Nanoparticles from a controlled polymerization process

2003 ◽  
Vol 22 (2) ◽  
pp. 126-136 ◽  
Author(s):  
Vijaya R. Tirumala ◽  
Gerard T. Caneba ◽  
Yadunandan Dar ◽  
Hsien-Hau Wang ◽  
Derrick C. Mancini
Keyword(s):  
Polymerization Process ◽  
Controlled Polymerization

scholarly journals Synthesis of poly (n-butyl acrylate) with tempo by nitroxide mediated polymerization method

2021 ◽  
pp. 096739112110245
Author(s):  
Amrita Sharma ◽  
PP Pande
Keyword(s):  
Butyl Acrylate ◽  
Low Cost ◽  
Polymerization Process ◽  
Polymerization Reaction ◽  
High Concentration ◽  
Acrylate Monomer ◽  
Controlled Polymerization ◽  
Acrylate Monomers ◽  
Nitroxide Mediated Polymerization ◽  
Polymerization Method

It has been observed that acrylate monomers are very difficult to polymerize with the low cost nitroxide catalyst 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Therefore, costly acyclic nitroxides such as N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl)-N-oxyl, (SG1), 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and TIPNO derivatives have to be used for the polymerization of the acrylic acid derivatives. There are very few reports on the use of TEMPO-derivatives toward the polymerization of n-butyl acrylate. Generally different reducing agents viz. glucose, ascorbic acid, hydroxyacetone etc. have been used to destroy excess TEMPO during the polymerization reaction. The acrylate polymerizations fail in the presence of TEMPO due to the strong C–O bond formed between the acrylate chain end and nitroxide. To the best of our knowledge, no literature report is available on the use of TEMPO without reducing agent or high temperature initiators, toward the polymerization of n-butyl acrylate. The present study has been carried out with a view to re-examine the application of low cost nitroxide TEMPO, so that it can be utilized towards the polymerization of acrylate monomers (e.g. n-butyl acrylate). We have been able to polymerize n-butyl acrylate using the nitroxide TEMPO as initiator (via a macroinitiator). In this synthesis, a polystyrene macroinitiator was synthesized in the first step from TEMPO, after this TEMPO end-capped styrene macroinitiator (PSt-TEMPO) is used to polymerize n-butyl acrylate monomer. The amount of macroinitiator taken was varied from 0.05% to 50% by weight of n-butyl acrylate monomer. The polymerization was carried out at 120°C by bulk polymerization method. The experimental findings showed a gradual increase in molecular weight of the polymer formed and decrease in the polydispersity index (PDI) with increase in amount of PSt-TEMPO macroinitiator taken. In all experiments conversion was more than 80%. These results indicate that the polymerization takes place through controlled polymerization process. Effect of different solvents on polymerization has also been investigated. In the following experiments TEMPO capped styrene has been used as macroinitiator leading to the successful synthesis of poly n-Butyl acrylate. It has been found that styrene macroinitiator is highly efficient for the nitroxide mediated polymerization, even in very small concentration for the synthesis of poly n-butyl acrylate. High concentration of macroinitiator results in the formation of block copolymers of polystyrene and poly ( n-butyl acrylate) viz. polystyrene-block-poly-( n-butyl acrylate). The use of TEMPO toward controlled polymerization is of much importance, because it is the nitroxide commercially available at the lowest cost.

Neue aromatische Bisguanidin-Kupfer-Komplexe und ihre Anwendung in der ATRP / New Aromatic Bisguanidine Copper Complexes and Their Application in ATRP

2014 ◽  
Vol 69 (5) ◽  
pp. 589-595 ◽  
Author(s):  
Alexander Hoffmann ◽  
Olga Bienemann ◽  
Ines dos Santos Vieira ◽  
Sonja Herres-Pawlis
Keyword(s):  
Copper Complexes ◽  
Polymerization Process ◽  
Planar Geometry ◽  
Orthorhombic Space Group ◽  
Controlled Polymerization ◽  
Coordination Environment ◽  
Highly Active ◽  
Molecular Weight Distributions ◽  
Square Planar ◽  
Weight Distributions

