Synthesis of A<Subscript>2</Subscript>B<Subscript>2</Subscript> miktoarm star copolymers from a new heterobifunctional initiator by combination of ROP and ATRP

Abstract  

A new heterobifunctional initiator, 2,3-bis(2-bromo-2-methylpropionyloxy) succinic acid, was synthesized and used in preparation of A₂B₂ miktoarm star copolymers, (polystyrene)₂(poly(ε-caprolactone))₂, by combination of atom transfer radical polymerization (ATRP) and Controlled ring-opening polymerization (ROP). The structures of products were confirmed by the ¹H NMR, ¹³C NMR, FT–IR, elemental analysis, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). GPC traces show that the obtained polymers have a relatively narrow molecular weight distribution. The compositions of resulting miktoarm star copolymers were very close to theoretical.     

用大分子多官能团引发剂合成杂臂星形苯乙烯-异戊二烯-丁二烯共聚物(英文)

采用负离子聚合技术,将合成的二烯烃活性链与SnCl4偶联,再与双锂短链偶联,制备出含碳锡键的大分子多官能团引发剂,并用其制备了2种杂臂星形苯乙烯-异戊二烯-丁二烯共聚物.结果表明,杂臂星形共聚物的偶联度可达80%.在聚异戊二烯(PI)-Sn-[丁苯橡胶(SBR)]3的PI臂中,1,4-结构摩尔分数为93.3%;在无规共聚SBR臂中,聚苯乙烯摩尔分数为28.8%,PI和SBR臂的玻璃化转变温度(Tg)分别为-91.3 ℃和-31.4 ℃.在聚丁二烯(PB)-Sn-(SBR)3的PB臂中,1,4-结构摩尔分数为90.1%;在无规共聚SBR臂中,聚苯乙烯摩尔分数为25.6%,PB和SBR臂的Tg分别为-87.9 ℃和-48.0 ℃.     

Synthesis of block copolymers by combination of ATRP and photoiniferter processes

BACKGROUND: Block copolymers of monomers polymerizing by different mechanisms can be prepared by the transformation approach. A wide range of combinations of different polymerization modes has been reported in the literature. In this work, the transformation approach was further extended to the preparation of block copolymers by combining atom transfer radical polymerization (ATRP) and photoiniferter processes. RESULTS: Photoactive morpholine‐4‐dithiocarbamate‐terminated polystyrene (MDC‐PS‐MDC) was prepared by the reaction of dibrominated polystyrene, obtained by ATRP, with morpholine‐4‐dithiocarbamate sodium salt in dimethylformamide. The structure of MDC‐PS‐MDC was confirmed by ¹H NMR and UV‐visible spectral analysis. The ability of MDC‐PS‐MDC to act as a photoiniferter for the block copolymerization of methyl acrylate was examined. The polymerization shows a ‘living’ character at up to 25% conversion and produces well‐defined polymers with molecular weights close to those predicted from theory and relatively narrow polydispersities (M_w/M_n ≈ 1.40). CONCLUSION: It is demonstrated that the end groups of polymers obtained by ATRP can be converted into morpholino‐4‐dithiocarbamate groups which act as photoiniferters. In this way, the desired mechanistic transformation between two controlled free radical polymerization methods can be achieved. Copyright © 2008 Society of Chemical Industry     

An all ATRP route to PMMA-PEO-PS and PMAA-PEO-PS miktoarm ABC star terpolymer

An all Atom Transfer Radical Polymerization (ATRP) route to synthesize miktoarm ABC star terpolymer, μ-(poly(methyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PMMA-PEO-PS)), was demonstrated. Poly(methyl methacrylate) (PMMA) with a halide end group was first prepared by ATRP of MMA. It was then activated under ATRP conditions at 30 °C to add a styrenic-terminated PEO macromonomer, resulting in the formation of PMMA-b-PEO. Finally, the active halide at the junction point of the diblock copolymer was used to initiate the ATRP of St at higher temperature. By a similar approach, μ-(poly(phenyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PhMA-PEO-PS)) was synthesized, hydrolysis of which in basic medium gave μ-(PMAA-PEO-PS). The polymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography.     

