Synthesis of Amphiphilic Poly(ethylene oxide‐co‐glycidol)‐graft‐polyacrylonitrile Brush Copolymers and their Self‐assembly in Aqueous Media

An amphiphilic copolymer brush poly(ethylene oxide‐co‐glycidol)‐graft‐polyacrylonitrile [poly(EO‐co‐Gly)‐g‐PAN], is successfully prepared for the first time by a combination of anionic polymerization and redox free radical polymerization. The final products and intermediates are characterized by NMR and GPC. Aggregates made from the brush copolymers, poly(EO‐co‐Gly)‐g‐PAN, with a long hydrophobic graft length in water are studied by TEM and DLS. The effects of hydrophobic graft length and water content on the morphologies are discussed. Some rare morphologies of aggregates are observed, such as lamellae, bicontinuous networks, bowls or nanosheets, and large compound rods with a brittleness that can be ascribed to the orientation of high content semi‐crystalline PAN segments.     

Graft Copolymers with Complex Polyether Structures: Poly(ethylene oxide)‐graft‐Poly(isobutyl vinyl ether) by Combination of Living Anionic and Photoinduced Cationic Graft Polymerization

A novel polymerization mechanism transformation strategy, involving anionic ring‐opening polymerization and photoinduced cationic polymerization, is successfully applied for the synthesis of poly(ethylene oxide)‐graft‐poly(isobutyl vinyl ether) (PEO‐g‐PIBVE). First, poly(ethylene oxide‐co‐ethoxyl vinyl glycidyl ether) [P(EO‐co‐EVGE)] is synthesized by living anionic polymerization. The vinyl moieties of the functional PEO‐based polymer are converted to the hydrogen iodide adduct by photolysis of diphenyliodonium iodide, monitored using NMR spectroscopy. A modified mode of Lewis acid‐catalyzed living cationic polymerization is performed as a “grafting from” method to generate PIBVE segments grafted onto the PEO main chain. Both the intermediates and the final graft copolymers are characterized by gel‐permeation chromato­graphy (GPC) and ¹H NMR analysis.

     

Amphiphilic PEG‐co‐PGL‐g‐PCL Copolymer Brushes: Synthesis,Micellization and Controlled Drug Delivery

A series of amphiphilic graft copolymers of poly(ethylene glycol)‐co‐glycidol‐graft‐(ε‐caprolactone) (PEG‐co‐PGL‐g‐PCL) with PEG as the hydrophilic backbone chain and hydrophobic PCL as side chains have been synthesized by living anionic polymerization and ring‐opening polymerization. By changing the composition of the PEG‐co‐PGL backbone chains, and the molar ratio of CL monomer to PEG‐co‐PGL in the feed, copolymers with well‐defined architecture and controllable numbers and length of graft chains can be obtained. The micellization and drug release of the PEG‐co‐PGL‐g‐PCL graft copolymers have been studied in terms of dependence on graft numbers and length, and the results indicate that the micelles with shorter PCL side chains have more compact cores and a relatively small size which are favorable for drug loading and controlled release.

     

A Novel,Amphiphilic Ethyl Cellulose Grafting Copolymer with Poly(2‐Hydroxyethyl Methacrylate) Side Chains and Its Micellization

Ethyl cellulose‐graft‐poly(2‐hydroxyethyl methacrylate) (EC‐graft‐PHEMA) graft copolymers were synthesized by atom‐transfer radical polymerization (ATRP) in methanol. The graft copolymers were characterized by means of gel‐permeation chromatography (GPC) and ¹H NMR spectroscopy. The kinetic study indicated that the polymerization was controllable. The EC‐graft‐PHEMA copolymers self‐assembled in water into spherical micelles. The morphology of the micelles was characterized by dynamic light scattering (DLS) and transmission electric microscopy (TEM) and the formation process of the micelles was discussed.