We synthesized and structurally characterized two new copper(II) monochelate complexes with the ligand 2,2'-(1,2-phenylenebis(1,1,3,3-tetramethyl)guanidine) (TMG2b), [Cu(TMG2b)Cl2] and [Cu(TMG2b)Br2]. Single-crystal structure determination has shown that the complexes [Cu(TMG2b)Cl2] and [Cu(TMG2b)Br2] both crystallize in the orthorhombic space group Pbcn. The copper atoms in all complex cations reside in a coordination environment between tetrahedral and square-planar geometry. Furthermore, the application of the copper complexes with TMG2b as ligand in atom transfer radical polymerization (ATRP) was investigated with styrene as monomer. This study has shown a controlled polymerization process with moderate conversions, but excellent molecular weight distributions that are evidence of a well-controlled ATRP. However, small changes in the ligand structure can have a high impact, and therefore process optimizations and ligand tuning are necessary to develop highly active catalysts for ATRP.

The Effects of Amines on the Esterase Activities of Thrombin and Thrombokinase and on Several Clotting Tests

1974 ◽  
Vol 31 (02) ◽  
pp. 309-318
Author(s):  
Phyllis S Roberts ◽  
Raphael M Ottenbrite ◽  
Patricia B Fleming ◽  
James Wigand
Keyword(s):  
Choline Chloride ◽  
Polymerization Process ◽  
Ammonium Bromide ◽  
Bovine Thrombin ◽  
One Stage ◽  
Human Proteins ◽  
Rate Of Hydrolysis ◽  
The One ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of

Summary1. Choline chloride, 0.1 M (in 0.25 M Tris. HCl buffer, pH 7.4 or 8.0, 37°), doubles the rate of hydrolysis of TAME by bovine thrombokinase but has no effect on the hydrolysis of this ester by either human or bovine thrombin. Only when 1.0 M or more choline chloride is present is the hydrolysis of BAME by thrombokinase or thrombin weakly inhibited. Evidence is presented that shows that these effects are due to the quaternary amine group.2. Tetramethyl ammonium bromide or chloride has about the same effects on the hydrolysis of esters by these enzymes as does choline chloride but tetra-ethyl, -n.propyl and -n.butyl ammonium bromides (0.1 M) are stronger accelerators of the thrombokinase-TAME reaction and they also accelerate, but to a lesser degree, the thrombin-TAME reaction. In addition, they inhibit the hydrolysis of BAME by both enzymes. Their effects on these reactions, however, do not follow any regular order. The tetraethyl compound is the strongest accelerator of the thrombokinase-TAME reaction but the tetra-ethyl and -butyl compounds are the strongest accelerators of the thrombin-TAME reaction. The ethyl and propyl compounds are the best (although weak) inhibitors of the thrombokinase-BAME and the propyl compound of the thrombin-BAME reactions.3. Tetra-methyl, -ethyl, -n.propyl and -n.butyl ammonium bromides (0.01 M) inhibit the clotting of fibrinogen by thrombin (bovine and human proteins) at pH 7.4, imidazole or pH 6.1, phosphate buffers and they also inhibit, but to a lesser degree, a modified one-stage prothrombin test. In all cases the inhibition increases regularly as the size of the alkyl group increases from methyl to butyl. Only the ethyl com pound (0.025 M but not 0.01 M), however, significantly inhibits the polymerization of bovine fibrin monomers. It was concluded that inhibition of the fibrinogen-thrombin and the one-stage tests by the quaternary amines is not due to any effect of the com pounds on the polymerization process but probably due to inhibition of thrombin’s action on fibrinogen by the quaternary amines.

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.

ANALYSIS OF WORK ON NANOSTRUCTURED MATERIALS IN ORTHOPEDIC DENTISTRY UNDER THE DIRECTION OF PROFESSOR E.S. KALIVRADZHIYAN

2020 ◽  
pp. 8-13
Author(s):  
Жанна Владимировна Вечеркина ◽  
Наталия Владимировна Чиркова ◽  
Михаил Анатольевич Крючков ◽  
Виктор Сергеевич Калиниченко
Keyword(s):  
Nanostructured Materials ◽  
Dental Materials ◽  
Physical And Mechanical Properties ◽  
High Strength ◽  
Barrier Properties ◽  
Working Time ◽  
Polymerization Process ◽  
High Tech ◽  
Acrylic Polymer ◽  
Removable Plate

