Sequential Monomer Addition Research Articles

Synthesis and aqueous solution properties of novel sugar methacrylate-based homopolymers and block copolymers.

We report the facile preparation of a range of novel, well-defined cyclic sugar methacrylate-based polymers without recourse to protecting group chemistry. 2-Gluconamidoethyl methacrylate (GAMA) and 2-lactobionamidoethyl methacrylate (LAMA) were prepared directly by reacting 2-aminoethyl methacrylate with D-gluconolactone and lactobionolactone, respectively. Homopolymerization of GAMA and LAMA by atom transfer radical polymerization (ATRP) gave reasonably low polydispersities as judged by aqueous gel permeation chromatography. A wide range of sugar-based block copolymers were prepared using near-monodisperse macroinitiators based on poly(ethylene oxide) [PEO], poly(propylene oxide) [PPO], or poly(e-caprolactone) [PCL] and/or by sequential monomer addition of other methacrylic monomers such as 2-(diethylamino)ethyl methacrylate [DEA], 2-(diisopropylaminoethyl methacrylate [DPA], or glycerol monomethacrylate [GMA]. The reversible micellar self-assembly of selected sugar-based block copolymers [PEO23-GAMA50-DEA100, PEO23-LAMA30-DEA50, PPO33-GAMA50, and PPO33-LAMA50] was studied in aqueous solution as a function of pH and temperature using dynamic light scattering, transmission electron microscopy, surface tensiometry, and 1H NMR spectroscopy.

Preparation and properties of semifluorinated block copolymers of 2-(dimethylamino)ethyl methacrylate and fluorooctyl methacrylates

Semifluorinated block copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(fluorooctyl methacrylates) (PFOMA) were prepared using group transfer polymerisation via sequential monomer addition. Wide ranges of copolymers were obtained with good control over both molecular weight and composition by adjusting the monomers/initiator ratio. The micellar characteristics of the copolymers in water and chloroform were investigated by quasi-elastic light scattering and transmission electron microscopy. The size and morphologies of micelles were greatly influenced by copolymer composition, pH, and temperature. In addition, the solubility of copolymers and the formation of water-in-carbon dioxide (W/C) microemulsions were described in terms of the cloud points. The block copolymers exhibited the excellent ability of stabilizing W/C microemulsions.

Anionic Polymerization of p-Pentamethyldisilyl-, p-Heptamethyltrisilyl-, and p-nonamethyltetrasilylstyrenes

The anionic polymerizations of p-pentamethyldisilylstyrene (1), p-heptamethyltrisilylstyrene (2), and p-nonamethyltetrasilylstyrene (3) were carried out under various conditions. The polymerizations of 1 and 2 proceeded in a living manner in THF at −78 °C to quantitatively afford polymers with predictable molecular weights and narrow molecular weight distributions. Suitable initiators for these living anionic polymerizations were sec-BuLi, lithium, sodium, and potassium naphthalenides, cumylpotassium, and living oligomers of α-methylstyrene lithium, sodium, and potassium salts. Well-defined diblock copolymers, poly(1)-block-polystyrene, poly(2)-block-polystyrene, polystyrene-block-poly(1), and polystyrene-block-poly(2) were successfully synthesized under similar conditions by a two-step sequential monomer addition, namely, styrene followed by 1 or 2, or vice versa. In contrast, the polymerization of 3 was problematic. No polymer was obtained in the polymerization of 3 in either THF at −78 °C or benzene at 40 °C with sec-BuLi and oligo(α-methylstyryl)lithium. Using oligo(α-methylstyryl)potassium as an initiator, 3 was polymerized quantitatively in THF at −78 °C for 0.5 h. Unfortunately, the side reaction, presumably attack of the Si−Si−Si−Si bond by the growing chain-end anion, could not be completely suppressed during the polymerization, which resulted in the formation of high molecular weight polymers by coupling between polymer chains.

Well-Defined Biocompatible Block Copolymers via Atom Transfer Radical Polymerization of 2-Methacryloyloxyethyl Phosphorylcholine in Protic Media

2-Methacryloyloxyethyl phosphorylcholine (MPC) is commonly used to prepare biocompatible copolymers that have delivered clinically proven benefits in various biomedical applications. Recently, we reported that MPC could be homopolymerized to high conversions with good control via atom transfer radical polymerization (ATRP) in protic media. In the present study we describe the synthesis of a wide range of well-defined MPC-based block copolymers using either near-monodisperse macroinitiators or sequential monomer addition. With the former approach, the macroinitiators were based on either poly(alkylene oxides) or poly(dimethylsiloxane). With the latter approach, suitable comonomers included a wide range of methacrylic and other monomers, including 2-(dimethylamino)ethyl methacrylate (DMA) and its quaternized derivatives, 2-(diethylamino)ethyl methacrylate (DEA), 2-(diisopropylamino)ethyl methacrylate (DPA), methyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and glycerol monometh...

