Relevance of a prereaction for the in situ NMP of styrene using the C‐Phenyl‐N‐tert‐butylnitrone/2,2′‐azobis(isobutyronitrile) pair

In this article, we compare two routes for carrying out in situ nitroxide‐mediated polymerization of styrene using the C‐phenyl‐N‐tert‐butylnitrone (PBN)/2,2′‐azobis(isobutyronitrile) (AIBN) pair to identify the best one for an optimal control. One route consists in adding PBN to the radical polymerization of styrene, while the other approach deals with a prereaction between the nitrone and the free radical initiator prior to the addition of the monomer and the polymerization. The combination of ESR and kinetics studies allowed demonstrating that when the polymerization of styrene is initiated by AIBN in the presence of enough PBN at 110 °C, fast decomposition of AIBN is responsible for the accumulation of dead polymer chains at the early stages of the polymerization, in combination with controlled polystyrene chains. On the other hand, PBN acts as a terminating agent at 70 °C with the formation of a polystyrene end‐capped by an alkoxyamine, which is not labile at this temperature but that can be reactivated and chain‐extended by increasing the temperature. Finally, the radical polymerization of styrene is better controlled when the nitrone/initiator pair is prereacted at 85 °C for 4 h in toluene before styrene is added and polymerized at 110 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1085–1097, 2009     

End‐group fidelity in nitroxide‐mediated living free‐radical polymerizations

In this study, new nitroxides based on the 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐oxy skeleton were used to examine chain‐end control during the preparation of polystyrene and poly(t‐butyl acrylate) under living free‐radical conditions. Alkoxyamine‐based initiators with a chromophore attached to either the initiating fragment or the mediating nitroxide fragment were prepared, and the extent of the incorporation of the chromophores at either the initiating end or the propagating chain end was determined. In contrast to 2,2,6,6‐tetramethyl piperidinoxy (TEMPO), the incorporation of the initiating and terminating fragment into the polymer chain was extremely high. For both poly(t‐butyl acrylate) and polystyrene with molecular weights less than or equal to 70,000, incorporations at the initiating end of greater than 97% were observed. At the terminating chain end, incorporations of greater than 95% were obtained for molecular weights less than or equal to 50,000. The level of incorporation tended to decrease slightly at higher molecular weights because of the loss of the alkoxyamine propagating unit, which had important consequences for block copolymer formation. These results clearly show that these new α‐H nitroxides could control the polymerization of vinyl monomers such as styrene and t‐butyl acrylate to an extremely high degree, comparable to anionic and atom transfer radical polymerization procedures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4749–4763, 2000     

Synthesis of star polymers via nitroxide mediated free‐radical polymerization: A “core‐first” approach using resorcinarene‐based alkoxyamine initiators

The synthesis of new octafunctional alkoxyamine initiators for nitroxide‐mediated radical polymerization (NMRP), by the derivatization of resorcinarene with nitroxide free radicals viz TEMPO and a freshly prepared phosphonylated nitroxide, is described. The efficiency of these initiators toward the controlled radical polymerization of styrene and tert‐butyl acrylate is investigated in detail. Linear analogues of these multifunctional initiators were also prepared to compare and evaluate their initiation efficiency. The favorable conditions for polymerization were optimized by varying the concentration of initiators and free nitroxides, reaction conditions, etc., to obtain well‐defined star polymers. Star polystyrene thus obtained were further used as macro‐initiator for the block copolymerization with tert‐butyl acrylate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5559–5572, 2007     

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     

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     

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     

A styryl tipno‐based nitroxide as efficient mediator for the synthesis of multiblock polystyrenes and well‐grafted polymers

