Simultaneous control of the stereospecificity and molecular weight in the ruthenium‐catalyzed living radical polymerization of methyl and 2‐hydroxyethyl methacrylates and sequential synthesis of stereoblock polymers

The stereospecific living radical polymerizations of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) were achieved with a combination of ruthenium‐catalyzed living radical and solvent‐mediated stereospecific radical polymerizations. Among a series of ruthenium complexes [RuCl₂(PPh₃)₃, Ru(Ind)Cl(PPh₃)₂, and RuCp*Cl(PPh₃)₂], Cp*–ruthenium afforded poly(methyl methacrylate) with highly controlled molecular weights [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.08] and high syndiotacticity (r = 88%) in a fluoroalcohol such as (CF₃)₂C(Ph)OH at 0 °C. On the other hand, a hydroxy‐functionalized monomer, HEMA, was polymerized with RuCp*Cl(PPh₃)₂ in N,N‐dimethylformamide and N,N‐dimethylacetamide (DMA) to give syndiotactic polymers (r = 87–88%) with controlled molecular weights (M_w/M_n = 1.12–1.16). This was the first example of the syndiospecific living radical polymerization of HEMA. A fluoroalcohol [(CF₃)₂C(Ph)OH], which induced the syndiospecific radical polymerization of MMA, reduced the syndiospecificity in the HEMA polymerization to result in more or less atactic polymers (mm/mr/rr = 7.2/40.9/51.9%) with controlled molecular weights in the presence of RuCp*Cl(PPh₃)₂ at 80 °C. A successive living radical polymerization of HEMA in two solvents, first DMA followed by (CF₃)₂C(Ph)OH, resulted in stereoblock poly(2‐hydroxyethyl methacrylate) with syndiotactic–atactic segments. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3609–3615, 2006     

Tacticity control in the radical polymerization of 2,2,2-trifluoroethyl methacrylate with fluoroalcohol

The free-radical polymerization of 2,2,2-trifluoroethyl methacrylate (TEMA) was carried out in fluoroalcohols to achieve stereoregulation. The polymerization reactivity at low temperature and syndiotactic specificity were enhanced by the use of fluoroalcohol as a solvent. The polymer having triad syndiotacticity (rr) of 70% was obtained in perfluoro-t-butyl alcohol. It was noted that the stereochemistry was nearly independent of reaction temperature. The stereoeffect of fluoroalcohols seemed to be due to the hydrogen-bonding interaction between the alcohol and the monomer or growing species. The hydrogen-bonding formation was determined by FTIR. The copolymerization of TEMA with methyl methacrylate (MMA) in hexafluoroisopropanol afforded a copolymer with syndiotactic specificity. By this method, a cladding material for an optical fiber based on poly(methyl methacrylate) (PMMA) with high mechanical strength and low refractive index could be obtained.     

Rare‐earth‐metal‐initiated polymerizations of (meth)acrylates and block copolymerizations of olefins with polar monomers

The organo‐rare‐earth‐metal‐initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C₅Me₅)₂LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (>96%) poly(methyl methacrylate) (PMMA) with a high number‐average molecular weight (M_n > 1000 × 10³) and a very narrow molecular weight distribution [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) < 1.04] quantitatively in a short period. Bridged rare‐earth‐metallocene derivatives were used to perform the block copolymerization of ethylene or 1‐hexene with MMA, methyl acrylate, cyclic carbonate, or ?‐caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (M_n > 500 × 10³, M_w/M_n < 1.1) PMMA was first obtained in 1998 with [(Me₃Si)₃C]₂Yb. Stereocomplexes prepared by the mixing of the resulting syndiotactic and isotactic PMMA revealed improved physical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1955–1959, 2001     

Visible light‐induced controlled radical polymerization of methacrylates with perfluoroalkyl iodide as the initiator in conjugation with a photoredox catalyst fac‐[Ir(ppy)]3

