ISSN 18112382, Polymer Science, Ser. C, 2015, Vol. 57, No. 1, pp. 20–31. © Pleiades Publishing, Ltd., 2015. Original Russian Text © S.A. Kurochkin, V.P. Grachev, 2015, published in Vysokomolekulyarnye Soedineniya, Ser. C, 2015, Vol. 57, No. 1, pp. 25–37.
Reversible Deactivation Radical Polymerization of Polyfunctional Monomers S. A. Kurochkin* and V. P. Grachev Institute of Problems of Chemical Physics, Russian Academy of Sciences, pr. Akademika Semenova 1, Chernogolovka, Moscow oblast, 142432 Russia *email:
[email protected] Received September 22, 2014
Abstract—In this review, the results of modern theoretical and experimental investigations of threedimen sional reversibledeactivation radical polymerization are discussed. The most important factors affecting the critical gelation conversion, the probability of cyclization, and the topological structures of polymers are underlined. Examples of the most promising application of the reversible deactivation radical polymerization to produce new polymer materials are given. DOI: 10.1134/S1811238215010063
Radical polymerization of polyfunctional mono mers attracted interest from researchers in the field of polymer synthesis even at the earliest stage of the development of polymer science. The radical poly merization of divinylbenzene, including its copoly merization with styrene, was investigated in detail by Staudinger, et al., back in 1935 [1]. It was first stated that the product of this reaction is a threedimensional molecule, and the reaction received the name three dimensional radical polymerization [2–9]. This is the term that is most frequently used in the Russian liter ature [10–22], whereas outside Russia, apart from threedimensional polymerization, different terminol ogy is used—crosslinking polymerization [23–27], branching polymerization [28, 29], network polymeriza tion [30], etc.—depending on the process conditions and the structures of the resulting polymers. In spite of the versatile conditions of performing threedimen sional radical polymerization that result in a wide vari ety of polymer materials strongly differing in proper ties (polymer networks, branched polymers, micro and nanogels) [13, 31–35], from the chemical point of view, the same process is used. The difference consists in the creation of special conditions leading to the absence or, in contrast, the occurrence of various physical phenomena (microsyneresis, precipitation, occlusion, etc.) [36].
nitroxyls [41–57], atomtransfer radical polymeriza tion [58–66], and reversible chaintransfer radical polymerization via the addition–fragmentation mechanism [67–76] extended the capabilities of poly mer synthesis via threedimensional radical polymer ization. The key distinction of living radical polymeriza tion, which received the name reversible deactivation radical polymerization (RDRP), recommended by IUPAC [77], is in the pattern of change in molecular mass of the polymer throughout the process. During the usual radical polymerization, the final length of forming polymer chains is attained almost instanta neously (in comparison to the total polymerization time) according to the classical equation for the aver age chain length, chainpropagation rate , Pn = chaintermination rate and in the course of the process, new polymer chains appear continuously, with the average length differing from the length of chains formed at the earlier stage according to changes in the polymerization conditions (decreases in the concentrations of the monomers, initiator, chainpropagation regulators and an increase in the viscosity of the medium, which has a significant effect on the rate constants of diffusion controlled elementary reactions). During RDRP, the final length of polymer chains is attained only at the end of polymerization, when monomers are exhausted (in the case close to the ideal occurrence of the living chain mechanism), according to the equation [M]0 (1) Pn = C, [X]0 where [M]0 is the initial concentration of double bonds (during the polymerization of a monofunc
The investigation of the reversible interaction of the stable radical 2,2,6,6tetramethylpiperidin1oxyl with the cyanisopropyl radical [37] and the theoretical analysis of the scheme of radical polymerization involving alkoxyamines [38, 39] and of “living” radical polymerization [40] opened up a new chapter in poly mer chemistry, in particular, in the radical polymeriza tion of polyfunctional monomers. The evident progress in radical polymerization in the presence of 20
REVERSIBLE DEACTIVATION RADICAL POLYMERIZATION
tional monomer, this is the monomer concentration; during the polymerization of a polyfunctional mono mer, all its double bonds are taken into account), [X]0 is the concentration of an deactivator (a stable nitroxyl radical, a reversiblechaintransfer agent, a complex of metal with a varying valence, etc.), and С is the dou blebond conversion. In the ideal case, the number of chains remains almost the same and their propagation begins simulta neously at the early stage of polymerization and con tinues in steps, i.e., via addition of new units to a mac romolecule in the active state. The chain length is determined only by the ratio of the monomer and deactivator concentrations and is independent of the kinetic parameters of the reaction other than conver sion. However, the kinetic parameters influence the length of the “step” corresponding to an increase in the chain length within its residence in the active state, which is equal to k [M] Pni = p , k x[X] where kp and kx are the rate constants of the elemen tary reactions of chain propagation and deactivation, respectively, and [M] and [X] are the actual concentra tions of double bonds and deactivator, respectively. The length of steps and, hence, their number throughout the polymer chain predetermine an important parameter: polydispersity index Mw/Mn [78]. For the Schultz distribution, it depends on the number of steps, i, as (i + 1)/i [79]; therefore, to obtain polymers with a narrow molecularmass distri bution, Mw/Mn < 1.3, it is sufficient that, until the end of polymerization, more than three steps on average fall on one polymer chain. Note that the main indica tions of the polymer formation via the RDRP mecha nism are a low polydispersity index (Mw/Mn < 1.5), a linear dependence of Mn on conversion according to Eq. (1), and a recommenced increase in the molecular mass of the polymer after its extraction and addition to a new polymerizing system. The fulfillment of the above conditions suffices for confirming the imple mentation of the RDRP mechanism. Other features of RDRP, such as suppression of the autoacceleration of radical polymerization at high conversions, should be regarded as indirect indications rather than direct evi dence of the implementation of the RDRP mecha nism. During the consideration of threedimensional radical polymerization, the concept of the primary polymer chain (PPC), which grows at one active cen ter, is introduced. The chain length is equal to the number of opened double bonds of monofunctional and polyfunctional monomers involved in a PPC. (In chain termination via recombination, they are involved in two PPCs.) A PPC is a structural unit of forming macromolecules that can consist of one or more unified PPCs. The crosslinking junction of two PPCs is a polyfunctional monomer with two formed POLYMER SCIENCE
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double bonds, with each chain possessed by only one PPC and regarded as one unit. For radical polymerization of polyfunctional monomers, all peculiarities of the RDRP mechanism are of special importance. Equation (1) for the PPC length must be obeyed even at early stages of the pro cess; i.e., the amount of PPCs in the active or “dor mant” state is equal to the amount of the added deac tivator, even at conversions of ~10–20%. The length of the first step, Pni , must be at least three times shorter than the PPC length at the critical instant of gelation, so that, until this instant, the Mw/Mn value of PPC is below 1.3. In the opposite case, the mixed mechanism is active. In this case, the critical gelation conversion, which influences the yield and properties of the result ing product, is determined by factors typical of usual radical polymerization, which, as a rule, are con trolled to a lesser extent. Moreover, the occurrence of the RDRP mechanism substantially affects the topol ogy of forming macromolecules by decreasing the probability of intramolecular cyclization [80, 81]. CRITICAL GELATION CONVERSION: THEORY In threedimensional radical polymerization, gela tion means the formation of a continuous polymer network extending over the entire reactionvessel vol ume. The characteristic indication of gelation is the loss of fluidity in the reaction mass. The formed gel retains its integrity even during the continuous addi tion of a thermodynamically good solvent and with an increase in temperature. (Network polymers do not dissolve and do not melt.) In this polymerization, unlike polycondensation processes during three dimensional radical polymerization, the instant of gelation may be easily recorded even visually owing to the rapid transition of the reaction system from a rela tively low viscosity state to the rubberlike state. The gelation can be observed from almost the earliest stage of the process even for minor additives of a polyfunc tional monomer. For example, during the radical copolymerization of styrene with divinylbenzene (1 wt %) initiated by tertbutylhydroperoxide (0.0053 mol/L) at 120°C, the gelation begins at a con version of ~7% [82]. Until the instant of gelation (gel point), a macromolecule has a finite molecular mass; after this point, the molecular mass is equal to infinity [83]. The gel point is characterized by critical gelation conversion Cg, which is one of the most important fun damental and technological parameters of three dimensional radical polymerization. At present, several theoretical approaches are being developed for a calculation of the critical gelation con version to establish the relationship between this value and the polymerization conditions [84].
