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     

Synthesis and characterization of poly[styrene‐b‐methyl(3,3,3‐trifluoropropyl)siloxane] diblock copolymers via anionic polymerization

A series of narrow molecular weight distribution (MWD) polystyrene‐b‐poly[methyl(3,3,3‐trifluoropropyl)siloxane] (PS‐b‐PMTFPS) diblock copolymers were synthesized by the sequential anionic polymerization of styrene and trans‐1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane in tetrahydrofuran (THF) with n‐butyllithium as the initiator. The diblock copolymers had narrow MWDs ranging from 1.06 to 1.20 and number‐average molecular weights ranging from 8.2 × 10³ to 37.1 × 10³. To investigate the properties of the copolymers, diblock copolymers with different weight fractions of poly[methyl(3,3,3‐trifluoropropyl)siloxane] (15.4–78.8 wt %) were prepared. The compositions of the diblock copolymers were calculated from the characteristic proton integrals of ¹H NMR spectra. For the anionic ring‐opening polymerization (ROP) of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (F₃) initiated by polystyryllithium, high monomer concentrations could give high polymer yields and good control of MWDs when THF was used as the polymerization solvent. It was speculated that good control of the block copolymerization under the condition of high monomer concentrations was due to the slowdown of the anionic ROP rate of F₃ and the steric hindrance of the polystyrene precursors. There was enough time to terminate the ROP of F₃ when the polymer yield was high, and good control of block copolymerization could be achieved thereafter. The thermal properties (differential scanning calorimetry and thermogravimetric analysis) were also investigated for the PS‐b‐PMTFPS diblock copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4431–4438, 2005     

Living anionic polymerization of lauryl methacrylate and synthesis of block copolymers with methyl methacrylate

Anionic polymerization of lauryl methacrylate (LMA) with 1,1‐diphenylhexyl lithium in tetrahydrofuran (THF) at ?40 °C resulted in a multimodal and broad molecular weight distribution (MWD) with poor initiator efficiency. In the presence of additives such as dilithium salt of triethylene glycol (G₃Li₂), LiCl, and LiClO₄, the polymerization resulted in polymers with a narrow MWD (≤ 1.10). Diblock copolymers of methyl methacrylate (MMA) and LMA were synthesized by anionic polymerization using DPHLi as initiator in THF at ?40 °C with the sequential addition of monomers. The molecular weight distribution of the polymers was narrow and without homopolymer contamination when LMA was added to living PMMA chain ends. Diblock copolymers with broad/bimodal MWD were obtained with a reverse‐sequence monomer addition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 875–882, 2004     

Synthesis of polystyrene-polysiloxane side-chain liquid crystalline block copolymers

The synthesis of a new liquid crystalline block copolymer consisting of a polystyrene block and a side-chain liquid crystalline siloxane block is reported. The synthetic approach described is based on the anionic polymerization of styrene and cyclic trimethyltrivinyltrisiloxane monomers, followed by functionalization of the siloxane block with side chain mesogens. The siloxane block has a T_g well below 25°C and is designed to exhibit a chiral smectic C^* phase at room temperature. These block copolymers are the first side-chain liquid crystalline block copolymers which contain both a high T_g glassy block and a low T_g liquid crystalline block.     

Synthesis of well-defined ABC triblock copolymers with polypeptide segments by ATRP and click reactions

Well-defined ABC block copolymers consisting of poly(ethylene oxide) monomethylene ether (MPEO) as A block, poly(styrene) (PS) as B block and poly(γ-benzyl-l-glutamate) (PBLG) as C block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. The bromine-terminated diblock copolymer poly(ethylene oxide) monomethylene ether-block-poly(styrene) (MPEO-PS-Br) was prepared by ATRP of styrene initiated with macro-initiator MPEO-Br, which was prepared from the esterification of MPEO and 2-bromoisobutyryl bromide, and converted into the azido-terminated diblock copolymer MPEO-PS-N₃ by simple nucleophilic substitutions in DMF in the presence of sodium azide. Propargyl-terminated PBLGs were synthesized by ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride in DMF at room temperature using propargyl amine as an initiator. ABC triblock copolymers MPEO-PS-PBLG with a wide range of number-average molecular weights from 1.55 to 3.75 × 10⁴ and a narrow polydispersity from 1.07 to 1.10 were synthesized via the click reaction of MPEO-PS-N₃ and the propargyl-terminated PBLG in the presence of CuBr and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABC block copolymers and corresponding precursors were characterized by NMR, IR and GPC. The results showed that click reaction was efficient. Therefore, a facile approach was offered to synthesize ABC triblock copolymers composed of crystallizable polymer MPEO, conventional vinylic polymer PS and rod-like α-helix polypeptide PBLG.     

