ATNRC and SET‐NRC synthesis of PtBA‐g‐PEO well‐defined amphiphilic graft copolymers

A series of new well‐defined amphiphilic graft copolymers containing hydrophobic poly(tert‐butyl acrylate) backbone and hydrophilic poly(ethylene oxide) side chains were reported. Reversible addition‐fragmentation chain transfer homopolymerization of tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate was first performed to afford a well‐defined backbone with a narrow molecular weight distribution (M_w/M_n = 1.07). The target poly(tert‐butyl acrylate)‐g‐poly(ethylene oxide) (PtBA‐g‐PEO) graft copolymers with low polydispersities (M_w/M_n = 1.18–1.26) were then synthesized by atom transfer nitroxide radical coupling or single electron transfer‐nitroxide radical coupling reaction using CuBr(Cu)/PMDETA as catalytic system. Fluorescence probe technique was employed to determine the critical micelle concentrations (cmc) of the obtained amphiphilic graft copolymers in aqueous media. Furthermore, PAA‐g‐PEO graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA backbone while PEO side chains kept inert. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

An efficient way to tune grafting density of well‐defined copolymers via an unusual Br‐containing acrylate monomer

A series of well‐defined amphiphilic graft copolymers, containing hydrophilic poly(acrylic acid) backbone and hydrophobic poly(butyl acrylate) side chains, were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) without any postpolymerization functionality modification followed by selective acidic hydrolysis of poly(tert‐butyl acrylate) backbone. tert‐Butyl 2‐((2‐bromopropanoyloxy)methyl)‐acrylate was first homopolymerized or copolymerized with tert‐butyl acrylate by RAFT in a controlled way to give ATRP‐initiation‐group‐containing homopolymers and copolymers with narrow molecular weight distributions (M_w/M_n < 1.20) and their reactivity ratios were determined by Fineman‐Ross and Kelen‐Tudos methods, respectively. The density of ATRP initiation group can be regulated by the feed ratio of the comonomers. Next, ATRP of butyl acrylate was directly initiated by these macroinitiators to synthesize well‐defined poly(tert‐butyl acrylate)‐g‐poly(butyl acrylate) graft copolymers with controlled grafting densities via the grafting‐from strategy. PtBA‐based backbone was selectively hydrolyzed in acidic environment without affecting PBA side chains to provide poly(acrylic acid)‐g‐poly(butyl acrylate) amphiphilic graft copolymers. Fluorescence probe technique was used to determine the critical micelle concentrations in aqueous media and micellar morphologies are found to be spheres visualized by TEM. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2622–2630, 2010     

Star‐like PAA‐g‐PPO well‐defined amphiphilic graft copolymer synthesized by ATNRC and SET‐NRC reaction

A series of well‐defined amphiphilic star graft copolymers consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(propylene oxide) side chains were synthesized by the sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and atom transfer nitroxide radical coupling (ATNRC) or single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction followed by the selective hydrolysis of poly(tert‐butyl acrylate) backbone. A Br‐containing acrylate monomer, tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate, was first homopolymerized via RAFT polymerization using a new star‐like chain‐transfer agent with four arms in a controlled way to give a well‐defined star‐like backbone with a narrow molecular weight distribution (M_w/M_n = 1.23). The grafting‐onto strategy was used to synthesize the well‐defined PtBA‐g‐PPO star graft copolymers with narrow molecular weight distributions (M_w/M_n = 1.14–1.25) via ATNRC or SET‐NRC reaction between the Br‐containing PtBA‐based star‐like backbone and poly(propylene oxide) with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl end group using CuBr/PMDETA or Cu/PMDETA as catalytic system. PAA‐g‐PPO amphiphilic star graft copolymers were obtained by the selective acidic hydrolysis of star‐like PtBA‐based backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media and brine were determined by the fluorescence probe technique. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2084–2097, 2010     

Synthesis of starlike PtBA‐g‐PEO amphiphilic graft copolymer via highly efficient Cu‐catalyzed SET‐NRC reaction at ambient temperature