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The simplest scheme of RDRcP of monofunc tional monomer M1 and bifunctional monomer M2 with the example of the reversibleinhibition mecha nism involves the following reactions. Real Initiation kd I ⎯⎯⎯ → 2R i• k′i1 R i• + M1 ⎯⎯⎯ → R 1• k′i 2 R i• + M 2 ⎯⎯⎯ → R •2 + M′2 k′i 2′ R i• + M′2 ⎯⎯⎯ → R′2• + J
Chain Propagation • k11 R 1• + M1 ⎯⎯⎯ → R1 •
obtain the analytical equation for the critical gelation conversion [85, 86]:
[RX]0 (2) 2[M 2]0 This equation reflects the main peculiarity of RDRP of polyfunctional monomers. Here, unlike in the usual threedimensional radical polymerization, Cg is independent of the rate constants of elementary reactions and is determined only by the initial ratio of the concentration of PPCs RX to the concentration of divinyl monomer M2. Real systems are always characterized by the length distribution of PPCs; thus, in Eq. (2), a correction for polydispersity index Mw/Mn is introduced [32, 87, 88]: Cg =
•
k12 → R 2 + M'2 R 1 + M 2 ⎯⎯⎯ •
k12′ → R '2• + J R 1 + M'2 ⎯⎯⎯ •
•
•
•
k 21 → R1 R 2 + M1 ⎯⎯⎯
k 22 → R 2 + M'2 R 2 + M 2 ⎯⎯⎯ •
k 22′ → R '2• + J R 2 + M'2 ⎯⎯⎯ •
•
k 2′1 → R1 R′2 + M1 ⎯⎯⎯
•
k 2′2 → R 2 + M'2 R '2• + M 2 ⎯⎯⎯ k 2′2′ → R '2• + J R '2• + M'2 ⎯⎯⎯
Reversible Inhibition k
d1 ⎯⎯⎯ → R 1• + X • R 1X ←⎯⎯ ⎯
k c1 k
d2 ⎯⎯⎯ → R •2 + X • R 2 X ←⎯⎯ ⎯
k c2
k d 2′
⎯⎯⎯ → R '2• + X • R '2 X ←⎯⎯ ⎯ k c2′
Square Chain Termination •
•
k
tij R i + R j ⎯⎯⎯ →P
Here, M '2 is a pendant double bond; R •i is the primary radical forming during the decay of initiator I; R1• , R •2 , and R '2• are radicals forming in the reaction of any rad ical with the double bond of a monofunctional mono mer, with the double bond of a bifunctional monomer, and with a pendant double bond, respectively; J is a network junction, i.e., a bifunctional monomer with two formed double bonds transformed into two mac romolecule units possessed by two different primary polymer chains; and P is a dead polymer chain. In the approximation of instantaneous initiation (the amount of PPCs RX from the beginning of the process is equal to the amount of added deactivator X), Pni = 1—i.e., the number of steps, i, equals the number of monomer units in a PPC, n—and Mw/Mn → 1. Because all reactivity ratios are equal to unity, we
Cg =
[ RX ] 1 0 2 [ M 2 ] 0 M w /M n
The decrease in Cg with broadening of the molecu larmass distribution of PPCs is a result of an increase in their weightaverage functionality via pendant dou ble bonds [83]. During polymerization of monomers differing in reactivity of double bonds in the presence of a positive or a negative effect of substitution via the reaction of one double bond of a polyfunctional monomer, which results in a change in the reactivity of pendant double bonds, an analytical equation for Cg was obtained in the implicit form [16, 88]:
[M 2]0 1 2α − β ⎡(1 − C g ) = ⎢ [RX]0 2 2αβ ⎣⎢ 2α
2α
−1
(1 − C g )β + 2α − β⎤ (3) − ⎥ β
2αβ ⎥⎦ Here, α is the ratio of the propagation rate constant of any radical reacting with the double bond of bifunc tional monomer M2 to the propagation rate constant of the same radical reacting with the double bond of monofunctional monomer M1, while β is the ratio of the propagation rate constant of any radical reacting with the pendant double bond of M '2 to the propaga tion rate constant of the same radical reacting with the double bond of monofunctional monomer M1. With regard to the different reactivities of mono mers M1 and M2 and the substitution effect, the first term of expansion on the right side of Eq. (3) for Cg gives the following expression for the critical gelation conversion [16]: 1 [RX]0 αβ 2[M 2]0 Note that, in real systems, the presence of the sub stitution effect (β ≠ 1) may be due both to a change in reactivity of pendant double bonds and to diffusion or structural–topological limitations (occlusion of pen dant double bonds by macromolecules). During RDRP of polyfunctional monomers con taining more than two double bonds or a mixture of Cg =
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polyfunctional monomers, the critical gelation con version is determined as follows [89]:
[RX]0 , (4) Ф 22(0) where Ф 22 (0) = ∑ i (i − 1) [M i ]0 is the second moment of the generating function for functionality at t = 0, while [Mi]0 is the initial concentration of the ifunc tional monomer. For comparison, let us give equations for Cg during threedimensional radical polymerization with irre versible square chain termination, Cg =
kt wi k pФ22(0) and with irreversible chain transfer, k [TR]0 Cg = 0.5 tr k pФ22(0) Here, kp, kt, and ktr are the rate constants of chain propagation, square chain termination, and chain transfer; [TR]0 is the initial concentration of the chaintransfer agent; and wi is the initiation rate [90]. Evidently, the mechanism of threedimensional RDRP has an advantage in the level of the macromol eculeformation control and in providing the desired critical gelation conversion. Cg = 0.33
CRITICAL GELATION CONVERSION: EXPERIMENT As was shown with the example of radical copoly merization of styrene and 4,4'divinylbiphenyl via the mechanism of reversible inhibition in the presence of nitroxyl radicals [80, 91], compared to the usual poly merization characterized by the microheterogeneous mechanism [13], the RDRP mode substantially reduces the probability of the intramolecular crosslinking, which results in cycle formation in the macromolecular structure. A similar result was obtained during copolymerization of methyl oligo(ethylene glycol methacrylate) and oligo(ethyl ene glycol dimethacrylate) via the mechanism of reversible chain transfer in the presence of AIBN and benzyl dithiobenzoate or reversible atom transfer with the participation of αbromophenyl acetate, CuBr, and N,N,N,Ntetramethylethylenediamine [92] and similar systems [82, 93]. The decreasing probability of cyclization during threedimensional RDRP is related to two specific features of the process that affect the kinetic [94] and dynamic [32, 95] parameters of the system. The kinetic factor determining the cyclization sup pression is that, in threedimensional RDRP, from the early stages of the process, PPCs are short and their concentration is equal to the initial concentration of the deactivator/initiator, [X]0. Thus, as a result of the reaction of growing PPCs with a bifunctional mono POLYMER SCIENCE
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mer, pendant double bonds are uniformly distributed between PPCs, with a few double bonds in one chain. Because of the high concentration of PPCs even at low conversions of the monomer, the overlapping of poly mer coils is observed. The local concentration of pen dant double bonds, [M '2 ]loc, in volume VPPC occupied by a coil of propagating PPC is comparable to total concentration [M '2 ] of pendant double bonds (which are almost completely possessed by “foreign” PPCs) or below this value. In this case, the cyclization is not the predominant reaction. During the usual threedimensional radical poly merization, the PPCs are accumulated in the course of the initiation reaction proceeding at rate wi and they become long almost instantaneously. Therefore, the forming pendant double bonds are distributed over few long PPCs, with a high number of bonds in one chain. Local concentration [M '2 ]loc is much greater than [M '2 ], and in this case, the cyclization is the predominant reaction. In general, the criterion condition of the cyclization suppression can be writ ten as k p[R •]loc[M '2 ]loc k p[R •]loc[M '2 ]. The local con centration of pendant double bonds is where [M '2 ]loc = nloc / V PPC = [M '2 ] / (N A [PPC]V PPC ) , nloc is the number of pendant double bonds in moles possessed by one PPC and NA is Avogadro’s number. By substituting [M '2 ]loc into the criterionbased