ABA型两亲嵌段共聚物的合成及表征

以α ,α′ 二溴代二甲苯为引发剂 ,CuBr/2 ,2′ 联吡啶为催化体系 ,制备了双溴端基的分子量分布窄的聚苯乙烯 (MWD =1 18) .再以此作为大分子引发剂 ,实现了甲基丙烯酸对硝基苯酯的原子转移自由基聚合 ,制得了分子量可控且分子量分布窄的ABA型嵌段共聚物 ,再经水解、酸化 ,得到了聚甲基丙烯酸 b 聚苯乙烯 b 聚甲基丙烯酸ABA型两亲嵌段共聚物     

Anionic polymerization of lactones initiated by alkali graphitides. IV. Copolymerization of ε-caprolactone initiated by KC24

The copolymerization of ε-caprolactone (ε-CL) with octamethylcyclotetrasiloxane (D₄) and styrene (St) under the action of the second-stage potassium graphitide KC₂₄ was investigated. The copolymerizations were carried out in bulk or in xylene at 20°C. The content of the block copolymer ε-CL/D₄ in the polymerization mixture was 60–95%, the molecular weight ranging between 150,000 and 300,000. The data for the copolymers' composition obtained by ¹H-NMR and GPC showed 14–20% of D₄-units in the copolymer. The amount of the block copolymer ε-CL/St in the polymerization products was 0–87%, and the molecular weights in the case of copolymer formation were between 100,000 and 500,000. The content of St-units in the copolymers was from 10 to 75% as shown by GPC and ¹H-NMR. The mechanism of action of the initiator is discussed.     

Synthesis of poly(n‐butyl acrylate) homopolymer and poly(styrene‐b‐n‐butyl acrylate‐b‐styrene) triblock copolymer via AGET emulsion ATRP using a cationic surfactant

Cationic emulsions of triblock copolymer particles comprising a poly(n‐butyl acrylate) (PⁿBA) central block and polystyrene (PS) outer blocks were synthesized by activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP). Difunctional ATRP initiator, ethylene bis(2‐bromoisobutyrate) (EBBiB), was used as initiator to synthesize the ABA type poly(styrene‐b‐n‐butyl acrylate‐b‐styrene) (PS‐PⁿBA‐PS) triblock copolymer. The effects of ligand and cationic surfactant on polymerizations were also discussed. Gel permeation chromatography (GPC) was used to characterize the molecular weight (M_n) and molecular weight distribution (MWD) of the resultant triblock copolymers. Particle size and particle size distribution of resulted latexes were characterized by dynamic light scattering (DLS). The resultant latexes showed good colloidal stability with average particle size around 100–300 nm in diameter. Glass transition temperature (T_g) of copolymers was studied by differential scanning calorimetry (DSC). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 611–620     

Synthesis of Poly(Styrene)-block-poly(methacrylate)-block-poly(styrene) via Site Transformation Reaction

Abstract

Triblock copolymers with polystyrene outer blocks and an inner polymethacrylate block were synthesized by a site transformation reaction using anionic and cationic polymerization techniques. In order to obtain such ABA block copolymers, two synthetic routes have been applied. In the first case, different methacrylates (methyl methacrylate, 2-ethylhexyl methacrylate) were polymerized anionically with a bifunctional initiator to get poly(methacrylate) dianions later forming the inner block whereas in the second case poly(styrene)-block-poly(methacrylate) anions were synthesized by monofunctional initiation via sequential monomer addition. In a subsequent step, the living chain ends of the methacrylate dianions on one side, and the diblock copolymer anions on the other side, were functionalized with 1,4-bis(l-bromoethyl)benzene in order to obtain a potential bifunctional or monofunctional macroinitiator for the cationic polymerization of styrene. Then, styrene was polymerized cationically with the macroinitiator in the presence of SnCl₄ as coinitiator and _n Bu₄NBr as a common ion salt in CH₂Cl₂ at -15°C. Block formation was proven by SEC measurements, preparative SEC and NMR characterization.     

