Controlled free radical polymerization - a world of new possibilities acid
A variety of commercially available plastics based on polymers made by free radical initiated polymerization. This process does not give good control of chain length and structure as the growing polymer chains are constantly undergoing various non-verifiable termination or transfer reactions. If you want polymers with well-controlled chain lengths, special chemical functionality such. at the chain ends or in well-defined blocks, has so far been used anionic or cationic living polymerization techniques. The living polymerisationskoncept means that the polymeric structure acid can be extremely well controlled by well-defined, rapid initiation, propagation and termination without conservation of the active, ionic chain end, when all of the monomer has reacted. Subsequently, block copolymers can be prepared by the addition of a new monomer. Technically, it is very difficult, and only a very limited number of monomers can be used in this way.
Atom Transfer Radical Polymerization Within the last eight years, a number of controlled free radical techniques, however, have been developed. The main innovation is that they are usually unavoidable transfer and termination reactions, acid which occur in the free radical polymerization, can be suppressed almost completely. This is due to the growing chains in the greater part of the polymerization process is in a quiescent state for the momentary being activated acid to a polymer chain radical, adding one or more monomers and then return to the off state. For Atom Transfer Radical Polymerization acid (ATRP) [1] of styrene this is illustrated in Figure 1, the reversible redox process of polymer radicals are formed, acid catalyzed by a copper complex undergoes a one-electron oxidation, while the halogen (here bromide) simultaneously transferred from the dormant polymer acid chain end. Deaktiveringshastighedskonstanten, acid kd, however, is 108 times greater than aktiveringskonstanten, ka, so the resting state is restored after a few monomeradditioner. Polymer radical concentration acid during polymerization acid is very small, so termination reactions acid occur only slightly, as these are second order with respect to polymer radical concentration. The technique is experimentally simple and can be carried acid out under bulk conditions or in solution. It usually demands only that the polymerization is carried out under oxygen-free conditions. ATRP has been successfully acid applied to a wide variety of vinyl monomers, for example, substituted styrenes, acrylates and methacrylates, acrylonitrile, (meth) acrylamides acid and (meth) acrylic acids.
Polymers with complex structures acid and built-in functionality A major advantage of ATRP is also that the chain ends of the activity is retained when the polymerization is stopped and the polymer was isolated. Block copolymers are prepared by using the isolated polymer acid as an initiator, so-called macroinitiator acid for the polymerization of a new monomer. This can be repeated and linear block copolymers with many blocks acid or block copolymers with long regular side chains, popularly referred to as polymer brushes are made. Also very regular star-shaped or super branched polymers can be synthesized. Functionalized colloids, surface treated fibers and modified surfaces are produced acid by simultaneously initiate polymerization of multiple, activated sites on the respective objects. As monomers with very different structure, functionality and affinity for example. water can sampolymeriseres this way, the design of a variety of new polymer materials with very specific uses, inter alia, for medical use notice. Specific chemical or physical functionality can be built through special acid monomers or initiator that starts the growing acid polymer chain. Since a large number of different functional groups, for example. of the initiator (e.g., allyl, hydroxy, carboxylic acid, cyano), at the same time has been found not to inhibit the polymerization, acid may be polymers with different chemical end group functionality are prepared. acid Further, the halogen atom at the opposite end of the polymer chain through simple reactions quantitatively transformed to other functional groups, for example. amino, hydroxy, or epoxy. Thus, it is also possible to produce a number of different, very well-controlled linear polymers with different chemical functionality in the two end groups.