A new visible light‐induced controlled radical polymerization of methacrylate with perfluoro‐1‐iodohexane (CF₃(CF₂)₅I) as the initiator in the presence of a photoredox catalyst (fac‐[Ir(ppy)₃]) was developed. Mechanistically, a photoexcited fac‐[Ir(ppy)₃]* complex reacted with dormant C‐I species to generate the chain propagating radical and Ir^IVI complex, which could be reversibly reduced by the propagating radical. The molecular weight (M_n) and the corresponding distribution index (M_w/M_n = 1.4) were controlled in the polymerization of methyl methacrylate (MMA). For the polymerization of functional monomers, such as glycidyl methacrylate (GMA) and trifluoroethyl methacrylate, their monomer conversions could be up to 96 and 94%, respectively. No polymerization reaction took place without external light stimulation, indicating that the system was an ideal photo “on?off” switchable system. Furthermore, a clean diblock copolymer PMMA‐b‐PGMA was successfully synthesized with PMMA‐I as the macroinitiator. With CF₃(CF₂)₅I as the initiator, short CF₃(CF₂)₅? group tags were introduced on the produced polymer chains. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3283–3291     

Synthesis of star‐shaped copolymers with methyl methacrylate and n‐butyl methacrylate by metal‐catalyzed living radical polymerization: Block and random copolymer arms and microgel cores

Various star‐shaped copolymers of methyl methacrylate (MMA) and n‐butyl methacrylate (nBMA) were synthesized in one pot with RuCl₂(PPh₃)₃‐catalyzed living radical polymerization and subsequent polymer linking reactions with divinyl compounds. Sequential living radical polymerization of nBMA and MMA in that order and vice versa, followed by linking reactions of the living block copolymers with appropriate divinyl compounds, afforded star block copolymers consisting of AB‐ or BA‐type block copolymer arms with controlled lengths and comonomer compositions in high yields (≥90%). The lengths and compositions of each unit varied with the amount of each monomer feed. Star copolymers with random copolymer arms were prepared by the living radical random copolymerization of MMA and nBMA followed by linking reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 633–641, 2002; DOI 10.1002/pola.10145     

Synthesis, Characterization and Application of Benzyl-substituted Cyclopentadienyl lanthanide Complexes as Catalyst Precursors for the Syndiotactic Polymerization of Methyl Methacrylate

Benzyl-substituted cyclopentadienyl lanthanide complexes were synthesized and characterized by elemental analysis, MS and IR spectroscopy. The analytical data point out the formation of monomeric, unsolvated complexes.In conjunction with AI(Et)3 as co-catalyst, the title complexes are efficient catalysts for the syndiotactic polymerization of methyl methacrylate. For the complex (C6HsCH2C5H4)2YCl, under the optimum polymerization conditions(60℃,n(MMA):n(catalyst):n(co-catalyst)=1000:1:10),a predominantly syndiotactic (rr=66%) polymerof high molecular weight (Mη=105000) was obtained.     

High polymerization of methyl methacrylate with organonickel/MMAO systems

A series of nickel complexes, including Ni(acac)₂, (C₅H₅)Ni(η³‐allyl), and [NiMe₄Li₂(THF)₂]₂, that were activated with modified methylaluminoxane (MMAO) exhibited high catalytic activity for the polymerization of methyl methacrylate (MMA) but showed no catalytic activity for the polymerization of ethylene and 1‐olefins. The resulting polymers exhibited rather broad molecular weight distributions and low syndiotacticities. In contrast to these initiators, the metallocene complexes (C₅H₅)₂Ni, (C₅Me₅)₂Ni, (Ind)₂Ni, and (Me₃SiC₅H₄)₂Ni provided narrower molecular weight distributions at 60 °C when these initiator were activated with MMAO. Half‐metallocene complexes such as (C₅H₅)NiCl(PPh₃), (C₅Me₅)NiCl(PPh₃), and (Ind)NiCl(PPh₃) produced poly(methyl methacrylate) (PMMA) with much narrower molecular weight distributions when the polymerization was carried out at 0 °C. Ni[1,3‐(CF₃)₂‐acac]₂ generated PMMA with high syndiotacticity. The NiR(acac)(PPh₃) complexes (R = Me or Et) revealed high selectivity in the polymerization of isoprene that produced 1,2‐/3,4‐polymer at 0 °C exclusively, whereas the polymerization at 60 °C resulted in the formation of cis‐1,4‐rich polymers. The polymerization of ethylene with Ni(1,3‐tBu₂‐acac)₂ and Ni[1,3‐(CF₃)₂‐acac]₂ generated oligo‐ethylene with moderate catalytic activity, whereas the reaction of ethylene with Ni(acac)₂/MMAO produced high molecular weight polyethylene. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4764–4775, 2000     