Block and star block copolymers by mechanism transformation. VIII Synthesis and characterization of triblock poly(LLA-b-St-b-MMA) by combination of ATRP and ROP

Block copolymers, poly(LLA-b-St)s and triblock copolymes, poly(LLA-b-St-b-MMA)s have been synthesized by the combination of the atom transfer radical polymerization (ATRP) with ring-opening polymerization (ROP) using bifunctional initiator β-hydroxylethyl α-bromoisobutyrate (HEBIB) without intermediate function transformation. The molecular weight (MW) and the molecular weight distribution (MWD) can be controlled. The structures of the copolymers were confirmed by ¹H NMR spectroscopy and GPC.     

Synthesis of PCL-b-PVAc block copolymers by combination of click chemistry, ROP, and RAFT polymerizations

Abstract  

The synthesis of new poly(ε-caprolactone)(PCL)-b-poly(vinyl acetate)(PVAc) block copolymers was investigated using different combinations of click chemistry, reversible addition-fragmentation transfer (RAFT), and ring opening polymerization (ROP) techniques. Two approaches, “coupling” and “macroinitiator” routes were studied. For the coupling approach, a chain transfer agent comprising an azide function was synthesized and used as initiator for the VAc polymerization. PCL containing an alkyne termination was obtained from a bifunctional initiator bearing an alkyne function and an hydroxyl group. These two functionalized precursors, PVAc and PCL, were coupled by a 1,3 cyclo addition reaction “click chemistry” in order to obtain the corresponding block copolymer. For the macroinitiator approach, PCL-b-PVAc block copolymers were synthesized using a two-step procedure: at first, a PCL macroinitiator with a xanthate end group was prepared by coordinated anionic polymerization of ε-caprolactone; then, the RAFT polymerization of VAc was initiated from the PCL, for the preparation of PCL-b-PVAc block copolymers. Whatever the method used, no detectable quantities of unreacted PVAc or PCL were observed. ¹H NMR and size exclusion chromatography analyses indicated successful synthesis of the block copolymers with well-defined structures.     

Synthesis of deuterobutadiene-butadiene AB2 and AB3 miktoarm star copolymers

The synthesis of well-defined, monodisperse AB₂ and AB₃ miktoarm star copolymers, in which A is polydeuterobutadiene and B is polybutadiene, is described. The synthetic procedure involved reacting living polydeuterobutadiene with a large excess of either methyltrichlorosilane or tetrachlorosilane to yield a ‘one-arm star’. SEC traces of this ‘one-arm star’ are indistinguishable from that of the uncoupled polydeuterobutadiene indicating no further coupling to form multi-arm stars occurs. Unreacted chlorosilane was removed by distillation and the introduction of an excess of living polybutadiene generates the star. The star polymer was isolated from the precursor polybutadiene by fractionation. Received: 27 April 1998/Revised version: 15 June 1998/Accepted: 16 June 1998     

Synthesis of liquid crystalline–amorphous block copolymers by combination of CFRP and ATRP mechanisms

Block copolymers of liquid crystalline 6‐(4‐cyanobiphenyl‐4′‐oxy) hexyl acrylate (LC6) and styrene (St) were obtained by the combination of two different free‐radical polymerization mechanisms namely conventional free‐radical polymerization (CFRP) and atom transfer radical polymerization (ATRP). In the first part, thermosensitive azo alkyl halide, difunctional initiator (AI), was prepared and then used for CFRP of LC6 monomer. The obtained bromine‐ended difunctional liquid crystalline polymers (PLC6) were used as initiators in ATRP of St, in bulk in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalyst. In the second part, AI was firstly polymerized by CFRP in the presence of St and then the obtained difunctional bromine ended polystyrenes (PSt) were used as initiators in ATRP of LC6 in diphenyl ether solvent in conjuction with CuBr/PMDETA. The spectral, thermal, and optical measurements confirmed a fully controlled living polymerization, which results in formation of ABA‐type block copolymers with very narrow polydispersities. In both cases, blocks of the different chemical composition were segregated in the solid and melt phases. The mesophase transition temperatures of the liquid crystalline block were found to be very similar to those of the corresponding homopolymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis of amphiphilic copolymers by ATRP initiated with a bifunctional initiator containing trichloromethyl groups