Развитие технологий, основанных на использовании низкотоксичных материалов, позволит в скором будущем начать их применение в медицине. Применение наночастиц серебра, меди, кремния, цинка, титана, кобальта в качестве модифицирующей добавки позволит оказать активное влияние на структуру исходных материалов и изменение их свойств, а именно улучшение физико-механических, физико-химических и токсико-гигиенических свойств материалов. Наноразмерные частицы кремния, введенные в фиксирующие стоматологические материалы, приводят к улучшению физико-химических, физико-механических свойств кристаллизующихся материалов, а малая теплопроводность кремния может увеличить его рабочее время и снизить выделение тепла при реакции кристаллизации. Так как от этих характеристик зависит объем манипуляций, при фиксации ортопедических конструкций на опорных зубах целесообразно было бы привести рабочее время твердения к чистому времени твердения, что позволит увеличить объем манипуляций приготовленной массой без ухудшения ее свойств. Разработка высокопрочных, биосовместимых, высокотехнологичных нанопластмасс для базисов съемных пластиночных протезов является актуальной проблемой повышения качества жизни пациентов. Модификация наноразмерными частицами серебра, кремния акрилового полимера позволит улучшить такие физико-механические свойства, как ударную вязкость, прочность, температуростойкость, барьерные свойства, уменьшить усадку полимера на этапе полимеризации, в отличие от уже известных отечественных и дорогостоящих импортных полимеров. Наноразмерные частицы кремния, серебра являются сокатализаторами метилметакрилата, влияющими на уменьшение количества остаточного мономера после процесса полимеризации, тем самым повышая санитарно-химические и токсико-гигиенические характеристики полимера. Все вышеизложенное позволило сформулировать цель исследований по наноструктурированным материалам под руководством профессора …посвящается памяти профессора, д.м.н. Каливраджияна Э.С. The development of technologies based on the use of low-toxic materials will make it possible to begin their application in medicine in the near future. The use of nanoparticles of silver, copper, silicon, zinc, titanium, cobalt as a modifying additive will make it possible to actively influence the structure of the starting materials and change their properties, namely, improve the physicomechanical, physicochemical and toxicohygienic properties of materials. Nanosized silicon particles introduced into fixing dental materials lead to an improvement in the physicochemical, physicomechanical properties of crystallizing materials, and the low thermal conductivity of silicon can increase its working time and reduce heat generation during the crystallization reaction. Since the volume of manipulations depends on these characteristics, when fixing orthopedic structures on abutment teeth, it would be advisable to bring the working time of hardening to a pure hardening time, which will increase the volume of manipulations with the prepared mass without deteriorating its properties. The development of high-strength, biocompatible, high-tech nanoplastics for the bases of removable plate prostheses is an urgent problem to improve the quality of life of patients. Modification of acrylic polymer with nano-sized particles of silver and silicon will improve such physical and mechanical properties as impact strength, strength, temperature resistance, barrier properties, and reduce polymer shrinkage at the stage of polymerization, in contrast to the already known domestic and expensive imported polymers. Nanosized particles of silicon, silver are cocatalysts of methyl methacrylate, affecting the reduction of the amount of residual monomer after the polymerization process, thereby increasing the sanitary-chemical and toxic-hygienic characteristics of the polymer. All of the above made it possible to formulate the goal of research on nanostructured materials under the guidance of the professor …dedicated to the memory of the professor, d.m.s. Kalivrajiyan E.S.

Influence of Constructive and Technological Parameters at Generated Spiral Parts with DLP 3D Printing Process

2019 ◽  
Vol 56 (4) ◽  
pp. 801-811
Author(s):  
Mircea Dorin Vasilescu
Keyword(s):  
3D Printing ◽  
Great Influence ◽  
Polymerization Process ◽  
Generation Process ◽  
Technological Parameters ◽  
Printing Process ◽  
The Third ◽  
Solid Models ◽  
Specific Factors ◽  
Printing Processes

This work are made for determine the possibility of generating the specific parts of a threaded assembly. If aspects of CAD generating specific elements was analysed over time in several works, the technological aspects of making components by printing processes 3D through optical polymerization process is less studied. Generating the threaded appeared as a necessity for the reconditioning technology or made components of the processing machines. To determine the technological aspects of 3D printing are arranged to achieve specific factors of the technological process, but also from the specific elements of a trapezoidal thread or spiral for translate granular material in supply process are determined experimentally. In the first part analyses the constructive generation process of a spiral element. In the second part are identified the specific aspects that can generation influence on the process of realization by 3D DLP printing of the two studied elements. The third part is affected to printing and determining the dimensions of the analysed components. We will determine the specific value that can influence the process of making them in rapport with printing process. The last part is affected by the conclusions. It can be noticed that both the orientation and the precision of generating solid models have a great influence on the made parts.

