Synthesis Of ABA Triblock Copolymers Research Articles

Synthesis of Polyesters Containing Long Aliphatic Methylene Units by ADMET Polymerization and Synthesis of ABA-Triblock Copolymers by One-Pot End Modification and Subsequent Living Ring-Opening Polymerization.

The synthesis of high-molecular-weight (Mn up to 62,000 g/mol) polyesters has been achieved by acyclic diene metathesis (ADMET) polymerization of α,ω-dienes prepared from biobased bis(undec-10-enoate) and diols [ethylene glycol (M1), propylene glycol (M2), 1,9-nonanediol (M3), 1,4-benzenedimethanol (M4), and hydroquinone (M5)] using ruthenium-carbene catalysts. Replacement of the solvent during the ADMET polymerization was effective for obtainment of the high-molecular-weight polymers (expressed as P1-P5). The melting temperatures (Tm) in the resultant polyesters were dependent upon the diol (middle) segment employed, and the polymer prepared from M5 exceeded 100 °C (a Tm value of 122.5 °C). The polymerization of M3 and M4 in the presence of 1,4-cis-diacetoxy-2-butene (DAB, as the chain transfer agent) afforded the telechelic polyesters [P3(OAc)2 and P4(OAc)2, respectively] containing acetoxy end groups exclusively. The resultant polymers containing hydroxy group termini [P3(OH)2 and P4(OH)2], prepared by the selective deprotection of the acetoxy end groups, were treated with AlEt3 followed by addition of ε-caprolactone to afford the ABA-type triblock copolymers exclusively, through a living ring-opening polymerization. The depolymerization (hydrolysis) under basic conditions (NaOH aqueous solution) of P3 was explored.

Ring-opening polymerization of ɛ-caprolactone and L-lactide initiated by a hydroxy-terminated aromatic polyimide

A facile synthesis of ABA triblock copolymers composed of aliphatic polyesters and aromatic polyimides was performed by ring-opening polymerization ɛ-caprolactone and L-lactide initiated by hydroxy-terminated polyimide.

RAFT Synthesis of ABA Triblock Copolymers as Ionic Liquid-Containing Electroactive Membranes

2-(Dimethylamino)ethyl acrylate (DMAEA) imparts versatile functionality to poly[Sty-b-(nBA-co-DMAEA)-b-Sty] ABA triblock copolymers. A controlled synthetic strategy minimized chain transfer reactions and enabled the preparation of high-molecular-weight ABA triblock copolymers with relatively narrow PDIs between 1.39 and 1.44 using reversible addition-fragmentation chain transfer (RAFT) polymerization. The presence of tertiary amine functionality and their zwitterionic derivatives in the central blocks of the triblock copolymers afforded tunable polarity toward ionic liquids. Gravimetric measurements determined the swelling capacity of the triblock copolymers for ionic liquids (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIm TfO) and 1-ethyl-3-methylimidazolium ethylsulfate (EMIm ES). A correlation of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small-angle X-ray scattering (SAXS) results revealed the impact of ionic liquid incorporation on the thermal transitions, thermomechanical properties, and morphologies of the triblock copolymers. IL-containing membranes of DMAEA-derived triblock copolymers and EMIm TfO exhibited desirable rubbery plateau moduli of ~100 MPa and electromechanical actuation to a 4 V electrical stimulus. Maintaining the mechanical ductility of polymer matrices while increasing their ion-conductivity is paramount for future electroactive devices.

Synthesis of novel ABA triblock and (ABA) n multiblock copolymers comprised of polyisobutylene and poly(γ-benzyl- l-glutamate) segments

The synthesis of ABA triblock copolymers comprised of polyisobutylene (PIB) and poly(γ-benzyl- l-glutamate) (PBLG) segments has been demonstrated for the first time by the polymerization of γ-benzyl- l-glutamate N-carboxyanhydride (BLG-NCA) initiated with well-defined α,ω-primary amino-functional PIBs. The ammonium-mediated polymerization of BLG-NCA provided better control of molecular weights and lower polydispersity indices (PDIs) compared to the conventional polymerization. The compositional homogeneity of the block copolymers has been confirmed by GPC-MALLS and 1H NMR spectroscopy. Since the resulting ABA triblock copolymer possessed primary amino groups at α,ω-ends, further extension reaction with 4,4′-methylene-bis(phenyldiisocyanate) was possible to afford a novel (ABA) n multiblock copolymer.

