAIC VIRUS

1955 ◽  
Vol 38 (4) ◽  
pp. 459-473 ◽  
Author(s):  
Barry Commoner ◽  
Mas Yamada
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Infected Plant ◽  
Infected Leaf ◽  
Low Molecular Weight ◽  
Tobacco Plants ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Derivatives Of ◽  
Virus Proteins

1. Exhaustive fractionation of leaves from tobacco plants systemically infected with TMV has led to the isolation of two non-virus proteins, B3 and B6, and the detection of a third, A4, which do not occur in comparable uninfected plants. 2. Components B3 and B6 have been found consistently in a series of ten extracts from plants grown over an 18 month period in all seasons of the year. It is concluded that these components are as characteristic of the infected plant as TMV itself. 3. As they occur in the initial extracts, the non-virus proteins are of low molecular weight (S20 ca. 3). On treatment, each component tends to form a high molecular weight polymer with an electrophoretic mobility considerably greater than that of the starting material. The high molecular weight derivatives of A4, B3, and B6 have been designated A8, B8, and B7 respectively. There is no evidence that these high molecular weight components occur as such in the infected leaf. 4. The non-virus proteins are free of nucleic acid and are not infectious. They cross-react immunochemically with TMV. 5. Compared with TMV content, the amounts of the non-virus proteins found in infected leaf are relatively small, falling in the range of 10 to 150 micrograms per gm. of tissue.

scholarly journals Preparation of zirconia granules with a low molecular weight dispersant

2020 ◽  
Vol 14 (2) ◽  
pp. 154-160
Author(s):  
Fariba Zerafati ◽  
Hudsa Majidian ◽  
Leila Nikzad
Keyword(s):  
Molecular Weight ◽  
Cross Sections ◽  
Feeding Rate ◽  
Low Molecular Weight ◽  
Stabilized Zirconia ◽  
Granule Formation ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Hausner Ratio ◽  
Dense Shell

In the present work, different conditions, such as PVA content as a high molecular weight polymer, Dolapix CE64 level with a lower molecular weight and pH adjusted by HCl, were investigated for the preparation of the yttria-stabilized zirconia (YSZ) granules from nanosized YSZ particles. It was found that the suspension prepared at pH = 4 and with 0.1 wt.% Dolapix CE64 has a reasonable value of viscosity for spray drying. The morphology of granules and their cross-sections were characterized through microstructural observation. The flowability of the prepared granules and the Hausner ratio were also evaluated. The results indicated that the addition of only 0.1 wt.% of PVA binder and the use of Dolapix can produce the YSZ granules with good flowability. Replacement of PAA by Dolapix has the benefits of achieving uniform granules with a dense shell layer, decreasing the amount of binder and accelerating the feeding rate of suspensions. The mechanism of the solid and hollow granule formation by a low molecular weight dispersant was suggested.

Determination of low molecular weight chlorinated organic compounds in polyamideanine epichlorohydrin solution

2019 ◽  
Vol 34 (3) ◽  
pp. 326-333
Author(s):  
Qi Wei ◽  
Hao Cheng ◽  
Shubin Wu ◽  
Chunxia Chen
Keyword(s):  
Molecular Weight ◽  
Organic Compounds ◽  
Accurate Determination ◽  
Simultaneous Detection ◽  
Low Molecular Weight ◽  
Extraction Temperature ◽  
Chlorinated Organic Compounds ◽  
Relative Standard ◽  
Chlorinated Organic

Abstract A convenient and quick method has been developed for simultaneous detection of several low molecular weight chlorinated organic compounds (LMWC) in polyamideamine-epichlorohydrin (PAE) solution, using headspace-solid phase microextraction-gas chromatography (HS-SPME-GC). The method consists of extracting a sample containing 0.42 g/mL NaCl with an 85 µm polyacrylate (PA) coated fiber at an extraction temperature of {45^{\circ }}\text{C}, for an extraction time of 30 mins, and desorbing the analytes at {240^{\circ }}\text{C} for 6 mins. Under these optimized conditions, relatively low limits of detection (LOD) of the analytes, good linearity ({r^{2}}\ge 0.9934) and precision (relative standard deviation (\text{RSD}\le 4.38\hspace{0.1667em}\% )) were obtained. Taking into account the matrix effect, standard addition methodology was applied to validate this method and recovery values were between 91.59 % and 109.69 %. This method is therefore well-suited for accurate determination of low levels of LMWC in PAE.

scholarly journals Variation of the Hydrodynamic Polymer Layer Thickness on Solid Surfaces with Molecular Weight and Concentration

1995 ◽  
Vol 12 (3) ◽  
pp. 259-265 ◽  
Author(s):  
S. Millot ◽  
J.L. Loubet ◽  
J.M. Georges
Keyword(s):  
Molecular Weight ◽  
Layer Thickness ◽  
Polymer Concentration ◽  
Surface Force ◽  
Extensive Study ◽  
Solid Surfaces ◽  
Low Molecular Weight ◽  
Molecular Weight Polymer ◽  
Molecular Weights

An extensive study on the determination of the 'hydrodynamic' layer thickness of polymer solutions and melt polymers was conducted with a surface force apparatus. For different concentrations and polymer molecular weights, a 'hydrodynamic layer' of fluid was detected on each solid surface which did not contribute to the flow. These thicknesses, denoted as LH, are compared to the characteristic polymer dimensions and the hydrodynamic (RH) and gyration (Rg) radii. It appears that in contrast to the molecular weight, polymer concentration has little effect on the relative hydrodynamic layer thickness (LH/2RH, LH/2Rg). Indeed, this ratio indicates that two coils of low molecular weight and one coil of high molecular weight are 'immobile' on the solid surfaces. The mechanism responsible could be entanglement of the free (unattached) chains in the bulk with immobilized chains on the surface.

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