Controlled radical polymerization of styrene mediated by the C‐phenyl‐N‐tert‐butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis

Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10^?10 mol L^?1 at 110 °C. At this temperature, the dissociation rate constant (k_d) is 3.7 × 10^?3 s^?1, the recombination rate constant (k_c) is 4.3 × 10⁶ L mol^?1 s^?1, whereas the activation energy (E_a,diss.), for the dissociation of the alkoxyamine at the chain‐end is ～125 kJ mol^?1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007     

Polymerization of 1,3‐dienes with functional groups. II. Free‐radical polymerization of N‐(2‐methylene‐3‐butenoyl)piperidine

The free‐radical homopolymerization and copolymerization behavior of N‐(2‐methylene‐3‐butenoyl)piperidine was investigated. When the monomer was heated in bulk at 60 °C for 25 h without an initiator, about 30% of the monomer was consumed by the thermal polymerization and the Diels–Alder reaction. No such side reaction was observed when the polymerization was carried out in a benzene solution with 1 mol % 2,2′‐azobisisobutylonitrile (AIBN) as an initiator. The polymerization rate equation was found to be R_p ∝ [AIBN]^0.507[M]^1.04, and the overall activation energy of polymerization was calculated to be 89.5 kJ/mol. The microstructure of the resulting polymer was exclusively a 1,4‐structure that included both 1,4‐E and 1,4‐Z configurations. The copolymerizations of this monomer with styrene and/or chloroprene as comonomers were carried out in benzene solutions at 60 °C with AIBN as an initiator. In the copolymerization with styrene, the monomer reactivity ratios were r₁ = 6.10 and r₂ = 0.03, and the Q and e values were calculated to be 10.8 and 0.45, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1545–1552, 2003     

Kinetics and electron spin resonance study of the radical polymerization of n‐butyl acrylate mediated by a nitroxide precursor: C‐phenyl‐N‐tert‐butylnitrone

The C‐phenyl‐N‐tert‐butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n‐butyl acrylate as long as a two‐step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 °C for 4 h followed by the addition and polymerization of n‐butyl acrylate at 110 °C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 × 10^?12 mol L^?1 at 110 °C. The dissociation rate constant and the activation energy for the C? ON bond homolysis are 1.9 × 10^?3 s^?1 and 122 ± 15 kJ mol^?1, respectively. The rate constant of recombination between the propagating radical and the nitroxide is as high as 1.2 × 10⁹ L mol^?1 s^?1. Finally, well‐defined poly(n‐butyl acrylate)‐b‐polystyrene block copolymers have been successfully prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6299–6311, 2006     

In situ nitroxide‐mediated polymerization of styrene promoted by the N‐tert‐butyl‐α‐isopropylnitrone/bpo pair: ESR investigations

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N‐tert‐butyl‐α‐isopropylnitrone as nitroxide precursor is well‐controlled provided that a prereaction between the nitrone and BPO is carried out in suitable conditions prior to polymerization at a higher temperature. Electron spin resonance (ESR) spectroscopy was implemented to probe the nitroxides formed during both steps, that is, the prereaction and polymerization, and to get crucial information regarding the structure of the nitroxides responsible for the polymerization control. ESR studies combined with first principles calculations have evidenced that nitroxides observed during the prereaction in the presence of styrene and during the polymerization steps consist of a mixture of two macronitroxides. One is formed by the addition of a growing polystyrene chain to the nitrone as would be expected. However, the second one results from the addition of a polystyrene chain to tert‐butyl nitroso that is in situ formed presumably by decomposition of the first macronitroxide type. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Polymerization of 1,3‐dienes with functional groups. III. Free‐radical polymerization of N,N‐diethyl‐2‐methylene‐3‐butenamide