ine quality, we obtain the condition of cyclization sup pression: The concentration of PPCs must be much greater than their inverse molar volume, [PPC] (N AVPPC )−1 . In the RDRP, almost from the beginning of the process, the concentration of PPCs is equal to the concentration of the added deactivator: [PPC] = [X]0. For oligomers consisting of 10 monomer units, the radius of gyration equals ~3 nm (VPPC ≈ 1.13 × 10–22 L, NAVPPC ≈ 68 L/mol); thus, for significant suppression of cyclization, the condition [X]0 0.015 mol/L, which meets the common experimental conditions for threedimensional RDRP, must be fulfilled. In con trast, during the usual radical polymerization, the concentration of PPCs increases in time according to the relationship [PPC] = wit (chain termination via dis proportionation). For polymers with high molecular masses (∼5 × 105), the radius of gyration nears 15 nm (VPPC ≈ 1.41 × 10–20 L, NAVPPC ≈ 8500 L/mol); hence, for the substantial suppression of cyclization, the con centration of PPCs formed from the beginning of the process must be far greater than 1.2 × 10–4 mol/L. At the typical initiation rate wi ∼ 10⎯7 mol/(L s), such a number of PPCs can be formed only at t 20 min. In other words, at the beginning of the process, the crite rionbased condition of cyclization suppression is not fulfilled and, within a short lifetime of the radical, most of the pendant double bonds possessed by form
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ing PPCs are consumed via the intramolecular crosslinking reaction. On the basis of the aforesaid, the accumulated PPCs contain a fewer pendant double bonds than do freshly formed chains and the probability of intermo lecular crosslinking remains low, even over long peri ods. As a result of the dominant cyclization reaction during the usual threedimensional radical polymer ization, from the outset of the process, microgel parti cles are formed and the microheterogeneous mecha nism with all its specific features occurs [13]. The dynamic factor leading to the cyclization sup pression consists in that, during threedimensional RDRP, PPCs grow slowly via the addition of fresh por tions of monomer units at the instant of a shortterm “revival.” Most of the time the PPCs are in the inac tive dormant state and do not participate in the prop agation reaction, but are capable of diffusion and approaching foreign PPCs, a circumstance that enhances the probability of intermolecular crosslink ing. Simultaneously, a PPC can change its conforma tion to a more unfolded one, thereby decreasing [M '2 ]loc . The propagating radical reacts with double bonds of a foreign PPC or its own PPC with the prob ability determined by their uniformly spaced distribu tion. In contrast, during the usual threedimensional radical polymerization, a PPC grows very rapidly; hence, in the vicinity of the propagating radical, a deficiency in pendant double bonds of foreign PPCs is observed because of their low diffusion coefficients. As a result, the diffusion control of the intermolecular crosslinking occurs. The propagating radicals react predominantly with pendant double bonds of their own chains to yield microgel particles. This mode of occurrence of the microheterogeneous mechanism of threedimensional radical polymerization can be interpreted within the concepts of nonuniformly spaced radical polymerization [96]. With the use of dynamic light scattering, it was shown [81] that, during threedimensional radical polymerization of styrene and pdivinylbenzene per formed via the common mechanism (AIBN as an ini tiator, 60°C) and via reversible chain transfer (cumyl dithiobenzoate, AIBN, 60°C), after a particular instant, the autocorrelation function has two modes, regardless of the polymerization mechanism. The fast mode corresponds to diffusion of individual macro molecules with the characteristic relaxation time τf = 0.01–0.1 ms. The slow mode corresponds to transla tional diffusion of macromolecular aggregates arising at a conversion of ~10% (a semidilute solution) and microgel particles with a characteristic relaxation time of τs = 0.1–1.0 ms that increases exponentially near a gel point of up to 10–100 ms. The relative amplitude of intensity of the slow mode depends on the polymer ization mechanism in magnitude (higher during the usual polymerization), in the instant of appearance, and in the rate of increase. During RDRP, the slow mode arises only near the gel point, whereas, during
the usual polymerization, it persists almost from the outset of the process. Thus, threedimensional RDRP occurs at a low probability of cyclization and makes it possible to obtain homogeneous solutions and gels (Fig. 1). With phenomenological consideration for cycliza tion as a monomolecular elementary reaction, during the simulation of radical polymerization of polyfunc tional monomers with reversible chain transfer, it was shown [88] that, at a moderate probability of cycliza tion, the intramolecular crosslinking begins only in the vicinity of the gel point when, in the system, highly branched macromolecules with a number of pendant double bonds are present. It is important that the cyclization has a strong effect on Cg at small ratios [M2]0:[RX]0 with a limited content of pendant double bonds. In other words, the cyclization affects Cg to a greater extent when gelation is observed at high con versions. During the usual threedimensional radical poly merization, a decrease in the concentration of mono mers (an increase in the solvent fraction) results in a higher probability of cyclization. In the case of RDRP of polyfunctional monomers, significant cyclization is observed only when the system is diluted to a concen tration of PPCs with molecular mass M corresponding to the critical overlap concentration с* = M/(VPPCNA), which separates the region of dilute solutions from the residual concentration region [97]. It was shown [98] that the radical copolymerization of methyl methacry late with bis(2methacryloyl)oxyethyldisulfide in tol uene performed via reversible chain transfer (cumyl dithiobezoate, 1,1'azobis(cyclohexanecarbonitrile), 90°C) and reversible atom transfer (3methylphenyl bromoisobutyrate, CuCl, N(npropyl)2pyridyl methanimine, 90°C) occurs with a significant proba bility of intramolecular crosslinking at a monomer content of ~10 wt %. For a PPC involving 50 mono mer units, this corresponds to the region of crossover c*. In the studied systems with monomer concentra tions of 30 wt % or above, weak cyclization is observed. In addition, it was shown that the mechanism of reversible atom transfer provides stronger suppres sion of cyclization than the mechanism with revers ible chain transfer, but the effect of differences in the chemistry of RDRP is not as considerable as the effect of the monomer concentration in the region of critical overlap concentration c*. The influence of the functionality of a branching comonomer in the copolymerization of methyl acry late with ethylene glycol diacrylate and 1,1,1trimeth ylolpropane triacrylate on the critical gelation conver sion during threedimensional radical polymerization with atom transfer ([ethyl2bromopropionate]0 : [CuBr]0 : [CuBr2]0 : [N,N,N',N'',N''pentamethyldi ethylenetriamine]0 = 1.0 : 0.45 : 0.05 : 0.5) was studied [99]. As was shown, at equal molar ratios of double bond concentrations ([=]) for polyfunctional mono mers and the initiator, [RX]0/[=]0 (for diacrylate, POLYMER SCIENCE
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Common TRP
Microgel
Intramolecular crosslinking
Dilute solution
Semidilute solution
Gelation
Intermolecular crosslinking
Intermolecular crosslinking
Living TRP Fig. 1. Scheme of the crosslinking process in (top panels) the usual and (bottom panels) living threedimensional radical poly merization.