Bifunctional polystyrene macroinitiators, having various molecular weights, were prepared by atom transfer radical polymerization (ATRP), initiated with bifunctional initiator 1,3-bis{1-methyl-1[(2,2,2-trichloroethoxy) carbonylamino]ethyl}benzene in conjunction with CuCl catalyst and polyamine ligands. These macroinitiators were subsequently used for ATRP of tert-butyl acrylate (t-BuA), giving BAB triblocks poly[(t-BuA)-b-(Sty)-b-(t-BuA)] as precursors of amphiphilic copolymers. Both the polymerization steps proceeded as controlled processes with linear semi-logarithmic conversion plots and lengths of the blocks following theoretical predictions. Hydrolysis of outer poly(t-BuA) blocks led to triblock copolymers with the central polystyrene block and outer blocks of poly(acrylic acid), the molecular weights of which ranged from ca. 5 × 10³ to almost 1 × 10⁵ Da.     

Synthesis of amphiphilic triarm star block copolymers

We describe the synthesis and the characterization of amphiphilic triarm star block copolymers based on polystyrene, poly(methyl methacrylate), poly(ε caprolactone), poly(l lactide) and poly(ethylene oxide) blocks. This synthesis has been achieved by a new route consisting in 2 successive initiation steps on a core molecule (a 1,1-diphenyl-ethylene derivative bearing a protected hydroxy function) located at the end of a first block. Some results on adsorption onto TiO₂ and micellization studies are given. Preliminary results on solid state indicate an increase of the miscibility of the different incompatible blocks. Received: 3 November 1997/Revised version: 1 December 1997/Accepted: 2 December 1997     

Synthesis of well-defined star polymers and star block copolymers from dendrimer initiators by atom transfer radical polymerization

Novel polyarylether dendrimers with 1,3,5-tri(4-hydroxyphenoxy)benzene core, polybenzylether interior, and benzyl 2-bromoisobutyrate surface group (CMGn-Br, n=1-3, with functionality of 6, 12, and 24, respectively) were prepared by convergent procedure. ATRP of tert-butyl acrylate (tBA) and styrene (St) with CMGn-Br dendrimer initiators in the presence of CuBr/pentamethyldiethylenetriamine catalytic system was investigated in detail, and a series of well-defined dendrimer-like star PtBA and PSt with precise arm numbers were synthesized under suitable conditions. The quantitative initiation of the dendrimer initiators was demonstrated by high initiation efficiency, ¹H NMR spectra, hydrolysis, and MALLS/SEC approach. Star block copolymers comprising PSt and PtBA segments with low polydispersity (1.08<M_w/M_n<1.18) were also successfully synthesized using functional macroinitiators by block copolymerization. In addition, the thermal properties of the resultant polymers were characterized by DSC and TGA.     

Synthesis of acetophenone formaldehyde resin containing ABA type block copolymers by ATRP

Well‐defined ABA type block copolymers of acetophenone formaldehyde resin (AFR) and methyl methacrylate (MMA) were synthesized via atom transfer radical polymerization. In the first step, acetophenone formaldehyde resin containing hydroxyl groups was modified with 2‐bromopropionyl bromide. Resulting difunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr)/N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as the catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, and molecular weight measurement. Gel permeation chromatography (GPC) was used to study the molecular weight distributions of the AFR block copolymers. M_n up to 24,000 associated with narrow molecular weight distributions (PDI < 1.5) were obtained with conversions up to 79%. Coating properties of obtained block copolymers such as adhesion and reflectance values were investigated. They showed good adhesion properties on Plexiglass substrates. Reflectance values increased as the resin content of polymer increased. The thermal properties of all polymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All block copolymers showed higher thermal stability than their precursor AFR resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

