scholarly journals New Nanocomposite Derivatives From Thiadiazole Polymers /Silica Synthesis and Characterization using Free Radical Polymerization

2019 ◽  
Vol 32 (1) ◽  
pp. 27 ◽  
Author(s):  
Nasir Sadoon Abid ◽  
Maha T. Sultan ◽  
Jumbad H. Tomma
Keyword(s):  
Free Radical ◽  
Silica Nanoparticles ◽  
Radical Polymerization ◽  
Chemical Properties ◽  
Free Radical Polymerization ◽  
Polymer Chains ◽  
X Ray ◽  
Silica Nanocomposites ◽  
Ft Ir ◽  
Physical And Chemical

A new class of thiadiazole /silica nanocomposites with chemical bonds between thiadiazole monomers and modified nanosilica surface were synthesized by free radical polymerization. Presence silica nanoparticles in the structure of  nanocomposite showed effectively improve the physical and chemical properties of Producing polymers. A nanocomposite material with feature properties comparison with their polymers, The structure and morphology of the synthesis materials were investigated by FT-IR spectrum which display preparation new thiadiazole compounds and polymerization monomers. FT-IR showed disappeared double bond (C=C) of monomers, due to produce long chains of thiadiazole polymers and nanocomposite. X-ray diffraction gave idea about crystalline structure of nanoparticles and nanocomposite , X-ray showed that silica nanoparticles have high intensity at 18000 , due to nanoscale of particles which allowed for particles aggregation together. While nanocomposite show low intensity due to reacted thiadaizole polymer chains with silica nanoparticles surface. The distribution of nanoparticles had characterized by Atomic forces microscopy AFM. AFM results shown roughness in the surfaces of nanocomposites C1 and C2, comparison with silica nanoparticles which gave smooth surface. The roughness attributed to reaction between functionalized surface of silica nanoparticles and chains of thiadaizole polymers, which led to change in size particles distribution and surface of particles that refer to nanocomposite.    

scholarly journals Method of Moments Applied to Most-Likely High-Temperature Free-Radical Polymerization Reactions

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 656 ◽  
Author(s):  
Hossein Riazi ◽  
Ahmad Arabi Shamsabadi ◽  
Michael Grady ◽  
Andrew Rappe ◽  
Masoud Soroush
Keyword(s):  
High Temperature ◽  
Free Radical ◽  
Radical Polymerization ◽  
Chain Length ◽  
Method Of Moments ◽  
Length Distribution ◽  
Free Radical Polymerization ◽  
Polymer Chains ◽  
Rate Equations ◽  
Chain Length Distribution

Many widely-used polymers are made via free-radical polymerization. Mathematical models of polymerization reactors have many applications such as reactor design, operation, and intensification. The method of moments has been utilized extensively for many decades to derive rate equations needed to predict polymer bulk properties. In this article, for a comprehensive list consisting of more than 40 different reactions that are most likely to occur in high-temperature free-radical homopolymerization, moment rate equations are derived methodically. Three types of radicals—secondary radicals, tertiary radicals formed through backbiting reactions, and tertiary radicals produced by intermolecular chain transfer to polymer reactions—are accounted for. The former tertiary radicals generate short-chain branches, while the latter ones produce long-chain branches. In addition, two types of dead polymer chains, saturated and unsaturated, are considered. Using a step-by-step approach based on the method of moments, this article guides the reader to determine the contributions of each reaction to the production or consumption of each species as well as to the zeroth, first and second moments of chain-length distributions of live and dead polymer chains, in order to derive the overall rate equation for each species, and to derive the rate equations for the leading moments of different chain-length distributions. The closure problems that arise are addressed by assuming chain-length distribution models. As a case study, β-scission and backbiting rate coefficients of methyl acrylate are estimated using the model, and the model is then applied to batch spontaneous thermal polymerization to predict polymer average molecular weights and monomer conversion. These predictions are compared with experimental measurements.

scholarly journals Novel Multifunctional Epoxy (Meth)acrylate Resins and Coatings Preparation via Cationic and Free-Radical Photopolymerization

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1718
Author(s):  
Paulina Bednarczyk ◽  
Izabela Irska ◽  
Konrad Gziut ◽  
Paula Ossowicz-Rupniewska
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Ring Opening ◽  
Free Radical Polymerization ◽  
Matter Content ◽  
Polymer Chains ◽  
Rate Coefficients ◽  
Structural Factors ◽  
Yellowness Index ◽  
Free Radical Photopolymerization