Free‐radical homo‐ and copolymerization behavior of N,N‐diethyl‐2‐methylene‐3‐butenamide (DEA) was investigated. When the monomer was heated in bulk at 60 °C for 25 h without initiator, rubbery, solid gel was formed by the thermal polymerization. No such reaction was observed when the polymerization was carried out in 2 mol/L of benzene solution with with 1 mol % of azobisisobutyronitrile (AIBN) as an initiator. The polymerization rate (R_p) equation was R_p ∝ [DEA]^1.1[AIBN]^0.51, and the overall activation energy of polymerization was calculated 84.1 kJ/mol. The microstructure of the resulting polymer was exclusively a 1,4‐structure where both 1,4‐E and 1,4‐Z structures were included. From the product analysis of the telomerization with tert‐butylmercaptan as a telogen, the modes of monomer addition were estimated to be both 1,4‐ and 4,1‐addition. The copolymerizations of this monomer with styrene and/or chloroprene as comonomers were also carried out in benzene solution at 60 °C. In the copolymerization with styrene, the monomer reactivity ratios obtained were r₁ = 5.83 and r₂ = 0.05, and the Q and e values were Q = 8.4 and e = 0.33, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 999–1007, 2004     

Synthesis of poly(vinyl acetate)‐b‐polystyrene and poly(vinyl alcohol)‐b‐polystyrene copolymers by cobalt‐mediated radical polymerization

Well‐defined poly(vinyl acetate) macroinitiators, with the chains thus end‐capped by a cobalt complex, were synthesized by cobalt‐mediated radical polymerization and used to initiate styrene polymerization at 30 °C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)‐b‐polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)‐b‐polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)‐b‐polystyrene copolymers self‐associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 81–89, 2007     

Synthesis of well‐defined multigraft copolymers by a two‐step living radical polymerization with nitroxyl‐functionalized poly(methyl methacrylate)

Novel multigraft copolymers of poly(methyl methacrylate‐graft‐polystyrene) (PMMA‐g‐PS) in which the number of graft PS side chains was varied were prepared by a subsequent two‐step living radical copolymerization approach. A polymerizable 4‐vinylbezenyl 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) monomer (STEMPO), which functioned as both a monomer and a radical trapper, was placed in a low‐temperature atom transfer radical polymerization (60°C) process of methyl methacrylate with ethyl 2‐bromopronionate (EPNBr) as an initiator to gain ethyl pronionate‐capped prepolymers with TEMPO moieties, PMMA‐STEMPOs. The number of TEMPO moieties grafted on the PMMA backbone could be designed by varying STEMPO/EPNBr, for example, the ratios of 1/2, 2/3, or 3/4 gained one, two, or three graft TEMPO moieties, respectively. The resulting prepolymers either as a macromolecular initiator or a trapper copolymerized with styrene in the control of stable free‐radical polymerization at an elevated temperature (120 °C), producing the corresponding multigraft copolymers, PMMA‐g‐PSs. The nitroxyl‐functionalized PMMA prepolymers produced a relatively high initiation efficiency (>0.8) as a result of the stereohindrance and slow diffusion of TEMPO moieties connected on the long PMMA backbone. The polymerization kinetics in two processes showed a living radical polymerization characteristic. The molecular structures of these prepolymers and graft copolymers were well characterized by combining Fourier transform infrared spectroscopy, gel permeation chromatography, chemical element analysis, and ¹H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1876–1884, 2002     

Synthesis and kinetic analysis of DPE controlled radical polymerization of MMA

The 1,1‐diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k₂, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10^?5 s^?1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Novel miktofunctional initiator for the preparation of an ABC‐type miktoarm star polymer via a combination of controlled polymerization techniques

An ABC‐type miktoarm star polymer was prepared with a core‐out method via a combination of ring‐opening polymerization (ROP), stable free‐radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, ROP of ϵ‐caprolactone was carried out with a miktofunctional initiator, 2‐(2‐bromo‐2‐methyl‐propionyloxymethyl)‐3‐hydroxy‐2‐methyl‐propionic acid 2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yl oxy)‐ethyl ester, at 110 °C. Second, previously obtained poly(ϵ‐caprolactone) (PCL) was used as a macroinitiator for SFRP of styrene at 125 °C. As a third step, this PCL–polystyrene (PSt) precursor with a bromine functionality in the core was used as a macroinitiator for ATRP of tert‐butyl acrylate in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 100 °C. This produced an ABC‐type miktoarm star polymer [PCL–PSt–poly(tert‐butyl acrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.37). The obtained polymers were characterized with gel permeation chromatography and ¹H NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4228–4236, 2004     

Acrylonitrile‐containing polymers via a combination of metal‐catalyzed living radical and nitroxide‐mediated free‐radical polymerization routes

