scholarly journals Polystyrene Microbeads by Dispersion Polymerization: Effect of Solvent on Particle Morphology

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Lei Jinhua ◽  
Zhou Guangyuan
Keyword(s):  
Molecular Weight ◽  
Dispersion Polymerization ◽  
Particle Morphology ◽  
Polystyrene Microspheres ◽  
Pure Ethanol ◽  
Molecular Weights ◽  
Effect Of Solvent ◽  
Ethanol Content ◽  
Ubbelohde Viscometer ◽  
Scanning Electron

Polystyrene microspheres (PS) were synthesized by dispersion polymerization in ethanol/2-Methoxyethanol (EtOH/EGME) blend solvent using styrene (St) as monomer, azobisisobutyronitrile (AIBN) as initiator, and PVP (polyvinylpyrrolidone) K-30 as stabilizer. The typical recipe of dispersion polymerization is as follows: St/Solvent/AIBN/PVP = 10 g/88 g/0.1 g/2 g. The morphology of polystyrene microspheres was characterized by the scanning electron microscopy (SEM) and the molecular weights of PS particles were measured by the Ubbelohde viscometer method. The effect of ethanol content in the blend solvent on the morphology and molecular weight of polystyrene was studied. We found that the size of polystyrene microspheres increased and the molecular weight of polystyrene microspheres decreased with the decreasing of the ethanol content in the blend solvent from 100 wt% to 0 wt%. What is more, the size monodispersity of polystyrene microspheres was quite good when the pure ethanol or pure 2-Methoxyethanol was used; however when the blend ethanol/2-Methoxyethanol solvent was used, the polystyrene microspheres became polydisperse. We further found that the monodispersity of polystyrene microspheres can be significantly improved by adding a small amount of water into the blend solvent; the particles became monodisperse when the content of water in the blend solvent was up to 2 wt%.

scholarly journals Scanning Electron Microscopy Analysis of Changes of Hydroxiapatite/Poly-L-Lactide with Different Molecular Weight of PLLAaAfter Intraperitoneal Implantation

2016 ◽  
Vol 66 (2) ◽  
pp. 234-244
Author(s):  
Ljubiša Đorđević ◽  
Stevo Najman ◽  
Perica Vasiljević ◽  
Miroslav Miljković ◽  
Nenad Ignjatović ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Scanning Electron Microscopy ◽  
Bone Tissue ◽  
Tissue Loss ◽  
Practical Applications ◽  
Molecular Weights ◽  
Significant Difference ◽  
Tissue Reactions ◽  
Scanning Electron

Abstract Implantation of a biomaterial is one of the important trends in solving the problem of bone tissue loss. Calcium hydroxiapatite (HAp), as the most representative bone component is a serious candidate for such implantations. The synthetic polymer poly-L-lactide (PLLA) in HAp/PLLA is often used as a polymeric material, with a role in the substitution of bone tissue collagen fibers. Fibers of PLLA may strengthen HAp and its good bioresorption provides space for tissue remodeling. Differences in porosity, microstructure, compressive consistency as well as bioresorbility of HAp/ PLLA may be achieved by using PLLA with different molecular weights. In this study HAp/PLLA composites with PLLA of different molecular weights (50,000; 160,000 and 430,000) were implanted in mouse peritoneum in order to examine the influence of the molecular weight of PLLA on morphology changes. Microstructural changes of biomaterial (HAp/PLLA) surface were analyzed one week, three weeks and four months after their implantation using Scanning Electron Microscopy. The results showed a significant difference in tissue reactions on the applied biocomposites, depending on their molecular weight. The most intense proliferation of cells was induced by HAp/PLLA 50,000 compared to HAp/PLLA 430,000 and HAp/PLLA 160,000. In the vicinity of HAp/PLLA 430,000 abundant erythrocytes were observed. The differences in biological reactions on the examined biocomposites are significant for their practical applications. HAp/PLLA composite biomaterials of different types and resorption rates require specific designing and programming to become suitable for particular purposes in an organism.

scholarly journals Effect of the molecular weight of polyvinylpyrrolidone on the structure and morphology of materials based on substituted hydroxyapatite for bone implants

2018 ◽  
Vol 226 ◽  
pp. 03012
Author(s):  
Elizaveta A. Mukhanova ◽  
Inna A. Suprunova ◽  
Yana A. Suprunova ◽  
Igor Yu. Zabiyaka
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Scanning Electron Microscopy ◽  
Thermodynamic Stability ◽  
Structural Transformations ◽  
Experimental Results ◽  
Molecular Weights ◽  
Structure And Morphology ◽  
Size And Morphology ◽  
Scanning Electron

In this work, we study the influence of various molecular weights of polyvinylpyrrolidone (PVP) on synthesis substituted hydroxyapatite. Using the scanning electron microscopy we estimated the size and morphology of the particle. We studied the structural transformations of phosphates and the effect of polymer sizes on the structure and morphology. We revealed the thermodynamic stability of the structure of hydroxyapatite due to experimental results.