熱可塑性エラストマーの最前線 各種リビング重合とブロック共重合体

The characteristics of various types of living polymerization such as free-radical, cationic, anionic, coordination and ring-opening metathesis polymerizations and the formation of block copolymers by sequential monomer addition method were reviewed. In the case of free-radical polymerization, three individual methods such as nitroxide-mediated polymerization (NMP), atom-transfer radical polymerization (ATRP) and reversible addition fragmentation chain-transfer (RAFT) processes were compared concerning with the reaction condition and the kinds of applicable monomers. For anionic processes, principle mechanisms of immortal polymerizations and group transfer polymerization (GTP) as well as classical living anionic polymerization were reviewed. The unique feature of ring-opening metathesis polymerization (ROMP) was also described.

Method of preparing clean poly(4‐methylstyrene)‐block‐polyisobutene by the combination of sequential monomer addition and sequential initiation in the solvent CH3Cl

A novel method of synthesizing a clean diblock copolymer via cationic polymerization was developed. First, a poly(4-methylstyrene) macroinitiator was prepared, and then a second comonomer (isobutene) and a coinitiator (AlEt2Cl) were added for the initiation of block copolymerization.

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

AbstractThe 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

Synthesis, Characterization, and Properties of ABA Type Triblock Copolymer Brushes of Styrene and Methyl Acrylate Prepared by Atom Transfer Radical Polymerization

A tethered triblock copolymer has been synthesized by sequential monomer addition to a self-assembled monolayer of (11-(2-bromo-2-methyl)propionyloxy)undecyltrichlorosilane. Si/SiO2//polystyrene-b-poly(methyl acrylate)-b-polystyrene (PS-b-PMA-b-PS) and Si/SiO2//PMA-b-PS-b-PMA were prepared by the “grafting from” method using atom transfer radical polymerization. The resulting triblock brushes were characterized by ATR−FTIR, water contact angles, ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Free polymer formed during the brush formation was characterized by gel permeation chromatography. Treatment of the triblock brushes with block-selective solvents caused reversible changes in the water contact angles and AFM. AFM analysis revealed a patterned nanomorphology when the brush was treated with a good solvent for the mid-block. We have interpreted this nanomorphology in terms of a folded brush structure where the two end blocks aggregate and force the mid-block to t...

Living and Monomer-Selective Copolymerization of n-Butyl Acrylate and Methyl Methacrylate with the Aid of Bis(2,6-di-tert-butylphenoxy)ethylaluminum

Anionic polymerizations of n-butyl acrylate (n-BuA) and methyl methacrylate (MMA) in toluene with a combination of tert-butyllithium (t-BuLi) and bis(2,6-di-tert-butylphenoxy)ethylaluminum [EtAl(ODBP)2] proceed in a living manner at low temperatures. Block copolymerizations of n-BuA and MMA with t-BuLi/EtAl(ODBP)2 (1/5 mol/mol) by sequential monomer addition were successful in both directions, that is, from poly(n-BuA) anions and from poly(MMA) anions. The conventional copolymerizations of n-BuA and MMA with the same initiator in toluene at low temperatures proceeded in a living and monomer-selective fashion; n-BuA was polymerized first, followed by the polymerization of MMA by the preformed poly(n-BuA) anions to give a block-like copolymer with narrow molecular weight distribution.

Solution Self-Assembly of Poly(ferrocenylphenylphosphine)-block-polydimethylsiloxane: Formation of Spherical Micelles with an Organometallic Poly(ferrocenylphenylphosphine) Core

The novel organometallic-inorganic diblock copolymer, poly(ferrocenylphenylphosphine)-block-polydimethylsiloxane (PFP-b-PDMS), with narrow molecular weight distribution has been synthesized by living anionic polymerization through sequential monomer addition. These block copolymers self-assemble into “star-like” spherical micelles in hexane with a dense organometallic PFP core surrounded by a swollen corona of the PDMS chains. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize these micellar aggregates. It was found that the block copolymer micelles have a relatively narrow core size distribution, but an overall broader distribution of hydrodynamic size in hexane. Significantly, the preparation method of the micelle solution was also found to have an influence on the size and size distribution of the resulting micellar structures.