Two new amphiphilic star graft copolymers bearing hydrophobic poly(tert‐butyl acrylate) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains with different molecular weights were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction under mild conditions. RAFT homopolymerization of tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate was mediated by a four‐armed chain transfer agent in a controlled way to afford a well‐defined starlike backbone with a narrow molecular weight distribution (M_w/M_n = 1.26). The target poly(tert‐butyl acrylate)‐g‐PEO (PtBA‐g‐PEO) star graft copolymers were synthesized by SET‐NRC reaction between Br‐containing PtBA‐based starlike backbone and PEO end functionalized with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group using copper/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as catalytic system at ambient temperature via grafting‐onto strategy. The critical micelle concentration values of the obtained amphiphilic star graft copolymers in aqueous media and brine were determined by fluorescence probe technique using pyrene as probe. Diverse micellar morphologies were formed by varying the content of hydrophilic PEO segment as well as the initial concentration of stock solution. In addition, poly(acrylic acid)‐g‐PEO double hydrophilic star graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA starlike backbone without affecting PEO side chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Convenient synthesis of thermo‐responsive PtBA‐g‐PPEGMEMA well‐defined amphiphilic graft copolymer without polymeric functional group transformation

A series of well‐defined amphiphilic graft copolymers bearing hydrophobic poly(tert‐butyl acrylate) backbone and hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate)] (PPEGMEMA) side chains were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and single‐electron‐transfer living radical polymerization (SET‐LRP) without any polymeric functional group transformation. A new Br‐containing acrylate monomer, tert‐butyl 2‐((2‐bromoisobutanoyloxy)methyl)acrylate (tBBIBMA), was first prepared, which can be homopolymerized by RAFT to give a well‐defined PtBBIBMA homopolymer with a narrow molecular weight distribution (M_w/M_n = 1.15). This homopolymer with pendant Br initiation group in every repeating unit initiated SET‐LRP of PEGMEMA at 45 °C using CuBr/dHbpy as catalytic system to afford well‐defined PtBBIBMA‐g‐PPEGMEMA graft copolymers via the grafting‐from strategy. The self‐assembly behavior of the obtained graft copolymers in aqueous media was investigated by fluorescence spectroscopy and TEM. These copolymers were found to be stimuli‐responsive to both temperature and ions. Finally, poly(acrylic acid)‐g‐PPEGMEMA double hydrophilic graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA backbone while PPEGMEMA side chains kept inert. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

PAA-g-PVAc Amphiphilic Graft Copolymer Synthesized by Atom Transfer Radical Polymerization

A new amphiphilic graft copolymer containing hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chains was synthesized via sequential atom transfer radical polymerization (ATRP) followed by selective hydrolysis of poly(methoxymethyl acrylate) backbone. Grafting‐from strategy was employed to synthesize PMOMA‐g‐PVAc graft copolymer (M_w/M_n=1.64) via ATRP. The final PAA‐g‐PVAc amphiphilic graft copolymer was obtained by selective acidic hydrolysis of PMOMA backbone in acidic environment without affecting the side chains. The critical micelle concentrations (cmc) in aqueous media were determined by a fluorescence probe technique. The micelle morphologies were found to be spheres.     

Amphiphilic copolymers with poly(meth)acrylic acid chains “grafted from” caprolactone 2‐(methacryloyloxy)ethyl ester‐based backbone