[=]0 = 2[M2]0; for triacrylate, [=]0 = 3[M3]0), critical gelation conversion Cg for triacrylate is lower than that for diacrylate. On the basis of these data, the authors have made the conclusion that, during the use of tria crylate at a concentration 1.5 times lower than the concentration of diacrylate, the probability of inter molecular crosslinking increases because the intro duction of a free diacrylate molecule into the polymer chain generates two pendant double bonds character ized by a high probability of participation in intermo lecular crosslinking relative to that of one pendant double bond in the presence of diacrylate as a branch ing comonomer. The interpretation of these results can differ if two systems are compared not in terms of the total concentration of double bonds of polyfunc tional monomers, but in terms of the second moment of the distribution of the generating function for func tionality Φ22(0). The dependence of Cg on [RX]0/Φ22(0) plotted in logarithmic coordinates of Eq. (4) (Fig. 2) gives an order for the [RX]0/Φ22(0) ratio equal to 0.44 for dia crylate and to 0.52 for triacrylate, results that agree well with 0.5 for the theoretical dependence. However, in both cases, the experimental Cg value is higher than the theoretical value, a result that may be due both to POLYMER SCIENCE
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the substitution effect (β < 1) and to intramolecular crosslinking, which results in cyclization. At equal [RX]0/Φ22(0) values, Cg for triacrylate is greater than that for diacrylate, an outcome that is probably related to the negative effect of substitution for the third dou ble bond (β < 1) because its participation in the prop agation reaction is strongly limited owing to its occlu sion by four branches of the polymer chain. From the experimental point of view, providing a mechanism of living chains close to the ideal mode is of great importance. For the example of radical copo lymerization of methyl methacrylate and ethylene gly col dimethacrylate with reversible atom transfer in the presence of CuBr, CuBr2, and 2,2'bipyridine, the effect of the chemical nature of the initiator with an increase in the initiation efficiency (in this case, the initiation efficiency is a fraction of that of the initiator entering in the reaction to the given conversion) in the series 2bromopropionate < 2bromoisobutyrate < 2bromopropionitrile on the experimental Cg value was studied [100]. The use of lowefficiency initiators when the amount of propagating PPCs is smaller than the amount of added initiator results in a decrease in Cg. At [M2]0 : [X]0 = 1, for example, the highly efficient initiator 2bromopropionitrile (an initiation efficiency
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KUROCHKIN, GRACHEV logCg 0 2
−0.2
1 −0.4
3
−0.6 −0.8 −1.6
−1.2
−0.8 −0.4 log([RX]0/Φ22(0))
Fig. 2. (1, 2) Logarithmic dependences of Cg on [RX]0/Φ22(0) during radical copolymerization of monoacrylate with (1) diacrylate and (2) triacrylate via the mechanism of reversible atom transfer (according to the data of [99]) and (3) the theoretical dependence calculated through Eq. (4).
of 0.95 at a monomer conversion of 0.65) provides the polymerization process without gelation, 2bro moisobutyrate (an initiation efficiency of 0.68 at a monomer conversion of 0.93) generates fewer PPCs and Cg = 0.75, while 2bromopropionate (an initiation efficiency of 0.34 at a monomer conversion of 0.99) gives even fewer PPCs and Cg = 0.25. The decrease in the [M2]0to[X]0 ratio to 0.7 with 2bromoisobutyrate (compare the initiation efficiency of 0.68) and to 0.2 with 2bromopropionate (compare the initiation effi ciency of 0.34) made it possible to perform the process without gelation. In both cases, the broad primary chainlength distributions (Mw/Mn = 1.47 and 1.54, respectively) have an additional effect. With the use of the advantages of the mechanism of reversible atom transfer in a version of ARGET (activators regenerated by electron transfer) [101, 102], which allows con trolled variation of the molecularmass distribution of primary chains, in the same study [100], the influence of Mw/Mn of PPCs on Cg was studied. At [M2]0 : [X]0 = 1 and Mw/Mn = 1.12, 1.47, and 2.01, only in the first case, with a narrow primarychain distribution (Mw/Mn = 1.12), was gelation not observed. For the broad distributions, the Cg values were 0.86 and 0.64, respectively. CONCLUSIONS Thus, during threedimensional RDRP in an approximation to the ideal mode of living chains, the critical gelation conversion is determined only by the
ratio of the initial concentrations of the deactivator and the crosslinking monomer. The intramolecular crosslinking is suppressed if the process occurs in con centrated and semidilute monomer solutions (above critical overlap concentration c*). The probability of cyclization and the topological structuring of forming polymers can be judged from the difference in the experimental and theoretical Cg values. However, the conclusions made may be taken into account only if the mechanism of living chains is confirmed (if the number of propagating primary polymer chains corre sponds to the amount of the added initiator–deactiva tor and a narrow primary chain length distribution exists). The conclusions on the presence of cycles in macromolecules and the homogeneity of polymer net work otherwise can be untrue. In conclusion, let us give several examples of the application of threedimensional RDRP to produce different promising polymer materials. The key parameters predetermining the polymer structure and properties are Cg and the final total conversion of monomers (Fig. 3). Network or branched polymers are obtained via threedimensional RDRP in bulk or in semidilute solutions (among this is suspension polymerization) with a low probability of the cyclization reaction. At low Cg values and a total conversion of monomers, the following polymers can be obtained: network poly mers based on poly(ethylene glycol dimethacrylates) with a homogeneous network structuring and reduced glasstransition temperatures [92, 103], network poly mers with enhanced microheterogeneity based on sty rene [104, 105] and methyl methacrylate [106] with dimethacrylates, microgranules of network polymers based on styrene and divinylbenzene [107–109], N,N'methylenebis(acrylamide) polymer microtubes [110], pHsensitive polycation nanoparticles of net work polymers based on 2(diethylamino)ethyl meth acrylate with homogeneous network structuring [111, 112], plates of butyl acrylatebased network polymers with controlled crosslink densities for controlled delivery of functional compounds [113], styrene–divi nylbenzene monolithic porous network polymers [114], hydrogels based on Nvinylpyrrolidone and N isopropylacrylamide [115], photodegradable hydro gels based on Nacryloylmorpholine with homoge neous network structuring providing a high photodeg radation rate [116], thermo and pHsensitive hydro gel particles based on Nisopropylacrylamide and acrylic acid [117], nanostructured nanoporous (a pore diameter of 16 ± 4 nm) network block copolymers of D,Llactide and styrene [118], and polymer dental composites with low internal stresses [119]. At high values of Cg > 0.5 and conversions C < Cg, the following polymers are obtained: branched and highly branched polymers based on methyl methacry late and dimethacrylates [98, 120, 121]; 2vinyloxy ethyl methacrylate [122]; styrene and divinylbenzene [123]; styrene, acrylonitrile, and divinylbenzene POLYMER SCIENCE
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REVERSIBLEDEACTIVATION THREEDIMENSIONAL RADICAL POLYMERIZATION kact
In bulk or in semidilute solutions >c*
RX
kdeact
R• +
X•
Dilute solutions Cg
+
Intermolecular crosslinking is suppressed
M2
Macrogelation is absent Good solvent
Conversion < Cg
Uniform polymer network
Polymer nanogels and stars
Branched polymer
Poor solvent
Polymer microbeads
Fig. 3. Polymer materials prepared via threedimensional RCD radical polymerization.