Ruthenium‐catalyzed fast living radical polymerization of methyl methacrylate: The R?Cl/Ru(Ind)Cl(PPh3)2/n‐Bu2NH initiating system

A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)₂? Cl/Ru(Ind)Cl(PPh₃)₂ initiating system in the presence of n‐Bu₂NH as an additive [where (MMA)₂? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (M_n's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (M_n ～ 10⁵) and narrow MWD (M_w/M_n ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu₃N, whereas n‐BuNH₂ resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148     

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (M_n) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured M_n's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr₂) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]₀/[methyl α‐bromoisobutyrate]₀/[CuBr]₀/[CuBr₂]₀/[Me₆TREN]₀ = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of Cu^IBr/Me₆TREN in HFIP, there were [Cu(Me₆TREN)Br]⁺ and [Cu(Me₆TREN)OCH(CF₃)₂]⁺, indicating that HFIP should coordinate to the Cu^I/Me₆TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006     

Polymerization of methyl methacrylate by metallocene imido complexes and tris(pentafluorophenyl)alane

The polymerization of methyl methacrylate (MMA) was investigated with tris(pentafluorophenyl)alane [Al(C₆F₅)₃] and four metallocene imido complexes that varied in the complex symmetry/chirality, metal, and R group in the ?NR moiety, as well as a zirconocene enolate preformed from the imido zirconocene and MMA. This study examined four aspects of MMA polymerization: the effects of the metallocene imido complex structure on the polymerization activity and polymer tacticity, the degree of polymerization control, the elementary reactions of the imido complex with Al(C₆F₅)₃ and MMA, and the polymerization kinetics and mechanism. There was no effect of the imido complex symmetry/chirality on the polymerization stereochemistry; the polymerization followed Bernoullian statistics, producing syndiotactic poly(methyl methacrylate)s with moderate (～70% [rr]) to high (～91% [rr]) syndiotacticity, depending on the polymerization temperature. Polymerization control was demonstrated by the number‐average molecular weight, which increased linearly with an increase in the monomer conversion to 100%, and the relatively small and insensitive polydispersity indices (from 1.21 to 1.17) to conversion. The reactions of the zirconocene imido complex with Al(C₆F₅)₃ and MMA produced the parent base‐free imido complex and the [2 + 4] cycloaddition product (i.e., zirconocene enolate), respectively; the latter product reacted with Al(C₆F₅)₃ to generate the active zirconocenium enolaluminate. The MMA polymerization with the metallocene imido complex and the alane proceeded via intermolecular Michael addition of the enolaluminate to the alane‐activated MMA involved in the propagation step. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3132–3142, 2003     

“Living”/controlled free radical polymerization of MMA in the presence of cobalt(II) 2‐ethylhexanoate: A switch from RAFT to ATRP mechanism

