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     

Synthesis and characterization of ABA‐type amphiphilic tri‐block copolymers through anionic polymerization using end functionalized poly(ethylene oxide) oligomers

ABA‐type amphiphilic tri‐block copolymers were successfully synthesized from poly(ethylene oxide) derivatives through anionic polymerization. When poly(styrene) anions were reacted with telechelic bromine‐terminated poly(ethylene oxide) ( 1 ) in 2:1 mole ratio, poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers were formed. Similarly, stable telechelic carbanion‐terminated poly(ethylene oxide), prepared from 1,1‐diphenylethylene‐terminated poly (ethylene oxide) ( 2 ) and sec‐BuLi, was also used to polymerize styrene and methyl methacrylate separately, as a result, poly (styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) and poly (methyl methacrylate)‐b‐poly(ethylene oxide)‐b‐poly(methyl methacrylate) tri‐block copolymers were formed respectively. All these tri‐block copolymers and poly(ethylene oxide) derivatives, 1 and 2 , were characterized by spectroscopic, calorimetric, and chromatographic techniques. Theoretical molecular weights of the tri‐block copolymers were found to be similar to the experimental molecular weights, and narrow polydispersity index was observed for all the tri‐block copolymers. Differential scanning calorimetric studies confirmed the presence of glass transition temperatures of poly(ethylene oxide), poly(styrene), and poly(methyl methacrylate) blocks in the tri‐block copolymers. Poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers, prepared from polystyryl anion and 1 , were successfully used to prepare micelles, and according to the transmission electron microscopy and dynamic light scattering results, the micelles were spherical in shape with mean average diameter of 106 ± 5 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

One‐step synthesis of hyperbranched polyethylene macroinitiator and its block copolymers with methyl methacrylate or styrene via ATRP

Block copolymers of hyperbranched polyethylene (PE) and linear polystyrene (PS) or poly(methyl methacrylate) (PMMA) were synthesized via atom transfer radical polymerization (ATRP) with hyperbranched PE macroinitiators. The PE macroinitiators were synthesized through a “living” polymerization of ethylene catalyzed with a Pd‐diimine catalyst and end‐capped with 4‐chloromethyl styrene as a chain quenching agent in one step. The macroinitiator and block copolymer samples were characterized by gel permeation chromatography, ¹H and ¹³C NMR, and differential scanning calorimetry. The hyperbranched PE chains had narrow molecular weight distribution and contained a single terminal benzyl chloride per chain. Both hyperbranched PE and linear PS or PMMA blocks had well‐controlled molecular weights. Slow initiation was observed in ATRP because of steric effect of hyperbranched structures, resulting in slightly broad polydispersity index in the block copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3024–3032, 2010     

PP/PMMA Block Copolymers by Combination of ATRP and Metallocene Catalysis

PP-b-PMMA has been synthesized by a combination of metallocene catalysis and the controlled radical polymerization technique ATRP. Cp₂ZrCl₂/MAO and (Me₄Cp)SiMe₂(N-tert-Bu)TiCl₂/MAO were used for the synthesis of atactic polypropylene. By a series of chemical modifications pp macroinitiators for the ATRP polymerization of MMA were synthesized. The PP-b-PMMA with polydispersities from 1.8–2.8 and an M_n ranging from 8 to 26 kg/mol was characterized by ¹H-NMR,SEC and DSC.     

Property modification of poly(methyl methacrylate) through copolymerization with fluorinated aryl methacrylate monomers

Copolymers of methyl methacrylate (MMA) with 2,3,5,6‐tetrafluorophenyl methacrylate (TFPMA), pentafluorophenyl methacrylate (PFPMA), and 4‐trifluoromethyl‐2,3,5,6‐tetrafluorophenyl methacrylate (TFMPMA) were investigated. All the three systems showed a random copolymerization character. The composition, glass transition temperature (T_g), and refractive index of the copolymers obtained were studied. T_gs of TFPMA/MMA and PFPMA/MMA copolymers were found to deviate positively from the Gordon–Taylor equation. However, T_gs of TFMPMA/MMA copolymers were well fit with the Gordon–Taylor equation. These results indicated the existence of interaction between MMA and either TFPMA or PFPMA units in copolymers. This interaction resulted in the enhancement of the T_g of MMA polymers through the copolymerization with TFPMA and PFPMA. The refractive index and the light transmittance of copolymers were close to those of PMMA. Copyright © 2007 John Wiley & Sons, Ltd.     

