Atom Transfer Radical Polymerization Of Styrene Research Articles

Preparation of dendron-like polystyrenes from atom transfer radical polymerization (ATRP) and direct chain-end functionalization

Dendron-like branched polystyrenes are prepared using atom transfer radical polymerization (ATRP) and chain-end functionalization. The growing chain ends of polystyrene from ATRP are end-capped with 1,4-benzoquinone to incorporate branching points and ATRP initiating groups to the chain ends. Sequential ATRP of styrene initiated from the chain ends builds up the polystyrene arms. The number-averaged molecular weights of the first, second, and third generations of dendron-like polystyrene polymers calculated from their respective 1H NMR spectra are 5960, 6850, and 9150 g/mol, respectively. The NMR-data are consistent with the molecular weights determined by GPC. An approach to prepare dendron-like polymers through ATRP and chain-end functionalization is developed.

Synthesis of Organic/Inorganic Hybrid Quatrefoil-Shaped Star-Cyclic Polymer Containing a Polyhedral Oligomeric Silsesquioxane Core

We report the synthesis of quatrefoil-shaped star-cyclic polystyrene, star-cyclic PS, containing a polyhedral oligomeric silsesquioxane (POSS) core via the combination of atom transfer radical polymerization (ATRP) and click chemistry techniques. The obtained star-cyclic PS represents a new chain topology in the category of nonlinear-shaped polymers. Using octa(3-chloropropyl) polyhedral oligomeric silsesquioxane, POSS-(Cl)8, as the starting material, its azidation and subsequent click reaction with a slight excess of propargyl 2-bromobutyrate afforded octafunctional initiator, POSS-(Br)8. 8-arm star-linear PS-N3 was obtained by the azidation of star-linear PS-Br, which was synthesized by the ATRP of styrene using POSS-(Br)8 as the initiator. Model reaction between α,ω-diazido-terminated PS (N3-PS-N3) and difunctional propargyl ether confirmed that bimolecular click cyclization reaction can effectively occur under highly dilute conditions. Next, intramolecular click ring closure of star-linear PS-N3 was c...

Iron(III) complexes of bidentate nitrogen ligands as catalysts in reverse atom transfer radical polymerization of styrene

Three iron(III) complexes of bidentate nitrogen ligands, namely 3,5-dimethyl-bispyrazolylmethane (bpzm), 2,2′-dipyridyl (bipy) and 1,1-bis(4,4-dimethyl-1,3-oxazolyn-2-yl)-ethane (box), have been tested in atom transfer radical polymerization (ATRP) of styrene at 120 °C using the 1,1,2,2-tetraphenyl-1,2-ethanediol (TPED) initiator under reverse protocol. Good control of the polymerization reaction and narrow average molecular weight distribution (PDI) have been found for the TPED/FeCl 3/box catalyst whereas TPED/FeCl 3/bpzm and TPED/FeCl 3/bipy produce linear dependence of M n vs polymerization time but PDI values broader than that expected for a controlled mechanism. Attempts to clarify the performances of these catalysts were carried out, evaluating the formation constants β III and the electrochemical parameters E 1/2 of the FeCl 3/L adducts (L = bpzm; bipy; box) by means of UV–vis spectroscopy and cyclic voltammetry, respectively. A regular increase of both β III and E 1/2 values was observed as the Lewis basic properties of the ligands increase in the order bpzm < bipy < box. The best performances of the FeCl 3/box catalyst have been thus attributed to the highest formation constant that produce easy and reversible reduction of the iron(III) metal centre to the corresponding iron(II). Lower reducibility and reversibility were found for the iron(III)/iron(II) redox couple in FeCl 3/bipy and FeCl 3/bpzm in agreement with the modest performances in ATRP of styrene of these complexes.

New Strategy Targeting Well‐Defined Polymethylene‐block‐Polystyrene Copolymers: The Combination of Living Polymerization of Ylides and Atom Transfer Radical Polymerization

Well-defined polymethylene-block-polystyrene (PM-b-PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl-terminated polymethylenes (PM-OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM-MIs ($\overline M _{\rm n}$ = 1 900-15 000; PDI = 1.12-1.23)) transformed from PM-OHs in ≈ 100% conversion initiated ATRPs of styrene to construct PM-b-PS copolymers. The GPC traces indicated the successful extension of PS segment ($\overline M _{\rm n}$ of PM-b-PS = 5 000-41 800; PDI = 1.08-1.23). Such copolymers were characterized by (1) H NMR and DSC.