A Bipedal Silica-Immobilized Azo-Initiator for Surface-Confined Radical Polymerizations

2009 ◽  
Vol 62 (11) ◽  
pp. 1473 ◽  
Author(s):  
Robert Rotzoll ◽  
Philipp Vana
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Scanning Electron Microscopy ◽  
Methyl Acrylate ◽  
Chain Transfer ◽  
Molecular Weights ◽  
Surface Initiated Polymerization ◽  
Reversible Addition ◽  
Azo Initiator ◽  
Scanning Electron

The present study introduces the silica-anchored azo-initiator 4,4′-azobis(4-cyano-N-(3″-triethoxysilylpropyl)-valeric amide) (ACTA) for the surface-initiated polymerization of methyl acrylate (MA) with and without additional grafted reversible addition–fragmentation chain transfer (RAFT) agents 1,4-bis(3′-trimethoxysilylpropyltrithiocarbonylmethyl)benzene and 1,6-bis(o,p-2′-trimethoxysilylethylbenzyltrithiocarbonyl)hexane. While the sole use of silica-linked ACTA produced grafted poly(methyl acrylate) (pMA) of high molecular weight, due to a 2D Trommsdorff effect, the polymerization in combination with the fixed RAFT agents exhibited living behaviour with increasing molecular weights during polymerization. Silica-pMA hybrids were further analyzed via thermogravimetric analysis and scanning electron microscopy, which revealed significant differences between the three approaches.

scholarly journals Molecular spectroscopy analysis of the substitution of bone tissue by HAp/PLLA composite biomaterial

2004 ◽  
Vol 18 (4) ◽  
pp. 553-565 ◽  
Author(s):  
Nenad Ignjatovic ◽  
Dragan Uskokovic
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Scanning Electron Microscopy ◽  
Ir Spectroscopy ◽  
Molecular Spectroscopy ◽  
Absorption Bands ◽  
Molecular Weights ◽  
Ft Ir ◽  
Scanning Electron ◽  
Ft Ir Spectroscopy

Due to its pronounced osteoinductive properties, calcium hydroxyapatite (HAp) has been widely used in medicine. Bioresorptive poly-L-lactide (PLLA) as a polymer biomaterial has been also used extensively in medicine for its non-toxicity and biocompatibility. To combine the advantages exhibited by each of these materials, a HAp/PLLA composite biomaterial has been synthesized and used for reconstruction and repair of bone defects. Hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterial with PLLA of 50,000 and 430,000 g/mole molecular weight was studiedin vivo. The biocomposite with PLLA of both molecular weights was implanted into mice, then removed from their organisms and analyzed by the Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and histopathologic analysis. Characteristic absorption bands, registered and defined by FT-IR spectroscopy, confirm the formation of new functional groups and compounds during the bone repair process using HAp/PLLA biocomposite with PLLA of 50,000 and 430,000 molecular weights. Analysis of the microstructures of the sample surfaces by scanning electron microscopy (SEM) before and after implantation revealed bioresorption of the PLLA polymer phase in the system with PLLA of lower molecular weight and generation of collagen fibers at the sites of implanted bioresorptive PLLA. As the studied synthetic materials behave as the natural bone, i.e., they are phagocytosed and resorpable, they can be considered as biocompatible.

scholarly journals Cinnamyl-Imine-Chitosan Hydrogels. Morphology Control

2018 ◽  
Vol 26 (2) ◽  
pp. 221-232
Author(s):  
Anda M. Craciun
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Scanning Electron Microscopy ◽  
Functional Groups ◽  
Molar Ratio ◽  
Crosslinking Degree ◽  
Molecular Weights ◽  
Amine Groups ◽  
Chitosan Hydrogels ◽  
Scanning Electron

Abstract The study deals with the exploration of the possibilities to control the morphology of cinnamyl-imine-chitosan hydrogels in view of their bio-application. Three series of hydrogels were synthetized from chitosan of three different molecular weights and cinnamaldehyde, varying the molar ratio between the amine groups on chitosan and aldehyde functional groups. The hydrogel morphology has been monitored by scanning electron microscopy. The variation of the hydrogel morphology as a function of chitosan molecular weight, crosslinking degree, and incubation conditions has been monitored. It was concluded that there are multiple possibilities of tuning the morphology of these hydrogels in function of the targeted application.