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     

Emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate and methyl methacrylate

The emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ～0.903 and ～0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006     

Synthesis of carbosilane block copolymers by means of a living anionic polymerization of 1,1-diethylsilacyclobutane

Block polymerization of 1,1-diethylsilacyclobutane with styrene derivatives and methacrylate derivatives was investigated. Sequential addition of styrene to a living poly(1,1-diethylsilabutane), which was prepared from phenyllithium and 1,1-diethylsilacyclobutane in THF–hexane at −48°C, gave poly(1,1-diethylsilabutane)-b-polystyrene. Similarly, addition of 4-(tert-butyldimethylsiloxy)styrene to the living poly(1,1-diethylsilabutane) provided poly(1,1-diethylsilabutane)-b-poly(4-(tert-butyldimethylsiloxy)styrene). Poly(1,1-diethylsilabutane)-b-poly(methyl methacrylate) was obtained by treatment of living poly(1,1-diethylsilabutane) with 1,1-diphenylethylene followed by an addition of methyl methacrylate. Poly(1,1-diethylsilabutane)-b-poly(2-(tert-butyldimethylsiloxy)ethyl methacrylate) was also synthesized by adding 2-(tert-butyldimethylsiloxy)ethyl methacrylate to the living poly(1,1-diethylsilabutane) which was end-capped with 1,1-diphenylethylene in the presence of lithium chloride. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2699–2706, 1998     

Synthesis of densely branched poly(methyl methacrylate)s via ATR copolymerization of methyl methacrylate and ethylene glycol dimethacrylate

Densely branched poly(methyl methacrylate)s have been synthesized by copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) using atom transfer free radical polymerization (ATRP). By employing the phenyl and benzyl esters of 2-bromo-2-methylpropionic acid as the initiators with 2,2-bipyridyl and Cu(I)Cl it has been possible to use high field ¹H nuclear magnetic resonance spectroscopy to evaluate in some detail the composition and structure of the branched PMMAs obtained. Parallel molar mass size exclusion chromatographic analysis using a multi-angle light scattering detector with a refractive index detector (MALS/SEC) has allowed the branched architecture of the products to be confirmed. Rather remarkably, high yields of branched PMMAs can be obtained without crosslinking using MMA/EGDMA molar feed ratios of up to 5/1 by appropriate adjustment of the molar feed of initiator. In particular by maintaining the EGDMA/initiator molar feed ratio ∼1/1 fully soluble products can be obtained that are densely branched since this feed ratio ensures that on average each living primary chain initiated contains on average only one branching EGDMA segment. As might be expected this controlled free radical process offers better control in the synthesis of branched polymer than the corresponding system we have reported using conventional free radical polymerization, and unlike the latter which requires the use of a chain transfer agent, the ATRP system requires no additional chain regulating component. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2375–2386, 2007     

A novel route to poly(2-hydroxyethyl methacrylate) and its amphiphilic block copolymers

The vinyl of the ester group of 2-vinyloxyethyl methacrylate was first selectively reacted with acetic acid to obtain 2-[1-(acetoxy)ethoxy]ethyl methacrylate ( 2 ). This protected monomer was subjected to anionic polymerization in tetrahydrofuran at −60°C in the presence of LiCl, using 1,1-diphenylhexyllithium as initiator. The molecular weight of the polymer could thus be controlled and a narrow molecular weight distribution obtained. The protecting group, 1-(acetoxy)ethyl, could be easily eliminated (by quenching the polymerization reaction with methanol and water) to generate poly(2-hydroxyethyl methacrylate) (poly(HEMA)). Block copolymers were also prepared by the sequential anionic polymerization of MMA and 2 or styrene and 2 . They possess narrow molecular weight distributions, and controlled molecular weights and compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1865–1872, 1998     

