Arenesulfonyl bromides: The second universal class of functional initiators for the metal‐catalyzed living radical polymerization of methacrylates,acrylates, and styrenes

The metal‐catalyzed living radical polymerization of methyl methacrylate, n‐butyl acrylate, and styrene, initiated with p‐toluenesulfonyl bromide and phenoxybenzene‐4,4′‐disulfonyl bromide and catalyzed with CuBr/2,2′‐bipyridine (bpy) and various self‐regulated Cu‐based catalytic systems such as Cu₂O/bpy, Cu₂S/bpy, Cu₂Se/bpy, and Cu₂Te/bpy, is reported. Similarities and differences between the arenesulfonyl chloride and arenesulfonyl bromide initiators are discussed. The arenesulfonyl bromide initiators require reduced reaction times to produce polymers in high conversions under milder reaction conditions than the corresponding arenesulfonyl chloride initiators. At the same time, they exhibit 100% initiator efficiency and generate polymers with narrow molecular weight distributions and functional chain ends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 319–330, 2005     

Catalytic effect of dimethyl sulfoxide in the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical polymerization of methyl methacrylate at 0–90 °C initiated with CH3CHClI as a model compound for α,ω‐di(iodo)poly(vinyl chloride) chain ends

A variety of conditions, including catalysts [CuCl, CuI, Cu₂O, and Cu(0)], ligands [2,2′‐bipyridine (bpy), tris(2‐dimethylaminoethyl)amine (Me₆‐TREN), polyethyleneimine, and hexamethyl triethylenetetramine], initiators [CH₃CHClI, CH₂I₂, CHI₃, and F(CF₂)₈I], solvents [diphenyl ether, toluene, tetrahydrofuran, dimethyl sulfoxide (DMSO), dimethylformamide, ethylene carbonate, dimethylacetamide, and cyclohexanone], and temperatures [90, 25, and 0 °C] were studied to assess previous methods for poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) synthesis by the living radical block copolymerization of methyl methacrylate (MMA) initiated with α,ω‐di(iodo)poly(vinyl chloride). CH₃CHClI was used as a model for α,ω‐di(iodo)poly(vinyl chloride) employed as a macroinitiator in the living radical block copolymerization of MMA. Two groups of methods evolved. The first involved CuCl/bpy or Me₆‐TREN at 90 °C, whereas the second involved Cu(0)/Me₆‐TREN in DMSO at 25 or 0 °C. Related ligands were used in both methods. The highest initiator efficiency and rate of polymerization were obtained with Cu(0)/Me₆‐TREN in DMSO at 25 °C. This demonstrated that the ultrafast block copolymerization reported previously is the most efficient with respect to the rate of polymerization and precision of the PMMA‐b‐PVC‐b‐PMMA architecture. Moreover, Cu(0)/Me₆‐TREN‐catalyzed polymerization exhibits an external first order of reaction in DMSO, and so this solvent has a catalytic effect in this living radical polymerization (LRP). This polymerization can be performed between 90 and 0 °C and provides access to controlled poly(methyl methacrylate) tacticity by LRP and block copolymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1935–1947, 2005     

Multifunctional ATRP initiators: Synthesis of four‐arm star homopolymers of methyl methacrylate and graft copolymers of polystyrene and poly(t‐butyl methacrylate)

Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four‐armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated free‐radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t‐butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated stable free‐radical polymerization process from the copolymerization of styrene and p‐(chloromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t‐butyl methacrylate polymerization, giving the desired graft copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 650–655, 2001     

Vanadium alkoxide catalyzed polymerization of vinyl chloride

The polymerization of vinyl chloride (VC) with vanadium complex/alkylaluminum catalyst was investigated. In the case of polymerization with vanadium oxytriethoxide (VO(OEt)₃), poly(vinyl chloride) was obtained in a good yield. The effect of cocatalyst, solvent, and cocatalyst/precatalyst ratio was observed. The structure of the polymer obtained with VO(OEt)₃/i‐Bu₃Al catalyst consisted of regular head‐to‐tail sequence and isobutyl chain‐end structure. VO(OEt)₃/alkylaluminum catalyst was able to copolymerize VC with styrene, 1‐butene, methyl methacrylate, and methyl acrylate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Kinetics of graft copolymerization of methyl methacrylate onto polychloroprene with tricaprylylmethylammonium chloride as a phase‐transfer catalyst