[124]; methyl methacrylate and vinyl methacrylate [125]; acrylamide and N,N'methylenebis(acryl amide) [126–128]; methyl acrylate, nbutyl acrylate, and 1,6hexanediol diacrylate [129]; 2(dimethyl amino)ethyl methacrylate, 2(dimethylamino)ethyl methacrylate, and ethylene glycol dimethacrylate [130]; 2hydroxypropyl methacrylate and dimethacrylates [131, 132]; 2aminoethyl methacry late [133]; styrene and triethylene glycol dimethacry late [134]; and methyl methacrylate and allyl meth acrylate [135]. With the use of RDRP in dilute solutions (in the region of critical overlap concentration c*, corre sponding to the high probability of intramolecular crosslinking), either micro and nanogels or star poly mers with polymer cores are obtained. As a result of RDRP in a thermodynamically good solvent [136] and in a thermodynamically poor solvent with an added polymer stabilizer (dispersion polymerization) [34, 35, 137–139], the following polymer products can be prepared: monodisperse functional microbeads based on methyl methacrylate [140]; narrowly disperse, densely crosslinked, surfacefunctionalized micro beads based on 4vinylpyridine, glycidyl methacrylate, and 2hydroxyethyl methacrylate [141]; thermosensi tive nanogels based on a macrodeactivator (poly(N,N'dimethylacrylamide with a trithiocarbon POLYMER SCIENCE
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ate group at the chain end), 2methoxyethyl acrylate, methoxy poly(ethylene glycol acrylate), and poly(eth ylene glycol diacrylate) [142]; biocompatible ther mosensitive nanogels based on methoxy(diethylene glycol methacrylate), methoxy poly(ethylene glycol methacrylate), and poly(ethylene glycol dimethacry late) [143]; microbeads with immobilized surface dithioester groups [144]; watercompatible polymer microbeads [145]; Atrazineimprinted polymer microbeads (a capacity up to 2.89 mg/g) based on methacrylic acid and 4vinylpyridine [146]; diben zothiopheneimprinted (a capacity up to 2.89 mg/g) silica gel particles modified by methacrylic acid and 4vinylpyridine copolymers [147]; Cefalexin imprinted (a capacity up to 59.4 mg/g) thermosensi tive polymer shell of yeast based on Nisopropylacryl amide and ethylene glycol dimethacrylate [148]; 2,4 dichlorophenoxyacetic acid– and phenoxyacetic acid–imprinted polymer microbeads made from Nisopropylacrylamide [149]; lysozymeimprinted thermosensitive spherical nanogels of Nisopropyl acrylamide [150]; and polymer microbeads based on styrene, methyl methacrylate, and divinylsulfide [22, 151]. Star polymers with crosslinked polymer cores were prepared via a twostage procedures of two types [32, 152–156]: (i) First, the synthesis of linear polymer
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chains is performed and then followed by crosslinking of their propagating ends during the addition of a bifunctional monomer and the formation of a nano core of network polymer (the “armfirst method”). (ii) At the first stage, a nanogel is formed; at the second stage, it acts as a multiinitiator of polymerization of the monofunctional monomer (the “corefirst method”). With the use of these methods, star poly mers with poly(butyl acrylate) arms and cores of net work polydivinylbenzene [157], with polymethoxy poly(ethylene glycol methacrylate) arms and cores of network poly(ethylene glycol diacrylate) and ethylene glycol dimethacrylate [158], with polymethoxy oligo(ethylene glycol acrylate) arms and cores of net work N,N'bis(acryloyl)cystamine [159], and with polymer arms of various polarities (poly(N,Ndimeth ylacrylamide) and poly(2methoxyethyl acrylate)) and cores of network 1,6hexanediol diacrylate [160] were prepared. The above mentioned examples are a clear demon stration of the potential of threedimensional RDRP to produce advanced polymer materials. ACKNOWLEDGMENTS This work was supported by the Program of Basic Research no. 24 of the Presidium of the Russian Acad emy of Sciences. REFERENCES 1. H. Staudinger and E. Husemann, Ber. Dtsch. Chem Ges 68 (8), 1618 (1935). 2. P. J. Flory, J. Am. Chem. Soc. 63 (11), 3091 (1941). 3. J. Kope c ek and D. Lím, J. Polym. Sci., Part A: Polym. Chem. 9 (1), 147 (1971). 4. S. H. Dickens, J. W. Stansbury, K. M. Choi, and C. J. E. Floyd, Macromolecules 36 (16), 6043 (2003). 5. E. Badamshina and M. Gafurova, J. Mater. Chem. 22 (19), 9427 (2012). 6. J. O. Karlssona, A. Henrikssona, J. Michálekb, and P. Gatenholm, Polymer 41 (4), 1551 (2000). 7. T. Baldacchini, C. N. LaFratta, R. A. Farrer, M. C. Teich, B. E. A. Saleh, M. J. Naughton, J. T. Fourkas, J. Appl. Phys. 95 (11), 6072 (2004). 8. S. A. Kurochkin, M. A. Silant’ev, E. O. Perepelitsyna, and V. P. Grachev, Polymer 54 (1), 31 (2013). 9. S. A. Kurochkin, M. A. Silant’ev, E. O. Perepelitsyna, and V. P. Grachev, Eur. Polym. J. 57 (2014). 10. A. G. Kondrat’eva, N. N. Tvorogov, and A. A. Berlin, Vysokomol. Soedin., Ser. A 17 (3), 593 (1975). 11. N. M. Bol’bit and S. Ya. Frenkel’, Vysokomol. Soe din., Ser. A. 20 (2), 294 (1978). 12. G. V. Korolev and M. M. Mogilevich, Threedimen sional Radical Polymerization. Crosslinked and Hyper branched Polymers (Khimizdat, St. Petersburg, 2006) [in Russian]. 13. G. V. Korolev, Russ. Chem. Rev. 72 (3), 197 (2003).