A metal complex, cobalt(II) 2‐ethylhexanoate (CEH), was added to the system of thermal‐initiated reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent at 115 °C. The polymerization rate was remarkably enhanced in the presence of CEH in comparison with that in the absence of CEH, and the increase of the CPDN concentration also accelerated the rate of polymerization. The polymerization in the concurrence of CPDN and CEH demonstrated the characters of “living”/controlled free radical polymerization: the number‐average molecular weights (M_n) increasing linearly with monomer conversion, narrow molecular weight distributions (M_w/M_n) and obtained PMMA end‐capped with the CPDN moieties. Meanwhile, CEH can also accelerate the rate of RAFT polymerization of MMA using the PMMA as macro‐RAFT agent instead of CPDN. Similar polymerization profiles were obtained when copper (I) bromide (CuBr)/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine was used instead of CEH. Extensive experiments in the presence of butyl methacrylate, bis(cyclopentadienyl) cobalt(II) and cumyl dithionaphthalenoate were also conducted; similar results as those of MMA/CPDN/CEH system were obtained. A transition of the polymerization mechanism, from RAFT process without CEH addition to atom transfer radical polymerization in the presence of CEH, was possibly responsible for polymerization profiles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5722–5730, 2007     

Silylium dual catalysis in living polymerization of methacrylates via In situ hydrosilylation of monomer

Silylium ions (“R₃Si⁺”) are found to catalyze both 1,4‐hydrosilylation of methyl methacrylate (MMA) with R₃SiH to generate the silyl ketene acetal initiator in situ and subsequent living polymerization of MMA. The living characteristics of the MMA polymerization initiated by R₃SiH (Et₃SiH or Me₂PhSiH) and catalyzed by [Et₃Si(L)]⁺[B(C₆F₅)₄]^– (L = toluene), which have been revealed by four sets of experiments, enabled the synthesis of the polymers with well‐controlled M_n values (identical or nearly identical to the calculated ones), narrow molecular weight distributions (? = 1.05–1.09), and well defined chain structures {H? [MMA]_n? H}. The polymerization is highly efficient too, with quantitative or near quantitative initiation efficiencies (I* = 96–100%). Monitoring of the reaction of MMA + Me₂PhSiH + [Et₃Si(L)]⁺[B(C₆F₅)₄]^– (0.5 mol%) by ¹H NMR provided clear evidence for in situ generation of the corresponding SKA, Me₂C?C(OMe)OSiMe₂Ph, via the proposed “Et₃Si^+”‐catalyzed 1,4‐hydrosilylation of monomer through “frustrated Lewis pair” type activation of the hydrosilane in the form of the isolable silylium‐silane complex, [Et₃Si? H? SiR₃]⁺[B(C₆F₅)₄]^–. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1895–1903     

Methacrylic acid and methyl methacrylate oligomers adsorbed to porous isotactic poly(methyl methacrylate) ultrathin films and mechanistic studies of living template polymerization

Methacrylic acid (MAA), methyl methacrylate (MMA), methacrylamide, and oligomers of MAA and MMA were selected as a model of active radical species in living template polymerization using stereocomplex formation. The adsorption behaviors of the aforementioned model compounds were examined toward porous isotactic‐(it‐) poly(methyl methacrylate) (PMMA) ultrathin films on a quartz crystal microbalance, which was prepared by the extracting of syndiotactic‐(st‐) poly(methacrylic acid) (PMAA) from it‐PMMA/st‐PMAA stereocomplexes. The apparent predominant adsorption of oligomers to monomers was observed in both PMAA and PMMA oligomers, suggesting that the mechanism of template polymerization follows the pick up mechanism. Although vinyl monomers were not incorporated into the porous it‐PMMA ultrathin film, both PMMA and PMAA oligomers were adsorbed at the initial stages. However, adsorbed amounts were limited to about 5 and 15% at 0.1 mol L^?1, respectively, which are much smaller values than corresponding st‐polymers. The results imply that radical coupling reaction is prevented during template polymerization to support the resulting living polymerization. ATR‐IR spectral patterns of oligomer complexes and it‐PMMA slightly changed in both cases, suggesting complex formation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5879–5886, 2008     

Synthesis and characterization of linear ABC triblock copolymer of ethylene oxide,methyl methacrylate,and styrene

