Synthesis of poly(chloromethylstyrene‐b‐styrene) block copolymers by controlled free‐radical polymerization

The controlled free‐radical polymerization of styrene and chloromethylstyrene monomers in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO) has been studied with the aim of synthesizing block copolymers with well‐defined structures. First, TEMPO‐capped poly(chloromethylstyrene) was prepared. Among several initiating systems [self‐initiation, dicumyl peroxide, and 2,2′‐azobis(isobutyronitrile)], the last offered the best compromise for obtaining a good control of the polymerization and a fast polymerization rate. The rate of the TEMPO‐mediated polymerization of chloromethylstyrene was independent of the initial concentration of TEMPO but unexpectedly higher than the rate of the thermal self‐initiated polymerization of chloromethylstyrene. Transfer reactions to the chloromethyl groups were thought to play an important role in the polymerization kinetics and the polydispersity index of the resulting poly(chloromethylstyrene). Second, this first block was used as a macroinitiator in the polymerization of styrene to obtain the desired poly(chloromethylstyrene‐b‐styrene) block copolymer. The kinetic modeling of the block copolymerization was in good agreement with experimental data. The block copolymers obtained in this work exhibited a low polydispersity index (weight‐average molecular weight/number‐average molecular weight < 1.5) and could be chemically modified with nucleophilic substitution reactions on the benzylic site, opening the way to a great variety of architectures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3845–3854, 2000     

Well‐defined complex macromolecular architectures by anionic polymerization of styrenic single and double homo/miktoarm star‐tailed macromonomers

Styrenic single and double star‐tailed macromonomers were synthesized by selective reaction of living homo/miktoarm stars with the chlorosilane groups of 4‐(chlorodimethylsilyl)‐ and 4‐(dichloromethylsilyl)styrene, respectively. The in situ anionic homopolymerization of macromonomers with sec‐BuLi and copolymerization with butadiene and styrene, led to single/double homo/miktoarm star‐tailed molecular brushes and combs, as well as a block copolymer consisting of a linear polystyrene chain and a double miktoarm (PBd/PS) star‐tailed brush‐like block. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two‐angle laser light scattering, and NMR spectroscopy, revealed the high molecular/compositional homogeneity of all intermediate and final products. These are only a few examples of the plethora of complex architectures possible using the above macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1826–1842, 2008     

Block and star block copolymers by mechanism transformation. II. Synthesis of poly(DOP‐b‐St) by combination of ATRP and CROP

Styrene underwent the ATRP process using an asymmetric difunctional initiator, 2‐hydroxylethyl 2′‐bromobutyrate in combination with CuBr and 2,2′‐bipyridine (bpy). Polystyrene with hydroxyl and bromine groups at each end of the polymer (HO‐PSt‐Br) was obtained, and used as a chain‐transfer agent in the cationic ring‐opening polymerization of 1,3‐dioxepane with triflic acid as initiator. The structures of the polymerization products were analyzed by ¹H NMR and GPC analyses, indicating the formation of block copolymer. The molecular weight distribution of the block copolymer was relatively narrow and the molecular weight of the polyDOP block was high. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 436–443, 2000     

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     

Further Studies on Homo- and Copolymerization of Styrene through Metallocenic Initiator Systems

Summary: Binary metallocene-MAO and ternary diphenylzinc-metallocene-MAO initiator systems have been tested as initiators in the homopolymerization of styrene and also in its copolymerization with several diverse comonomers including substituted styrenes, styrene derivatives, α-olefins and dienes. Various titanocenes and zirconocenes and some exploratory experiment with hafnocene were carried out. The results indicate that titanocenes were more effective than zirconocenes in the homopolymerization of styrene while zirconocenes did better in α-olefin polymerization. It was found that titanocenes generated mainly syndiotactic polystyrene, s-PS, while zirconocenes yielded atactic polystyrene or, depending on the zirconocene, a low percentage of s-PS. For these types of initiators the polymerization process depends largely on the inductive effect of the substituents linked to the benzene ring of styrene and on its position (ortho, meta or para). Substituent multiplicity reduced markedly the effectiveness of these initiator systems. Styrene/isoprene polymerization was also studied using binary zirconocene-MAO initiator systems that yielded low conversions and also low molecular weight polymers.     

