Studies on microcapsules. VI. Effect of variations in polymerization condition on microcapsule size

1970 ◽  
Vol 48 (13) ◽  
pp. 2047-2051 ◽  
Author(s):  
Yoshimichi Shigeri ◽  
Masumi Koishi ◽  
Tamotsu Kondo ◽  
Motoharu Shiba ◽  
Suiichi Tomioka
Keyword(s):  
Monomer Concentration ◽  
Degree Of Polymerization ◽  
Interfacial Polycondensation ◽  
Polymerization Condition

The effect of variations in polymerization condition on the size of microcapsules prepared by the interfacial polycondensation method was studied. Factors lowering the rate and degree of polymerization, such as a decrease in temperature or monomer concentration, were found to increase the microcapsule size. A mechanism was proposed for the formation of large microcapsules in the polycondensation step.

scholarly journals Mechanical Characterization of a Dynamic and Tunable Methacrylated Hyaluronic Acid Hydrogel

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Matthew G. Ondeck ◽  
Adam J. Engler
Keyword(s):  
Hyaluronic Acid ◽  
Elastic Modulus ◽  
Monomer Concentration ◽  
Degree Of Polymerization ◽  
Force Microscopy ◽  
3T3 Fibroblasts ◽  
Atomic Force ◽  
Spread Area ◽  
Nih 3T3

Hyaluronic acid (HA) is a commonly used natural polymer for cell scaffolding. Modification by methacrylate allows it to be polymerized by free radicals via addition of an initiator, e.g., light-sensitive Irgacure, to form a methacrylated hyaluronic acid (MeHA) hydrogel. Light-activated crosslinking can be used to control the degree of polymerization, and sequential polymerization steps allow cells plated onto or in the hydrogel to initially feel a soft and then a stiff matrix. Here, the elastic modulus of MeHA hydrogels was systematically analyzed by atomic force microscopy (AFM) for a number of variables including duration of UV exposure, monomer concentration, and methacrylate functionalization. To determine how cells would respond to a specific two-step polymerization, NIH 3T3 fibroblasts were cultured on the stiffening MeHA hydrogels and found to reorganize their cytoskeleton and spread area upon hydrogel stiffening, consistent with cells originally cultured on substrates of the final elastic modulus.

The polymerization of styrene by sulphuric acid - I. Theory of fast-initiated non-stationary polymerization

1961 ◽  
Vol 263 (1312) ◽  
pp. 58-62 ◽  
Keyword(s):  
Sulphuric Acid ◽  
Time Course ◽  
Monomer Concentration ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Chain Reaction ◽  
First Order ◽  
Chain Lengths ◽  
Special Case ◽  
Termination Process

Theoretical relationships are derived for the time course, yield, and number-average degree of polymerization in a non-stationary chain reaction having a very rapid initiation process and a first-order termination process. The distribution of chain lengths is derived for the special case of constant monomer concentration.

Radio-iodide uptake by modified poly (glycidyl methacrylate) as anion exchange resin

2017 ◽  
Vol 105 (1) ◽  
Author(s):  
Sameh H. Othman ◽  
Ahmed M. Elbarbary ◽  
Ghada Rashad ◽  
T. W. Fasih
Keyword(s):  
Anion Exchange ◽  
Glycidyl Methacrylate ◽  
Exchange Resin ◽  
Anion Exchange Resin ◽  
Epoxy Group ◽  
Monomer Concentration ◽  
Absorbed Dose ◽  
Degree Of Polymerization ◽  
Iodide Uptake ◽  
Factors Affecting