Copper(I)‐mediated radical polymerization of methacrylates in aqueous solution

Abstractα‐Methoxypolyethylene oxide methacrylate was polymerized by copper(I)‐mediated living radical polymerization in aqueous solution to give polymers with controlled number‐average molecular masses and narrow polydispersities. When equimolar quantities of initiator with respect to copper(I) bromide were used, the reaction was extremely fast with quantitative conversion achieved in less than 5 min at ambient temperature. However, the molecular weight distribution was broad, and control over the number‐average molecular weight (Mn) growth was extremely poor; this is ascribed to an increase in termination because of the increased rate as a result of the coordination of water at the copper center. The complex formed between copper(I) bromide and N‐(n‐propyl)‐2‐pyridylmethanimine, bis[N‐(n‐propyl)‐2‐pyridylmethanimine]copper(I), was demonstrated to be stable in aqueous solution by 1H NMR over 10 h at 25 °C. However, on increasing the temperature to 50 °C, decomposition occurred rapidly. Thus, polymerization temperatures were maintained at ambient temperature. When longer alkyl chains were utilized in the ligand, that is, pentyl and octyl, the complex acted as a surfactant leading to heterogeneous solutions. When the catalyst concentration was reduced by two orders of magnitude, the rate of polymerization was reduced with 100% conversion achieved after 60 min with the Mn of the final product being higher than that predicted and the polydispersity equal to 1.43. Copper(II) was added as an inhibitor to circumvent these problems. When 10% of Cu(I) was replaced by Cu(II) {[Cu(I)] + [Cu(II)]/[I] = 1/100}, the mass distribution showed a bimodal distribution, and the rate of polymerization decreased significantly. With a catalyst composition [Cu(I)]/[Cu(II)] = 0.5/0.5 {[Cu(I)] + [Cu(II)]}/[I] = 1/100, polymerization proceeded slowly with 80% conversion reached after 22 h. Thus, the concentration of Cu(I) was further reduced with [Cu(I)]/[Cu(II)] = 10/90, {[Cu(I)] + [Cu(II)]}/[I] = 1/100. The system then contained [Initiator]/[Cu(I)] = 1000/1 and [I]/[Cu(II)] = 1000/9. Under these conditions, the reaction reached 50% after 5 h with the polymer having both an Mn close to the theoretical value and a narrow polydispersity of PDi = 1.15. Optimum results were obtained by increasing the amount of catalyst. When a ratio of [Cu(I)]/[Cu(II)] = 10/90 with a ratio of [Cu]/[I] = 1/1, a conversion of 100% was achieved after less than 20 h, leading to a product having Mn = 8500 and PDi = 1.15. Decreasing the amount of Cu(II) relative to Cu(I) to [Cu(I)]/[Cu(II)] = 0.5/0.5 (maintaining the overall amount of copper) led to 100% conversion after 75 min: Mn = 9500, PDi = 1.10. Block copolymers have been demonstrated by sequential monomer addition with excellent control over Mn and PDi. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1696–1707, 2001

ROMP of n-alkyl norbornene dicarboxyimides: from classical to well-defined initiators, an overview

The ring opening metathesis polymerisation (ROMP) of n-alkyl norbornene dicarboxyimides using a wide range of initiators has been extensively studied. ROMP of exo- n-alkyl norbornene dicarboxyimides with classical initiators WCl 6/Me 4Sn ( I) and MoCl 5/Me 4Sn ( II) gave polymers with 63% and 85% trans vinylene content, respectively. In contrast, the endo-isomer could not be polymerised in any of several attempts. Both exo-and endo- n-alkyl norbornene dicarboxyimides were polymerised using well-defined initiators Mo(CH- t-Bu)( N-2,6- i-Pr 2C 6H 3)(OCMe 3) 2 ( III) and Mo(CHCPhMe 2)( N-2,6- i-Pr 2C 6H 3)(OCMe(CF 3) 2) 2 ( IV). In the case of exo isomers, III gave polymers with 97% trans vinylene content and IV gave polymers with about 30% trans vinylene content. In the case of endo isomer, III gave polymer with 93% trans vinylene content and IV gave polymer with 57% trans vinylene content. The living nature of these polymerisations was confirmed by synthesising AB diblock copolymers by sequential addition of monomers. Both exo- and endo- n-alkyl norbornene dicarboxyimides were also polymerised using well-defined initiator RuCl 2(CHPh)(PCy 3) 2 ( V). The polymers obtained from exo and endo monomers contain 82% and 100% trans vinylene content respectively. The course of the polymerisation reactions using well-defined initiators III– V were followed by 1H NMR and both the initiator and propagating alkylidenes signals were observable. The multiplicity and broadening of the backbone resonances in 13C NMR, in all cases, is consistent with a multiplicity of overlapping environments associated with atactic microstructures.