     

Synthesis of a Poly(vinyl alcohol)‐Based Graft Copolymer Having Poly(ε‐caprolactone) Side Chains by Solution Polymerization

Poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) (PVA‐g‐PCL) was synthesized by ring‐opening polymerization of ε‐caprolactone with poly(vinyl alcohol) in the presence of tin(II) 2‐ethylhexanoate as a catalyst in dimethyl sulfoxide. The relationship between the reaction conditions of the solution polymerization and the chemical structure of the graft copolymer was investigated. The degree of substitution (DS) and degree of polymerization (DP) of the PCL side chains were roughly controlled by varying the reaction periods and feed molar ratios of the monomer and the catalyst to the backbone. PVA‐g‐PCL with a PCL content of 97 wt.‐% (DP = 22.8, DS = 0.54) was obtained in 56 wt.‐% yield. The graft copolymer was soluble in a number of organic solvents, including toluene, tetrahydrofuran, chloroform, and acetonitrile, which are solvents of PCL. The molecular motion of the graft copolymer from ¹H NMR measurements appears to be restricted to some extent at 27–50°C, however the ¹H NMR signal intensities measured at temperatures higher than ca. 50°C reflect the actual chemical structure of the graft copolymer as determined by elemental analysis. The graft copolymer having a short PCL side chain (DP = 4.4, DS = 0.15) was amorphous. The melting temperature of a sample with relatively high PCL content (DP = 22.8, DS = 0.54) was observed at 39°C. Thermogravimetric analysis revealed that the thermal stability of PVA was improved by introducing PCL side chains. The surface free energies of the air‐side of a graft copolymer film, as calculated by Owens' equation using contact angles, were comparable to that of PCL homopolymer.     

Synthesis and characterization of dextran grafted with poly(N‐isopropylacrylamide‐co‐N,N‐dimethyl‐acrylamide)

Graft copolymers consisting of dextran as a main chain and poly(N‐isopropylacrylamide‐co‐N,N‐dimethylacrylamide) (poly(NIPAAm‐co‐DMAAm)) as graft chains were synthesized. For the synthesis of the graft copolymers, a semitelechelic poly(NIPAAm‐co‐DMAAm) with an amino end‐group was obtained by radical copolymerization with ethanethiol as a chain transfer agent, followed by a coupling reaction of its hydroxyl end‐group with ethylenediamine. Graft copolymers with various length of the grafts were obtained from coupling reactions between carboxymethyl dextran and poly‐(NIPAAm‐co‐DMAAm) in the presence of a water‐soluble carbodiimide. The graft copolymers in phosphate buffer exhibit lower critical solution temperatures due to thermosensitivity of their grafts. There is no significant change in the hydration‐dehydration behavior of the poly(NIPAAm‐co‐DMAAm) chain after the grafting reaction. The existence of such grafts in dextran may play an important role for modulated degradation in synchronization with temperature.     

Nano‐Scale Molecular Shapes of Water‐Soluble Chitin Derivatives Having Monodisperse Poly(2‐alkyl‐2‐oxazoline) Side Chains