Synthesis of highly reactive polyisobutylenes using solvent‐ligated manganese(II) complexes as catalysts

Manganese complexes with benzonitrile ligands were synthesized, characterized, and applied for the preparation of the isobutylene polymerization. Low and medium molecular weight polyisobutylenes containing high amount of exo‐type double bond end groups (70–80%) were successfully prepared using these manganese(II) complexes as catalysts at room temperature. The influence of monomer and catalyst concentration was intensively analyzed for achieving high monomer conversion and high exo double bond content of the products. Details on end group distribution in the products and development of the exo‐type end group content with reaction time were evaluated by ¹H NMR. The catalysts are also active for the homopolymerization of styrene and the copolymerization of isobutylene and styrene. The highly reactive polyisobutylene products obtained by these manganese complexes show features similar to products obtained by conventional cationic polymerization, but the polymerization characteristics clearly deviate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5636–5648, 2007     

Block copolymers based on 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone by RAFT polymerization: Experimental and computational studies

The ability of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2‐cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS‐b‐PVDM and PMA‐b‐PVDM well‐defined block copolymers can be prepared either by polymerization of VDM from PS‐ and PMA‐macroCTAs, respectively, or polymerization of S and MA from a PVDM‐macroCTA. In contrast, PMMA‐b‐PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Preparation of novel macromonomers and study of their polymerization

Novel macromonomers of polystyrene and poly(tert‐butyl acrylate) containing a methacryloyl group as a polymerizable unit and two chains of the same length were prepared in two steps: the synthesis of the precursors through the atom transfer radical polymerization of styrene and tert‐butyl acrylate initiated by 1‐hydroxymethyl‐1,1‐di[(2‐bromoisobutyryloxy)methyl] ethane and the esterification of the hydroxyl group in the precursors with methacryloyl chloride. The molecular weight and polydispersity of the macromonomers were controllable because of the living nature of the atom transfer radical polymerization. Gel permeation chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and hydrolysis confirmed the structure of the novel macromonomers. The homopolymerization and copolymerization of the macromonomers were investigated to prepare branched copolymers in which two chains were grafted from every repeating unit. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3887–3896, 2004     

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene,propylene homopolymerizations,and their copolymerization

A series of ethylene, propylene homopolymerizations, and ethylene/propylene copolymerization catalyzed with rac‐Et(Ind)₂ZrCl₂/modified methylaluminoxane (MMAO) were conducted under the same conditions for different duration ranging from 2.5 to 30 min, and quenched with 2‐thiophenecarbonyl chloride to label a 2‐thiophenecarbonyl on each propagation chain end. The change of active center ratio ([C^*]/[Zr]) with polymerization time in each polymerization system was determined. Changes of polymerization rate, molecular weight, isotacticity (for propylene homopolymerization) and copolymer composition with time were also studied. [C^*]/[Zr] strongly depended on type of monomer, with the propylene homopolymerization system presented much lower [C^*]/[Zr] (ca. 25%) than the ethylene homopolymerization and ethylene–propylene copolymerization systems. In the copolymerization system, [C^*]/[Zr] increased continuously in the reaction process until a maximum value of 98.7% was reached, which was much higher than the maximum [C^*]/[Zr] of ethylene homopolymerization (ca. 70%). The chain propagation rate constant (k_p) of propylene polymerization is very close to that of ethylene polymerization, but the propylene insertion rate constant is much smaller than the ethylene insertion rate constant in the copolymerization system, meaning that the active centers in the homopolymerization system are different from those in the copolymerization system. Ethylene insertion rate constant in the copolymerization system was much higher than that in the ethylene homopolymerization in the first 10 min of reaction. A mechanistic model was proposed to explain the observed activation of ethylene polymerization by propylene addition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 867–875     

Isospecific copolymerization of styrene and a styrene‐terminated polyisoprene macromonomer with the Ni(acac)2/MAO catalyst

The copolymerization of styrene (St) with a styrene‐terminated polyisoprene macromonomer (SIPM) by a nickel(II) acetylacetonate [Ni(acac)₂] catalyst in combination with methylaluminoxane (MAO) was investigated. A SIPM with a high terminal degree of functionalization and a narrow molecular weight distribution was used for the copolymerization of St. The copolymerization proceeded easily to give a high molecular weight graft copolymer. After fractionation of the resulting copolymer with methyl ethyl ketone, the insoluble part had highly isotactic polystyrene in the main chain and polyisoprene in the side chain. Lowering the MAO/Ni molar ratio and the polymerization temperature were favorable to producing isospecific active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1241–1246, 2000     

Nitroxide‐mediated homo‐ and block copolymerization of styrene and multifunctional acryl‐ and methacryl derivatives