Block Copolymers of Styrene and Stearyl Methacrylate. Synthesis and Micellization Properties in Selective Solvents

Block copolymers of styrene and stearyl methacrylate were prepared using anionic polymerization high-vacuum techniques by sequential addition of monomers. Narrow molecular weight distribution copolymers of different molecular weight and composition were obtained. The molecular characteristics of the copolymers were obtained by size exclusion chromatography, membrane osmometry, low-angle laser light scattering (LALLS), and differential scanning calorimetry. Comparative studies in the selective solvents for the polystyrene block, ethyl and methyl acetate, showed that mainly unimolecular micelles are formed in the former, whereas larger aggregates are observed in the latter solvent. LALLS, viscometry, and dynamic light scattering were used to characterize the micelles.

Direct Living Cationic Polymerization of p-Hydroxystyrene with Boron Trifluoride Etherate in the Presence of Water

Direct living cationic polymerization of p-hydroxystyrene (pHS) has been developed in the presence of a fairly large amount of water using BF3OEt2 as a Lewis acid catalyst and the adducts (1−4) of p-methoxystyrene (pMOS) and a series of protonic compounds as initiators. In contrast to most living cationic polymerizations, the water and the alcohol adducts (3 and 4, respectively) produced polymers with number-average molecular weights (Mn) close to the calculated values from the monomer/initiator mole ratios. With 4/BF3OEt2, the Mn increased with monomer conversion, and the living nature of the chains was confirmed by sequential monomer addition experiments. The polymerization proceeded even in the presence of a large amount water to afford polymers whose Mn increased in direct proportion to monomer conversion with fairly narrow MWDs (Mw/Mn < 1.4). This initiating system was also effective at or above ambient temperature (from −15 to +60 °C). The success of this controlled cationic polymerization of unprotected pHS is due to the stability of BF3OEt2 and to its tolerance of the hydroxy groups in the monomer and water and the proper selection of the initiator. This initiator contains a covalent C−O bond that is preferentially dissociated by an oxophilic Lewis acid, BF3. This is the first example of a direct living polymerization of pHS, by any mechanism, without protecting the hydroxy groups.

Controlled polymerization of methylmethacrylate and ethylacrylate using tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide

The radical polymerization of methylmethacrylate and ethylacrylate was carried out in the presence of tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide. The molecular weight of the synthesized polyethylacrylates increased proportionally with conversion, whereas the polymerization of methylmethacrylate revealed a nonlinear behavior. The polydispersities of the molecular weight distributions observed were between 1.09 and 1.34. Poly(styrene-block-polymethylmethacrylate) was synthesized by sequential monomer addition.

Synthesis of Poly(α-methylstyrene-b-isobutylene) Copolymers by Living Cationic Sequential Block Copolymerization: Investigation on the Crossover from Living Poly(α-methylstyrene) Chain End to Isobutylene

The synthesis of poly(α-methylstyrene-b-isobutylene) (P(αMeSt-b-IB)) copolymers via sequential monomer addition was studied using the adduct of the olefinic αMeSt dimer and HCl (DiαMeSt·HCl) as ini...

Living cationic polymerization ofp-alkoxystyrenes by free ionic species

In contrast to the common view, living cationic polymerization of p-methoxy- and p-t-butoxystyrenes proceeded in polar solvents such as EtNO2/CH2Cl2 mixtures, and involvement of free ionic growing species therein was examined. For example, the two alkoxystyrenes were polymerized with the isobutyl vinyl ether-HCl adduct/ZnCl2 initiating system at −15°C in such polar solvents as CH2Cl2 or EtNO2/CH2Cl2 [1/1 (v/v)], as well as toluene. The number average molecular weight (M̄n) of the polymers increased in direct proportion to the monomer conversion, even after sequential monomer addition, and the molecular weight distribution (MWD) stayed very narrow throughout the reaction. In addition, the M̄n agreed with the calculated values, assuming that one adduct molecule generates one living polymer chain. In these polar media the addition of a common ion salt retarded the polymerization, indicating that dissociated ionic species are involved in the propagating reaction. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3694–3701, 1999