The chloromagnesium exchange of 4‐chlorostyrene provides an easy access to a new versatile polymerizable 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide (TIPNO)‐based nitroxide. Indeed, first, its alkoxyamine based on the α‐methyl benzyl radical fragment efficiently mediates the polymerization of styrene (respectively n‐butyl acrylate) to yield branched polystyrene [respectively poly(n‐butyl acrylate)] with alkoxyamine function as branch point and well‐defined branches. Second, the self‐condensing of this polymerizable nitroxide by manganese coupling affords a mixture of oligomeric linear polyalkoxyamines. Polymerization of styrene mediated with these polyalkoxyamines gives multiblock polystyrenes with alkoxyamine group as linker between polystyrene blocks and exhibits the following features: the synthesis of the polystyrene blocks is controlled as their average molecular weight M_n(block) increases linearly with conversion and their average dispersity M_w/M_n(block) decreases with it. At a given temperature, the molecular weight and the dispersity of the polyalkoxyamines weakly impact M_n(block) and M_w/M_n(block). In contrast, the molecular weight of the multiblock polystyrene increases linearly with conversion until reaching a constant value. The number of block is independent of the molecular weight of the polyalkoxyamines. These unusual results can be explained by the fact that during polymerization, mediating TIPNO‐based polymeric nitroxides with different lengths are generated and are exchanged. Finally the dispersity of the multiblock polystyrene is quite broad and lies between 1.7 and 2.8. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Controlled/living polymerization of methyl methacrylate using new sterically hindered imidazoline nitroxides prepared via intramolecular 1,3‐dipolar cycloaddition reaction

A series of imidazoline nitroxides with bulky spirocyclic moieties at the positions 2 or 5 of imidazole ring were synthesized using intramolecular 1,3‐dipolar cycloaddition in 2H‐imidazole 1‐oxides or 4H‐imidazole 3‐oxides with pent‐4‐enyl groups followed by isoxazolidine ring opening and oxidation. Capability of the nitroxides to control radical polymerization of methyl methacrylate (MMA) and styrene was investigated. For that purpose, alkoxyamines were synthesized from the aforementioned nitroxides and tert‐butyl α‐bromoisobutyrate. Homolysis rate constants of the alkoxyamines were measured and possible contributions of side reactions were quantified. Nitroxide‐mediated polymerization of styrene and MMA was studied using the alkoxyamines as initiators. MMA polymerization was found to proceed in controlled regime up to 55% of monomer conversion and the polymer obtained was able to reinitiate the polymerization of styrene. Quota of “living” chains estimated to reach 90%. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 929–943     

Suppressing the long‐chain branching in the synthesis of poly(styrene‐b‐butyl acrylate‐b‐styrene) in RAFT emulsion polymerization by tuning the interfacial properties

Reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization is becoming an important technique to synthesize the latex of block copolymers. A previous study showed that in the synthesis of polystyrene‐b‐poly(butyl acrylate)‐b‐polystyrene triblock copolymer via RAFT emulsion polymerization using amphiphilic oligo(acrylic acid‐styrene) macroRAFT as surfactant and mediator, the molecular weight distribution could be much broadened to PDI higher than 2. In this study, an in‐depth investigation was performed to decrease PDI. It was found that long‐chain branches could be formed in the synthesis of triblock block copolymer, leading to the appearance of a higher molecular weight shoulder in the GPC curve of the final product. The lower neutralization degree of acrylic acid (AA) units on the macroRAFT and shorter AA chains would help to suppress the formation the long‐chain branches, leading to PDI around 1.5. It is evidenced that the successful suppression is due to the promotion of radical entry as a result of decreased interfacial transport impedance. It is also evidenced that the presence of styrene during the polymerization of butyl acrylate could promote the formation of long chain branches. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1464–1473     

Synthesis of graft copolymers with “V‐shaped” and “Y‐shaped” side chains via controlled radical and anionic polymerizations