2‐Phenyl‐2‐[(2,2,6,6‐tetramethylpiperidino)oxy] ethyl 2‐bromopropanoate was successfully used as an initiator in consecutive living radical polymerization routes, such as metal‐catalyzed living radical polymerization and nitroxide‐mediated free‐radical polymerization, to produce various types of acrylonitrile‐containing polymers, such as styrene–acrylonitrile, polystyrene‐b‐styrene–acrylonitrile, polystyrene‐b‐poly(n‐butyl acrylate)‐b‐polyacrylonitrile, and polystyrene‐b‐polyacrylonitrile. The kinetic data were obtained for the metal‐catalyzed living radical polymerization of styrene–acrylonitrile. All the obtained polymers were characterized with ¹H NMR, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3374–3381, 2006     

Block and star block copolymers by mechanism transformation. I. Synthesis of PTHF‐PSt‐PTHF by the transformation of ATRP into CROP

Polystyrene (PSt) with end‐terminal bromine (Br‐PSt‐Br) was synthesized by the atom transfer radical polymerization of styrene with the difunctional initiator 1,2‐bis(2′‐bromobutyryloxy)ethane in combination with CuBr and bipyridine. The Br‐PSt‐Br reacted with silver perchlorate at −78 °C, and the resulting macromolecular initiator was used to initiate the polymerization of tetrahydrofuran. Triblock poly(tetrahydrofuran)‐polystyrene‐poly(tetrahydrofuran) (PTHF‐PSt‐PTHF) diol was obtained after propagation at −15 °C. The conversion of the polymerization was measured by gas chromatography. The structures of the triblock copolymer PTHF‐PSt‐PTHF diol were characterized by ¹H NMR and gel permeation chromatography. The mechanism of cationic ring‐opening polymerization is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 337–344, 2000     

Radical and cationic polymerizations of 3‐ethyl‐3‐methacryloyloxymethyloxetane

3‐Ethyl‐3‐methacryloyloxymethyloxetane (EMO) was easily polymerized by dimethyl 2,2′‐azobisisobutyrate (MAIB) as the radical initiator through the opening of the vinyl group. The initial polymerization rate (R_p) at 50 °C in benzene was given by R_p = k[MAIB]^0.55 [EMO]^1.2. The overall activation energy of the polymerization was estimated to be 87 kJ/mol. The number‐average molecular weight (M?_n) of the resulting poly(EMO)s was in the range of 1–3.3 × 10⁵. The polymerization system was found to involve electron spin resonance (ESR) observable propagating poly(EMO) radicals under practical polymerization conditions. ESR‐determined rate constants of propagation (k_p) and termination (k_t) at 60 °C are 120 and 2.41 × 10⁵ L/mol s, respectively—much lower than those of the usual methacrylate esters such as methyl methacrylate and glycidyl methacrylate. The radical copolymerization of EMO (M₁) with styrene (M₂) at 60 °C gave the following copolymerization parameters: r₁ = 0.53, r₂ = 0.43, Q₁ = 0.87, and e₁ = +0.42. EMO was also observed to be polymerized by BF₃OEt₂ as the cationic initiator through the opening of the oxetane ring. The M?_n of the resulting polymer was in the range of 650–3100. The cationic polymerization of radically formed poly(EMO) provided a crosslinked polymer showing distinguishably different thermal behaviors from those of the radical and cationic poly(EMO)s. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1269–1279, 2001     

Synthesis and characterization of well‐defined poly(2‐hydroxyethyl methacrylate‐co‐styrene)‐graft‐poly(ε‐caprolactone) by sequential controlled polymerization

A new graft copolymer, poly(2‐hydroxyethyl methacrylate‐co‐styrene) ‐graft‐poly(?‐caprolactone), was prepared by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with coordination‐insertion ring‐opening polymerization (ROP). The copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 60 °C in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDTB) using AIBN as initiator. The molecular weight of poly (2‐hydroxyethyl methacrylate‐co‐styrene) [poly(HEMA‐co‐St)] increased with the monomer conversion, and the molecular weight distribution was in the range of 1.09 ～ 1.39. The ring‐opening polymerization (ROP) of ?‐caprolactone was then initiated by the hydroxyl groups of the poly(HEMA‐co‐St) precursors in the presence of stannous octoate (Sn(Oct)₂). GPC and ¹H‐NMR data demonstrated the polymerization courses are under control, and nearly all hydroxyl groups took part in the initiation. The efficiency of grafting was very high. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5523–5529, 2004     