14. V. P. Roshchupkin and S. V. Kurmaz, Russ. Chem. Rev. 73 (3), 225 (2004). 15. T. R. Deberdeev, R. M. Garipov, R. Ya. Deberdeev, T. F. Irzhak, V. I. Irzhak, Polym. Sci., Ser. A 46 (3), 231 (2004). 16. T. F. Irzhak and V. I. Irzhak, Polym. Sci., Ser. B 53 (7– 8), 427 (2011). 17. S. V. Kurmaz and V. V. Ozhiganov, Polym. Sci., Ser. B 51 (5–6), 157 (2009). 18. S. A. Kurochkin, V. P. Grachev, and G. V. Korolev, Polym. Sci., Sci. A 50 (9), 921 (2008). 19. S. M. Usmanov, F. R. Gaisin, and Yu. M. Sivergin, Plast. Massy, No. 8, 19 (2005). 20. D. P. Kiryukhin, High Energy Chem. 39 (5), 291 (2005). 21. S. A. Kurochkin, M. A. Silant’ev, E. O. Perepelitsina, M. P. Berezin, A. A. Baturina, V. P. Grachev, G. V. Korolev, Polym. Sci., Ser. B 54 (3–4), 223 (2012). 22. E. I. Biryukova, S. V. Amosova, S. A. Zhivet’eva, and M. V. Edeleva, Polym. Sci., Ser. B 51 (11–12), 438 (2009). 23. H. Galina and A. Szustalewicz, Macromolecules 22 (7), 3124 (1989). 24. H. Tobita, Macromolecules 26 (20), 5427 (1993). 25. A. Matsumoto, S. Asai, and H. Aota, Macromol. Chem. Phys. 201 (18), 2735 (2000). 26. A. Matsumoto, T. Tani, H. Aota, K. Fushihara, M. Yamada, J. Polym. Sci., Part A: Polym. Chem. 50 (5), 1018 (2012). 27. I. Kryven and P. D. Iedema, Polymer 55 (16), 3475 (2014). 28. X. L. Wang, Z. Chen, and R. Ran, J. Appl. Polym. Sci. 112 (4), 2486 (2009). 29. I. Bannister, N. C. Billingham, and S. P. Armes, Soft Matter 5 (18), 3495 (2009). 30. H. Galina and J. B. Lechowicz, Macromol. Symp. 174 (1), 307 (2001). 31. K. Matyjaszewski, Science 333 (6046), 1104 (2011). 32. H. Gao and K. Matyjaszewski, Prog. Polym. Sci. 34 (4), 317 (2009). 33. G. V. Korolev and M. L. Bubnova, Polym. Sci., Ser. C 49 (4), 332 (2007). 34. P. B. Zetterlund, Y. Kagawa, and M. Okubo, Chem. Rev. 108 (9), 3747 (2008). 35. H. Zhang, Eur. Polym. Sci. 49 (3), 579 (2013). 36. V. I. Irzhak and S. M. Mezhikovskii, Russ. Chem. Rev. 78 (2), 165 (2009). 37. V. M. Lagunov, I. V. Golikov, B. R. Smirnov, and G. V. Korolev, Vysokomol. Soedin., Ser. A 29 (7), 1442 (1987). 38. B. R. Smirnov, Vysokomol. Soedin., Ser. A 32 (3), 583 (1990). 39. C. H. J. Jonson, G. Moad, D. H. Solomon, T. H. Spurling, D. J. Vearing, Aust. J. Chem. 43, 1215 (1990). 40. M. K. Georges, R. P. N. Veregin, P. M. Kazmaier, and G. K. Hamer, Macromolecules 26 (11), 2987 (1993). POLYMER SCIENCE
Series C
Vol. 57
No. 1
2015
ˆ
REVERSIBLE DEACTIVATION RADICAL POLYMERIZATION 41. J. Nicolas, Y. Guillaneuf, C. Lefay, D. Bertin, D. Gigmes, B. Charleux, Prog. Polym. Sci. 38 (1), 63 (2013). 42. M. Ahmed and R. Narain, Prog. Polym. Sci. 38 (5), 767 (2013). 43. D. Bertin, D. Gigmes, S. R. A. Marque, and P. Tordo, Chem. Soc. Rev. 40 (5), 2189 (2011). 44. R. B. Grubbs, Polym. Rev. 51 (2), 104 (2011). 45. V. Sciannamea, R. Jerome, and C. Detrembleur, Chem. Rev. 108 (3), 1104 (2008). 46. M. A. Lazarev, I. A. Kirilyuk, I. A. Grigor’ev, and D. F. Grishin, Polym. Sci., Ser. B 49 (9–10), 224 (2007). 47. M. Yu. Zaremski, O. V. Borisova, A. V. Plutalova, and V. B. Golubev, Polym. Sci., Ser. B 49 (1–2), 51 (2007). 48. M. Yu. Zaremski, E. S. Garina, A. V. Plutalova, and V. B. Golubev, Polym. Sci., Ser. A 50 (4), 365 (2008). 49. D. I. Kalugin, M. Yu. Zaremski, V. B. Golubev, and E. S. Garina, Polym. Sci., Ser. B 53 (5–6), 307 (2011). 50. M. Yu. Zaremskii, Chen. Sin, A. P. Orlova, and I. V. Blagodatskikh, Polym. Sci., Ser. B 55 (9–10), 526 (2013). 51. O. V. Borisova, M. Yu. Zaremski, O. V. Borisov, and L. Billon, Polym. Sci., Ser. B 55 (11–12), 573 (2013). 52. M. Yu. Zaremski, Chen. Xin, A. P. Orlova, V. B. Gol ubev, S. A. Kurochkin, V. P. Grachev, Polym. Sci., Ser. B 52 (9–10), 528 (2010). 53. S. A. Kurochkin, V. P. Grachev, and G. V. Korolev, Polym. Sci., Ser. A 49 (4), 373 (2007). 54. M. Edeleva, E. Bagryanskaya, S. R. A. Marque, K. Kabytaev, Y. Guillaneuf, D. Gigmes, J. Polym. Sci., Part A: Polym. Chem. 51 (6), 1323 (2013). 55. E. Bagryanskaya, M. Edeleva, D. Parkhomenko, P. Bremond, S. R. A. Marque, V. Roubaud, D. Siri, Macromol. Rapid Commun. 33 (2), 152 (2012). 56. M. V. Edeleva, D. A. Parkhomenko, Y. P. Tsentalovich, E. G. Bagryanskaya, I. A. Kirilyuk, I. F. Zhurko, Org. Chem. 76 (14), 5558 (2011). 57. D. P. Zubenko, I. A. Kirilyuk, S. Marque, I. P. Chuikov, E. G. Bagryanskaya, Polym. Sci., Ser. B 52 (5–6), 327 (2010). 58. K. Matyjaszewski and N. V. Tsarevsky, J. Am. Chem. Soc. 136 (18), 6513 (2014). 59. W. A. Braunecker and K. Matyjaszewski, Prog. Polym. Sci. 32 (1), 93 (2007). 60. K. Matyjaszewski, Macromolecules 45 (10), 4015 (2012). 61. D. F. Grishin, Polym. Sci., Ser. A 50 (3), 221 (2008). 62. I. D. Grishin, I. T. Chizhevskii, and D. F. Grishin, Dokl. Chem. 423 (1), 290 (2008). 63. L. B. Vaganova, E. V. Kolyakina, A. V. Lado, A. V. Piskunov, D. F. Grishin, Polym. Sci., Ser. B 51 (3–4), 96 (2009). 64. I. D. Grishin, I. T. Chizhevskii, and D. F. Grishin, Kinet. Catal. 50 (4), 550. 65. D. F. Grishin, Polym. Sci, Ser. C 53 (1), 3 (2011). 66. S. A. Bulgakova, E. S. Tumakova, A. V. Zhizhikina, S. D. Zaitsev, L. V. Kurushina, Yu. D. Semchikov, Polym. Sci, Ser. B 53 (1–2), 57 (2011). 67. G. Moad, Macromol. Chem. Phys. 215 (1), 9 (2014). POLYMER SCIENCE