The molecular shapes and the sizes of structures formed by chitin derivatives with monodisperse poly(2‐alkyl‐2‐oxazoline) side chains were investigated using atomic force microscopy (AFM), cryo‐transmission electron microscopy (cryo‐TEM), and small‐angle neutron scattering (SANS) analyses. A ring structure with an outside diameter of 45–60 nm and a cross‐sectional diameter of 10–18 nm was observed in the AFM image for chitin‐graft‐poly(2‐methyl‐2‐oxazoline) 1d (DP of the side chain, 8.5; [side chain]/[glucosamine unit], 0.53). From the cryo‐TEM observation of the graft copolymer 1d in 0.5 wt.‐% D₂O solution, an average diameter of 40 nm for the particles was determined, with a narrow size distribution. SANS measurements of the 0.5 wt.‐% D₂O solution of 1d revealed that the outside diameter of the particles and the cross‐sectional diameter were 57 nm and 8 nm, respectively. The absolute weight average molecular weight of 1d was determined to be 5.4 × 10⁵ by static light scattering. From these results it was concluded that 1d can form a unimolecular ring structure in aqueous solution. However, graft copolymers with fewer side chains ( 1c ; [side chain]/[glucosamine unit], 0.30) and with more side chains ( 1e ; [side chain]/[glucosamine unit], 0.96) did not form rings but instead formed monodisperse unimolecular spherical particles of diameters of 28–36 nm by AFM. A graft copolymer 1f with relatively long side chains (DP of side chain, 19.6; [side chain]/[glucosamine unit], 1.00) was also observed as a spherical particle by AFM (diameter: 30–40 nm by AFM; 40 nm by SANS). On the other hand, an intermolecular aggregate formation (diameter of the aggregate: 36–143 nm) was observed for graft copolymers 1a and 1b having short side chains (DP of side chains, 5.6; [side chain]/[glucosamine unit], 0.35 and 0.48, respectively), with a spherical molecular particle of diameter 36 nm by the AFM analysis. Chitin‐graft‐poly(2‐ethyl‐2‐oxazoline) ( 2 ) (DP of side chains, 21.7; [side chain]/[glucosamine unit], 0.95) generated larger aggregates of diameter 100–400 nm by AFM. The complexation behavior of graft copolymer 1d with magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS) and with N‐phenyl‐1‐naphthylamine (PNA) was also examined by fluorescence measurement in an aqueous solution. It was found that graft copolymer 1d complexed with both ANS and PNA, and the binding constants were calculated to be 7.5 × 10⁴ M ^?1 and 5.3 × 10⁴ M ^?1, respectively.

Chemical structure of chitin‐graft‐poly(2‐alkyl‐2‐oxazoline).     

Combining ATRP of Methacrylates and ROP of L,L‐Dilactide and ε‐Caprolactone

Coupling atom transfer radical polymerization (ATRP) and coordination‐insertion ring‐opening polymerization (ROP) provided a controlled two‐step access to polymethacrylate‐graft‐polyaliphatic ester graft copolymers. In the first step, copolymerization of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 80 °C at high MMA concentration by using ethyl 2‐bromoisobutyrate and [NiBr₂(PPh₃)₂] as initiator and catalyst, respectively. Kinetic and molar masses measurements, as well as ¹H NMR spectra analysis of the resulting poly(MMA‐co‐HEMA)s highlighted the controlled character of the radical copolymerization, while the determination of the reactivity ratios attested preferential incorporation of HEMA. The second step consisted of the ROP of ε‐caprolactone or L ,L ‐dilactide, in THF at 80 °C, promoted by tin octoate (Sn(Oct)₂) and coinitiated by poly(MMA‐co‐HEMA)s obtained in the first step. Once again, kinetic, molar mass, and ¹H NMR data demonstrated that the copolymerization was under control and started on the hydroxyl functions available on the poly(MMA‐co‐HEMA) multifunctional macroinitiator.

Comparison of the SEC traces for the poly(MMA‐co‐HEMA) macroinitiator P2 (line only), the polymethacrylate‐g‐PLA copolymer C2 (line marked by ○), and the polymethacrylate‐g‐PLA C3 (line marked by ?).     

Synthesis and Characterization of Amphiphilic Poly(ethylene oxide)‐block‐poly(hexyl methacrylate) Copolymers

We describe the preparation of amphiphilic diblock copolymers made of poly(ethylene oxide) (PEO) and poly(hexyl methacrylate) (PHMA) synthesized by anionic polymerization of ethylene oxide and subsequent atom transfer radical polymerization (ATRP) of hexyl methacrylate (HMA). The first block, PEO, is prepared by anionic polymerization of ethylene oxide in tetrahydrofuran. End capping is achieved by treatment of living PEO chain ends with 2‐bromoisobutyryl bromide to yield a macroinitiator for ATRP. The second block is added by polymerization of HMA, using the PEO macroinitiator in the presence of dibromobis(triphenylphosphine) nickel(II), NiBr₂(PPh₃)₂, as the catalyst. Kinetics studies reveal absence of termination consistent with controlled polymerization of HMA. GPC data show low polydispersities of the corresponding diblock copolymers. The microdomain structure of selected PEO‐block‐PHMA block copolymers is investigated by small angle X‐ray scattering experiments, revealing behavior expected from known diblock copolymer phase diagrams.