Preparation of Tadpole-Shaped Amphiphilic Cyclic PS-b-linear PEO via ATRP and Click Chemistry

Amphiphilic tadpole-shaped copolymers consisting of a polystyrene (PS) ring and a poly(ethylene oxide) (PEO) tail were synthesized via atom transfer radical polymerization (ATRP) and click chemistry. First, PEO with a propargyl group and an ATRP initiating group was prepared via click chemistry and esterification. Then, a diblock copolymer, PEO-b-PS, which contained a propargyl group at the junction point and an azide group at the PS chain end, was prepared via ATRP of styrene, followed by transformation of the PS bromo end to an azide group. Finally, cyclization of the PS segment via click chemistry in dilute solution led to the formation of cyclic PS-b-linear PEO (c-PS-b-PEO). Because both the chain length of PEO and the ring size of cyclic PS can be easily tuned, a series of c-PS-b-PEOs was prepared. All of the polymers were characterized with gel permeation chromatography, NMR spectroscopy, FTIR, and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). c-PS-b-PEOs showed smaller hydrodynamic volumes compared with their linear precursors. Self-assembly of one c-PS-b-PEO sample and its linear precursor in water was preliminarily investigated by transmission electron microscopy. We found that vesicles were the main morphologies for both polymers, but they were different in size; those from c-PS-b-PEO were much larger.

A general synthesis approach toward halloysite‐based composite nanotube

AbstractWe have demonstrated a general template synthesis halloysite‐based composite nanotube. Starting from a parent halloysite nanotube, polymer composite nanotubes were synthesized by atom transfer radical polymerization (ATRP). The shell thickness and the cavity size of the polymer composite nanotubes were tunable by altering the polymerization time. Composition of the polymer layer could be tuned by the monomers, for example, polystyrene (PS) layer was achieved by ATRP of styrene. Sulfonated PS layer (sPS) can be derived by the sulfonation of the PS layer. By specific interactions of desired materials with the sPS gel, a favorable growth of other materials, for example, metallic Ni, conductive polyaniline, inorganic titania is allowed. Besides, sPS can self‐catalyze into carbon at high temperature. Thus, the composition of the composite layers can be broadly controlled ranging within metal or metallic compounds, polymer, inorganic, carbon, and their composites. This concept is general and can be extended to other polymeric gels and grown materials, expecting a huge family of composite nanotube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of the Ligand in Atom Transfer Radical Polymerization Reactions Initiated by Photodimers of 9‐Bromoanthracene

AbstractSlow initiation from the bridgehead radical in atom transfer radical polymerization (ATRP) reactions initiated by 9‐bromoanthracene photodimers leads to polymers' products possessing high PDI values and higher than expected $\overline M _{\rm n}$ values. We report here the effects of changing the ligand from N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) to the highly active tris[2‐(dimethylamino)ethyl]amine (Me6TREN) or tris[(2‐pyridyl)methyl]amine (TPMA) in an attempt to push the initial equilibrium further toward the initiating bridgehead radical. Overall, the ligand choice was found to add negligible control to the ATRP of styrene with any increase in the rate of initiation offset by an increase in the rate of propagation, leading to anthracene‐labeled polystyrene with similar PDI (≈1.6) and $\overline M _{\rm n}$ values regardless of the ligand choice.magnified image

Facile Functionalization of Multilayer Fullerenes (Carbon Nano‐Onions) by Nitrene Chemistry and “Grafting from” Strategy