Series C
Vol. 57
No. 1
2015
29
68. G. Moad, E. Rizzardo, and S. H. Thang, Aust. J. Chem. 65, 985 (2012). 69. E. V. Chernikova, A. V. Morozov, M. B. Kaziev, E. S. Garina, V. B. Golubev, Polym. Sci., Ser. A 49 (9), 962 (2007). 70. A. V. Serbin, E. N. Karaseva, I. V. Dunaeva, E. B. Krut’ko, Yu. A. Talyzenkov, M. P. Filatova, E. V. Chernikova, Polym. Sci, Ser. B 53 (3–4), 116 (2011). 71. E. V. Chernikova, D. V. Vishnevetskii, E. S. Garina, A. V. Plutalova, E. A. Litmanovich, B. A. Korolev, A. V. Shlyakhtin, Yu. V. Kostina, G. N. Bondarenko, Polym. Sci, Ser. B 54 (3–4), 127 (2012). 72. E. V. Chernikova, P. S. Terpugova, A. A. Baskakov, A. V. Plutalova, E. S. Garina, E. V. Sivtsov, Polym. Sci, Ser. B 52 (3–4), 119 (2010). 73. S. D. Zaitsev, Yu. D. Semchikov, and E. V. Chernikova, Polym. Sci, Ser. B 51 (3–4), 84 (2009). 74. S. D. Zaitsev, Yu. D. Semchikov, E. V. Vasil’eva, and L. V. Kurushina, Polym. Sci, Ser. B 54 (3–4), 205 (2012). 75. E. V. Vasilyeva, N. A. Kopylova, S. D. Zaitsev, and Yu. D. Semchikov, Polym. Sci, Ser. B 53 (9–10), 491 (2011). 76. I. V. Terekhov, N. V. Timoshenko, V. V. Kireev, and S. N. Filatov, Usp. Khim. Khim. Tekhnol. 24 (4), 95 (2010). 77. A. D. Jenkins, R. G. Jones, and G. Moad, Pure Appl. Chem. 82 (2), 483 (2010). 78. M. Yu. Zaremski, Polym. Sci., Ser. A 48 (3), 234 (2006). 79. S. Ya. Frenkel’, Introduction into Statistical Theory of Polymerization (Nauka, Moscow; Leningrad, 1965), p. 41 [in Russian]. 80. N. Ide and T. Fukuda, Macromolecules 32 (1), 95 (1999). 81. T. Norisuye, Q. TranCongMiyata, A. Goto, T. Mori naga, T. Fukuda, M. Shibayama, Polymer 46 (6), 1982 (2005). 82. A. J. Scott, A. Nabifar, J. C. HernandezOrtiz, N. T. McManus, E. VivaldoLima, A. Penlidis, Eur. Polym. J. 51, 87 (2014). 83. T. F. Irzhak and V. I. Irzhak, Russ. Chem. Rev. 79 (10), 921 (2010). 84. V. I. Irzhak, Russ. Chem. Rev. 73 (3), 251 (2004). 85. S. A. Kurochkin, Polym. Sci., Ser. B 52 (1–2), 109 (2010). 86. S. A. Kurochkin, V. P. Grachev, and G. V. Korolev, Polym. Sci., Ser. A 49 (2), 227 (2007). 87. H. Gao, P. Polanowski, and K. Matyjaszewski, Macro molecules 42 (16), 5925 (2009). 88. R. Wang, Y. Luo, B. G. Li, and S. Zhu, Macromole cules 42 (1), 85 (2009). 89. G. V. Korolev, T. F. Irzhak, and V. I. Irzhak, Polym. Sci., Ser. A 43 (6), 594 (2001). 90. G. V. Korolev, T. F. Irzhak, and V. I. Irzhak, Polym. Sci., Ser. A 43 (12), 1236 (2001). 91. N. Ide and T. Fukuda, Macromolecules 30 (15), 4268 (1997).
30
KUROCHKIN, GRACHEV
92. Q. Yu, S. Xu, H. Zhang, Y. Ding, S. Zhu, Polymer 50 (15), 3488 (2009). 93. H. Gao, W. Li, and K. Matyjaszewski, Macromole cules 41 (7), 2335 (2008). 94. Y. Saka, P. B. Zetterlund, and M. Okubo, Polymer 48 (5), 1229 (2007). 95. J. Huang, W.J. Wang, B.G. Li, and S. Zhu, Macro mol. Mater. Eng 298 (4), 391 (2013). 96. I. P. Kim and V. A. Benderskii, High Energy Chem. 45 (5), 372 (2011). 97. V. P. Budtov, Physical Chemistry of Polymer Solutions (Khimiya, St. Petersburg, 1992) [in Russian]. 98. J. Rosselgong, S. P. Armes, W. R. S. Barton, and D. Price, Macromolecules 43 (5), 2145 (2010). 99. H. Gao, K. Min, and K. Matyjaszewski, Macromole cules 42 (21), 8039 (2009). 100. W. Li, H. Gao, and K. Matyjaszewski, Macromole cules 42 (4), 927 (2009). 101. W. Jakubowski and K. Matyjaszewski, Angew. Chem. 45 (27), 4482 (2006). 102. W. Jakubowski, K. Min, and K. Matyjaszewski, Mac romolecules 39 (1), 39 (2006). 103. Q. Yu, M. Zhou, Y. Ding, B. Jiang, S. Zhu, Polymer 48 (24), 7058 (2007). 104. G. V. Korolev, I. S. Kochneva, G. M. Bakova, and M. P. Berezin, Polym. Sci., Ser. A 43 (5), 482 (2001). 105. G. V. Korolev, I. S. Kochneva, G. M. Bakova, M. P. Berezin, L. I. Makhonina, Polym. Sci., Ser. A 44 (9), 936 (2002). 106. A. R. Wang and S. Zhu, Macromolecules 35 (27), 9926 (2002). 107. T. Tanaka, T. Suzuki, Y. Saka, P. B. Zetterlund, M. Okubo, Polymer 48 (13), 3836 (2007). 108. M. A. D. Gonçalves, V. D. Pinto, R. C. S. Dias, and M. R. P. F. N. Costa, L. G. Aguiar, R. Giudici, Macro mol. React. Eng. 7 (3–4), 155 (2013). 109. M. A. D. Gonçalves, V. D. Pinto, R. C. S. Dias, J. C. HernandesOrtiz, M. R. P. F. N. Costa, Macro mol. Symp. 333, 273 (2013). 110. Q. Li, L. Tang, Y. Xia, and B. Li, Macromol. Rapid Commun. 34 (2), 185 (2013). 111. D. C. Forbes and N. A. Peppas, Polymer 54 (17), 4486 (2013). 112. D. C. Forbes, M. Creixell, H. Frizzell, and N. A. Pep pas, Eur. J. Pharm. Biopharm. 84 (3), 472 (2013). 113. J. Huang, W.J. Wang, B.G. Li, and S. Zhu, Macro mol. Mater. Eng. 298 (4), 391 (2013). 114. K. J. Barlow, X. Hao, T. C. Hughes, O. E. Hutt, A. Polyzos, K. A. Turner, G. Moad, Polym. Chem. 5 (3), 722 (2014). 115. J. Song, R. Yu, L. Wang, S. Zheng, X. Li, Polymer 52 (10), 2340 (2011). 116. F. Ercole, H. Thissen, K. Tsang, R. A. Evans, J. S. For sythe, Macromolecules 45 (20), 8387 (2012). 117. M. A. D. Gonçalves, V. D. Pinto, R. A. S. Costa, R. C. S. Dias, J. C. HernándesOrtiz, M. R. P. F. N. Costa, Macromol. Symp. 333, 41 (2013). 118. M. Seo, C. J. Murphy, and M. A. Hillmyer, ACS Macro Lett. 2 (7), 617 (2013).