星形杂臂异戊二烯-丁二烯共聚橡胶的合成与表征

以环己烷为溶剂、正丁基锂(n-BuLi)为引发剂、四氢呋喃(THF)和五甲基二乙基三胺(PMDETA)为微观结构调节剂、二乙烯基苯(DVB)为偶联剂,采用"臂先"和"核先"相结合的方法合成了星形杂臂异戊二烯-丁二烯共聚橡胶[S-(PI)n-(PB)n],并对其结构进行了表征。结果表明,最佳聚合工艺条件为单体质量浓度0.1 g/mL、温度50~60℃、异戊二烯(Ip)聚合时间1 h;在偶联反应时间为1 h、[DVB]/[Li](摩尔比)为1.0、聚异戊二烯的单臂数均分子量为6×104~10×104的条件下,采用Ip与DVB(摩尔比5∶1)混合后的加入方式进行偶联反应,偶联效率可达70%,S-(PI)n-(PB)n的数均分子量为2.2×105~4.9×105,分子量分布可控制在1.80~2.10,PI和PB的平均臂数可达3~4,凝胶质量分数低于1.0%;当[THF]/[Li](摩尔比)为0.5、[PMDETA]/[Li](摩尔比)为1.0时,S-(PI)n-(PB)n中乙烯基质量分数可以达到63%。     

Swelling behavior of ordered miktoarm star block copolymer-homopolymer blends

We report the morphological characterization of asymmetric miktoarm star block copolymers of the (PS-b-PI)_nPS type where n=2,3 (denoted 2DB and 3DB miktoarm stars, respectively) and a symmetric super H-shaped block copolymer of the (PS-b-PI)₃PS(PI-b-PS)₃ type (denoted SH) which were synthesized by anionic polymerization. The initial volume fraction of PS (φ_PS) for each copolymer was 0.51-0.56, giving a lamellar morphology. Addition of homopolystyrene (hPS) with a molecular weight lower than the respective PS blocks in the neat materials lead to a transition from the lamellar structure to hexagonally packed cylinders. Addition of low molecular weight homopolyisoprene (hPI) on the other hand, only resulted in swollen lamellae even when the overall composition was highly asymmetric (80/20). Changes in the lamellar spacing as well as in the respective PS and PI layer thickness were measured by SAXS. The transition from lamellae to cylinders with increased PS content occurred without the observation of an intervening cubic morphology for the 2DB and 3DB miktoarm stars. However, blends with 30 and 35% hPS ((φ_PS)_total=0.68-0.70) with the super H-shaped block copolymer lead to the observation of lamellar-catenoid structures.     

含端基氯低聚物引发剂的合成及其引发苯乙烯聚合的研究

通过对４种端羟基低聚物进行氯乙酰化反应,制备了一系列含端基氯的低聚物,然后以这些含端基氯的低聚物为大分子引发剂,在ＣｕＣｌ／ｂｐｙ存在下引发苯乙烯的ＡＴＲＰ反应,得到ＡＢＡ嵌段共聚物。用＾１Ｈ－ＮＭＲ分析证明了聚合物的嵌段结构,以ＳＥＣ测定了聚合物的相对分子质量及其分布,发现嵌段聚合物的相对分子质量和单体转化率成正比,并和相对分子质量的理论值Ｍ↑－ｎ,ｔｈ＝（Δ［Ｍ］／［ｏｌｉｇｏｍｅｒ－Ｃｌ］）     

One-pot synthesis of poly(vinyl alcohol)-based biocompatible block copolymers using a dual initiator for ROP and RAFT polymerization