SAXS diffractograms of PEO‐block‐PHMA diblock copolymers with 16, 44, 68 wt.‐% PEO showing spherical (A), cylindrical (B), and lamellae (C) morphologies, respectively.     

A Novel Macroinitiator for the Synthesis of Triblock Copolymers via Atom Transfer Radical Polymerization: Polystyrene‐block‐poly(bisphenol A carbonate)‐block‐polystyrene and Poly(methyl methacrylate)‐block‐poly(bisphenol A carbonate)‐block‐poly(methyl methacrylate)

Summary: Bis(hydroxy)telechelic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(III ) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α‐chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS‐block‐PC‐block‐PS and PMMA‐block‐PC‐block‐PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.

Formation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.     

Poly(ε‐caprolactone)‐graft‐poly(2‐(dimethylamino)ethyl methacrylate) Amphiphilic Copolymers Prepared via a Combination of ROP and ATRP: Synthesis,Characterization, and Self‐Assembly Behavior

Poly(ε‐caprolactone)‐graft‐poly(2‐(dimethylamino) ethyl methacrylate) (PCL‐g‐PDMAEMAs), a kind of amphiphilic graft copolymer, was prepared by combination of ROP and ATRP. The FTIR, ¹H NMR, and GPC results indicate that well‐defined polymers with controlled graft density and length of side chain were successfully synthesized. We prepared PCL‐g‐PDMAEMA nanoparticles by employing a nanoprecipitation technique. The pH‐ and thermosensitive properties of PCL‐g‐PDMAEMA nanoparticles were investigated by ¹H NMR, TEM, and DLS. It was found that the nanoparticles with an average size of 120 nm presented core–shell structure in aqueous dispersion. Furthermore, the nanoparticles are sensitive to temperature in base while not in an acidic environment.

     

Synthesis and Characterization of Semicrystalline Polyethylene‐graft‐Poly(acrylic acid) Copolymers

Hydrophilic polyolefin materials were prepared by grafting tBA from PE macroinitiators bearing functionalized norbornene units capable of initiating an ATRP. This method produced semicrystalline graft copolymers (PE‐graft‐PtBA) with narrow molecular weight distributions (1.2–1.4) and tunable tBA content (2–21 mol‐%). Incorporation of tBA resulted in a decrease in crystallinity, but little change in the melting point of the products. Subsequently, the tBA moieties were converted into acrylic acid units through chemical and thermal means to generate PE‐graft‐PAA copolymers. The increased hydrophilicity of the resulting materials was verified by ATR‐IR, solid‐state ¹³C NMR spectroscopy, contact angle measurements, and TGA.

     

A Poly(vinyl alcohol)‐graft‐Copolyester: Synthesis of a Novel Graft Copolymer Containing Adamantane Moieties as Guest for Cyclodextrin

A novel graft copolymer is synthesized from commercially available poly(vinyl alcohol) using ring‐opening polymerization. For the polymerization reaction of novel brush‐like poly(vinyl alcohol)‐graft‐poly(?‐caprolactone‐co‐(3‐/7‐(prop‐2‐ynyl)oxepan‐2‐one) 5 Sn(Oct)₂ is used as a catalyst. The formation of the graft copolymer is confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the modification of the novel synthesized graft copolymer via a “click” reaction to implement adamantane groups is described. The success of the “click” reaction is proven by ¹H NMR spectroscopy and visualized by decomplexation of cyclodextrin with included phenolphthalein.