The phase‐transfer catalyzed graft copolymerization of methyl methacrylate onto polychloroprene was carried out using tricaprylylmethylammonium chloride as a phase‐transfer catalyst in a two‐phase system of an aqueous Na₂S₂O₈ solution and toluene at 55 °C under a nitrogen atmosphere. The initial rate of graft copolymerization was expressed as the combined terms of quaternary onium cation and peroxydisulfate anion in the aqueous phase rather than the fed concentrations of catalyst and Na₂S₂O₈. The observed initial rate of graft copolymerization was used to analyze the graft copolymerization mechanism with a cycle phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3543–3549, 2000     

N‐chloro amides,lactams, carbamates,and imides. New classes of initiators for the metal‐catalyzed living radical polymerization of methacrylates

Metal‐catalyzed living radical polymerization of methyl methacrylate initiated with N‐chloro amides (N‐chloro N‐ethyl propionamide, N‐chloro benzanilide, N‐chloro methylbenzamide, and N‐chloro acetanilide), lactams (N‐chloro caprolactam and N‐chloro 2‐pyrrolidinone), carbamates or urethanes (N‐chloro ethylcarbamate or N‐chlorourethane), imides (N‐chloro phtalimide, N‐chloro succinimide, trichloroisocyanuric acid, and N‐chloro saccharin) and catalyzed with the self‐regulated catalytic system Cu₂S/2,2′‐bipyridine is reported. The initiation efficiency of these initiators is determined by their structure. Regardless of the initiator efficiency, in all cases, poly (methyl methacrylate) with narrow molecular weight distribution and functionalized chain‐ends was obtained. These new classes of initiators open new strategies for the functionalization of polymer chain‐ends and for the synthesis of complex architectures by graft copolymerization initiated from N‐chloro proteins, aliphatic, aromatic and semiaromatic polyamides, and polyurethanes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5283–5299, 2005     

Arenesulfonyl iodides: The third universal class of functional initiators for the metal‐catalyzed living radical polymerization of methacrylates and styrenes

The metal‐catalyzed living radical polymerization of methyl methacrylate and styrene initiated with freshly prepared p‐toluenesulfonyl iodide (TsI) and catalyzed with CuX/2,2′‐bipyridine (bpy), where X is Cl, Br, or I, and various self‐regulated copper‐based catalytic systems, such as copper/bpy, copper(I) oxide/bpy, copper(I) sulfide/bpy, copper(I) selenide/bpy, and copper(I) telluride/bpy, is reported. The exchange of C? I into C? Br and C? Cl takes place when the living radical polymerization of methyl methacrylate is catalyzed by copper(I) bromide/bpy and copper(I) chloride/bpy, respectively. Therefore, the use of the TsI initiator facilitates the synthesis, starting from a single initiator, of poly(methyl methacrylate) containing C? I, C? Br, and C? Cl chain ends. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3920–3931, 2005     

Synthesis of aromatic polyethersulfone‐based graft copolyacrylates via ATRP catalyzed by FeCl2/isophthalic acid

The atom transfer radical polymerization (ATRP) catalyzed by the FeCl₂/isophthalic acid system was used for the preparation of novel aromatic polyethersulfone (PSF)‐based graft copolymers in N,N‐dimethylformamide (DMF), such as aromatic PSF‐graft‐poly(methyl methacrylate), aromatic PSF‐graft‐polymethylacrylate, and aromatic PSF‐graft‐poly(butyl acrylate). The route consisted of two steps. The first step included the chloromethylation of aromatic PSF, and the second step involved the ATRP of acrylate monomers using chloromethylated aromatic PSF as the macroinitiator and FeCl₂/isophthalic acid as the catalyst in DMF. Characterization data by gel permeation chromatography, DSC, IR, ¹H NMR, and thermogravimetric analysis confirmed that the graft copolymerization was successful. Only one glass‐transition temperature (T_g) was observed for aromatic PSF‐graft‐poly(methyl methacrylate), and two T_g's were detected for aromatic PSF‐graft‐methyl acrylate and aromatic PSF‐graft‐poly(butyl acrylate). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2943–2950, 2001     