Investigation of the effect of reaction conditions on the synthesis of multiarm-star polyisobutylene-polystyrene block copolymers

New multi-arm star block copolymers comprising of rubbery polyisobutylene (PIB) midsegment and glassy polystyrene (PS) end blocks have been synthesized by carbocationic polymerization using a new multifunctional initiator, hexaepoxy squalene (HES), with TiCl₄ coinitiator, di-t-butylpyridine (DtBP) as a proton trap and N,N-dimethylacetamide (DMA) as an electron pair donor in methylcyclohexane (MeCHx)/methyl chloride (MeCl) solvent mixtures at −80 °C. It was found that reaction conditions, such as solvent composition, HES/isobutylene (IB) ratio and TiCl₄ concentration, have profound influence on initiator efficiency and functionality. Living conditions were achieved in the presence of DMA in MeCHx/MeCl 60/40 v/v, while in the absence of DMA, the M_n-conversion plot showed a considerable intercept. Depending on the reaction conditions, the PIB midblocks had 3-10 arms. Reaction rates increased with increasing solvent polarity and TiCl₄ concentration. Living narrow molecular weight distribution PIBs (M_w/M_n=1.1-1.2) were reacted with styrene (St) solution containing DtBP and DMA to yield multiarm-star PIB-PS block copolymers. Blocking was evidenced by SEC analysis and copolymers with 8.9-28.6 wt.% PS, M_n∼164,000-609,000 g/mol and M_w/M_n=1.32-1.88 were successfully synthesized.     

Anionic polymerization of n‐hexyl isocyanate with monofuctional initiators. Synthesis of well‐defined diblock copolymers with styrene and isoprene

Several monofunctional initiators, such as s‐BuLi, 1,1‐diphenyl‐4‐methylpentyl lithium (DPMPL), benzyl potassium (BzK), triphenylmethyl sodium (trityl sodium, TrNa) and benzyl sodium (BzNa) were tested and evaluated for the polymerization of n‐hexyl isocyanate (HIC) in THF at ?98 °C. The polymerizations were conducted either without or with additives, such as LiBPh₄, NaBPh₄, and crown ether 18C6. The products were characterized by size exclusion chromatography (SEC), membrane osmometry (MO), and ¹H NMR spectroscopy. The best results regarding polymerization yield, molecular weight distribution, and agreement between the stoichiometric and the experimentally observed molecular weight were obtained by the initiating system BzNa/NaBPh₄ in a molar ratio 1/10. By using BzNa/NaBPh₄ system, well‐defined block copolymers of HIC with styrene or isoprene were synthesized for the first time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3533–3542, 2005     

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me₆TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. ¹H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.     

Synthesis of Star‐Shaped Poly(ϵ‐caprolactone)‐b‐Poly(styrene) Block Copolymer by Combining Ring‐Opening Polymerization and Atom Transfer Radical Polymerization

Newly designed star‐shaped block copolymers made of poly(?‐caprolactone) (PCL) and polystyrene (PS) were synthesized by combining ring‐opening polymerization (ROP) of ?‐caprolactone (CL) and atom transfer radical polymerization (ATRP) of styrene (St). The switch from the first to the second mechanism was obtained by selective transformation of “living” radical sites. First, tri‐ and tetrafunctional initiators were used as an initiator for the “living” ring opening polymerization (ROP) of ?‐caprolactone producing a hydroxyl terminated three or four arm star‐shaped polymer. Next, the OH end groups of PCL star branches were derivatized into 2‐bromoisobutyrate groups which gave rise to the corresponding tri‐ and tetrabromoester ended‐PCL stars; the latter served as macroinitiators for the ATRP of styrene at 110°C in the presence of CuBr/2,2‐bipyridine (Bipy) catalyst system affording star‐shaped block copolymers PCL_n‐b‐PS_n (n=3 or 4). The samples obtained were characterizated by ¹H‐NMR spectroscopy and GPC (gel permeation chromatograph). These copolymers exhibited the expected structure. The crystallization of star‐shaped block copolymers was studied by DSC (differential scanning calorimetry). The results show that when the content of the PS block increased, the T_m of the star‐shaped block copolymer decreased.     

Synthesis of Vinyl Polymer—Poly (α-Amino Acid) Block Copolymers by End-Reactive Oligomers