In this work, a series of novel multifunctional epoxy (meth)acrylate resins based on a low-viscosity aliphatic triepoxide triglycidyl ether of trimethylolethane (TMETGE) and acrylic acid (AA) or methacrylic acid (MMA) have been synthesized. Thanks to the performed modification, the obtained prepolymers have both epoxides as well as carbon–carbon double bonds and differ in their amount. The obtained results indicate that the carboxyl-epoxide addition esterification occurs in the presence of a catalyst (triphenylphosphine) at a temperature of 90 °C, whilst the required degree of conversion can be achieved simply by varying both the reagents ratio and reaction time. The structure of synthesized copolymers was confirmed by spectroscopic analyses (FT-IR, 1H NMR, 13C NMR) and studied regarding its nonvolatile matter content (NV), acid value (PAVs), as well as its epoxy equivalent value (EE). Due to the presence of both epoxy and double carbon–carbon pendant groups, one can apply two distinct mechanisms: (i) cationic ring-opening polymerization or (ii) free-radical polymerization to crosslink polymer chains. Synthesized epoxy (meth)acrylate prepolymers were further employed to formulate photocurable coating compositions. Hence, when cationic photoinitiators were applied, polyether-type polymer chains with pending acrylate or methacrylate groups were formed. In the case of free-radical polymerization, epoxy (meth)acrylates certainly formed a poly(meth)acrylate backbone with pending epoxy groups. Further, photopolymerization behavior and properties of cured coatings were investigated regarding some structural factors and parameters. Moreover, reaction rate coefficients of photo-cross-linking by both cationic ring-opening and free-radical photopolymerization of the received epoxy (meth)acrylate resins were determined via real-time infrared spectroscopy (RT-IR). Lastly, basic physicomechanical properties, such as tack-free time, hardness, adhesion, gloss, and yellowness index of cured coatings, were evaluated.

Ferrocene-Based Polymers, and Additional Phosphorus- and Boron-Containing Polymers

2005 ◽  
Author(s):  
James E. Mark ◽  
Harry R. Allcock ◽  
Robert West
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Hydrogen Exchange ◽  
Free Radical Polymerization ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Polymerization Reaction ◽  
Radical Chain ◽  
Polymeric Product ◽  
Molecular Weights

Ferrocene is an inexpensive, stable molecule with an interesting and reversible electrochemistry. It is synthesized by the metal-hydrogen exchange reaction of cyclopentadiene with sodium followed by treatment of the resultant sodium cyclopentadienide anion with ferrous chloride. The high stability and electroactivity of the ferrocene molecule has prompted numerous attempts to incorporate it into polymer structures. So, too, has the inherent torsional freedom of the cyclopentadienyl groups around the iron atoms and their capacity to serve as swivel group sites. Polymerization attempts range from the addition reactions of vinylferrocene and its derivatives, to condensation reactions, ringopening polymerizations, and dendrimer assemblies. These will be considered in turn. Considerable effort in the 1970s by Pittman, George, Hayes, Korshak, and others was applied to exploring the addition polymerization of vinylferrocene to give organic polymers with pendent ferrocenyl side groups. This type of polymerization reaction has been attempted with the use of free radical, cationic, anionic, and Ziegler–Natta methods. For free radical polymerization reactions, the initiating radicals must be generated from azo-initiators because peroxides cause oxidation of the metal. In polymerizations of the type shown in reaction (2) the side group ferrocene units are the source of both the thermal stability of the product polymers and complications inherent in the free radical polymerization process. For example, electron donation from the iron atoms to a growing radical chain end can convert an active radical to an anion, which terminates the polymerization. The Fe+ center then rearranges to form a paramagnetic, ionically bound Fe(III) species. Ultimately this leads to extensive chain-transfer, limitation of the chain length, and formation of branched structures. This does not occur if the ferrocene unit is insulated from the vinyl group by a spacer unit, as in, because these monomers polymerize normally. For example, monomer gives polymers with Mn molecular weights as high as 250,000. However, the electron-transfer process outlined in reaction (2) has serious practical consequences in the free-radical polymerization of. First, directly or indirectly, it causes precipitation of the growing polymer chains until, at monomer to polymer conversions of 90% or more, all of the polymeric product is insoluble in most organic solvents.

New Sterically Hindered Nitroxides for the Living Free Radical Polymerization:  X-ray Structure of an α-H-Bearing Nitroxide

2004 ◽  
Vol 37 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Armido Studer ◽  
Klaus Harms ◽  
Christoph Knoop ◽  
Christoph Müller ◽  
Tobias Schulte
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Free Radical Polymerization ◽  
X Ray ◽  
Living Free Radical Polymerization ◽  
Sterically Hindered

scholarly journals Inhibition Effect on Molecular Weight Distribution Generated Under Free Radical Polymerization by Laser Pulses

1996 ◽  
Vol 16 (3) ◽  
pp. 139-149 ◽  
Author(s):  
A. V. Evseev ◽  
A. N. Nikitin
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Free Radical Polymerization ◽  
Laser Pulses ◽  
Polymer Chains ◽  
Arbitrary Sequence ◽  
High Concentration ◽  
Effective Lifetime ◽  
Irradiation Period

Molecular weight distributions (MWDs) under free radical polymerization initiation by an arbitrary sequence of radiation pulses have been investigated. Analytical expressions enabling to account for influence of the polymer chains linear termination (for example, inhibition) have been obtained. On the basis of these expressions the MWDs generated by pulse-periodic radiation have been investigated theoretically. The calculated MWDs for polymerization in the presence of high concentration of retarder have been given and the influence of the inhibitor burning within the irradiation process on the MWDs character have been studied. It has been shown that possibility to employ the PLP method for determination of polymerization rate constant (kp) depends significantly on the efficiency ofchains linear termination: the PLP method can be confidently used at τ > T (where τ is the effective lifetime of growing radicals, T is the pulse irradiation period) and it is doubtful if τ < T/3. The expression for specifying of pulses number required for establishment of pseudostationary polymerization has been obtained for the polymerization at high concentration of retarder. The calculated MWDs for polymerization of MMA are presented.

Sign in / Sign up

Export Citation Format

Share Document