Atom transfer graft copolymerization of 2‐ethyl hexylacrylate from labile chlorines of poly(vinyl chloride) in an aqueous suspension

Copper‐mediated atom transfer radical polymerization (ATRP) is presented as a versatile tool for the graft copolymerization of 2‐ethyl hexylacrylate with poly(vinyl chloride) (PVC) in an aqueous suspension. The appreciable solubility of PVC in 2‐ethyl hexylacrylate (30%) at temperatures around 130 °C makes grafting of the monomer possible from labile chlorines of PVC in aqueous suspensions without the use of additional solvent. The first‐order kinetics (rate constant k = 4.2 × 10^?6 s^?1) of the mass percentage increase reveals a typical ATRP fashion of the graft copolymerization at low conversions. The use of a completely organosoluble copper(I) complex of hexylated triethylene tetramine, in combination with α‐methylcellulose as a stabilizer, makes the graft copolymerization possible in a dispersed organic phase. Nearly spherical, green particles can be obtained with moderate stirring rates (1000 rpm) in high graft yields. Although the kinetics of the reaction deviates from the first order at high conversions, reasonable graft yields (146%) can be attained within a reaction period of 24 h. In this study, the reaction conditions of the grafting have been studied, and graft products have been confirmed by common techniques such as ¹H NMR, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1900–1907, 2006     

Tetramethylguanidino‐tris(2‐aminoethyl)amine: A novel ligand for copper‐based atom transfer radical polymerization

With CuBr/tetramethylguanidino‐tris(2‐aminoethyl)amine (TMG₃‐TREN) as the catalyst, the atom transfer radical polymerization (ATRP) of methyl methacrylate, n‐butyl acrylate, styrene, and acrylonitrile was conducted. The catalyst concentration of 0.5 equiv with respect to the initiator was enough to prepare well‐defined poly(methyl methacrylate) in bulk from methyl methacrylate monomer. For ATRP of n‐butyl acrylate, the catalyst behaved in a manner similar to that reported for CuBr/tris[2‐(dimethylamino)ethyl]amine. A minimum of 0.05 equiv of the catalyst with respect to the initiator was required to synthesize the homopolymer of the desired molecular weight and low polydispersity at the ambient temperature. In the case of styrene, ATRP with this catalyst occurred only when a 1:1 catalyst/initiator ratio was used in the presence of Cu(0) in ethylene carbonate. The polymerization of acrylonitrile with CuBr/TMG₃‐TREN was conducted successfully with a catalyst concentration of 50% with respect to the initiator in ethylene carbonate. End‐group analysis for the determination of the high degree of functionality of the homopolymers synthesized by the new catalyst was determined by NMR spectroscopy. The isotactic parameter calculated for each system indicated that the homopolymers were predominantly syndiotactic, signifying that the tacticity remained the same, as already reported for ATRP. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5906–5922, 2005     

Graft copolymerization of butyl acrylate and 2‐ethyl hexyl acrylate from labile chlorines of poly(vinyl chloride) by atom transfer radical polymerization

Trace amounts of labile chlorines present in poly(vinyl chloride) (PVC) were found to act as initiation sites for the preparation of graft copolymers of PVC by copper‐mediated atom transfer radical polymerization (ATRP). High grafting yields were attained during the graft copolymerizations of n‐butyl acrylate (161.8%) and 2‐ethyl hexyl acrylate (51.2%) in 7.5 h. In both cases, the grafting proceeded with first‐order kinetics with respect to the monomer concentrations, this being typical for ATRP. Gel permeation chromatography traces of the resulting products did not exhibit additional peaks attributable to the formation of free homopolymers. The presented procedure offers an efficient means of preparing self‐plasticized PVC structures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3457–3462, 2003     