Synthesis of α,ω‐di(iodo)PVC and of four‐arm star PVC with identical active chain ends by SET‐DTLRP of VC initiated with bifunctional and tetrafunctional initiators

AbstractNa2S2O4‐catalyzed single‐electron transfer – degenerative chain transfer‐mediated living radical polymerization (SET‐DTLRP) of VC initiated with the bifunctional initiators 1,2‐bis(iodopropionyloxy)ethane, dimethyl 2,5‐diiodohexanedioate, and bis(2‐methoxyethyl)‐2,5‐diiodohexanedioate as well as the tetrafunctional initiator pentaerythritol tetrakis(2‐iodopropionate) is reported. This SET‐DTLRP was performed in water at ambient temperature in the presence of polyvinyl alcohol and hydroxypropyl methylcellulose surfactants and provides methods for the synthesis of α,ω‐di(iodo)PVC with two identical active chain ends and of four‐arm star PVC with four identical active chain ends. These difunctional and tetrafunctional derivatives of PVC are also macroinitiators for the synthesis of ABA triblock copolymers and four‐arm star block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 635–652, 2009

Synthesis of PDMAEMA–PCL–PDMAEMA triblock copolymers

The synthesis of ABA triblock copolymers of the type PDMAEMA–PCL–PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br–PCL–Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks.

Synthesis of ABA Triblock Copolymers via Ring Opening Metathesis Polymerization Using a Bimetallic Initiator: Influence of a Flexible Spacer in the Side Chain Liquid Crystalline Block

A series of monomers with side chain liquid crystals (SCLCs) were synthesized for ring opening metathesis polymerization (ROMP). The liquid crystals (LCs) used were 4-hydroxybenzoic acid 4-methoxyphenyl ester (MPOB-H), which is known to exhibit a nematic liquid crystalline phase, and biphenyl-4-carboxylic acid 4-(1-butoxycarbonylethoxy)phenyl ester (BPP4-H), which is known to exhibit a smectic phase. The side chains differed in spacer length, spacer type, and the nature of the LC. Monomers were polymerized using a bimetallic ROMP initiator [Mo(NAr)(OCMe3)2CH]2C6H4 (where Ar = 2,6-diisopropyl phenyl); both homopolymers and ABA type triblock copolymers, where the B block is the LC functional monomer, and A is methyltetracyclodocene (MTD) were prepared. The polymers gave unimodal peak distributions with polydispersities <1.22. Incorporation of a polyoxyethylene spacer decreased the glass transition temperature of the polymer block to −25 from +20 °C, the Tg when an alkyl spacer was used. Although no distinct LC phase was observed with the polyoxyethylene spacer when MPOB was used, when BPP4 was attached via a polyoxyethylene spacer, a distinct liquid crystalline transition was observed. Polymers with an alkyl spacer exhibited liquid crystalline behavior and good phase segregation on the basis of differential scanning calorimetry and small-angle X-ray scattering studies.

Bis‐dendritic polyethylene prepared by ring‐opening metathesis polymerization in the presence of bis‐dendritic chain transfer agents

AbstractThe synthesis of ABA triblock copolymers is described, in which the A blocks are poly(benzyl ether) dendrons and the B block is polycyclooctene or polyethylene. Bis‐dendritic cis‐olefins were synthesized and used as chain transfer agents in ring‐opening metathesis polymerization of cyclooctene in a process that inserts the dendrons at the polymer chain‐ends. Evaluation of the polymer products by spectroscopic, chromatographic, and titration methods supports their triblock structure. Hydrogenation of the unsaturated polycyclooctene B‐block of these ABA triblock copolymers provides the first reported synthesis of bisdendritic polyethylene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5429–5439, 2005