Cationic Macromolecular Design and Synthesis Using Furan Derivatives

General methodologies for the synthesis of block copolymers and functional polymers using furan derivatives are reported on the basis of a study of addition reactions of 2-substituted furans to living polyisobutylene (PIB+). Rapid and quantitative monoaddition of 2-methylfuran (2-MeFu) and 2-tert-butylfuran (2-tBuFu) to PIB+ has been observed in conjunction with TiCl4 as Lewis acid in hexanes (Hex)/CH2Cl2 or CH3Cl 60/40 v/v at −80 °C and with BCl3 in CH3Cl at −40 °C, in the presence of proton trap. Upon monoaddition, the formation of the stable allylic cation was confirmed by trapping the resulting cation with tributyltin hydride, which yielded PIB with dihydrofuran functionality. Quenching with methanol resulted in the quantitative formation of 2-alkyl-5-PIB-furan. The stable allylic cation was found to be an efficient initiating species for the polymerization of methyl vinyl ether (MeVE), yielding P(IB-b-MeVE) block copolymers by sequential monomer addition with up to 75% crossover efficiency. 2-PIB-Fu, a polymeric capping agent, was obtained in quantitative yields in a reaction of PIB+ with 2-Bu3SnFu in Hex/CH3Cl 60/40 v/v in the presence of TiCl4 at −80 °C. In a subsequent reaction of 2-PIB-Fu with living PIB+, under conditions similar to capping PIB+ with 2-tBuFu, close to quantitative coupling of the two PIB chains was achieved. The concept of coupling a living cationic polymer with an ω-furan functional polymer to obtain AB-type linear block copolymers and for the synthesis of ABC- and AA‘B-type three-arm star-block copolymers is presented.

Ring opening metathesis polymerisation of n-alkyl norbornene dicarboxyimides using well-defined initiators

Exo- n-alkyl norbornene dicarboxyimides and endo- n-octyl norbornene dicarboxyimide were polymerised by ring opening metathesis polymerisation using well-defined initiators Mo(CH- t-Bu)(NAr)(OCMe 3) 2 and Mo(CHCPhMe 2)(NAr)(OCMe(CF 3) 2) 2. Using Mo(CH- t-Bu)(NAr)(OCMe 3) 2 and Mo(CHCPhMe 2)(NAr)(OCMe(CF 3) 2) 2 as initiators with the exo-monomers gave polymers with 97% trans and 70% cis vinylene content, respectively, and with the endo-monomer gave polymers with 93% trans and 57% trans vinylene content. In both cases the 13C n.m.r. spectra were complex indicating that these polymers are essentially atactic. 1H n.m.r. Spectroscopy and GPC analyses of polymeric materials prepared from exo- and endo-monomers demonstrated that the initiator carrying t-butoxy ligands gives fairly well-defined living polymerisation; whereas with the initiator bearing fluorinated ligands propagation is significantly faster than initiation which leads to much higher molecular weights than expected on the basis of monomer to initiator ratio and a broadening of the molecular weight distribution. The living character of these systems was confirmed by the synthesis of AB diblock copolymers via sequential addition of monomers. A series of block copolymers were prepared using exo- n-alkyl norbornene dicarboxyimides as monomer and 2,3-bis(trifluoromethyl)norbornadiene as comonomer. The glass transition temperatures of the polymers obtained from endo-monomers are significantly higher than those of the poly( exo- n-alkyl norbornene dicarboxyimide)s, probably as a consequence of a stiffer less mobile backbone resulting from the endo repeat units.

Block copolymers from isobutyl vinyl ether and 2-chloroethyl vinyl ether

Scope and limitation of the vinyl ether block copolymerization of isobutyl vinyl ether (IBVE) and 2-chloroethyl vinyl ether (CEVE) initiated by CH3CHIOR/ZnI2 were studied. These polymerizations exhibit the characteristics of a living polymerization. Di- and triblock copolymers were synthesized by sequential monomer addition (IBVE, CEVE). The poly(2-chloroethyl vinyl ether) (PCEVE) segment in those block copolymers is of particular interest because of the possibility to modify this segment by nucleophilic substitution of the chlorine. This strategy allows the synthesis of tailor made amphiphilic block copolymers.