Electrochemically mediated atom transfer radical polymerization with dithiocarbamates as alkyl pseudohalides

Electrochemically mediated atom transfer radical polymerizations (ATRPs) provide well‐defined polymers with designed dispersity as well as under external temporal and spatial control. In this study, 1‐cyano‐1‐methylethyl diethyldithiocarbamate, typically used as chain‐transfer agent (CTA) in reversible addition–fragmentation chain transfer (RAFT) polymerization, was electrochemically activated by the ATRP catalyst Cu^I/2,2′‐bipyridine (bpy) to control the polymerization of methyl methacrylate. Mechanistic study showed that this polymerization was mainly controlled by the ATRP equilibrium. The effect of applied potential, catalyst counterion, catalyst concentration, and targeted degree of polymerization were investigated. The chain‐end functionality was preserved as demonstrated by chain extension of poly(methyl methacrylate) with n‐butyl methacrylate and styrene. This electrochemical ATRP procedure confirms that RAFT CTAs can be activated by an electrochemical stimulus. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 376–381     

Graft copolymers of polyethylene by atom transfer radical polymerization

Poly(ethylene‐g‐styrene) and poly(ethylene‐g‐methyl methacrylate) graft copolymers were prepared by atom transfer radical polymerization (ATRP). Commercially available poly(ethylene‐co‐glycidyl methacrylate) was converted into ATRP macroinitiators by reaction with chloroacetic acid and 2‐bromoisobutyric acid, respectively, and the pendant‐functionalized polyolefins were used to initiate the ATRP of styrene and methyl methacrylate. In both cases, incorporation of the vinyl monomer into the graft copolymer increased with extent of the reaction. The controlled growth of the side chains was proved in the case of poly(ethylene‐g‐styrene) by the linear increase of molecular weight with conversion and low polydispersity (M_w /M_n < 1.4) of the cleaved polystyrene grafts. Both macroinitiators and graft copolymers were characterized by ¹H NMR and differential scanning calorimetry. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2440–2448, 2000     

Synthesis of high molecular weight polymer nanoparticles by [Cp2ZrCl2] catalyzed emulsion polymerization

An early transition metal metallocene compound, Cp₂ZrCl₂, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier and NaBPh₄ as cocatalyst has been found to be an effective catalytic system for polymerization and copolymerization of monomers like styrene and methyl methacrylate in aqueous medium. The diameters of the latex particles were found to be in between 20 and 40 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Constructing novel double‐bond‐containing well‐defined amphiphilic graft copolymers via successive Ni‐catalyzed living coordination polymerization and SET‐LRP

A series of polyallene‐based well‐defined amphiphilic graft copolymers, poly(6‐methyl‐1,2‐heptadiene‐4‐ol)‐g‐poly(2‐(diethylamino)ethyl methacrylate) (PMHDO‐g‐PDEAEMA), was synthesized through the grafting‐from technique. First, double‐bond‐containing PMHDO backbone bearing pendant hydroxyls was prepared via [(η³‐allyl)NiOCOCF₃]₂‐initiated living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO). The pendant hydroxyls in the homopolymer were then reacted with 2‐chloropropionyl chloride to give PMHDO‐Cl macroinitiator. Finally, hydrophilic PDEAEMA side chains were formed by single electron transfer‐living radical polymerization (SET‐LRP) of 2‐(diethylamino)ethyl methacrylate (DEAEMA) in THF/H₂O initiated by the macroinitiator using CuCl/Me₆TREN as catalytic system to afford PMHDO‐g‐PDEAEMA graft copolymers. The narrow molecular weight distributions (M_w/M_n ≤ 1.35) and kinetics experiment showed the controllability of SET‐LRP graft copolymerization of DEAEMA. The critical micelle concentration (cmc) of PMHDO‐g‐PDEAEMA amphiphilic graft copolymer in aqueous media was determined by fluorescence probe technique and the relationships between cmc and pH or salinity were also investigated. Micellar morphologies were preliminarily explored using transmission electron microscopy. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