Facile functionalization of multilayer fullerenes (carbon nano-onions, CNOs) was carried out by [2+1] cycloaddition of nitrenes. The products were further derivatized by using the "grafting from" strategy of in situ ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Using one-step nitrene chemistry with high-energy reagents, such as azidoethanol and azidoethyl 2-bromo-2-methyl propanoate, in N-methyl-2-pyrrolidone at 160 degrees C for 16 h, hydroxyl and bromide functionalities were introduced onto the surfaces of CNOs. These hydroxyl CNOs (CNO-OH) and bromic CNOs (CNO-Br) were extensively characterized by various techniques such as thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photo electron spectroscopy (XPS). TGA measurements indicated that the surface hydroxyl and bromide group density reached 1.49 and 0.49 mmol g(-1), respectively. The as-functionalized CNOs showed much better solubility in solvents than pristine CNOs. The CNO-OH were also observed to fluoresce at lambda = 453 nm in water. The CNO-OH and CNO-Br can be conveniently utilized as macroinitiators to conduct surface-initiated in-situ polymerizations. Poly(epsilon-caprolactone) (PCL, 45 wt%) and polystyrene (PS, 60 wt%) were then grafted from surfaces of CNOs through the ROP of epsilon-caprolactone with the macroinitiator CNO-OH and the ATRP of styrene with the macroinitiator CNO-Br, respectively. The structures and morphology of the resulting products were characterized by (1)H NMR, scanning electron microscopy (SEM), TEM, and atomic force microscopy (AFM). The polymer functionalized CNOs have good solubility/dispersibility in common organic solvents. The facile and scalable functionalization approaches can pave the way for the comprehensive investigation of chemistry of CNOs and fabrication of novel CNO-based nanomaterials and nanodevices.

Thermal Self-Initiation in Stable Free-Radical Polymerization of Styrene

Stable free radical polymerization (SFRP) of styrene was carried out using bis(4-bromomethylbenzoyl)peroxide (BBMBPO)/4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (HTEMPO) or 4,4′-azobis(4-cyanopentyl)-α-bromoisobutyrate (ABCBIB)/HTEMPO as bimolecular initiating system. It was found that the molecular weights of obtained polystyrenes were controlled by the concentration of HTEMPO. Besides those generated by the initiators, some polystyrene chains were formed via thermal initiation. Polystyrene chains generated by the initiator had initiating groups for atom transfer radical polymerization (ATRP) at their ends, so they grew to higher molecular weights in ATRP of styrene. While the molecular weights of polystyrene chains generated by thermal initiation kept constant in ATRP conditions because of their inert terminals for ATRP. The amount of polystyrenes generated by thermal initiation was investigated quantitatively via gel permeation chromatography technique.

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

AbstractWell‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N3 were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 104 to 2.47 × 104 and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of Initiator and Ligand Structures on ATRP of Styrene and Methyl Methacrylate Initiated by Alkyl Dithiocarbamate

Atom transfer radical polymerization (ATRP) of styrene (St) and methyl methacrylate (MMA) initiated by various alkyl diethyldithiocarbamate (DC) initiators was successfully carried out in the presence of copper catalysts with nitrogen-based ligands. Well-controlled polymerizations with narrow molecular weight distribution (Mw/Mn < 1.1 (St) and Mw/Mn < 1.2 (MMA)) were achieved in both polymerizations. The polymerization rate followed first-order kinetics with respect to monomer conversion, and the molecular weight of the polymers increased linearly up to high conversion. Initiation efficiency of both polymerizations was strongly dependent on the structure of a DC. The results of 1H NMR analysis of low-mass model compounds and chain extension confirmed that well-defined polystyrene bearing a DC group as the active chain end was obtained via ATRP of St with a DC initiator. Ligand structure and ligand/copper ratio also strongly affected the degree of control attained in the polymerization. Activation rate constants and equilibrium constants of ATRP with DC initiators and copper complexes were determined. The results of cyclic voltammetry with the CuIIDC2 complex indicated that it has more negative reduction potential and, consequently, higher (pseudo)halidophilicity than those of CuIIBr2 or CuIICl2 with the same ligand Me6TREN.

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–N 3 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 × 10 4 and a narrow polydispersity from 1.07 to 1.10 were synthesized via the click reaction of MPEO–PS–N 3 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.