Synthesis and radical polymerization behavior of bifunctional vinyl monomer derived from N‐vinylacetamide and p‐chloromethylstyrene

The radical polymerization of N‐(p‐vinylbenzyl)‐N‐vinylacetamide ( 1 ) prepared by the reaction of N‐vinylacetamide with p‐chloromethylstyrene was carried out by using radical initiators such as AIBN or BPO in benzene, chlorobenzene, or bulk. As a result, poly 1 was successfully isolated by dialysis (yield, 10–36%). The crosslinking reaction of poly 1 was carried out at 60–100 °C for 8 h. By using a radical initiator such as AIBN or BPO (3 mol %), the crosslinking reaction proceeded (yield, 63–79%). Moreover, the crosslinking reaction of poly 1 proceeded at 100 °C without a radical initiator in 50% yield. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2714–2723, 2006     

Polymerization of o‐quinodimethanes. IV. Radical polymerization of 1‐cyano‐o‐quinodimethane in the presence of TEMPO

The radical polymerization behavior of 1‐cyano‐o‐quinodimethane generated by thermal isomerization of 1‐cyanobenzocyclobutene in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxide (TEMPO) and the block copolymerization of the obtained polymer with styrene are described. The radical polymerization of 1‐cyanobenzocyclobutene was carried out in a sealed tube at temperatures ranging from 100 to 150 °C for 24 h in the presence of di‐tert‐butyl peroxide (DTBP) as a radical initiator and two equivalents of TEMPO as a trapping agent of the propagation end radical to obtain hexane‐insoluble polymer above 130 °C. Polymerization at 150 °C with 5 mol % of DTBP in the presence of TEMPO resulted in the polymer having a number‐average molecular weight (M_n ) of 2900 in 63% yield. The structure of the obtained polymer was confirmed as the ring‐opened polymer having a TEMPO unit at the terminal end by ¹H NMR, ¹³C NMR, and IR analyses. Then, block copolymerization of the obtained polymer with styrene was carried out at 140 °C for 72 h to give the corresponding block copolymer in 82% yield, in which the unimodal GPC curve was shifted to a higher molecular weight region. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3434–3439, 2000     

Polymerization of styrene with tetramethylthiuram disulfide as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy

The bulk polymerization of styrene was investigated with tetramethylthiuram disulfide (TMTD) as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) at 123 °C. The polymerization proceeded in a controlled/living way; that is, the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with conversion. The molecular weights of the polymers obtained were close to the theoretical values, and the molecular weight distributions were relatively low (weight‐average molecular weight/number‐average molecular weight = 1.1–1.3). The rate of polymerization with TMTD as an initiator was faster than that with benzoyl peroxide, and the rate was independent of the initial concentration of TMTD in the presence of TEMPO. The obtained polystyrene was functionalized with ultraviolet‐light‐sensitive ? SC(S)N(CH₃)₂ groups, which was characterized with ¹H NMR spectroscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 543–551, 2005     

Atom transfer radical polymerization of styrene using the novel initiator ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate

The atom transfer radical polymerizations (ATRPs) of styrene initiated by a novel initiator, ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate (EDDCB), in both bulk and solution were successfully carried out in the presence of copper(I) bromide (CuBr) and N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 115 °C. The polymerization rate was first‐order with respect to the monomer concentration, and the molecular weights of the obtained polymers increased linearly with the monomer conversions with very narrow molecular weight distributions (as low as 1.17) up to higher conversions in both bulk and solution. The polymerization rate was influenced by various solvents in different degrees in the order of cyclohexanone > dimethylformamide > toluene. The molecular weight distributions of the produced polymers in cyclohexanone were higher than those in dimethylformamide and toluene. The results of ¹H NMR analysis and chain extension confirmed that well‐defined polystyrene bearing a photo‐labile N,N‐(diethylamino)dithiocarbamoyl group was obtained via ATRP of styrene with EDDCB as an initiator. The polymerization mechanism for this novel initiation system is a common ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 32–41, 2006     

Preparation of a copolymer of methyl methacrylate and 2‐(dimethylamino)ethyl methacrylate with pendant 4‐benzyloxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy and its initiation of the graft polymerization of styrene by a controlled radical mechanism