In order to synthesize block copolymers consisting of segments having dissimilar properties, vinyl polymer - poly (α-amino acid) block copolymers were synthesized by two different methods. In the first method, the terminal amino groups of polysarcosine, poly(γ-benzyl L-glutamate), and poly(γ-benzyloxycarbonyl-L-lysine) were haloacetylated. The mixture of the terminally haloacetylated poly (α-amino acid) and styrene or methyl methacrylate was photoirradiated in the presence of Mo (CO)₆ or heated with Mo(CO)₆, yielding A-B-A-type block copolymers consisting of poly(α-amino cid) (the A component) and vinyl polymer(the B component). The characterization of block copolymers revealed that the thermally initiated polymerization of vinyl compounds by the trichloroacetyl poly(α-amino acid)/Mo(CO)₆ system was most suitable for the synthesis of vinyl polymer - poly-(α-amino acid) block copolymers. In the second method, poly (methyl methacrylate) and polystyrene having a terminal amino group were synthesized by the radical polymerization in the presence of 2-mercaptoethylammonium chloride. Using these polymers having a terminal amino group as an initiator, the block polymerizations of γ-benzyl L-glutamate NCA and e-benzyloxycarbonyl-L-lysine NCA were carried out, yielding A-B-type block copolymer. By eliminating the protecting groups of the side chains of poly(α-amino acid) segment, block copolymers such as poly(methyl methacrylate) with poly(L-glutamic acid) or poly(L-lysine) and polystyrene with poly(L-glutamic acid) and poly(L-lysine) were successfully synthesized.     

Effects of polystyrene-b-poly(aminomethyl styrene)s as stabilizers on dispersion polymerization of styrene in alcoholic media

The effects of polystyrene-b-poly(aminomethyl styrene) (PS_n-b-PAMS_m) stabilizers on the particle size (D_n) and size distribution (PSD) in dispersion polymerization of styrene were investigated. The block copolymers, PS_n-b-PAMS_m, were prepared as follows: (i) atom transfer radical polymerization (ATRP) of styrene (PS-Br), (ii) ATRP of vinylbenzylphthalimide with the PS-Br (PS-b-PVBP), and (iii) treatment of the PS-b-PVBP with hydrazine. When the dispersion polymerization of styrene proceeded at 60 °C in ethanol with PS₁₉-b-PAMS₁₃₀ stabilizer, spherical polystyrene particles with D_n=0.91 μm (PSD = 1.01) were obtained. The particle size was strongly affected by the copolymer composition. With an increase in PAMS block length from m=54 to 100 in PS₁₇-b-PAMS_m, particle diameter became smaller from 1.55 to 0.91 μm. On the other hand, an increase in the length from m=20 to 82 in PS₃₄-b-PAMS_ms caused an increase in particle size from 0.35 to 0.70 μm. Titration of the particles suggests that 14–81% of stabilizers used in the polymerization system were attached on the polystyrene particle surfaces, depending on the composition of the block copolymers. Thus, for the dispersion polymerization of styrene, PS_n-b-PAMS_m block copolymers have both functions as a stabilizer during polymerization and surface-modification sites of polystyrene particles.     

Kinetics and mechanism of emulsifier-free emulsion polymerization. II. Styrene/water soluble comonomer (sodium methallyl sulfonate) system

The emulsifier-free emulsion polymerizations of styrene in the presence of about 1 wt% (related to styrene) of the water soluble comonomer, sodium methallyl sulfonate (NaMS), which has short hydrophobic group and strong hydrophilic ionic group, and of the initiator, potassium persulfate, are carried out. Under constant ionic strength, the number density of polymer particles (N_p) is found to depend on 0.5-power of the initiator concentration and shows a minimum in the comonomer concentration plot. Under constant concentration of monomer, comonomer and initiator, N_p is found to depend on ?1.1-power of the ionic strength. In the earlier period, the presence of styrene oligomer having MW about 1000 and water soluble poly(NaMS) or copolymer with high NaMS content suggests a micellar nucleation mechanism, by which the styrene oligomer behaves as emulsifier and the poly(NaMS) can either stabilize or destabilize the existing particles, depending on its concentration in the aqueous phase. The particle size is rather uniform having an uniformity very close to 1 (ca. 1.001) throughout the entire process. It is much larger than that of the conventional emulsion polymerization or emulsifier-free emulsion polymerization with the other comonomers by about 3 to 4 times in diameter or 27 to 64 times in volume, leading to that the average radical number in the particle could be much greater than 0.5. The (conversion)^2/3 versus time plot is found to be linear from 6 to 50% conversion. During this period, for the conversion from 10 to 40% the polymerization rate increases twice but the particle volume increases four-fold. In addition, MWD shows bimodal (excluding the styrene oligomer peak in the earlier period) during the growth period. But the lower MW peak shifts to higher MW and become larger, while the higher MW peak decreases, and finally the MWD becomes single mode after 58.6% conversion. These results suggest a “gradient polymerization” or “transition stage to core-shell structure” in the earlier stage of particle growth and a “shell part polymerization” in the later stage.     