     

Synthesis of Poly(ethylene‐co‐butylene)‐block‐Poly(methyl methacrylate) by Atom Transfer Radical Polymerization: Determination of the Macroinitiator Conversion

The synthesis of poly(ethylene‐co‐butylene)‐block‐poly(methyl methacrylate) via atom transfer radical polymerization (ATRP) of methyl methacrylate onto a poly(ethylene‐co‐butylene) macroinitiator is described. Copper bromide (CuBr), copper chloride (CuCl) and copper thiocyanate (CuSCN) were applied as active ATRP catalysts with N‐pentyl‐2‐pyridylmethanimine as ligand, in order to study the effect of the copper counter ion on the rate of activation of the bromine‐functional polyolefin macroinitiator. The reaction products were subjected to normal phase gradient polymer elution chromatography (NP‐GPEC) in order to separate residual macroinitiator from the block copolymers. The amount of residual macroinitiator was monitored for each catalyst system by evaporative light scattering detection, where the chromatograms were normalized on a PS standard, which was added to the reaction mixture before polymerization. The rate of activation of the macroinitiator is strongly affected by the copper counter ion and increases in the order CuSCN < CuBr < CuCl. The high reproducibility of this observation is in contrast with the significant effect of polymerization conditions like e. g. catalyst solubility, presence of water and trace amounts of oxygen, on the overall rate of polymerization.     

Synthesis of Silicone‐Methacrylate Copolymers by ATRP Using a Nickel‐Based Supported Catalyst

Summary: A nickel (II) bromide catalyst immobilized onto crosslinked diphenylphosphinopolystyrene (PS‐PPh₃/NiBr₂) was used for the synthesis of silicone‐methacrylate copolymers by atom transfer radical polymerization (ATRP) of various methacrylate monomers using ω‐bromide silicone chains as macroinitiator. The polymerization proved to be very well‐controlled when a sufficient amount of soluble ligand, i.e., triphenylphosphine (PPh₃), was added to the polymerization medium. Under these conditions, this technique efficiently led to the production of different copolymers with controlled compositions and molecular weights as well as narrow polydispersity indices ( < 1.5). The recovered copolymers proved to be almost free of catalyst residues. Indeed, inductively coupled plasma (ICP) analysis revealed a metal content lower than 100 ppm, representing only a few percent of the initial metal content in the polymerization medium.

Synthesis of PDMS block copolymer in toluene catalyzed by PS‐PPh₃/NiBr₂ in the presence of soluble PPh₃ at 90 °C.     

Novel Brush Copolymers via Controlled Radical Polymerization

Summary: A combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) techniques were applied for the synthesis of novel polymer brushes by using the “grafting from” approach or a combination of “grafting through” and “grafting from” methods. The procedure included the following steps: (1) Synthesis of 2‐(2‐bromoisobutyryloxy)ethyl methacrylate (BIEM), (2a) RAFT homopolymerization of BIEM to obtain PBIEM as the polymer backbone. (2b) RAFT copolymerization of BIEM and PEO macromonomer (PEOMA, = 450 g · mol^?1, = 9) to obtain a more hydrophilic polymer backbone. Well‐controlled copolymers containing almost 25 mol‐% of PEOMA were obtained, and (3) ATRP homopolymerization of methyl acrylate (MA) and copolymerization of MA with 1‐octene using both PBIEM homopolymer and poly(BIEM‐co‐PEOMA) as polyinitiators resulted in brushes with densely grafted homopolymer and copolymer side chains, respectively. Well‐controlled copolymer side chains containing 15 mol‐% of 1‐octene were obtained. Relatively narrow molar mass distributions (MMD) were obtained for the ATRP experiments. The formation of the side chains was monitored using size exclusion chromatography (SEC) and NMR spectroscopy. The copolymer composition in the side chain was confirmed using ¹H NMR spectroscopy. Contact angle measurements indicated that for the brush polymers, containing 1‐octene in the side chain, there was a decrease in the surface energy, as compared with the brush polymers containing only the homopolymer of MA in the side chain.