AbstractPoly(glycidyl methacrylate) (PGMA) microspheres were prepared by radiation induced polymerization of glycidyl methacrylate (GMA) monomer. The factors affecting the degree of polymerization and yield (%) of PGMA such as type of solvent, monomer concentration, and irradiation dose were investigated. It was found that the PGMA yield (%) increases with increasing monomer concentration up to 50% and absorbed dose of 5 kGy. The resulting PGMA containing the epoxy group waschemically modified by hydroxyl amine to act as anion-exchange resin for uptake of

scholarly journals Structural and dynamic states of actin in the erythrocyte

1983 ◽  
Vol 96 (3) ◽  
pp. 768-775 ◽  
Author(s):  
JC Pinder ◽  
WB Gratzer
Keyword(s):  
Guanidine Hydrochloride ◽  
Monomer Concentration ◽  
Degree Of Polymerization ◽  
Actin Monomer ◽  
Measured Concentration ◽  
Whole Cells ◽  
Cytoskeletal Network ◽  
Cytochalasin E ◽  
Oligomeric Complex ◽  
Low Ionic Strength

Analysis of the nucleotide tightly associated with isolated erythrocyte cytoskeletons show it to be ADP, rather then ATP. This confirms that at least a major part of the erythrocyte actin is in the F-form. A re-evaluation of the stoichiometry of spectrin and actin in the erythrocyte (taking account of a gross difference between the color responses of the two proteins on staining of electrophoretic gels) leads to values of 1x10(5) and 5x10(5) for the number of molecules of spectrin tetramer and actin respectively per cell. It has been found possible to perform spectrophotometric DNAase I assays fro actin on lysed whole cells. The concentration of monomeric actin at 0 degrees C is approximately 16 μg/ml packed cells. After washing the lysed cells the monomer pool is not re-established, indicating that only a small proportion of the actin subunits are free to dissociate. The actin monomer concentration in the cytosol remains unchanged after equilibration of the cells with cytochalasin E. The ability of actin-containing complexes in the membrane to nucleate the polymerization of added G-actin was measured fluorimetrically; it was found that membranes incubated with cytochalasin E were completely inert with respect to nucleating activity under conditions that favor appreciable growth at the slowly-growing ("pointed") ends of free actin filaments. This suggests that these ends of the actin "protofilaments" in the red cell are blocked or sterically obstructed. After treatment of the membranes with guanidine hydrochloride under conditions that dissociate F-actin, the measured concentration of actin monomer rises to approximately 180 μg/ml of packed cells, which is nearly 70 percent of the total actin content. On treatment with trypsin in the presence of DNAase, the spectrin and 4.1 are extensively degraded, but the actin remains undamaged. This treatment, followed by exposure to guanidine hydrochloride, causes a further rise in the concentration of actin responsive to the DNAase assay to 250 μg/ml of cells, compared with 270 μg/ml estimated by densitometry of stained gels. The oligomeric complex, consisting of actin, spectrin, and 4.1, that is extracted from the membrane at low ionic strength, generates no detectable actin monomer after the same treatment. From literature data on the number of cytochalasin binding sites per cell and our value for the total actin content, we obtain a number-average degree of polymerization for actin in the membrane of 12-17. The results lead to a model for the structure of the cytoskeletal network and suggest some consequences of metabolic depletion.

Effects of initiator loss by chain transfer in free-radical polymerization using batch operations

1992 ◽  
Vol 437 (1901) ◽  
pp. 489-499
Keyword(s):  
Free Radical ◽  
Molecular Mass ◽  
Radical Polymerization ◽  
Chain Transfer ◽  
Batch Reactor ◽  
Monomer Concentration ◽  
Free Radical Polymerization ◽  
Monomer Conversion ◽  
Degree Of Polymerization ◽  
Initial Monomer

In the free-radical polymerization of vinyl monomers, initiator can be lost by chain transfer. This loss affects the monomer conversion with time in a batch reactor and can influence the expected molecular mass of the polymer as the reaction proceeds. Expressions are developed which allow these effects to be quantified. Examples indicate when these effects are important. The instantaneous number-average degree of polymerization passes through a minimum as the initiator concentration is increased. The location of this minimum depends on the importance of initiator loss by chain transfer. Initial monomer concentration affects the absolute value of molecular mass but has little influence on the relative effects of initiator loss by chain transfer.