A well‐defined linear ABC triblock copolymer of ethylene oxide (EO), methyl methacrylate (MMA), and styrene (St) was prepared by sequential living anionic and photo‐induced charge transfer polymerization (CTP) using p‐aminophenol as parent compound. In the first step, the diblock copolymer of PEO‐b‐PMMA with a protected aniline end group at PEO end was prepared by initiating of phenoxo‐anion the polymerization of EO and MMA successively, then the diblock copolymer of PEO‐b‐PMMA via deprotection of aniline at PEO end constituted a binary initiation system with benzophenone (BP) by charge transfer complex mechanism to initiate the polymerization of St under UV‐irradiation. The GPC and NMR measurements support that in copolymerization, either in the first or second step, neither homopolymer nor side reactions, such as chain transfer or chain termination, was found. The effect of the concentration of PEO_a‐b‐PMMA and St, and the polarity of solvent on the polymerization rate (R_p) of CTP is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 825–833, 1999     

Synthesis of poly(tert‐butyl methacrylate)‐graft‐poly(dimethylsiloxane) graft copolymers via reversible addition‐fragmentation chain transfer polymerization

Well‐defined poly(tert‐butyl methacrylate)‐graft‐poly (dimethylsiloxane) (PtBuMA‐g‐PDMS) graft copolymers were synthesized via reversible addition‐fragmentation chain transfer (RAFT) copolymerization of methacryloyl‐terminated poly (dimethylsiloxane) (PDMS‐MA) with tert‐butyl methacrylate (tBuMA) in ethyl acetate, using 2,2′‐azobis(isobutyronitrile) (AIBN) as the initiator and 2‐cyanoprop‐2‐yl dithiobenzoate as the RAFT agent. The RAFT statistical copolymerization of PDMS‐MA with tBuMA is shown to be azeotropic and the obtained PtBuMA‐g‐PDMS graft copolymers have homogeneously distributed branches because of the similar reactivity of monomers (r_tBuMA ≈ r_PDMS‐MA ≈ 1). By the RAFT block copolymerization of PDMS‐MA with tBuMA, moreover, narrow molecular weight distribution (M_w/M_n < 1.3) PtBuMA‐g‐PDMS graft copolymers with gradient or blocky branch spacing were synthesized. The graft copolymers exhibit the glass transitions corresponding to the PDMS and PtBuMA phase, respectively. However, the arrangement of monomer units in copolymer chains and the length of PtBuMA moieties have important effects on the thermal behavior of PtBuMA‐g‐PDMS graft copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of well‐defined cyclodextrin‐core star polymers

The synthesis of 21‐arm methyl methacrylate (MMA) and styrene star polymers is reported. The copper (I)‐mediated living radical polymerization of MMA was carried out with a cyclodextrin‐core‐based initiator with 21 independent discrete initiation sites: heptakis[2,3,6‐tri‐O‐(2‐bromo‐2‐methylpropionyl]‐β‐cyclodextrin. Living polymerization occurred, providing well‐defined 21‐arm star polymers with predicted molecular weights calculated from the initiator concentration and the consumed monomer as well as low polydispersities [e.g., poly(methyl methacrylate) (PMMA), number‐average molecular weight (M_n) = 55,700, polydispersity index (PDI) = 1.07; M_n = 118,000, PDI = 1.06; polystyrene, M_n = 37,100, PDI = 1.15]. Functional methacrylate monomers containing poly(ethylene glycol), a glucose residue, and a tert‐amine group in the side chain were also polymerized in a similar fashion, leading to hydrophilic star polymers, again with good control over the molecular weight and polydispersity (M_n = 15,000, PDI = 1.03; M_n = 36,500, PDI = 1.14; and M_n = 139,000, PDI = 1.09, respectively). When styrene was used as the monomer, it was difficult to obtain well‐defined polystyrene stars at high molecular weights. This was due to the increased occurrence of side reactions such as star–star coupling and thermal (spontaneous) polymerization; however, low‐polydispersity polymers were achieved at relatively low conversions. Furthermore, a star block copolymer consisting of PMMA and poly(butyl methacrylate) was successfully synthesized with a star PMMA as a macroinitiator (M_n = 104,000, PDI = 1.05). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2206–2214, 2001     