Well‐defined amphiphilic graft copolymers containing hydrophilic poly((meth)acrylic acid) (PMAA) or poly(acrylic acid) (PAA) side chains with gradient and statistical distributions were synthesized. For this purpose, the hydroxy‐functionalized copolymers with various gradient degrees, in which 2‐(6‐hydroxyhexanoyloxy)ethyl (meth)acrylate units (caprolactone 2‐[methacryloyloxy]ethyl ester, CLMA) formed strong gradient with tert‐butyl acrylate (tBA), slight gradient copolymers with tert‐butyl (meth)acrylate (tBMA), and statistical copolymers with methyl (meth)acrylate (MMA) were modified to bromoester multifunctional macroinitiators, P(tBMA‐grad‐BrCLMA), P(BrCLMA‐grad‐tBA), and P(BrCLMA‐co‐MMA). In the next step, they were applied in controlled radical polymerization of tBMA and tBA yielding graft copolymers with various lengths of side chains as well as graft densities. Further, the tert‐butyl groups in copolymers were successfully removed via acidolysis in the presence of trifluoracetic acid, which caused transformation of the hydrophobic graft copolymers into amphiphilic ones with ability of self‐assembly for the future biomedical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Controlled synthesis of pH‐responsive amphiphilic A2B2 miktoarm star block copolymer by combination of SET‐LRP and RAFT polymerization

The pH‐responsive amphiphilic A₂B₂ miktoarm star block copolymer, poly(acrylic acid)₂‐poly(vinyl acetate)₂ [(PAA)₂(PVAc)₂], with controlled molecular weight and well‐defined structure was successfully synthesized via combination of single‐electron transfer‐mediated living radical polymerization (SET‐LRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization methods. First, the precursor two‐armed poly(t‐butyl acrylate) (PtBA)₂ functionalized with two xanthate groups was prepared by SET‐LRP of t‐butyl acrylate in acetone at 25 °C using the novel tetrafunctional bromoxanthate (Xanthate₂‐Br₂) as an Iniferter (initiator‐transfer agent‐terminator) agent. The polymerization behavior showed typical LRP natures by the first‐order polymerization kinetics and the linear dependence of molecular weight of the polymer on the monomer conversion. Second, the A₂B₂ miktoarm star block copolymer (PtBA)₂(PVAc)₂ was prepared by RAFT polymerization of VAc using (PtBA‐N₃)₂(Xanthate)₂ obtained as the macro‐RAFT agent. Finally, the pH‐sensitive A₂B₂ amphiphilic miktoarm star block copolymer poly(acrylic acid)₂‐poly(vinyl acetate)₂ ((PAA)₂(PVAc)₂) was obtained by selectively cleavage of t‐butyl esters of (PtBA)₂(PVAc)₂. All the miktoarm star block copolymers were characterized by GPC, ¹H‐NMR, and FT‐IR spectra. The self‐assembly behaviors of the amphiphilic A₂B₂ miktoarm block copolymers (PAA)₂(PVAc)₂ were also investigated by transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Synthesis and self‐assembly of well‐defined cyclodextrin‐centered amphiphilic A14B7 multimiktoarm star copolymers based on poly(ε‐caprolactone) and poly(acrylic acid)

Novel amphiphilic A₁₄B₇ multimiktoarm star copolymers composed of 14 poly(ε‐caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with β‐cyclodextrin (β‐CD) as core moiety were synthesized by the combination of controlled ring‐opening polymerization (CROP) and atom transfer radical polymerization (ATRP). 14‐Arm star PCL homopolymers (CDSi‐SPCL) were first synthesized by the CROP of CL using per‐6‐(tert‐butyldimethylsilyl)‐β‐CD as the multifunctional initiator in the presence of Sn(Oct)₂ at 125 °C. Subsequently, the hydroxyl end groups of CDSi‐SPCL were blocked by acetyl chloride. After desilylation of the tert‐butyldimethylsilyl ether groups from the β‐CD core, 7 ATRP initiating sites were introduced by treating with 2‐bromoisobutyryl bromide, which further initiated ATRP of tert‐butyl acrylate (tBA) to prepare well‐defined A₁₄B₇ multimiktoarm star copolymers [CDS(PCL‐PtBA)]. Their molecular structures and physical properties were in detail characterized by ¹H NMR, SEC‐MALLS, and DSC. The selective hydrolysis of tert‐butyl ester groups of the PtBA block gave the amphiphilic A₁₄B₇ multimiktoarm star copolymers [CDS(PCL‐PAA)]. These amphiphilic copolymers could self‐assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2961–2974, 2010     