Vinyl Polymerization. 431. Vinyl Polymerizations Initiated by Block and Random Poly(Styrene-co-Sodium Methacrylate)

Abstract

The polymerization of some kinds of vinyl monomer was found to occur without an ordinary initiator in aqueous solutions of AB-type block or random copolymers of sodium methacrylate with styrene as a so-called “uncatalyzed polymerization.” Although the spin trapping technique showed that the initiation mechanism by the block copolymer was the same as that by the random copolymer, the initiating ability of the block copolymer was lower than that of the random copolymer. Such results are attributable to the difference in the incorporating ability of monomer into the micelles formed by the block copolymer and into the hydrophobic areas formed by the random copolymer.     

Difunctional initiator based on 1,3-diisopropenylbenzene. IV. Synthesis and modification of poly(alkyl methacrylate- b-styrene-b-butadiene- b-styrene-b-alkyl methacrylate (MSBSM)) thermoplastic elastomers

MSBSM five-block copolymers where B stands for butadiene, S for styrene, and M for either methyl methacrylate (MMA) or tert-butyl methacrylate (tBMA) have been synthesized by sequential anionic polymerization in an apolar solvent by using a difunctional anionic initiator derived from 1,3-diisopropenylbenzene. These block copolymers show improved mechanical properties and an extended service temperature compared to traditional SBS thermoplastic elastomers. Upon hydrolysis and further neutralization of the PolytBMA end-blocks, the upper glass transition temperature (T_g) of the five-block copolymers has been raised up to about 150°C. A further increase in this service temperature (up to ca. 160°C) has resulted from the blending of sPMMA-SBS-sPMMA five-block copolymers with isotactic poly(methacrylate) (iPMMA), due to the formation of a stereocomplex. The tensile properties of these modified five-block copolymers have remained essentially unchanged. © 1996 John Wiley & Sons, Inc.     

Synthesis of poly(tetrahydrofuran)‐b‐polystyrene block copolymers from dual initiators for cationic ring‐opening polymerization and atom transfer radical polymerization

A dual initiator (4‐hydroxy‐butyl‐2‐bromoisobutyrate), that is, a molecule containing two functional groups capable of initiating two polymerizations occurring by different mechanisms, has been prepared. It has been used for the sequential two‐step synthesis of well‐defined block copolymers of polystyrene (PS) and poly(tetrahydrofuran) (PTHF) by atom transfer radical polymerization (ATRP) and cationic ring‐opening polymerization (CROP). This dual initiator contains a bromoisobutyrate group, which is an efficient initiator for the ATRP of styrene in combination with the Cu(0)/Cu(II)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system. In this way, PS with hydroxyl groups (PS‐OH) is formed. The in situ reaction of the hydroxyl groups originating from the dual initiator with trifluoromethane sulfonic anhydride gives a triflate ester initiating group for the CROP of tetrahydrofuran (THF), leading to PTHF with a tertiary bromide end group (PTHF‐Br). PS‐OH and PTHF‐Br homopolymers have been applied as macroinitiators for the CROP of THF and the ATRP of styrene, respectively. PS‐OH, used as a macroinitiator, results in a mixture of the block copolymer and remaining macroinitiator. With PTHF‐Br as a macroinitiator for the ATRP of styrene, well‐defined PTHF‐b‐PS block copolymers can be prepared. The efficiency of PS‐OH or PTHF‐Br as a macroinitiator has been investigated with matrix‐assisted laser desorption/ionization time‐of‐flight spectroscopy, gel permeation chromatography, and NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3206–3217, 2003     

New initiator system for the anionic polymerization of (meth)acrylates in toluene. IV. Random copolymerization of (meth)acrylates in toluene initiated by s-BuLi ligated by lithium silanolates

Copolymerization of binary mixtures of alkyl (meth)acrylates has been initiated in toluene by a mixed complex of lithium silanolate  (s-BuMe₂SiOLi) and s-BuLi (molar ratio > 21) formed in situ by reaction of s-BuLi with hexamethylcyclotrisiloxane (D₃). Fully acrylate and methacrylate copolymers, i.e., poly(methyl acrylate-co-n-butyl acrylate), poly(methyl methacrylate-co-ethyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate) of a rather narrow molecular weight distribution have been synthesized. However, copolymerization of alkyl acrylate and methyl methacrylate pairs has completely failed, leading to the selective formation of homopoly(acrylate). As result of the isotactic stereoregulation of the alkyl methacrylate polymerization by the s-BuLi/s-BuMe₂SiOLi initiator, highly isotactic random and block copolymers of (alkyl) methacrylates have been prepared and their thermal behavior analyzed. The structure of isotactic poly(ethyl methacrylate-co-methyl methacrylate) copolymers has been analyzed in more detail by Nuclear Magnetic Resonance (NMR). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2525–2535, 1999