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     

Copolymerization of allyl esters of some fatty acids

Attempts have been made unsuccessfully to homopolymerize a number of allyl esters of substituted fatty acids by radical initiation in emulsion systems. Copolymerizations of these allyl esters with styrene, methyl methacrylate, and vinyl chloride have been investigated. Of these comonomers, styrene and methyl methacrylate do not copolymerize well with the allyl esters, whereas vinyl chloride does. Reactivity ratios for the radical copolymerization of allyl 11-iodoundecanoate, M₁, and vinyl chloride, M₂, determined at 60°C. in benzene, are r₁ = 0.42 and r₂ = 1.64. A copolymer of allyl 10, 11-dibromoundecanoate and vinyl chloride was fractionated and found to be fairly homogeneous.     

Cuso4‐amine redox‐initiated radical polymerization of methyl methacrylate mediated by a CuCl2 complex: Homogeneous reverse ATRP

Kinetic results of CuSO₄/2,2'‐bipyridine(bPy)‐amine redox initiated radical polymerization of methyl methacrylate (MMA) at 70 to 90 °C in dimethylsulfoxide suggest that such initiation is characteristic of a slow rate and a low initiator efficiency, but tertiary amines exhibit a relatively higher rate. UV‐Vis spectroscopy confirms the alpha‐amino functionality of PMMA chains. CuCl₂/bPy successfully mediates the redox‐initiated radical polymerization of MMA with aliphatic tertiary amines in a fashion of slow‐initiated reverse atom transfer radical polymerization (ATRP), i.e. both the initiator efficiency of aliphatic tertiary amines and the average molecular weight of PMMA increase gradually, while the molecular weight distribution remains narrow but become broader with the conversions. As the PMMA chains contain alpha amino and omega C‐Cl moieties, UV‐induced benzophenone‐initiated radical polymerization and Cu^ICl/bPy‐catalyzed ATRP initiated from PMMA lead to block copolymers from terminal functionalities. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2562‐2578     

Luminescent polymeric ruthenium complexes with polystyrene‐b‐poly(methyl methacrylate) macroligands: The sequential activation of initiator sites for blocks generated by parallel polymerization mechanisms

The synthesis of polystyrene‐b‐poly(methyl methacrylate) diblock copolymers with a luminescent ruthenium(II) tris(bipyridine) [Ru(bpy)₃] complex at the block junction is described. The macroligand precursor, polystyrene bipyridine‐poly(methyl methacrylate) [bpy(PS–H)(PMMA)], was synthesized via the atom transfer radical polymerization of styrene and methyl methacrylate from two independent, sequentially activated initiating sites. Both polymerization steps resulted in the growth of blocks with sizes consistent with monomer loading and narrow molecular weight distributions (i.e., polydispersity index < 1.3). Subsequent reactions with ruthenium(II) bis(bipyridine) dichloride [Ru(bpy)₂Cl₂] in the presence of Ag⁺ generated the ruthenium tris(bipyridine)‐centered diblock, which is of interest for the imaging of block copolymer microstructures and for incorporation into new photonic materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4250–4255, 2002     

Copolymerizations of tetraethyl vinylidene phosphonate. Bisphosphonate units in the main polymer chain. II

This is the second part of the article with a subtitle “… The First Synthesis” published by us previously. For this, second part, we have chosen copolymers with low proportion of (‐b‐) units, as well as random copolymers with substantial proportions of (‐b‐) units. This is in contrast to the part I, in which we mostly described alternating copolymerization. In this article, radical copolymerization of tetraethyl vinylidene phosphonate (B) with several vinyl/ethylenic monomers (M₂), namely acrylamide, methacrylamide, methyl methacrylate, n‐butyl acrylate, n‐butyl methacrylate, and styrene has been described and reactivity ratios of monomers as well as the average length of the comonomer blocks (n) have been determined (r₁ = 0). It has been found, that (as it should be) there is a proportionality between r₂ (=k_m2M2/k_m2B) and n. Moreover, there is a proportionality between r₂ (or n) and the comonomer (M₂) “reactivity,” defined as the rate constant of M₂ addition to the styrene radical. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1614–1621