Synthesis of ABA Triblock Copolymers by a Tandem ROMP−RAFT Strategy

A symmetric, acyclic olefin possessing trithiocarbonate moieties, available in two synthetic steps from commercially available starting materials, is demonstrated to act as a chain transfer agent (CTA) in ring opening metathesis polymerizations (ROMP). The synthetic efficiency of the ruthenium-catalyzed ROMP of 1,5-cyclooctadiene in the presence of this new CTA is investigated as a means of producing telechelic polybutadienes bearing trithiocarbonate endgroups. Telechelic polymers thus synthesized are macromolecular chain transfer agents in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene and acrylate monomers, enabling the synthesis of ABA-type triblock copolymers of varying compositions possessing monomodal molecular weight distributions.

Synthesis of ABA triblock copolymer of poly(potassium acrylate-styrene-potassium acrylate) by atom transfer radical polymerization and the self-assembly in selective solvents

A series of well-defined ABA triblock copolymers of poly(methyl acrylate)-polystyrene-poly(methyl acrylate) (PMA- b-PS- b-PMA) with different molecular weights were synthesized using Cl-PS-Cl as macroinitiator, CuCl/ N, N, N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) as catalyst system via atom transfer radical polymerization (ATRP). Amphiphilic triblock copolymer poly(potassium acrylate)-polystyrene-poly(potassium acrylate) (PKAA- b-PS- b-PKAA) was obtained by hydrolyzing PMA- b-PS- b-PMA. The self-assembly behavior of the triblock copolymers in organic solutions, which is a good solvent for the PS block and in aqueous solutions, which is a good solvent for the PKAA blocks was studied by high performance particle sizer (HPPS). The results showed that the Z-average size of the micelles obviously increases with increase in molecular weight of triblock copolymers, and the micelles in organic solutions are relatively more stable than in aqueous solutions. The effect of the length of PS block on the Z-average size of the micelles is more obvious in organic solution than in aqueous solution. The morphology of triblock copolymers PKAA- b-PS- b-PKAA in aqueous solution, which is a nearly ‘pearl-necklace’-like shape, was examined by transmission electron microscopy (TEM) at room temperature.

Synthesis of ABA Triblock Copolymers via Acyclic Diene Metathesis Polymerization and Living Polymerization of α-Amino Acid−N-Carboxyanhydrides

The synthesis of poly(γ-benzyl-l-glutamate)-b-polyoctenamer-b-poly(γ-benzyl-l-glutamate) (13) and poly(γ-benzyl-l-glutamate)-b-polyethylene-b-poly(γ-benzyl-l-glutamate) (14) triblock copolymers is described. α,ω-Bisamino-terminated polyoctenamer (5) was used to prepare a difunctional macroinitiator (12) used for the living polymerization of γ-benzyl-l-glutamic acid−N-carboxyanhydride (Glu−NCA) to form the triblock copolymers. 5 was synthesized by acyclic diene metathesis polymerization of 1,9-decadiene (1) in the presence of 11-phthalimido-1-undecene (2) and Grubbs' metathesis catalyst, RuCl2(CHPh)(PCy3)2 (3). Deprotection of the resulting phthalimide end-functionalized polymers (4) was performed, leading to difunctional 5 with number-average functionalities close to two. These methods allow the controlled preparation of polypeptide/(hydrocarbon polymer) block architectures with good control over the chain lengths of both domains and without formation of homopolypeptide contaminants.