Chain-transfer constant of fluoroalcohols

Chain transfer constants of some fluoroalcohols [HCF₂(CF₂)_n?1CH₂OH, n = 2, 4, 6] in the catalyzed polymerization of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate at 60°C have been evaluated by a method based on degree of polymerization. Since fluoroalcohols are normally nonsolvents for polymers, a homogeneous reaction phase is maintained by carrying out the polymerization in benzene (except in case of acrylonitrile, where no solvent was used). The transfer constants vary, depending on the reactivity as well as the polarity of the radicals, in the following order: vinyl acetate > styrene > methyl methacrylate > acrylonitrile. Of the three fluoroalcohols studied, the transfer constants increase with the increasing value of n. The results have been interpreted in terms of polar structure contribution in the transition state of the transfer reactions.     

Raft polymerization of MMA in the presence of ferrocene: A new way to realize the rate enhancement

Ferrocene (Fe(Cp)₂) was added to a thermal initiation of reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent at 115 °C. It was found that the polymerization was greatly promoted after the addition of Fe(Cp)₂ while retaining the characteristics of a typical RAFT polymerization. It was proposed that the formation of a redox initiation system, in which the poly(methyl methacrylate) peroxide (PMMAP) generated in situ as the oxidizer and Fe(Cp)₂ as the reducer, was possibly the reason for the interesting polymerization phenomenon. Such a redox initiation mechanism was further validated with ascorbic acid (VC) as the reducer instead of Fe(Cp)₂. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3607–3615, 2009     

The synthesis of diene – alkyl methacrylate diblock and heteroarm star copolymers

The synthesis of A₂B₂ heteroarm stars, where A is either polyisoprene (PI) or polybutadiene (PB) and B is either poly(methyl methacrylate) (PMMA) or poly(butyl methacrylate) (PBMA) has been achieved using living anionic polymerization. Following polymerization of the diene in hexane by sec‐BuLi, the solvent was changed to THF and the living chains were linked in pairs – without loss of anionic reactivity – using 1,2‐bis[4‐(1‐phenylethenyl)]ethane (EPEB). Star synthesis was completed by the addition of MMA or BMA monomer at −78°C. The diblocks were prepared by sequential polymerization. The resulting stereochemistries were those of greatest interest from a practical standpoint, i.e., PI or PB with a high 1,4‐content (which is highly elastic) and syndiotactic PMMA (which has a high T_g).     

Synthesis of poly(β‐pinene)‐g‐poly(meth)acrylate by the combination of living cationic polymerization and atom transfer radical polymerization

New graft copolymers of β‐pinene with methyl methacrylate (MMA) or butyl acrylate (BA) were synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). β‐Pinene polymers with predetermined molecular weights and narrow molecular weight distributions (MWDs) were prepared by living cationic polymerization with the 1‐phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl initiating system, and the resultant polymers were brominated quantitatively by N‐bromosuccinamide in the presence of azobisisobutyronitrile, yielding poly(β‐pinene) macroinitiators with different bromine contents (Br/β‐pinene unit molar ratio = 1.0 and 0.5 for macroinitiators a and b , respectively). The macroinitiators, in conjunction with CuBr and 2,2′‐bipyridine, were used to initiate ATRP of BA or MMA. With macroinitiator a or b , the bulk polymerization of BA induced a linear first‐order kinetic plot and gave graft copolymers with controlled molecular weights and MWDs; this indicated the living nature of these polymerizations. The bulk polymerization of MMA initiated with macroinitiator a was completed instantaneously and induced insoluble gel products. However, the controlled polymerization of MMA was achieved with macroinitiator b in toluene and resulted in the desired graft copolymers with controlled molecular weights and MWDs. The structures of the obtained graft copolymers of β‐pinene with (methyl)methacrylate were confirmed by ¹H NMR spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1237–1242, 2003