Studies on the development of branching in ATRP of styrene and acrylonitrile in the presence of divinylbenzene

Branching atom transfer radical polymerization (ATRP) of styrene and acrylonitrile was attempted in the presence of divinylbenzene targeting toward soluble branched copolymer. The kinetics and the development of branching with monomer conversion were studied in detail. Gas chromatography (GC), gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), proton nuclear magnetic resonance (1H NMR) spectroscopy and intrinsic viscosity determination were used to monitor the polymerization process and characterize the obtained copolymer. Analysis of conversion of reactants, the growth manner of molecular weight with monomer conversion and GPC traces proved that the primary chains with low polydispersity formed mainly at the early stage and then were linked in a statistical manner to start the branching at the middle or late stage. The more the branching agent was used, the earlier the branching occurred, and too much higher level of branching agent resulted in gelation. For the selected ratio of [t-BBiB]/[DVB]/[St]/[AN]=1/0.9/15/15, with monomer conversion less than 40%, primary chains with low polydispersity formed from the polymerization of St, AN and DVB, and only a part of the primary chains contained pendent vinyl group. When monomer conversion was up to 40%, the pendent vinyl groups participated in polymerization, resulting in the linking of the primary chains statistically to start the branching. The branching became significant at monomer conversion up to 50%, giving rise to a steep increase in molecular weight and width in molecular weight distribution. As the polymerization proceeded, the polymer composition gradually approached the feed composition, identifying the obtained branched copolymer provided some gradients are in its primary chains. Finally, branched copolymer bearing about six primary chains was prepared at monomer conversion near to 80%, its absolute weight average molecular weight was about 8.87×104.

Synthesis of Poly(2-ethyl-2-oxazoline)-b-poly(styrene) Copolymers via a Dual Initiator Route Combining Cationic Ring-Opening Polymerization and Atom Transfer Radical Polymerization

Block copolymers of 2-ethyl-2-oxazoline (EtOx) and styrene were synthesized by a combination of cationic ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). Initially, a detailed kinetic investigation for the α-bromoisobutyrylbromide (BrEBBr) initiated CROP of EtOx was performed in acetonitrile at different polymerization temperatures ranging from 100 to 180 °C under microwave irradiation. Poly(2-ethyl-2-oxazoline) (PEtOx) homopolymers with controlled molecular weights and narrow polydispersity indices were synthesized in short reaction times. Polymers with relatively high molar masses and low polydispersity indices (Mn,SEC = 48 500 g/mol, PDI = 1.29) could also be obtained. Following the synthesis of a PEtOx macroinitiator (Mn,SEC = 3700 g/mol, PDI = 1.09), the ATRP of styrene was performed with CuBr and tris[2-(dimethylamino)ethyl]amine (Me6Tren) as catalytic system. The micellization behavior of the obtained amphiphilic block copolymers was further investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM).

Synthesis and properties of organic/inorganic hybrid nanoparticles prepared using atom transfer radical polymerization

AbstractThe synthesis of organic/inorganic hybrid materials was conducted by atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate (MMA) from the surface of silica colloids. Colloidal initiators were prepared by the functionalization of silica nanoparticles with (3‐(2‐bromoisobutyryl)propyl) dimethylethoxysilane (BIDS). Well‐defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well‐defined outer polystyrene (PS) or poly(methyl methacrylate) (PMMA) layer. Fourier transform infrared (FTIR) and solid state 13C and 29Si‐NMR spectroscopy confirmed the successful modification of nanosilica surfaces. Subsequent grafting of polymers on silica surfaces by ATRP was also performed with success based on FTIR and NMR data. Scanning electron microscopy (SEM) and silicon mapping showed both hybrid materials were homogeneous dispersion systems. Energy dispersive X‐ray spectrometer (EDS) analysis indicated that the BIDS initiator was covalently attached on surfaces of silica nanoparticles and ATRP of styrene and MMA were accomplished. Thermogravimetric analysis (TGA) results displayed higher thermal stabilities for both nanohybrids in comparison with the linear‐type vinyl polymers. Contact angle measurements revealed the nanomaterials character for both silica‐based hybrid materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis, characterization, and fluorescence of pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer with pentaerythritol core

