Protons and neutrons hang out together in a dense central nucleus and electrons whizz around them in an "electron cloud. Atoms can give, take, and share electrons with one another to form bonds. We call molecules with such lone single electrons radicals. You still have a lone electron, just in a different place. So then that one goes on the hunt. This leads to a chain reaction that causes the monomers to link up into a polymer in the propagation phase.
The polymer that forms depends on the monomers that are present. Every once in a while, instead of finding another acrylamide molecule to join with, it finds a bisacrylamide molecule. The higher the concentration of bisacrylamide, the more likely these mixed encounters will be and the more of these encounters there are, the tighter the mesh will be. Now imagine this grid projecting into multiple dimensions — viola, a 3D mesh! And when radicals get together, the chain terminates because you now have a pair they can just share.
So this leads to chain termination. So you have to get the chain started. And we get it started with the help of a redox pair. In redox reactions, one molecule the reductant gives electrons to another molecule the oxidant.
Earlier we looked at some reducing agents reductants and saw how they can be useful in maintaining a cell-like redox environment during protein purification. But oxidants can be useful in biochemistry too! We needed those reductants because in an oxidizing environment, crosslinks in and between proteins can be formed when 2 of the amino acid letters, cysteines, gets oxidized lose electrons and link together to form a disulfide bridge.
But we use a redox reaction to get the chain reaction going initiation , so it can keep going propagation and then stop termination. TEMED has a tertiary amine — this is a nitrogen bound to 3 non-hydrogens with a lone pair free to share. The " of charges" is referred to as the valency. Negatively-charged ions are attracted to one another and can form strong non-covalent bonds called "ionic bonds" or "salt bridges.
You want the thing that the radical attacks to be the thing you want it to attack. For fixed monomer concentration, at every point in conversion beyond very early points, M w was proportional to the inverse square root of the initiator concentration. Furthermore, the monomer decay time also scales in the same way, and M w vs conversion is linear during most of the conversion, with a negative slope. Hence, the overall reaction scheme falls within the quasi-steady state approximation QSSA of ideal polymerization kinetics.
The rate constant for initiator decay, as well as the ratio of propagation rate constant squared to termination rate constant were determined. The activation energy for the potassium persulfate initiator decomposition was also determined. Deviations from the ideal kinetics at early and late conversion are rationalized by existing models. Using a technique for determining instantaneous polydispersity from the derivative of M w , it was possible to follow the evolution of the polydispersity for the polyacrylamide reactions.
Text containing further details on the online method, lagtime, response time, and error considerations and figures showing R t for UV, a typical concentration profile, a typical plot of M w vs concentration, and a plot of the residuals. Such files may be downloaded by article for research use if there is a public use license linked to the relevant article, that license may permit other uses. View Author Information.
Cite this: Macromolecules , 34 , 5 , — Article Views Altmetric -. Citations Abstract An automatic, continuous, online monitoring technique was used to follow the polymerization of acrylamide under a variety of temperature and initiator conditions, without chromatographic columns. Supporting Information Available. Cited By. This article is cited by 75 publications. ACS Macro Letters , 9 2 , Macromolecules , 44 11 , Alb and Wayne F.
Macromolecules , 41 7 , Alb,, Pascal Enohnyaket,, Jeanette F. Craymer,, Tarik Eren,, E. Bryan Coughlin, and, Wayne F. Macromolecules , 40 3 , Alb,, Pascal Enohnyaket,, Michael F. Drenski,, Raja Shunmugam,, Gregory N. Tew, and, Wayne F. Macromolecules , 39 24 , Farinato,, Joe Calbick,, Gina A. Sorci,, Fabio H. Florenzano, and, Wayne F. Macromolecules , 38 4 , Drenski,, Emmanuel Mignard,, Alina M.
Alb, and, Wayne F. Journal of Combinatorial Chemistry , 6 5 , Alb,, Emmanuel Mignard,, Michael F. Drenski, and, Wayne F.
Macromolecules , 37 7 , Sorci and, Wayne F. Langmuir , 18 2 , Non-yellowish and heat-resistant adhesive for a transparent heat sinking film. Journal of Industrial and Engineering Chemistry , , Marien , Paul H. Van Steenberge , Dagmar R. Impact of side reactions on molar mass distribution, unsaturation level and branching density in solution free radical polymerization of n -butyl acrylate under well-defined lab-scale reactor conditions. Polymer Chemistry , 12 14 , Dynamic cross-linking of an alginate—acrylamide tough hydrogel system: time-resolved in situ mapping of gel self-assembly.
RSC Advances , 11 18 , Conventional and controlled radical polymerization redox-initiated by Cerium IV and Acrylamide as an intrinsically reducing inimer: a facile strategy to branched polyacrylamide.
Carboxylated single-walled carbon nanotubes as a semiconductor for adsorption of acrylamide in mainstream cigarette smoke. Physica E: Low-dimensional Systems and Nanostructures , , Afolabi , Gbenga F. Oluyemi , Simon Officer , Johnson O. Hydrophobically associating polymers for enhanced oil recovery — Part A: A review on the effects of some key reservoir conditions. Journal of Petroleum Science and Engineering , , Salas , J.
Romagnoli , S. Tronci , R. A geometric observer design for a semi-batch free-radical polymerization system. Nada , Eman A. Ali , Ahmed A. Biocompatible chitosan-based hydrogel with tunable mechanical and physical properties formed at body temperature.
International Journal of Biological Macromolecules , , Processes , 7 4 , Continuous control of a polymerization system with deep reinforcement learning. Journal of Process Control , 75 , Developing a nontoxic and biocompatible polymeric self-assembly by using RAFT methodology for biomedical application. Materials Today Communications , 18 , Polyacrylamide PAM. McOscar , William M. Hydrogels from norbornene-functionalized carboxymethyl cellulose using a UV-initiated thiol-ene click reaction.
Cellulose , 25 11 , Solvent-triggered self-folding of hydrogel sheets. Chinese Journal of Chemical Physics , 31 5 , Sumerlin , Weihong Tan. Angewandte Chemie , 36 , Angewandte Chemie International Edition , 57 36 , Modeling and simulation for acrylamide polymerization of super absorbent polymer. Korean Journal of Chemical Engineering , 35 9 , Salas , N.
Ghadipasha , W. Zhu , T. Mcafee , T. Zekoski , W. Reed , J. Framework design for weight-average molecular weight control in semi-batch polymerization. Control Engineering Practice , 78 , Journal of Macromolecular Science, Part B , 57 7 , Real-time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution. Polymer International , 67 6 , Influence of mixing performance on polymerization of acrylamide in capillary microreactors.
AIChE Journal , 64 5 , Jimmy Hsia.
0コメント