The ability of different alkoxyamines ( I1 , I2 , I3 , I4 , and I5 ) to initiate controlled radical polymerization of styrene was evaluated. Among them, 2‐hydroxymethyl‐2‐[(2‐methyl‐1‐phenyl‐propyl)‐(1‐phenyl‐ethoxy)‐amino]‐propane‐1,3‐diol ( I5 ) gave the highest polymerization rate of styrene, and the best control over the molecular weight and the molecular weight distribution of polystyrene. Kinetic studies confirmed that with initiator I5 the polymerization of styrene proceeded in a controlled way. The controlled radical homopolymerization of multifunctional acryl‐ and methacryl derivatives using initiator I5 could not be realized as demonstrated by the high polydispersities (PD) obtained. However, it was possible to polymerize multifunctional acryl‐ and methacryl derivatives using a polystyrene macroinitiator ( Pst ) and, thus, novel amphiphilic block copolymers with a narrow molecular weight distribution were obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1873–1882, 2005     

Synthesis and characterization of sulfonated block copolymers by atom transfer radical polymerization

Well‐defined sulfonated polystyrene and block copolymers with n‐butyl acrylate (nBA) were synthesized by CuBr catalyzed living radical polymerization. Neopentyl p‐styrene sulfonate (NSS) was polymerized with ethyl‐2‐bromopropionate initiator and CuBr catalyst with N,N,N′,N′‐pentamethylethyleneamine to give poly(NSS) (PNSS) with a narrow molecular weight distribution (MWD < 1.12). PNSS was then acidified by thermolysis resulting in a polystyrene backbone with 100% sulfonic acid groups. Random copolymers of NSS and styrene with various composition ratios were also synthesized by copolymerization of NSS and styrene with different feed ratios (MWD < 1.11). Well defined block copolymers with nBA were synthesized by sequential polymerization of NSS from a poly(n‐butyl acrylate) (PnBA) precursor using CuBr catalyzed living radical polymerization (MWD < 1.29). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5991–5998, 2008     

Mn2(CO)10‐induced controlled/living radical copolymerization of vinyl acetate and methyl acrylate: Spontaneous formation of block copolymers consisting of gradient and homopolymer segments

The controlled/living radical polymerization of vinyl acetate (VAc) and its copolymerization with methyl acrylate (MA) were investigated in bulk or fluoroalcohols using manganese complex [Mn₂(CO)₁₀] in conjunction with an alkyl iodide (R? I) as an initiator under weak visible light. The manganese complex induced the controlled/living radical polymerization of VAc even in the fluoroalcohols without any loss of activity. The R? I/Mn₂(CO)₁₀ system was also effective for the copolymerization of MA and VAc, in which MA was consumed faster than VAc, and then the remaining VAc was continuously and quantitatively consumed after the complete consumption of MA. The ¹H and ¹³C NMR analyses revealed that the obtained products are block copolymers consisting of gradient MA/VAc segments, in which the VAc content gradually increases, and homopoly(VAc). The use of fluoroalcohols as solvents increased the copolymerization rate, controllability of the molecular weights, and copolymerizability of VAc. The saponification of the VAc units in poly(MA‐grad‐VAc)‐block‐poly(VAc) resulted in the corresponding poly(MA‐co‐γ‐lactone)‐block‐poly(vinyl alcohol) due to the intramolecular cyclization between the hydroxyl and neighboring carboxyl groups in the gradient segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1343–1353, 2009     

An experimental and computational evaluation of ethylene/styrene copolymerization with a homogeneous single‐site titanium(IV)‐constrained geometry catalyst

Styrene was copolymerized with ethylene using the geometry constrained Me₂Si(Me₄Cp)(N‐tert‐butyl)TiCl₂ Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005     

Effect of 1‐hexene comonomer on polyethylene particle growth and copolymer chemical composition distribution

An investigation of the polymer particle growth characteristics and polymer molecular weight and composition distributions in ethylene homopolymerization and ethylene/1‐hexene copolymerization has been carried out with a catalyst comprising a zirconocene and methylaluminoxane immobilized on a silica support. The presence of 1‐hexene leads to higher productivity and easier fragmentation of the support during particle growth. Crystallization analysis fractionation and gel permeation chromatography analysis of ethylene/1‐hexene copolymers prepared at different polymerization times reveals a broadening of the chemical composition distribution with increasing polymerization time as a result of the gradual formation of a relatively high‐molecular‐weight, ethylene‐rich fraction. The results are indicative of significant monomer diffusion effects in both homopolymerization and copolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2883–2890, 2006     

Triblock copolymer synthesis via controlled radical polymerization in solution using S‐tert‐alkyl‐N,N‐alkoxycarbonylalkyldithiocarbamate RAFT agents