A combination of nitroxide‐mediated radical polymerization and living anionic polymerization was used to synthesize a series of well‐defined graft (co)polymers with “V‐shaped” and “Y‐shaped” branches. The polymer main chain is a copolymer of styrene and p‐chloromethylstyrene (PS‐co‐PCMS) prepared via nitroxide‐mediated radical polymerization. The V‐shaped branches were prepared through coupling reaction of polystyrene macromonomer, carrying 1,1‐diphenylethylene terminus, with polystyryllithium or polyisoprenyllithium. The Y‐shaped branches were prepared throughfurther polymerization initiated by the V‐shaped anions. The obtained branches, carrying a living anion at the middle (V‐shaped) or at the end of the third segment (Y‐shaped), were coupled in situ with pendent benzyl chloride of PS‐co‐PCMS to form the target graft (co)polymers. The purified graft (co)polymers were analyzed by size exclusion chromatography equipped with a multiangle light scattering detector and a viscometer. The result shows that the viscosities and radii of gyration of the branched polymers are remarkably smaller than those of linear polystyrene. In addition, V‐shaped product adopts a more compact conformation in dilute solution than the Y‐shaped analogy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4013–4025, 2007     

New 7‐membered diazepanone alkoxyamines for nitroxide‐mediated radical polymerization

The synthesis of new 7‐membered diazepanone alkoxyamines [2,2,7,7‐tetramethyl‐1‐(1‐phenyl‐ethoxy)‐[1,4]diazepan‐5‐one ( 3 ) and 2,7‐diethyl‐2,3,7‐trimethyl‐1‐(1‐phenyl‐ethoxy)‐[1,4]diazepan‐5‐one ( 8 )] through the Beckmann rearrangement of piperidin‐4‐one alkoxyamines was developed. Both 3 and 8 were evaluated as initiators and regulators for the nitroxide‐mediated radical polymerization of styrene and n‐butyl acrylate. 8 , a sterically highly hindered alkoxyamine readily available as a crystalline solid, allowed the fast and controlled polymerization and preparation of polymers with low polydispersity indices (1.2–1.4) up to a degree of polymerization of about 100. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3332–3341, 2004     

Optimization of the nitroxide‐mediated radical polymerization conditions for styrene and tert‐butyl acrylate in an automated parallel synthesizer

Automated parallel synthesizers provide fast and comparable screening of different polymerization parameters under similar conditions. In addition, these robotic systems eliminate handling errors, which may affect the results of a kinetic experiment more than the effect of an important parameter. The polymerization temperature and N,N‐tert‐butyl‐N‐[1′‐diethylphosphono‐2,2′‐dimethylpropyl]nitroxide concentration were optimized for the homopolymerization of both styrene and tert‐butyl acrylate to improve the control over the polymerization while reasonable polymerization rates were retained. Subsequently, polystyrene and poly(tert‐butyl acrylate) macro initiators were synthesized according to the knowledge obtained from the screening results. These macroinitiators were used for the preparation of block copolymers consisting of styrene and tert‐butyl acrylate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6202–6213, 2006     

Preparation of a copolymer of methyl methacrylate with a new monomer, 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate,and its initiation of the graft copolymerization of styrene with a controlled radical mechanism

A copolymer [P(MMA‐co‐TBPM)] was prepared by the radical polymerization of methyl methacrylate (MMA) and 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate (TBPM) with azobisisobutyronitrile as an initiator. TBPM was a new monomer containing an activated ester. Both the copolymer and TBPM were characterized with NMR, IR, and gel permeation chromatography in detail. It was confirmed that P(MMA‐co‐TBPM) could initiate the graft polymerization of styrene by the cleavage of the activated ester of the TBPM segment. This process was controllable, and the molecular weight of the graft chain of polystyrene increased with the increment of conversion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4398–4403, 2002     

Rapid additive‐free TEMPO‐mediated stable free radical polymerizations of styrene