Ring-Opening Dispersion Polymerization of ʟ-Lactide with Polylactide Stabilizer in Supercritical Carbon Dioxide

2017 ◽  
Vol 70 (6) ◽  
pp. 712 ◽  
Author(s):  
Jinjun Deng ◽  
Shiping Zhan ◽  
Jingchang Wang ◽  
Zhijun Liu ◽  
Zhiyi Li
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Ring Opening ◽  
Dispersion Polymerization ◽  
Triblock Copolymers ◽  
Molecular Weights ◽  
Fine Powders ◽  
Stabilizer Concentration ◽  
Scanning Electron ◽  
Supercritical Carbon

Non-fluorous triblock copolymers of poly(l-lactide)-block-hydroxypropyl-terminated poly(dimethyl siloxanes)-block-poly(l-lactide) (PLLA-HTPDMS-PLLA) with two different molecular weights in the range of 4800 to 6500 Da, were prepared by changing the ratio of HTPDMS to l-lactide (L-LA), and were used as stabilizers for the ring-opening dispersion polymerization (RODP) of L-LA to prepare poly(l-lactide) (PLLA) in supercritical carbon dioxide (ScCO2). The experimental results showed that the prepared non-fluorous triblock copolymers were very effective as new stabilizers for the RODP and fine powders of PLLA were obtained. The structure of the stabilizers and PLLA were characterized by 1H NMR and FTIR spectroscopy. The morphology of PLLA was investigated by scanning electron microscopy (SEM). The effects of the CO2-philic/lipophilic segment lengths of the stabilizers on the RODP were explored. The effects of the stabilizer concentration on the polymerization yield, molecular weight, and morphology of PLLA were investigated.

Investigation by HPLC of the Catabolism of Recombinant Tissue Plasminogen Activator in the Rat

1988 ◽  
Vol 60 (01) ◽  
pp. 107-112 ◽  
Author(s):  
Roy Harris ◽  
Louis Garcia Frade ◽  
Lesley J Creighton ◽  
Paul S Gascoine ◽  
Maher M Alexandroni ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Half Life ◽  
Recombinant Tissue Plasminogen Activator ◽  
Rat Plasma ◽  
High Molecular Weight Complex ◽  
Molecular Weights ◽  
Major Activity ◽  
Tissue Plasminogen

SummaryThe catabolism of recombinant tissue plasminogen activator (rt-PA) was investigated after injection of radiolabelled material into rats. Both Iodogen and Chloramine T iodination procedures yielded similar biological activity loss in the resultant labelled rt-PA and had half lives in the rat circulation of 1 and 3 min respectively. Complex formation of rt-PA was investigated by HPLC gel exclusion (TSK G3000 SW) fractionation of rat plasma samples taken 1-2 min after 125I-rt-PA injection. A series of radiolabelled complexes of varying molecular weights were found. However, 60% of the counts were associated with a single large molecular weight complex (350–500 kDa) which was undetectable by immunologically based assays (ELISA and BIA) and showed only low activity with a functional promoter-type t-PA assay. Two major activity peaks in the HPLC fractions were associated with Tree t-PA and a complex having a molecular weight of ̴ 180 kDa. HPLC fractionation to produce these three peaks at various timed intervals after injection of 125I-rt-PA showed each to have a similar initial rate half life in the rat circulation of 4-5 min. The function of these complexes as yet is unclear but since a high proportion of rt-PA is associated with a high molecular weight complex with a short half life in the rat, we suggest that the formation of this complex may be a mechanism by which t-PA activity is initially regulated and finally cleared from the rat circulation.

Permeability Enhancing and Chemotactic Activities of Lower Molecular Weight Degradation Products of Human Fibrinogen

1981 ◽  
Vol 45 (01) ◽  
pp. 090-094 ◽  
Author(s):  
Katsuo Sueishi ◽  
Shigeru Nanno ◽  
Kenzo Tanaka
Keyword(s):  
Molecular Weight ◽  
Degradation Products ◽  
Electron Microscopic Observation ◽  
Chemotactic Activity ◽  
Lower Molecular Weight ◽  
Electron Microscopic ◽  
Human Fibrinogen ◽  
Rabbit Skin ◽  
Molecular Weights ◽  
Active Fragments

SummaryFibrinogen degradation products were investigated for leukocyte chemotactic activity and for enhancement of vascular permeability. Both activities increased progressively with plasmin digestion of fibrinogen. Active fragments were partially purified from 24 hr-plasmin digests. Molecular weights of the permeability increasing and chemotactic activity fractions were 25,000-15,000 and 25,000 respectively. Both fractions had much higher activities than the fragment X, Y, D or E. Electron microscopic observation of the small blood vessels in rabbit skin correlated increased permeability with the formation of characteristic gaps between adjoining endothelial cells and their contraction.These findings suggest that lower molecular weight degradation products of fibrinogen may be influential in contributing to granulocytic infiltration and enhanced permeability in lesions characterized by deposits of fibrin and/or fibrinogen.

Sign in / Sign up

Export Citation Format

Share Document