Tapping‐mode SFM images for the poly(BIEM)‐graft‐poly(MA‐co‐octene) brush polymer, dip coated from dilute THF solution on mica.     

Cellulose Acetate‐graft‐Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer Composition

Summary: Several different series of cellulose acetate‐graft‐poly(hydroxyalkanoate)s (CA‐g‐PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L ‐lactide, (R,S)‐β‐butyrolactone, δ‐valerolactone and ε‐caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA‐g‐PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi‐empirical equations available for polymer blends or comb‐like polymers. In particular, the composition dependence of the T_gs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb‐like polymers, when CAs of acetyl DS ≈2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification.

     

Synthesis and Characterization of a Well‐Defined Graft Copolymer Containing Fluorine Grafts by “Living”/Controlled Radical Polymerization

The well‐defined graft copolymer consisting of side chains containing fluorine was synthesized by atom transfer radical polymerization (ATRP) of 2,2,3,3,4,4,5,5‐octafluoropentyl acrylate (OFPA) with the copolymer of styrene and chloromethylstyrene as macroinitiator, which was first synthesized by the nitroxide‐mediated copolymerization of styrene (St) and 4‐chloromethylstyrene (CMS) at 130°C with benzoyl peroxide/4‐hydro‐TEMPO as initiator. These copolymers, i. e. P(St‐co‐CMS) and P(St‐g‐OFPA), were characterized by means of GPC, IR and ¹H NMR, respectively. The water contact angles on polystyrene films containing small amount of P(St‐g‐OFPA) as additive were also measured and studied.     

Synthesis and Characterization of Poly(trimethylene oxide)‐block‐Polystyrene and Poly(trimethylene oxide)‐block‐Polystyrene‐block‐Poly(methyl methacrylate) by Combination of Atom Transfer Radical Polymerization (ATRP) and Cationic Ring‐Opening Polymerization (CROP)

Summary: Diblock copolymers, poly(trimethylene oxide)‐block‐poly(styrene)s abbreviated as poly(TMO)‐block‐poly(St), and triblock copolymers, poly(TMO)‐block‐poly(St)‐block‐poly(MMA)s (MMA = methyl methacrylate), with controlled molecular weight and narrow polydispersity have been successively synthesized by a combination of atom transfer radical polymerization (ATRP) and cationic ring‐opening polymerization using the bifunctional initiator, 2‐hydroxylethyl α‐bromoisobutyrate, without intermediate function transformation. The gel permeation chromatography (GPC) and NMR analyses confirmed the structures of di‐ and triblock copolymers obtained.

GPC curves of (a) poly(St); (b) diblock copolymer, poly(St)‐block‐poly(MMA) before precipitation; (c) poly(St)‐block‐poly(MMA) after precipitation in cyclohexane/ethanol (2:1); (d) triblock copolymer, poly(TMO)‐block‐poly(St)‐block‐poly(MMA).     

Block Copolymers from Organomodified Siloxane‐Containing Macroinitiators by Atom Transfer Radical Polymerization

Alternating copolymers of 1,3‐diisopropenylbenzene and 1,1,3,3‐tetramethyldisiloxane were synthesized by hydrosilylation–polyaddition. These linear copolymers were functionalized at both ends with 2‐bromoisobutyryl or benzyl chloride moieties. Subsequently, the obtained organomodified siloxane‐containing macroinitiators were successfully used for the preparation of ABA‐type block copolymers by atom transfer radical polymerization (ATRP) of styrene and tert‐butyl acrylate. The high chain‐end functionality of the macroinitiators was confirmed by ¹H NMR analysis of the macroinitiators and GPC measurements of the obtained ABA‐type block copolymers. The macroinitiator peaks disappeared in GPC traces after ATRP, and the obtained block copolymers showed a significantly narrower molecular‐weight distribution than the macroinitiators.

Synthesis of ABA‐type block copolymers by means of ATRP using organomodified siloxane‐containing, benzyl chloride functionalized macroinitiators.