This paper presents the solution homopolymerization, random and block copolymerization of acrylic monomers, mediated using an S‐(1,4‐phenylenebis(propane‐2,2‐diyl)) bis(N,N‐butoxycarbonylmethyldithiocarbamate) RAFT agent. Fair to good control was obtained over the solution homopolymerization of various acrylic monomers. Although inhibition periods were observed, nearly no retardation was found to occur. Satisfactory control was also obtained over the solution copolymerization of n‐butyl acrylate with methacrylic acid, mediated using this RAFT agent. Finally, triblock copolymer synthesis, starting from the macromolecular intermediates produced in the homo‐ and copolymerization experiments, was studied, and was shown to be successful. The observed relatively broad molar mass distributions could be explained by a partial decomposition of the dithiocarbamate‐based RAFT agent during synthesis and/or polymerization, for which strong indications were obtained by performing a careful MALDI‐ToF MS analysis. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6419–6434, 2006     

RAFT polymerization of alternating styrene‐pentafluorostyrene copolymers

Reversible addition‐fragmentation chain‐transfer (RAFT) polymerization was used to control the alternating copolymerization of styrene and 2,3,4,5,6‐pentaflurostyrene. The RAFT polymerization yields a high degree of control over the molecular weight of the polymers and does not significantly influence the reactivity ratios of the monomers. The controlled free‐radical polymerization could be initiated using AIBN at elevated temperatures or using a redox couple (benzoyl peroxide/N,N‐dimethylaniline) at room temperature, while maintaining control over molecular weight and dispersity. The influence of temperature and solvent on the molecular weight distribution and reactivity ratios were investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1555–1559     

Reversible addition fragmentation chain transfer polymerization of sterically hindered monomers: Toward well‐defined rod/coil architectures

The sterically hindered monomers dibutyl itaconate (DBI) and dicyclohexyl itaconate (DCHI) were polymerized via reversible addition fragmentation chain transfer (RAFT) free‐radical polymerization. S,S′‐Bis(α,α′‐dimethyl‐α″‐acetic acid) trithiocarbonate, cumyl dithiobenzoate, and cumyl phenyldithioacetate have been used as RAFT agents to mediate a series of polymerizations at 65 °C yielding rod polymers ranging in number average molecular weight from 9000 to 92,000 g mol^?1. The progress of the polymerization was followed via online Fourier transform–near infrared spectroscopy. The polydispersity indices of the obtained rod polymers were relatively high at 1.4–1.7. The RAFT polymerizations of the hindered monomers used in the present study displayed both ideal living and hybrid behavior between conventional and living polymerization, depending on the RAFT agent used. DCHI rod polymers generated via the RAFT process were subsequently reinitiated in the presence of styrene to produce a range of BAAB and A‐B rod‐coil block copolymers of molecular weights up to 164,000 g mol^?1. The chain extension yields molecular weight distributions that progressively shift to higher molecular weights and are unimodal. Thermogravimetric analysis of the pDCHI‐block‐pStyrene copolymers indicates thermal degradation in two separate steps for the pDCHI and pStyrene blocks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2432–2443, 2004     

Titanium(IV) nonmetallocene complex catalyzed aqueous homopolymerization and copolymerization of styrene and methyl methacrylate: An Environmentally friendly approach to ultrahigh molecular weight polymer nanoparticles

A new titanium(IV) complex bearing [ONO] type ligand has been synthesized, characterized, and employed as catalyst in homopolymerization and copolymerization of styrene and methyl methacrylate. In the presence of sodium tetraphenyl borate and sodium n‐dodecyl sulfate (SDS), it exhibits moderate to high activity and afford ultrahigh molecular weight polymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Aqueous RAFT polymerization of 2‐aminoethyl methacrylate to produce well‐defined,primary amine functional homo‐ and copolymers

We report the direct homopolymerization and block copolymerization of 2‐aminoethyl methacrylate (AEMA) via aqueous reversible addition‐fragmentation chain transfer (RAFT) polymerization. The controlled “living” polymerization of AEMA was carried out directly in aqueous buffer using 4‐cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent (CTA), and 2,2′‐azobis(2‐imidazolinylpropane) dihydrochloride (VA‐044) as the initiator at 50 °C. The controlled “living” character of the polymerization was verified with pseudo‐first order kinetic plots, a linear increase of the molecular weight with conversion, and low polydispersities (PDIs) (<1.2). In addition, well‐defined copolymers of poly(AEMA‐b‐HPMA) have been prepared through chain extension of poly(AEMA) macroCTA with N‐(2‐hydroxypropyl)methacrylamide (HPMA) in water. It is shown that the macroCTA can be extended in a controlled fashion resulting in near monodisperse block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5405–5415, 2009