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Reversible deactivation radical polymerizations are members of the class of reversible deactivation polymerizations which exhibit much of the character of living polymerizations, but cannot be categorized as such as they are not without chain transfer or chain termination reactions. Several different names have been used in literature, which are: *Living Radical Polymerization *Living Free Radical Polymerization *Controlled/"Living" Radical Polymerization *Controlled Radical Polymerization *Reversible Deactivation Radical Polymerization Though the term “living” radical polymerization was used in early days, it has been discouraged by IUPAC, because radical polymerization cannot be a truly living process due to unavoidable termination reactions between two radicals. The commonly used term controlled radical polymerization is permitted, but reversible-deactivated radical polymerization or controlled reversible-deactivation radical polymerization (RDRP) is recommended. ==History and character== RDRP – sometimes misleadingly called ‘free’ radical polymerization – is one of the most widely used polymerization processes since it can be applied *to a great variety of monomers *it can be carried out in the presence of certain functional groups *the technique is rather simple and easy to control *the reaction conditions can vary from bulk over solution, emulsion, miniemulsion to suspension *it is relatively inexpensive compared with competitive techniques The steady-state concentration of the growing polymer chains is 10−7 M by order of magnitude, and the average life time of an individual polymer radical before termination is about 5-10 s. A drawback of the conventional radical polymerization is the limited control of chain architecture, molecular weight distribution, and composition. In the late 20th century it was observed that when certain components were added to systems polymerizing by a chain mechanism they are able to react reversibly with the (radical) chain carriers, putting them temporarily into a ‘dormant’ state.〔 〕 This had the effect of prolonging the lifetime of the growing polymer chains (see above) to values comparable with the duration of the experiment. At any instant most of the radicals are in the inactive (dormant) state, however, they are not irreversibly terminated (‘dead’). Only a small fraction of them are active (growing), yet with a fast rate of interconversion of active and dormant forms, faster than the growth rate, the same probability of growth is ensured for all chains, i.e., on average, all chains are growing at the same rate. Consequently, rather than a most probable distribution, the molecular masses (degrees of polymerization) assume a much narrower Poisson distribution, and a lower dispersity prevails. IUPAC also recognizes the alternative name, ‘controlled reversible-deactivation radical polymerization’ as acceptable, "provided the controlled context is specified, which in this instance comprises molecular mass and molecular mass distribution." These types of radical polymerizations are not necessarily ‘living’ polymerizations, since chain termination reactions are not precluded".〔〔〔 The adjective ‘controlled’ indicates that a certain kinetic feature of a polymerization or structural aspect of the polymer molecules formed is controlled (or both). The expression ‘controlled polymerization’ is sometimes used to describe a radical or ionic polymerization in which reversible-deactivation of the chain carriers is an essential component of the mechanism and interrupts the propagation that secures control of one or more kinetic features of the polymerization or one or more structural aspects of the macromolecules formed, or both. The expression ‘controlled radical polymerization’ is sometimes used to describe a radical polymerization that is conducted in the presence of agents that lead to e.g. atom-transfer radical polymerization (ATRP), nitroxide-(aminoxyl) mediated polymerization (NMP), or reversible-addition-fragmentation chain transfer (RAFT) polymerization. All these and further controlled polymerizations are included in the class of reversible-deactivation radical polymerizations. Whenever the adjective ‘controlled’ is used in this context the particular kinetic or the structural features that are controlled have to be specified. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Reversible-deactivation radical polymerization」の詳細全文を読む スポンサード リンク
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