Binding of Thrombin to Fibrin

1979 ◽  
Author(s):  
L. Róka ◽  
F. G. Rademacher
Keyword(s):  
Antithrombin Iii ◽  
Monomer Concentration ◽  
Active State ◽  
Clot Formation ◽  
Constant Amount ◽  
Bovine Thrombin

After clot formation using bovine thrombin and bovine fibrinogen, one can detect no longer the total amount of thrombin. The amount missing in the supernatant is trapped in the clot and can be removed in active state after lysing the clot. The capacity for trapping thrombin by a constant amount of fibrin depends on the structure of the fibrinpolymer. This can be shown by producing different kinds of clots by variation of pH or monomer concentration during polymerisation or using Arvinmonomer insted of Thrombinmonomer. The trapped thrombin shows no clotting activity but some activity with chromogenic substrats remains. to neutralize trapped thrombin about 5 times more antithrombin III is necessary than for the same amount of free thrombin. The trapped thrombin diffuses out of the clot indicating the reversibility of the binding of thrombin to fribin.

The Pattern of Acetylation Defines the Priming Activity of Chitosan Tetramers

2019 ◽  
Author(s):  
Sven Basa ◽  
Malathi Nampally ◽  
Talita Honorato ◽  
Subha Narayan Das ◽  
Appa Rao Podile ◽  
...  
Keyword(s):  
Biological Activity ◽  
Degree Of Polymerization ◽  
Chitosan Oligosaccharides ◽  
Degree Of Acetylation ◽  
Bona Fide ◽  
First Time ◽  
Priming Activity

The biological activity of chitosans depends on their degree of polymerization (DP) and degree of acetylation (DA). However, information could also be carried by the pattern of acetylation (PA): the sequence of <i>β</i>-1,4-linked glucosamine (deacetylated/D) and <i>N</i>-acetylglucosamine (acetylated/A) units. To address this hypothesis, we prepared partially-acetylated chitosan oligosaccharides from a chitosan polymer (DA=35%, DP<sub>w</sub>=905) using recombinant chitosan hydrolases with distinct substrate and cleavage specificities. The mixtures were separated into fractions DP4–DP12, which were tested for elicitor and priming activities in rice cells. We confirmed that both activities were influenced by DP, <a>but also observed apparent DA-dependent priming activity, with the ADDD+DADD fraction proving remarkably effective</a>. We then compared all four mono-acetylated tetramers prepared using different chitin deacetylases and observed significant differences in priming activity. This demonstrates for the first time that PA influences the biological activity of chitosans, which can now be recognized as <i>bona fide</i> information-carrying molecules

The Pattern of Acetylation Defines the Priming Activity of Chitosan Tetramers

2019 ◽  
Author(s):  
Sven Basa ◽  
Malathi Nampally ◽  
Talita Honorato ◽  
Subha Narayan Das ◽  
Appa Rao Podile ◽  
...  
Keyword(s):  
Biological Activity ◽  
Degree Of Polymerization ◽  
Chitosan Oligosaccharides ◽  
Degree Of Acetylation ◽  
Bona Fide ◽  
First Time ◽  
Priming Activity

The biological activity of chitosans depends on their degree of polymerization (DP) and degree of acetylation (DA). However, information could also be carried by the pattern of acetylation (PA): the sequence of <i>β</i>-1,4-linked glucosamine (deacetylated/D) and <i>N</i>-acetylglucosamine (acetylated/A) units. To address this hypothesis, we prepared partially-acetylated chitosan oligosaccharides from a chitosan polymer (DA=35%, DP<sub>w</sub>=905) using recombinant chitosan hydrolases with distinct substrate and cleavage specificities. The mixtures were separated into fractions DP4–DP12, which were tested for elicitor and priming activities in rice cells. We confirmed that both activities were influenced by DP, <a>but also observed apparent DA-dependent priming activity, with the ADDD+DADD fraction proving remarkably effective</a>. We then compared all four mono-acetylated tetramers prepared using different chitin deacetylases and observed significant differences in priming activity. This demonstrates for the first time that PA influences the biological activity of chitosans, which can now be recognized as <i>bona fide</i> information-carrying molecules