Synthesis and characterization of fluorine‐containing PAA‐b‐PTPFCBPMA amphiphilic block copolymer

A series of perfluorocyclobutyl (PFCB) aryl ether‐based amphiphilic diblock copolymers containing hydrophilic poly(acrylic acid) (PAA) and fluorophilic poly(p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) segments were synthesized via successive atom transfer radical polymerization (ATRP). 2‐MBP‐initiated and CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine‐catalyzed ATRP homopolymerization of the PFCB‐containing methacrylate monomer, p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate, can be performed in a controlled mode as confirmed by the fact that the number‐average molecular weights (M_n) increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.38. The block copolymers with narrow molecular weight distributions (M_w/M_n ≤ 1.36) were synthesized by ATRP using Br‐end‐functionalized poly(tert‐butyl acrylate) (PtBA) as macroinitiator followed by the acidolysis of hydrophobic PtBA block into hydrophilic PAA segment. The critical micelle concentrations of the amphiphilic diblock copolymers in different surroundings were determined by fluorescence spectroscopy using N‐phenyl‐1‐naphthylamine as probe. The morphology and size of the micelles were investigated by transmission electron microscopy and dynamic laser light scattering, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of anionic amphiphilic diblock copolymers of poly(styrene) and poly(acrylic acid) by reverse iodine transfer polymerization (RITP) in solution and emulsion

Reverse iodine transfer polymerization (RITP), offering the appealing potential of the in situ generation of transfer agents out of molecular iodine I₂, is employed in the synthesis of anionic amphiphilic diblock copolymers of poly(styrene) and poly(acrylic acid). Starting with well‐characterized poly(styrene) as macro‐transfer agents synthesized by RITP, diblock copolymers poly(styrene)‐b‐poly(tert‐butyl acrylate) of various lengths are successfully yielded in solution with a good architectural control. These blocks are then subjected to acid deprotection and subsequent pH control to give rise to anionic amphiphilic poly(styrene)‐b‐poly(acrylic acid). Besides, homopolymers of tert‐butyl acrylate are produced by RITP both in solution and in emulsion. Furthermore, a fruitful trial of the synthesis of diblock copolymers poly(tert‐butyl acrylate)‐b‐poly(styrene) is carried out through chain extension of the poly(tert‐butyl acrylate) latex as a macro‐transfer agent in seeded emulsion polymerization of styrene. Finally, the prepared block copolymer is deprotected to bring about its amphiphilic nature and a pH control caters for its anionic character. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4389–4398     

Synthesis of poly(tert‐butyl methacrylate)‐graft‐poly(dimethylsiloxane) graft copolymers via reversible addition‐fragmentation chain transfer polymerization

Well‐defined poly(tert‐butyl methacrylate)‐graft‐poly (dimethylsiloxane) (PtBuMA‐g‐PDMS) graft copolymers were synthesized via reversible addition‐fragmentation chain transfer (RAFT) copolymerization of methacryloyl‐terminated poly (dimethylsiloxane) (PDMS‐MA) with tert‐butyl methacrylate (tBuMA) in ethyl acetate, using 2,2′‐azobis(isobutyronitrile) (AIBN) as the initiator and 2‐cyanoprop‐2‐yl dithiobenzoate as the RAFT agent. The RAFT statistical copolymerization of PDMS‐MA with tBuMA is shown to be azeotropic and the obtained PtBuMA‐g‐PDMS graft copolymers have homogeneously distributed branches because of the similar reactivity of monomers (r_tBuMA ≈ r_PDMS‐MA ≈ 1). By the RAFT block copolymerization of PDMS‐MA with tBuMA, moreover, narrow molecular weight distribution (M_w/M_n < 1.3) PtBuMA‐g‐PDMS graft copolymers with gradient or blocky branch spacing were synthesized. The graft copolymers exhibit the glass transitions corresponding to the PDMS and PtBuMA phase, respectively. However, the arrangement of monomer units in copolymer chains and the length of PtBuMA moieties have important effects on the thermal behavior of PtBuMA‐g‐PDMS graft copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of amphiphilic block–graft copolymers [poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)‐g‐poly(acrylic acid)] and their aggregation in water