The stable free radical polymerization (SFRP) of styrene, initiated with benzoyl peroxide in the presence of TEMPO, under bulk conditions, is demonstrated to proceed rapidly without the need for any rate enhancing additives such as camphorsulfonic acid, 2‐fluoro‐1‐methyl pyridinium p‐toluenesulfonate, or acetic anhydride. Monomer conversions as high as 70% can be achieved in 5 h or less while maintaining polydispersity indexes of 1.15. These results stand in stark contrast to earlier reactions that required 70 h to achieve similar conversions. This study demonstrates that the single largest factor governing the rates of polymerization is the molar concentration of excess TEMPO remaining in solution after initiation. A reduction in the TEMPO to BPO ratio is required when large amounts of BPO are used to target low molecular weight polystyrenes. However, when a lower molar amount of BPO is used to obtain high molecular weight polystyrenes, a higher TEMPO to BPO ratio is required. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5487–5493, 2007     

Nitroxide decomposition: Implications toward nitroxide design for applications in living free‐radical polymerization

Nitroxides bearing an α‐hydrogen decompose upon heating in a bimolecular reaction. A new mechanism is proposed for the decomposition of t‐butylisopropylphenyl nitroxide (TIPNO) involving the formation of a head‐to‐tail dimer, single electron transfer to form an oxammonium salt, epimerization to the corresponding nitrone, and elimination to form a conjugated oxime. This mechanism may provide insights into designing new nitroxides for use in controlled polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 697–717, 2006     

Preparation and characterization of optically active polystyrene via a chiral nitroxide‐mediated polymerization

2,2,6,6‐Tetramethyl‐4‐[d‐(+)‐10‐camphorsulfonyl]‐1‐piperidinyloxy was synthesized and used as a chiral nitroxide for the bulk polymerizations of styrene initiated with benzoyl peroxide (BPO), tetraethylthiuram disulfide (TETD), and thermal initiation. The results showed that the polymerizations proceeded in a controlled/living way; that is, the kinetics presented approximately first‐order plots, and the number‐average molecular weights of the polymers with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight) increased with the monomer conversion linearly. The molecular weight distributions in the case of thermal initiation were narrower than those in the case of BPO and TETD, whereas the polymerization rate with BPO or TETD as an initiator was obviously faster than that with thermal initiation. In addition, successful chain‐extension reactions were carried out, and the structures of the obtained polymers were characterized by gel permeation chromatography and ¹H NMR. The specific rotations of the polymers were also measured by polarimetric analysis. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1522–1528, 2006     

One‐pot synthesis of heterograft copolymers via “graft onto” by atom transfer nitroxide radical coupling chemistry

Heterograft copolymers poly(4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐co‐ ethylene oxide)‐graft‐polystyrene and poly(tert‐butyl acrylate) (poly (GTEMPO‐co‐EO)‐g‐PS/PtBA) were synthesized in one‐pot by atom transfer nitroxide radical coupling (ATNRC) reaction via “graft onto.” The main chain was prepared by the anionic ring‐opening copolymerization of ethylene oxide (EO) and 4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (GTEMPO) first, then the polystyrene and poly (tert‐butyl acrylate) with bromine end (PS‐Br, PtBA‐Br) were prepared by atom transfer radical polymerization (ATRP). When three of them were mixed each other in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at 90 °C, the formed secondary carbon radicals at the PS and PtBA chain ends were quickly trapped by nitroxide radicals on poly(GTEMPO‐co‐EO). The heterograft copolymers were well defined by ¹H NMR, size exclusion chromatography, fourier transform infrared, and differential scanning calorimetry in detail. It was found that the density of GTEMPO groups on main chain poly(GTEMPO‐co‐EO), the molecular weights of PS/PtBA side chains, and the structure of macroradicals can exert the great effects on the graft efficiency. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6770–6779, 2008     

Synthesis and characterization of amphiphilic heterograft copolymers with PAA and PS side chains via “Grafting from” approach