Electrogeneration of Conducting Poly(α-tetrathiophene). Effect of Solution Stirring and Detection of Linear Oligomers

2003 ◽  
Vol 68 (7) ◽  
pp. 1326-1344 ◽  
Author(s):  
Francesc Estrany ◽  
Ramon Oliver ◽  
Esther García ◽  
Esther Gualba ◽  
Pere-Lluís Cabot ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Anodic Process ◽  
Cathodic Peak ◽  
Linear Chains ◽  
Monomer Solution ◽  
Ir Analysis ◽  
Microscopy Images ◽  
Tof Ms

The anodic oxidation of α-tetrathiophene on Pt was studied in a 1.0 mM monomer solution in 0.1 M LiClO4 in 45:35:20 acetonitrile/ethanol/DMF. Three consecutive oxidation peaks were detected by cyclic voltammetry, along with a cathodic peak related to the reduction of electroactive polarons formed during the first anodic process. Uniform, adherent, insoluble and black polymer films were obtained by chronoamperometry at 1.000 V vs Ag|AgCl corresponding to the first oxidation-polymerization process. Stirring of monomer solution promotes the production of polymer, favoring the oxidation of polymer chains with the incorporation of more doping ClO4- ions and ion pairs of Li+ClO4- in their monomeric units. The conductivity of the polymer obtained under stirring was three orders of magnitude higher than that synthesized from a quiescent solution. The scanning electron microscopy images also showed much more uniform films under stirring. This behavior points to the existence of less crosslinking in the polymer and the production of longer linear chains when the solution is stirred. IR analysis of these materials confirmed the formation of crosslinked chains with predominance of β-β linkages. Short linear oligomers such as the dimer, trimer and tetramer were detected in all polymers by MALDI-TOF-MS, thus showing a radical polycondensation as initial electropolymerization mechanism. A larger proportion of linear oligomers is formed under solution stirring.

scholarly journals PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 99
Author(s):  
Konstantinos N. Raftopoulos ◽  
Edyta Hebda ◽  
Anna Grzybowska ◽  
Panagiotis A. Klonos ◽  
Apostolos Kyritsis ◽  
...  
Keyword(s):  
Glass Transition ◽  
Star Polymer ◽  
Polymerization Process ◽  
Degree Of Crystallinity ◽  
Dielectric Relaxation Spectroscopy ◽  
Scanning Calorimetry ◽  
Similar System ◽  
Soft Phase ◽  
Hard Segments ◽  
Star Molecules

A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation α′, slower than the bulky segmental α and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms.

scholarly journals Synthesis of Nanogels: Current Trends and Future Outlook

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 36
Author(s):  
Emanuele Mauri ◽  
Sara Maria Giannitelli ◽  
Marcella Trombetta ◽  
Alberto Rainer
Keyword(s):  
3D Printing ◽  
Ad Hoc ◽  
Sol Gel ◽  
Controlled Polymerization ◽  
Current Trends ◽  
Chip Technology ◽  
Physico Chemical ◽  
Physical Interactions ◽  
Sol Gel Transition ◽  
Gel Transition

Nanogels represent an innovative platform for tunable drug release and targeted therapy in several biomedical applications, ranging from cancer to neurological disorders. The design of these nanocarriers is a pivotal topic investigated by the researchers over the years, with the aim to optimize the procedures and provide advanced nanomaterials. Chemical reactions, physical interactions and the developments of engineered devices are the three main areas explored to overcome the shortcomings of the traditional nanofabrication approaches. This review proposes a focus on the current techniques used in nanogel design, highlighting the upgrades in physico-chemical methodologies, microfluidics and 3D printing. Polymers and biomolecules can be combined to produce ad hoc nanonetworks according to the final curative aims, preserving the criteria of biocompatibility and biodegradability. Controlled polymerization, interfacial reactions, sol-gel transition, manipulation of the fluids at the nanoscale, lab-on-a-chip technology and 3D printing are the leading strategies to lean on in the next future and offer new solutions to the critical healthcare scenarios.

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