The macroinitiator of a copolymer (PMD_BTM) of methyl methacrylate (MMA) and 2‐(dimethylamino)ethyl methacrylate (DAMA) with 4‐benzyloxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (BTEMPO) pendant groups was prepared by the photochemical reaction of tertiary amine groups of the copolymer with benzophenone in the presence of BTEMPO. The radical copolymerization of MMA and DAMA was carried out first with azo‐bis‐isobutyronitrile (AIBN) as an initiator; then, the dimethylamine groups of the copolymer constituted a charge‐transfer complex with benzophenone under UV irradiation, and the methylene of ternary amine and diphenyl methanol radicals were produced. The former was capped by BTEMPO, and the nitroxide (BTEMPO) was attached to the polymeric backbone. The amount of pendant BTEMPO on PMD_BTM was measured by ¹H NMR. PMD_BTM initiated the graft polymerization of styrene via a controlled radical mechanism, and the molecular weight of the PMD‐g‐polystyrene increased with the polymerization time. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 604–612, 2001     

The kinetics of enhanced spin capturing polymerization: Influence of the nitrone structure

Several nitrones and one nitroso compound have been evaluated for their ability to control the molecular weight of polystyrene via the recently introduced radical polymerization method of enhanced spin capturing polymerization (ESCP). In this technique, molecular weight control is achieved (at ambient or slightly elevated temperatures) via the reaction of a growing radical chain with a nitrone forming a macronitroxide. These nitroxides subsequently react rapidly and irreversibly with propagating macroradicals forming polymer of a certain chain length, which depends on the nitrone concentration in the system. Via evaluation of the resulting number‐average molecular weight, M_n, at low conversions, the addition rate coefficient of the growing radicals onto the different nitrones is determined and activation energies are obtained. For the nitrones N‐tert‐butyl‐α‐phenylnitrone (PBN), N‐methyl‐α‐phenylnitrone (PMN), and N‐methyl‐α‐(4‐bromo‐phenyl) nitrone (pB‐PMN), addition rate coefficients, k_ad,macro, in a similar magnitude to the styrene propagation rate coefficient, k_p, are found with spin capturing constants C_SC (with C_SC = k_ad,macro/k_p) ranging from 1 to 13 depending on the nitrone and on temperature. Activation energies between 23.6 and 27.7 kJ mol⁻¹ were deduced for k_ad,macro, congruent with a decreasing C_SC with increasing temperature. Almost constant M_n over up to high monomer to polymer conversions is found when C_SC is close to unity, while increasing molecular weights can be observed when the C_SC is large. From temperatures of 100 °C onward, reversible cleavage of the alkoxyamine group can occur, superimposing a reversible activation/deactivation mechanism onto the ESCP system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1098–1107, 2009     

Synthesis of poly(methyl methacrylate)‐b‐polystyrene containing a crown ether unit at the junction point via combination of atom transfer radical polymerization and nitroxide mediated radical polymerization routes

Poly(methyl methacrylate)‐b‐polystyrene (PMMA‐b‐PS) containing a benzo‐15‐crown‐5 unit at the junction point was prepared by combining atom transfer radical polymerization and nitroxide‐mediated radical polymerization. For this purpose, 6,7,9,10,12,13,15,16‐octahydro‐5,8,11,14,17‐pentaoxa‐benzocyclopentadecene‐2‐carboxylic acid 3‐(2‐bromo‐2‐methyl‐propionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yloxy)‐ethoxycarbonyl]‐propyl ester ( 3 ) was synthesized and used as an initiator in atom transfer radical polymerization of methyl methacrylate in the presence of CuCl and pentamethyldiethylenetriamine at 60°C. A linear behavior was observed in both plots of ln([M]₀/[M]) versus time and M_n,_GPC versus conversion indicating that the polymerization proceeded in a controlled/living manner. Thus obtained PMMA precursor was used as a macroinitiator in nitroxide‐mediated radical polymerization of styrene (St) at 125°C to give well‐defined PMMA‐b‐PS with crown ether per chain. Kinetic data were also obtained for copolymerization. Moreover, potassium picrate (K⁺ picrate) complexation of 3 and PMMA‐b‐PS copolymer was studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3242–3249, 2006