119. H. Y. Park, C. J. Kloxin, M. F. Fordney, and C. N. Bowman, Dent. Mater. 28 (8), 888 (2012). 120. B. Liu, A. Kazlauciunas, J. T. Guthrie, and S. Perrier, Macromolecules 38 (6), 2131 (2005). 121. F. Isaure, P. A. G. Cormack, S. Graham, D. C. Sher rington, S. P. Armes, V. Butun, Chem. Commun., No. 9, 1138 (2004). 122. Z. Jia, J. Liu, T. P. Davis, and V. Bulmus, Polymer 50 (25), 5928 (2009). 123. R. Qiang, G. Fanghong, L. Chunlin, Z. Guangqun, J. Bibiao, L. Chao, C. Yunhui, Eur. Polym. J. 42 (10), 2573 (2006). 124. G. Haidan, H. Wenyan, Z. Dongliang, G. Fanghong, L. Chunlin, Y. Yang, C. Jianhai, J. Bibiao, Polymer 49 (19), 4101 (2008). 125. M. Akiyama, K. Yoshida, and H. Mori, Polymer 55 (3), 813 (2014). 126. W.J. Wang, D. Wang, B.G. Li, and S. Zhu, Macro molecules 43 (9), 4062 (2010). 127. D. Wang, X. Li, W.J. Wang, X. Gong, B.G. Li, S. Zhu, Macromolecules 45 (1), 28 (2012). 128. D. Wang, W.J. Wang, B.G. Li, and S. Zhu, AIChE J. 59 (4), 1322 (2013). 129. W. Li, J. A. Yoon, M. Zhong, and K. Matyjaszewski, Macromolecules 44 (9), 3270 (2011). 130. V. Bütün, I. Bannister, N. C. Billingham, D. C. Sher rington, S. P. Armes, Macromolecules 38 (12), 4977 (2005). 131. I. Bannister, N. C. Billingham, S. P. Armes, S. P. Ran nard, P. Findlay, Macromolecules 39 (22), 7483 (2006). 132. S. P. Armes, Macromolecules 38 (20), 8155 (2005). 133. Y. Li and S. P. Armes, Macromolecules 42 (4), 939 (2009). 134. H.J. Yang, B.B. Jiang, W.Y. Huang, D.L. Zhang, L.Z. Kong, J.H. Chen, C.L. Liu, F.H. Gong, Q. Yu, Y. Yang, Macromolecules 42 (16), 5976 (2009). 135. Y. Bao, G. Shen, X. Liu, and Y. Li, J. Polym. Sci., Part A: Polym. Chem. 51 (13), 2959 (2013). 136. D. Klinger and K. Landfester, Polymer 53 (23), 5209 (2012). 137. Z. An, Q. Qui, and G. Liu, Chem. Commun. 47 (46), 12424 (2011). 138. G. Liu and Z. An, Polym. Chem. 5 (5), 1559 (2014). 139. Y. Hu, J. Pan, K. Zhang, H. Lian, G. Li, TrAC, Trends Anal. Chem. 43, 37 (2013). 140. J. Tan, X. Rao, X. Wu, H. Deng, J. Yang, Z. Zeng, Macromolecules 45 (21), 8790 (2012). 141. Y. Jiao, J. Jiang, H. Zhang, K. Shi, H. Zhang, Eur. Polym. J. 54, 95 (2014). 142. G. Liu, Q. Qui, and Z. An, Polym. Chem. 3 (2), 504 (2012). 143. W. Shen, Y. Chang, G. Liu, H. Wang, A. Cao, Z. An, Macromolecules 44 (8), 2524 (2011). 144. G. Pan, B. Zu, X. Guo, Y. Zhang, C. Li, H. Zhang, Polymer 50 (13), 2819 (2009). 145. H. Zhang, Polymer 55 (3), 699 (2014). 146. S. Xu, J. Li, and L. Chen, Talanta 85 (1), 282 (2011). POLYMER SCIENCE
Series C
Vol. 57
No. 1
2015
REVERSIBLE DEACTIVATION RADICAL POLYMERIZATION 147. W. Yang, L. Liu, Z. Zhou, H. Liu, B. Xie, W. Xu, Appl. Surf. Sci. 282, 809 (2013). 148. J. Pan, H. Hang, X. Li, W. Zhu, M. Meng, X. Dai, J. Dai, Y. Yan, Appl. Surf. Sci. 287, 211 (2013). 149. G. Pan, Y. Zhang, X. Guo, C. Li, H. Zhang, Biosens. Bioelectron 26 (3), 976 (2010). 150. G. Pan, Q. Guo, C. Cao, H. Yang, B. Li, Soft Matter 9 (14), 3840 (2013). 151. E. I. Biryukova, S. V. Amosova, S. A. Zhivet’eva, E. D. Bedoshvili, Y. V. Likhoshway, Polym. Sci., Ser. B 51 (3–4), 117 (2009). 152. A. Blencowe, J. F. Tan, T. K. Goh, and G. G. Qiao, Polymer 50 (1), 5 (2009). 153. A. Gregory and M. H. Stenzel, Prog. Polym. Sci. 37 (1), 38 (2012). 154. G. Moad, E. Rizzardo, and S. H. Thang, Chem. Asian. J. 8, 1634 (2013).
POLYMER SCIENCE
Series C
Vol. 57
No. 1
2015
31
155. Q. Chen, X. Cao, Y. Xu, and Z. An, Macromol. Rapid Commun. 34 (19), 1507 (2013). 156. P. Król and P. Chmielarz, Prog. Org. Coat. 77 (5), 913 (2014). 157. E. van Ruymbeke, E. B. Muliawan, D. Vlassopoulos, H. Gao, K. Matyjaszewski, Eur. Polym. J. 47 (4), 746 (2011). 158. C. Zhang, M. Miao, X. Cao, and Z. An, Polym. Chem. 3 (9), 2656 (2012). 159. J. Liu, H. Duong, M. R. Whittaker, T. P. Davis, C. Boyer, Macromol. Rapid Commun. 33 (9), 760 (2012). 160. X. Shi, M. Miao, and Z. An, Polym. Chem. 4 (6), 1950 (2013).
Translated by L. Tkachenko