Biocompatible poly(ε-caprolactone)-b-poly(vinyl alcohol) (PCL-b-PVA), poly(δ-valerolactone)-b-PVA, and poly(trimethylene carbonate)-b-PVA block copolymers were synthesized at 30 °C using a hydroxyl-functionalized xanthate reversible addition-fragmentation chain transfer (RAFT) agent, 2-hydroxyethyl 2-(ethoxycarbonothioylthio)propanoate, as a dual initiator for ring-opening polymerization (ROP) and RAFT polymerization in a one-pot procedure. The ROP of ε-caprolactone, δ-valerolactone, and trimethylene carbonate was first performed using diphenyl phosphate as the ROP catalyst followed by the RAFT polymerization of vinyl chloroacetate after quenching the ROP with 4-dimethyamino pyridine. The resulting block copolymers were aminolyzed directly to the PVA-based biocompatible block copolymers by adding hexylamine to the reaction mixture. To the best of our knowledge, this is the most convenient method for synthesizing PVA-based biocompatible block copolymers.     

Synthesis of biodegradable pentaarmed star-block copolymers via an asymmetric BIS-TRIS core by combination of ROP and RAFT: From star architectures to double responsive micelles

Biodegradable star-shaped poly(?-caprolactone) and poly(?-caprolactone-b-l-lactide) (5sPCL-b-PLLA) with five arms were synthesized by ring-opening polymerization (ROP) from an asymmetric BIS-TRIS core via “core-first” strategy. Subsequently, a series of amphiphilic and double responsive star-block copolymers were synthesized by Z-RAFT star polymerization of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) from the star-shaped macro-RAFT agent, which was prepared by attaching 3-benzylsulfanylthiocarbonylthiocarbonylsufanylpropionic acid (BSPA) to 5sPCL-b-PLLA using a simple two-step reaction sequence. GPC and ¹H NMR data demonstrated the polymerization courses are under control. The molecular weight of 5sPCL-b-PLLA-b-DMAEMA increased with the monomer conversion, and the molecular weight distribution was in the range of 1.19-1.37. The spherical micelles with degradable core and pH/thermo-double sensitive shell had been prepared from the aqueous medium of the amphiphilic star-shaped copolymers by dialysis method. Both pH and thermal-responsive behaviours of copolymer micelles obtained in this study were investigated. The micelle size and morphology were measured by DLS, AFM and TEM.     

Synthesis and characterization of diblock copolymer by enzymatic ring-opening polymerization and ATRP from a novel bifunctional initiator

Summary A new method is reported for synthesizing AB-type diblock copolymer polycaprolactone-block-polystyrene (PCL-b-PSt) from a novel bifunctional initiator 2.2.2-trichloroethanol (TCE) by combining two different polymerization techniques: enzymatic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Trichloromethyl terminated PCL was prepared by enzymatic ROP of ε-caprolactone (ε-CL) in the presence of Novozyme-435 and TCE as biocatalyst and initiator, respectively, and subsequently employed in ATRP of styrene (St) using CuCl/2, 2^′-bipyridine (bpy) as the catalyst system. The GPC and NMR analysis indicated the formation of the diblock copolymer including the biodegradable PCL block and the well-defined PSt block.     

Synthesis of symmetric H-shaped block copolymer by the combination of ATRP and living anionic polymerization

A novel fluorescent dye labeled H-shaped block copolymer, (PMMA-Fluor-PS)₂-PEO-(PS-Fluor-PMMA)₂, is synthesized by the combination of atom transfer radical polymerization (ATRP) and anionic polymerization (AP). To obtain the designated structure of the copolymer, a macroinitiator, 2,2-dichloro acetyl-PEO-2,2-dichloro acetyl (DCA-PEO-DCA), was prepared from DCAC and poly(ethylene oxide). The copolymer was characterized by ¹H NMR, GPC and fluorescence spectroscopy.     

One-pot synthesis of star polymer by ATRP of bismaleimide and an excess of styrene with a conventional initiator

A pragmatic one-pot approach to the synthesis of star polymers is reported using atom transfer radical copolymerization (ATRcP) of a bismaleimide and an excess of styrene (St) initiated with a conventional ATRP initiator.