Novel block–graft copolymers [poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)‐g‐poly(tert‐butyl acrylate)] were synthesized by the atom transfer radical polymerization (ATRP) of tert‐butyl acrylate (tBA) with chloromethylated poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) as a macromolecular initiator. The copolymers were composed of triblock SEBS as the backbone and tBA as grafts attached to the polystyrene end blocks. The macromolecular initiator (chloromethylated SEBS) was prepared by successive hydrogenation and chloromethylation of SEBS. The degree of chloromethylation, ranging from 1.6 to 36.5 mol % according to the styrene units in SEBS, was attained with adjustments in the amount of SnCl₄ and the reaction time with a slight effect on the monodispersity of the starting material (SEBS). The ATRP mechanism of the copolymerization was supported by the kinetic data and the linear increase in the molecular weights of the products with conversion. The graft density was controlled with changes in the functionality of the chloromethylated SEBS. The average length of the graft chain, ranging from a few repeat units to about two hundred, was adjusted with changes in the reaction time and alterations in the initiator/catalyst/ligand molar ratio. Incomplete initiation was detected at a low conversion; moreover, for initiators with low functionality, sluggish initiation was overcome with suitable reaction conditions. The block–graft copolymers were hydrolyzed into amphiphilic ones containing poly(acrylic acid) grafts. The aggregation behavior of the amphiphilic copolymers was studied with dynamic light scattering and transmission electron microscopy, and the aggregates showed a variety of morphologies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1253–1266, 2002     

Synthesis and characterization of novel resorcinarene‐centered amphiphilic star‐block copolymers consisting of eight ABA triblock arms by combination of ROP,ATRP, and click chemistry

Novel amphiphilic eight‐arm star triblock copolymers, star poly(ε‐caprolactone)‐block‐poly(acrylic acid)‐block‐poly(ε‐caprolactone)s (SPCL‐PAA‐PCL) with resorcinarene as core moiety were prepared by combination of ROP, ATRP, and “click” reaction strategy. First, the hydroxyl end groups of the predefined eight‐arm SPCLs synthesized by ROP were converted to 2‐bromoesters which permitted ATRP of tert‐butyl acrylate (tBA) to form star diblock copolymers: SPCL‐PtBA. Next, the bromide end groups of SPCL‐PtBA were quantitatively converted to terminal azides by NaN₃, which were combined with presynthesized alkyne‐terminated poly(ε‐caprolactone) (A‐PCL) in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine in DMF to give the star triblock copolymers: SPCL‐PtBA‐PCL. ¹H NMR, FTIR, and SEC analyses confirmed the expected star triblock architecture. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl acrylate) blocks gave the amphiphilic star triblock copolymers: SPCL‐PAA‐PCL. These amphiphilic star triblock copolymers could self‐assemble into spherical micelles in aqueous solution with the particle size ranging from 20 to 60 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2905–2916, 2009     

Modification of polysulfones by click chemistry: Amphiphilic graft copolymers and their protein adsorption and cell adhesion properties