Degree of Conversion of Light Cured Resin Cements Polymerized under Two Thicknesses of Different Lithium Silicate Ceramics

2020 ◽  
Author(s):  
Mohamed Abdel Rahman Maraghy
Keyword(s):  
Degree Of Polymerization ◽  
Resin Cement ◽  
Lithium Silicate ◽  
Resin Cements ◽  
Ceramic Disc ◽  
Ceramic Disk ◽  
The Difference ◽  
Light Cure Unit ◽  
Glass Slab ◽  
Finger Pressure

Objective: To show the consequence of two thicknesses of ceramic on the polymerization of resin cement light cured when three different lithium silicate ceramics were used. Materials and Methods: 42 ceramic slices were prepared from three types of ceramics, Emax CAD, Celtra Duo CAD and Vita suprinity CAD (n=14). They were further divided into two subgroups according to thicknesses into sub group thickness 0.5mm and sub group thickness 1mm (n=7). Teflon moulds were fabricated with specific dimensions, where the ceramic disc was placed followed by light cured resin cement Bisco choice 2 veneer and a glass slab with finger pressure applied. Curing with Ascent® PX LED light cure unit for 20 seconds took place, where the tip placed over the ceramic sample directly. Cement film was then separated from the ceramic disk and subjected to analysis by Fourier Transform Infrared Spectroscope. Uncured cement samples were also subjected to analysis. Results: Celtra DUO CAD ceramic showed higher degree of polymerization that of Emax and Vita suprinity while the difference between Emax and Suprinity on the degree of polymerization was not significant. Also, ceramic thicknesses had a significant effect on the degree of polymerization of the resin cement. Conclusion: Thickness of ceramics up to 1mm affects the polymerization of resin cement significantly.

Properties and Applications of Modified Bacterial Cellulose-Based Materials

2020 ◽  
Vol 16 ◽  
Author(s):  
Munair Badshah ◽  
Hanif Ullah ◽  
Fazli Wahid ◽  
Taous Khan
Keyword(s):  
Surface Modification ◽  
Bacterial Cellulose ◽  
Degree Of Polymerization ◽  
Biomedical Science ◽  
Hydroxyl Groups ◽  
Market Demand ◽  
Ideal Candidate ◽  
Fibrous Network ◽  
Potential Applications ◽  
Surface Modification Techniques

Background: Bacterial cellulose (BC) is purest form of cellulose as it is free from pactin, lignin, hemicellulose and other active constituents associated with cellulose derived from plant sources. High biocompatibility and easy molding into desired shape make BC an ideal candidate for applications in biomedical field such as tissue engineering, wound healing and bone regeneration. In addition to this, BC has been widely studied for applications in the delivery of proteins and drugs in various forms via different routes. However, BC lacks therapeutic properties and resistance to free movement of small molecules i.e., gases and solvents. Therefore, modification of BC is required to meet the research ad market demand. Methods: We have searched the updated data relevant to as-synthesized and modified BC, properties and applications in various fields using Web of science, Science direct, Google and PubMed. Results: As-synthesized BC possesses properties such as high crystallinity, well organized fibrous network, higher degree of polymerization, and ability of being produced in swollen form. The large surface area with abundance of free accessible hydroxyl groups makes BC an ideal candidate for carrying out surface functionalization to enhance its features. The various reported surface modification techniques including, but not limited to, are amination, methylation and acetylation. Conclusion: In this review, we have highlighted various approaches made for BC surface modification. We have also reported enhancement in the properties of modified BC and potential applications in different fields ranging from biomedical science to drug delivery and paper-making to various electronic devices.

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