AbstractNovel and well‐defined pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymers were successfully achieved by combination of esterification, atom transfer radical polymerization (ATRP), divergent reaction, ring‐opening polymerization (ROP), and coupling reaction on the basis of pentaerythritol. The reaction of pentaerythritol with 2‐bromopropionyl bromide permitted ATRP of styrene (St) to form four‐arm star‐shaped polymer (PSt‐Br)4. The molecular weights of these polymers could be adjusted by the variation of monomer conversion. Eight‐hydroxyl star‐shaped polymer (PSt‐(OH)2)4 was produced by the divergent reaction of (PSt‐Br)4 with diethanolamine. (PSt‐(OH)2)4 was used as the initiator for ROP of ε‐caprolactone (CL) to produce eight‐arm star‐shaped dendrimer‐like copolymer (PSt‐b‐(PCL)2)4. The molecular weights of (PSt‐b‐(PCL)2)4 increased linearly with the increase of monomer. After the coupling reaction of hydroxyl‐terminated (PSt‐b‐(PCL)2)4 with 1‐pyrenebutyric acid, pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer (PSt‐b‐(PCL‐pyrene)2)4 was obtained. The eight‐arm star‐shaped dendrimer‐like copolymers presented unique thermal properties and crystalline morphologies, which were different from those of linear poly(ε‐caprolactone) (PCL). Fluorescence analysis indicated that (PSt‐b‐(PCL‐pyrene)2)4 presented slightly stronger fluorescence intensity than 1‐pyrenebutyric acid when the pyrene concentration of them was the same. The obtained pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer has potential applications in biological fluorescent probe, photodynamic therapy, and optoelectronic devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2788–2798, 2008

Chemozymatic synthesis and characterization of H-shaped triblock copolymer

The synthesis of well-defined H-shaped block copolymer based on the enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP) is described. The dihydroxyl polycaprolactone (PCL) was synthesized by the eROP of e-caprolactone (e-CL) in the presence biocatalyst Novozyme 435 and initiator ethylene glycol. Subsequently, the resulting PCL was converted to tetrafunctional macroinitiator by the esterification with 2,2-dichloro acetyl chloride (DCAC). The H-shaped block copolymer was then synthesized by the ATRP of styrene. The polymers were characterized by NMR and GPC. Linear first-order kinetics, linearly increasing molecular weight with conversion, and low polydispersities observed from the ATRP of St showed that the polymerization was well controlled. (PSt)2-b-PCL-b-(PSt)2 block copolymers with varying molecular weight and controllable composition were obtained.

Synthesis, characterization and role of a novel dimeric α-diimine iron(II) complex in ATRP of styrene

A novel dimeric α-diimine iron(II) complex, [(dab)FeCl-(μ-Cl)]2 (dab=1,4-bis-cyclohexyl-1,4-diazabutadiene) was synthesized and structurally characterized by single crystal X-ray diffraction and VT 1H NMR spectroscopy. The performances of this complex in atom transfer radical polymerization (ATRP) of styrene have been studied and related to the molecular structure.

Interfacial aspects of polymer brushes prepared on conductive substrates by aryl diazonium salt surface‐initiated ATRP

AbstractThis article describes the use of aryl diazonium salts to attach halogenated functional groups that initiate atom transfer radical polymerization (ATRP) at the surface of conductive substrates. The interest of this procedure lies in the fact that aryl diazonium salts permit the grafting of high‐density initiators within a few minutes of electrochemical surface treatment, and subsequently promote the growth of very compact polymer chains.Several brominated aryl groups were tested for surface‐initiating ATRP of styrene and methacrylates. The chemical structure of the polymer brushes was characterized by high‐resolution XPS. Particularly, it is shown that grafting of poly(tert‐butyl methacrylate), PtBMA, from the surface of glassy carbon plates followed by hydrolysis resulted in carboxylated, tethered chains that were characterized in terms of hydrophilicity and propensity to uptake silver cations. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Synthesis and characterization of side-chain liquid crystalline ABC triblock copolymers withp-methoxyazobenzene moieties by atom transfer radical polymerization

A series of novel side-chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine-terminated diblock copolymer poly(ethylene oxide)-block-polystyrene (PEO-PS-Br) was prepared by the ATRP of styrene initiated with the macro-initiator PEO-Br, which was obtained from the esterification of PEO and 2-bromo-2-methylpropionyl bromide. An azobenzene-containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side-chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)-block-polystyrene-block-poly[6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate] (PEO-PS-PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442–4450, 2008