Synthesis and characterization of block copolymers from 2‐vinylnaphthalene by anionic polymerization

The anionic polymerization of 2‐vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at ?78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec‐butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at ?78 °C initiated by an adduct of sBuLi–LiCl. The crossover propagation from poly(2‐vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight‐average molecular/number‐average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo‐PDMS. Poly(2VN‐b‐nBA) (where nBA is n‐butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN‐b‐tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and ¹H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN‐b‐AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert‐butyl from the poly(2VN‐b‐tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387–4397, 2002     

Preparation of polyethylene block copolymers by a combination of postmetallocene catalysis of ethylene polymerization and atom transfer radical polymerization

The synthesis of block copolymers consisting of a polyethylene segment and either a poly(meth)acrylate or polystyrene segment was accomplished through the combination of postmetallocene-mediated ethylene polymerization and subsequent atom transfer radical polymerization. A vinyl-terminated polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight =1.70) was synthesized by the polymerization of ethylene with a phenoxyimine zirconium complex as a catalyst activated with methylalumoxane (MAO). This polyethylene was efficiently converted into an atom transfer radical polymerization macroinitiator by the addition of α-bromoisobutyric acid to the vinyl chain end, and the polyethylene macroinitiator was used for the atom transfer radical polymerization of n-butyl acrylate, methyl methacrylate, or styrene; this resulted in defined polyethylene-b-poly(n-butyl acrylate), polyethylene-b-poly(methyl methacrylate), and polyethylene-b-polystyrene block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 496–504, 2004     

Nanosphere formation in copolymerization of methyl methacrylate with poly(ethylene glycol) macromonomers

Polymeric nanospheres consisting of poly(methyl methacrylate) (PMMA) cores and poly(ethylene glycol) (PEG) branches on their surfaces were prepared by free radical copolymerization of methyl methacrylate (MMA) with PEG macromonomers in ethanol/water mixed solvents. PEG macromonomers having a methacryloyl (MMA‐PEG) and p‐vinylbenzyl (St‐PEG) end group were used. It has become clear that the obtained polymer dispersions form three kinds of states, particle dispersion (milky solution), clear solution, and gel/precipitation. It was found that the reaction parameters such as MMA concentration, molecular weight, and concentration of PEG macromonomers, and water content can affect nanosphere formation in a copolymerization system. The water volume fraction of mixed ethanol/water solvents affected the particle size of the nanospheres. These differences in the formation of nanospheres were due to the solvophilic/solvophobic balance between the copolymers and solvents during the self‐assembling process of the copolymers. The sizes of nanospheres can be controlled by varying concentration of PEG macromonomer and water content in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1811–1817, 2000     

Application of multifunctional initiation system in block copolymerization of ethylene oxide and methyl methacrylate

A block copolymer composed of hydrophilic and crystallinic polyethylene oxide and hydrophobic and non-crystallinic polymethyl methacrylate (PMMA) was prepared by sequential initiation of alkoxy-anion and charge transfer complex using p-aminophenol as parent compound. The structure of copolymer was characterized by GPC, IR, 1H NMR and DSC in detail. The propagation of PMMA chain is dependent on the molecular weight and concentration of the first block PEO and also the polarity of solvents. The reasons are discussed.     