Well‐defined amphiphilic graft copolymer with hydrophobic polysulfone (PSU) backbone and hydrophilic poly(acrylic acid) (PAA) side chains were synthesized and characterized. For this purpose, commercially available PSU was converted to azido‐functionalized polymer (PSU‐N₃) by successive chloromethylation and azidation processes. Independently, poly(tert‐butyl acrylate) (PtBA) with an alkyne‐end‐group is obtained by using suitable initiator in atom transfer radical polymerization (ATRP). Then, this polymer was successfully grafted onto PSU‐N₃ by click chemistry to yield polysulfone‐graft‐poly(tert‐butyl acrylate), (PSU‐g‐PtBA). Finally, amphiphilic polysulfone‐graft‐poly(acrylic acid), (PSU‐g‐PAA), membranes were obtained by hydrolyzing precursor the PSU‐g‐PtBA membranes in trifluoroacetic acid. The final polymer and intermediates at various stages were characterized by ¹H NMR, FTIR, GPC, and SEM analyses. Protein adsorption and eukaryotic and prokaryotic cell adhesion on PSU‐g‐PAA were studied and compared to those of PSU‐g‐PtBA and unmodified PSU. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and characterization of block copolymers containing poly(di(ethylene glycol) 2‐ethylhexyl ether acrylate) by reversible addition–fragmentation chain transfer polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerization has emerged as one of the important living radical polymerization techniques. Herein, we report the polymerization of di(ethylene glycol) 2‐ethylhexyl ether acrylate (DEHEA), a commercially‐available monomer consisting of an amphiphilic side chain, via RAFT by using bis(2‐propionic acid) trithiocarbonate as the chain transfer agent (CTA) and AIBN as the radical initiator, at 70 °C. The kinetics of DEHEA polymerization was also evaluated. Synthesis of well‐defined ABA triblock copolymers consisting of poly(tert‐butyl acrylate) (PtBA) or poly(octadecyl acrylate) (PODA) middle blocks were prepared from a PDEHEA macroCTA. By starting from a PtBA macroCTA, a BAB triblock copolymer with PDEHEA as the middle block was also readily prepared. These amphiphilic block copolymers with PDEHEA segments bearing unique amphiphilic side chains could potentially be used as the precursor components for construction of self‐assembled nanostructures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5420–5430, 2007     

Synthesis of PMHDO‐g‐PDEAEA well‐defined amphiphilic graft copolymer via successive living coordination polymerization and SET‐LRP

A series of well‐defined amphiphilic graft copolymer containing hydrophobic polyallene‐based backbone and hydrophilic poly(2‐(diethylamino)ethyl acrylate) (PDEAEA) side chains was synthesized by sequential living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO) and single electron transfer‐living radical polymerization (SET‐LRP) of 2‐(diethylamino)ethyl acrylate (DEAEA). Ni‐catalyzed living coordination polymerization of MHDO was first performed in toluene to give a well‐defined double‐bond‐containing poly(6‐methyl‐1,2‐heptadiene‐4‐ol) (PMHDO) homopolymer with a low polydispersity (M_w/M_n = 1.10). Next, 2‐chloropropionyl chloride was used for the esterification of pendant hydroxyls in every repeating unit of the homopolymer so that the homopolymer was converted to PMHDO‐Cl macroinitiator. Finally, SET‐LRP of DEAEA was initiated by the macroinitiator in tetrahydrofuran/H₂O using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system to afford well‐defined PMHDO‐g‐PDEAEA graft copolymers (M_w/M_n ≤ 1.22) through the grafting‐from strategy. The critical micelle concentration (cmc) was determined by ?uorescence spectroscopy with N‐phenyl‐1‐naphthylamine as probe and the micellar morphology was visualized by transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers by combining ATRP and RAFT polymerizations

The synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers using a combination of two living radical polymerization techniques, atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization, is reported. The use of two methods is due to the disparity in reactivity of the two monomers, viz. vinyl acetate is difficult to polymerize via ATRP, and a suitable RAFT agent that can control the polymerization of vinyl acetate is typically unable to control the polymerization of tert‐butyl acrylate. Thus, ATRP was performed to make poly(tert‐butyl acrylate) containing a bromine end group. This end group was subsequently substituted with a xanthate moiety. Various spectroscopic methods were used to confirm the substitution. The poly(tert‐butyl acrylate) macro‐RAFT agent was then used to produce (tert‐butyl acrylate‐block‐vinyl acetate). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7200–7206, 2008     