The amphiphilic heterograft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐(poly(acrylic acid)/polystyrene) (P(MMA‐co‐BIEM)‐g‐(PAA/PS)) were synthesized successfully by the combination of single electron transfer‐living radical polymerization (SET‐LRP), single electron transfer‐nitroxide radical coupling (SET‐NRC), atom transfer radical polymerization (ATRP), and nitroxide‐mediated polymerization (NMP) via the “grafting from” approach. First, the linear polymer backbones poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate) (P(MMA‐co‐BIEM)) were prepared by ATRP of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) and subsequent esterification of the hydroxyl groups of the HEMA units with 2‐bromoisobutyryl bromide. Then the graft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐poly(t‐butyl acrylate) (P(MMA‐co‐BIEM)‐g‐PtBA) were prepared by SET‐LRP of t‐butyl acrylate (tBA) at room temperature in the presence of 2,2,6,6‐tetramethylpiperidin‐1‐yloxyl (TEMPO), where the capping efficiency of TEMPO was so high that nearly every TEMPO trapped one polymer radicals formed by SET. Finally, the formed alkoxyamines via SET‐NRC in the main chain were used to initiate NMP of styrene and following selectively cleavage of t‐butyl esters of the PtBA side chains afforded the amphiphilic heterograft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐(poly(t‐butyl acrylate)/polystyrene) (P(MMA‐co–BIEM)‐g‐(PtBA/PS)). The self‐assembly behaviors of the amphiphilic heterograft copolymers P(MMA‐co–BIEM)‐g‐(PAA/PS) in aqueous solution were investigated by AFM and DLS, and the results demonstrated that the morphologies of the formed micelles were dependent on the grafting density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Nitroxide‐mediated controlled statistical copolymerizations of N‐isopropylacrylamide with N‐tert‐butylacrylamide

The copolymerization of N‐isopropylacrylamide (NIPAM) and N‐tert‐butylacrylamide (TBAM) via conventional radical polymerization and nitroxide‐mediated polymerization (NMP) with N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)]nitroxide (SG1) was investigated. The monomer reactivity ratios were determined to be 0.58 and 1.00 for NIPAM and TBAM, respectively. The reactivities were approximately the same at 120 and 60 °C in N,N‐dimethylformamide (DMF) and toluene, respectively, for the conventional copolymerizations and in DMF at 120 °C for NMP. Controlled/living characteristics for NMP were achieved with a 2,2′‐azobisisobutyronitrile/SG1 bimolecular system and a unimolecular polystyrene [poly(STY)]–SG1 macroinitiator in the presence of excess free SG1. Block copolymers of poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide) [poly(NIPAM‐stat‐TBAM)] with styrene {poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide)‐block‐polystyrene [poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)]} were obtained by chain extension of either poly(NIPAM‐stat‐TBAM)–SG1 with styrene or poly(STY)–SG1 with NIPAM/TBAM. A comparison of the number‐average molecular weight calculated from the end‐group content with the number‐average molecular weight measured by gel permeation chromatography for poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)–SG1 indicated that nearly all poly(NIPAM‐stat‐TBAM) chains were capped by SG1 and were thus living. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6410–6418, 2006     

Nonaqueous dispersion polymerization of styrene in methanol with the ionomer block copolymer poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer

The nonaqueous dispersion polymerization of styrene in methanol with poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer was investigated. There was no observable inducing period or autoacceleration in the polymerization process. The conversion increased almost linearly with the polymerization time as high as 80%. The average sizes of the obtained polystyrene particles increased, and the size distributions of the polystyrene particles tended to become narrower, with increasing conversion. The mechanism of the dispersion polymerization in the presence of polyisobutene‐b‐poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)] was nucleation/growth. When the stabilizer/monomer ratio (w/w) was greater than 2.0%, the polystyrene dispersion was stable, and there was no observable polymer particle coagulation taking place during the whole polymerization process. The average diameter of the polymer particles can be mediated through changes in the polymerization conversion, monomer, and stabilizer. Nearly monodispersed polystyrene particles with average diameters of approximately 0.45–2.21 μm were obtained under optimal conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2678–2685, 2004