New soluble functional polymers by free‐radical copolymerization of methacrylates and bipyridine ruthenium complexes

The luminescent complex [4‐(3‐hydroxypropyl)‐4′‐methyl‐2,2′‐bipyridine]‐bis(2,2′‐bipyridine)‐ruthenium(II)‐bis(hexafluoroantimonate) and its methacrylate derivative were successfully synthesized and fully characterized by two‐dimensional ¹H and ¹³C{¹H} NMR techniques [correlation spectroscopy (COSY) and heteronuclear multiple‐quantum coherence experiment (HMQC)], as well as matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry. The respective labeled methyl methacrylate‐ruthenium(polypyridyl) copolymers were obtained by free‐radical copolymerization with methyl methacrylate and were characterized utilizing NMR, IR, and UV–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3954–3964, 2003     

Biodegradations of block copolymers composed of L- or D,L-lactide and six-membered cyclic carbonates prepared with organolanthanide initiators

Diblock copolymerizations of L - or D,L -lactide (LA) with trimethylene carbonate (TMC) or 2,2-dimethyltrimethylene carbonate (2,2-DTMC) with SmMe(C₅Me₅)₂-(tetrahydrofuran) as an initiator and triblock copolymerizations of L - or D,L -LA/cyclic carbonates/L - or D,L -LA with [Sm(C₅Me₅)₂]₂(PhCCCCPh) as an initiator generated the desired block copolymers. This article describes the comparison of biodegradabilities by proteinase K and a compost and mechanical properties between the resulting di- or triblock copolymers and random copolymers composed of L - or D,L -LA and cyclic carbonates. The scanning electron microscopic profiles of resulting polymers were measured to understand the morphological change during biodegradation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3572–3588, 2003     

Living anionic homo- and block copolymerization of 2-(tert-butylamino)ethyl methacrylate

Anionic polymerization of 2-(tert-butylamino)ethyl methacrylate (tBAEMA), which bears an unprotected secondary amine moiety, has been investigated in THF at −78°C. The presence of lithium chloride has been shown to be desirable to afford narrow molecular weight distribution as well as a good agreement between theoretical and observed molecular weight. The living character of the polymerization has also been demonstrated, and the synthesis of block copolymers carried out successfully. They have been analyzed by SEC by adding a mixture of secondary and tertiary amines to the eluent (THF) so as to avoid any polymer adsorption during elution. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2035–2040, 1997     

Homo‐ and copolymerization of methyl methacrylate with ethylene by novel Ziegler‐Natta‐Type nickel catalysts based on N,O‐nitro‐substituted chelate ligands

New Nickel (II) catalytic systems based on N,O chelate ligands, activated by methylaluminoxane, have been checked in the homopolymerization of methyl methacrylate (MMA) and its copolymerization with ethylene. In particular, the bis(8‐hydroxy‐5‐nitro‐quinolate)nickel(II)/methylaluminoxane system as well as the catalysts obtained by oxidative addition of either 8‐hydroxy‐5‐nitro‐quinoline or 8‐hydroxy‐5,7‐dinitro‐quinoline or 4‐nitro‐2‐(p‐nitrobenzylideneamino)‐phenol to Ni(cod)₂, subsequently activated by methylaluminoxane, have been employed. The influence of the reaction parameters on the catalytic activity and the characteristics of the resulting polymers has been investigated. All the obtained poly(methyl methacrylate) samples display a largely prevailing syndiotacticity degree, high molecular weights and a rather large polydispersity. The catalytic systems obtained through the oxidative procedure are able also to give copolymers of MMA with ethylene producing highly linear polyethylenes containing a low amount (1.5–2 mol %) of MMA counits, thus affording materials with improved surface properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 620–633, 2006     

Multimonomer and cross-linked polymers formed by its copolymerization

Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to examine the thermal behavior of the multimonomer poly[2-(10-undecenoyloxy)ethyl methacrylate] (PUDEM) within the temperature range from -80 to 400°C. DSC measurements indicated that the polymer side chains were able to crystallize in paraffinic phase. PUDEM, added to methyl methacrylate (MM), can effectively copolymerize with essentially no homopolymer produced as shown by DSC (single T _g). The value of T _g depends on the PUDEM content, degree of cross-linking and the presence of free MM in the cross-linked product. This revised version was published online in August 2006 with corrections to the Cover Date.