Activities of the Danish Polymer Centre Worldwide controlled free-radical polymerization, especially ATRP, now the fastest growing area in polymer chemistry. The Danish Polymer Centre at DTU has controlled acid free-radical polymerization has been a large and active research and education field since its inception in the mid 90s. Two current project concepts acid in design of new polymer materials using ATRP to illustrate the technique scope and potential. Water-soluble polymers with a pH-and concentration-dependent acid morphology Amphiphilic block copolymers containing both hydrophilic (character
A variety of commercially available plastics based on polymers made by free radical initiated polymerization. This process does not give good control of chain length and structure as the growing polymer chains are constantly undergoing various non-verifiable termination or transfer reactions. If you want polymers with well-controlled chain lengths, special chemical functionality such. at the chain ends or in well-defined blocks, has so far been used anionic or cationic living polymerization techniques. The living polymerisationskoncept means that the polymeric structure acid can be extremely well controlled by well-defined, rapid initiation, propagation and termination without conservation of the active, ionic chain end, when all of the monomer has reacted. Subsequently, block copolymers can be prepared by the addition of a new monomer. Technically, it is very difficult, and only a very limited number of monomers can be used in this way.
Atom Transfer Radical Polymerization Within the last eight years, a number of controlled free radical techniques, however, have been developed. The main innovation is that they are usually unavoidable transfer and termination reactions, acid which occur in the free radical polymerization, can be suppressed almost completely. This is due to the growing chains in the greater part of the polymerization process is in a quiescent state for the momentary being activated acid to a polymer chain radical, adding one or more monomers and then return to the off state. For Atom Transfer Radical Polymerization acid (ATRP) [1] of styrene this is illustrated in Figure 1, the reversible redox process of polymer radicals are formed, acid catalyzed by a copper complex undergoes a one-electron oxidation, while the halogen (here bromide) simultaneously transferred from the dormant polymer acid chain end. Deaktiveringshastighedskonstanten, acid kd, however, is 108 times greater than aktiveringskonstanten, ka, so the resting state is restored after a few monomeradditioner. Polymer radical concentration acid during polymerization acid is very small, so termination reactions acid occur only slightly, as these are second order with respect to polymer radical concentration. The technique is experimentally simple and can be carried acid out under bulk conditions or in solution. It usually demands only that the polymerization is carried out under oxygen-free conditions. ATRP has been successfully acid applied to a wide variety of vinyl monomers, for example, substituted styrenes, acrylates and methacrylates, acrylonitrile, (meth) acrylamides acid and (meth) acrylic acids.
Polymers with complex structures acid and built-in functionality A major advantage of ATRP is also that the chain ends of the activity is retained when the polymerization is stopped and the polymer was isolated. Block copolymers are prepared by using the isolated polymer acid as an initiator, so-called macroinitiator acid for the polymerization of a new monomer. This can be repeated and linear block copolymers with many blocks acid or block copolymers with long regular side chains, popularly referred to as polymer brushes are made. Also very regular star-shaped or super branched polymers can be synthesized. Functionalized colloids, surface treated fibers and modified surfaces are produced acid by simultaneously initiate polymerization of multiple, activated sites on the respective objects. As monomers with very different structure, functionality and affinity for example. water can sampolymeriseres this way, the design of a variety of new polymer materials with very specific uses, inter alia, for medical use notice. Specific chemical or physical functionality can be built through special acid monomers or initiator that starts the growing acid polymer chain. Since a large number of different functional groups, for example. of the initiator (e.g., allyl, hydroxy, carboxylic acid, cyano), at the same time has been found not to inhibit the polymerization, acid may be polymers with different chemical end group functionality are prepared. acid Further, the halogen atom at the opposite end of the polymer chain through simple reactions quantitatively transformed to other functional groups, for example. amino, hydroxy, or epoxy. Thus, it is also possible to produce a number of different, very well-controlled linear polymers with different chemical functionality in the two end groups.
Activities of the Danish Polymer Centre Worldwide controlled free-radical polymerization, especially ATRP, now the fastest growing area in polymer chemistry. The Danish Polymer Centre at DTU has controlled acid free-radical polymerization has been a large and active research and education field since its inception in the mid 90s. Two current project concepts acid in design of new polymer materials using ATRP to illustrate the technique scope and potential. Water-soluble polymers with a pH-and concentration-dependent acid morphology Amphiphilic block copolymers containing both hydrophilic (character
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