The preparation of t‐butyl acrylate,methyl acrylate,and styrene block copolymers by atom transfer radical polymerization: Precursors to amphiphilic and hydrophilic block copolymers and conversion to complex nanostructured materials

Atom transfer radical polymerization conditions with copper(I) bromide/pentamethyldiethylenetriamine (CuBr/PMDETA) as the catalyst system were employed for the polymerization of tert‐butyl acrylate, methyl acrylate, and styrene to generate well‐defined homopolymers, diblock copolymers, and triblock copolymers. Temperature studies indicated that the polymerizations occurred smoothly in bulk at 50 °C. The kinetics of tert‐butyl acrylate polymerization under these conditions are reported. Well‐defined poly(tert‐butyl acrylate) (PtBA; polydispersity index = 1.14) and poly(methyl acrylate) (PMA; polydispersity index = 1.03) homopolymers were synthesized and then used as macroinitiators for the preparation of PtBA‐b‐PMA and PMA‐b‐PtBA diblock copolymers in bulk at 50 °C or in toluene at 60 or 90 °C. In toluene, the amount of CuBr/PMDETA relative to the macroinitiator was important; at least 1 equiv of CuBr/PMDETA was required for complete initiation. Typical block lengths were composed of 100–150 repeat units per segment. A triblock copolymer, composed of PtBA‐b‐PMA‐b‐PS (PS = polystyrene), was also synthesized with a well‐defined composition and a narrow molecular weight dispersity. The tert‐butyl esters of PtBA‐b‐PMA and PtBA‐b‐PMA‐b‐PS were selectively cleaved to form the amphiphilic block copolymers PAA‐b‐PMA [PAA = poly(acrylic acid)] and PAA‐b‐PMA‐b‐PS, respectively, via reaction with anhydrous trifluoroacetic acid in dichloromethane at room temperature for 3 h. Characterization data are reported from analyses by gel permeation chromatography; infrared, ¹H NMR, and ¹³C NMR spectroscopies; differential scanning calorimetry; and matrix‐assisted, laser desorption/ionization time‐of‐flight mass spectrometry. The assembly of the amphiphilic triblock copolymer PAA₉₀‐b‐PMA₈₀‐b‐PS₉₈ within an aqueous solution, followed by conversion into stable complex nanostructures via crosslinking reactions between the hydrophilic PAA chains comprising the peripheral layers, produced mixtures of spherical and cylindrical topologies. The visualization and size determination of the resulting nanostructures were performed by atomic force microscopy, which revealed very interesting segregation phenomena. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4805–4820, 2000     

Arborescent polystyrene‐graft‐poly(tert‐butyl methacrylate) copolymers: Synthesis and enhanced polyelectrolyte effect in solution

A technique is described for the preparation of arborescent graft copolymers containing poly(tert‐butyl methacrylate) (PtBMA) segments. For this purpose, tert‐butyl methacrylate is first polymerized with 1,1‐diphenyl‐2‐methylpentyllithium in tetrahydrofuran. The graft copolymers are obtained by addition of a solution of a bromomethylated polystyrene substrate to the living PtBMA macroanion solution. Copolymers incorporating either short (M_w ≈ 5000) or long (M_w ≈ 30,000) PtBMA side chains were prepared by grafting onto linear, comb‐branched (G0), G1, and G2 bromomethylated arborescent polystyrenes. Branching functionalities ranging from 9 to 4500 and molecular weights ranging from 8.8 × 10⁴ to 6.3 × 10⁷ were obtained for the copolymers, while maintaining a low apparent polydispersity index (M_w/M_n ≈ 1.14–1.25). Arborescent polystyrene‐graft‐poly(methacrylic acid) (PMAA) copolymers were obtained by hydrolysis of the tert‐butyl methacrylate units. Dynamic light scattering measurements showed that the arborescent PMAA copolymers are more expanded than their linear PMAA analogues when neutralized with NaOH. This effect is attributed to the higher charge density in the branched arborescent copolymer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2335–2346, 2008