A facile method for synthesis of ABA triblock copolymers with macro-iniferter technique

A facile method for synthesis of well-defined ABA triblock copolymers, such as poly(vinyl acetate-b-styrene-b-vinyl acetate), was investigated. The polymerization proceeds ‘living’ radical mechanism realized by macro-iniferter technique. The macro-iniferters were designed and synthesized by ‘living’ radical polymerization of vinyl monomers utilizing diethyl 2,3-dicyano-2,3-di(p-N,N-diethyldithiocarbamymethyl)phenylsuccinate (DDDCS) as a multi-functional iniferter, that is, under heating without ultra-violet (UV) light, DDDCS serve as a thermal iniferter by the reversible cleavage of the hexa-substituted C–C bond, while under UV light irradiation at ambient temperature, it serve as a photoiniferter by the reversible cleavage of the two diethyldithiocarbamyl (DC) functional groups. The polymers prepared via these two processes bearing α- and ω-DC end groups are macro-iniferters. The ABA triblock copolymers with different block components were easily synthesized via ‘living’ polymerization through these macro-iniferters. The formation of block copolymers were characterized by gel permeation chromatograph, 1H nuclear magnetic resonance and differential scanning calorimeter analyses.

Synthesis and characterization of ABA-triblock copolymers with poly(ethylene glycol) segments and LC-segments

This paper describes the synthesis of ABA-triblock copolymers with poly(ethylene glycol) A-blocks and a liquid crystalline polyester B-block. Three block copolymer series are presented with different block length of A- and B-blocks. The block copolymers show thermotropic liquid crystalline behavior up to a content of poly(ethylene glycol) segments of 50 wt%. Depending on their composition and chain length, the block copolymers are microphase separated or non-microphase separated. In the microphase separated block copolymers the poly(ethylene glycol) segments are able to crystallize. The degree of crystallinity and the spherulite diameter is strongly influenced by the length of the poly(ethylene glycol) segment itself as well as by the length of the incorporated polyester segment.

Synthesis of ABA triblock copolymers of N-substituted maleimides and methacrylates by group transfer polymerization

ABA type block copolymerization of N-phenylmaleimide (NPM), N-hexyl maleimide (NHM), methyl methacrylate (MMA), and butyl methacrylate (BMA) was investigated by group transfer polymerization (GTP) with [1,5-bis (trimethylsilyloxy)-1,5-dimethoxy-1,4-pentadiene] (1) as difunctional initiator. A novel block copolymers (2) of NPM and MMA (or BMA) could be prepared by sequential addition of NPM to the living PMMA (or PBMA) produced with 1. The reaction did not exhibit the characteristics of living polymerization when NPM was added. The resulting copolymers showed good thermal stability. On the other hand, gelation occurred in GTP of NHM.

Synthesis of ABA Triblock Copolymers of Styrene and p-Methylstyrene by Living Cationic Polymerization Using the Bifunctional Initiating System 1,4-Bis(1-chloroethyl)benzene/SnCl4 in the Presence of 2,6-Di-tert-butylpyridine

ABA triblock copolymers of styrene and p-methylstyrene were prepared by living cationic polymerization using a bifunctional initiating system in the presence of 2,6-di-tert-butylpyridine, which, as a proton-trapping agent, suppressed the initiation by adventitious impurities and thus enhanced the livingness of the styrene monomers. By using these characteristics, triblock copolymers of styrene and p-methylstyrene could be prepared easily. The polymers showed the same molecular weight as the theoretical value and narrow and unimodal molecular weight distributions (MWDs)

Synthesis of ABA triblock copolymers of iε-caprolactone and DL-lactide

Preparation d'un prepolymere vivant polycaprolactique-polylactide-polyoxyde d'ethylene termine par un hydroxy avec un catalyseur de Teyssie. Puis amorcage de la polymerisation de la caprolactone dans le toluene a 90°C

Synthesis of ABA triblock copolymers containing electrono-donor or electrono-acceptor pendant groups in A blocks

α,ω-p-Toluensulphonic acid ester of poly(ethyleneglycoladipate) was synthesized and used to initiate the cationic isomerization polymerization of 2-phenyl-2-oxazoline, 2-(β-N-Carbazolylethyl)-2-oxazoline and 2-(3,5-dinitrophenyl)-2-oxazoline. ABA triblock copolymers containing poly(N-benzoylethylenimine), poly [N-β(N-carbazolyl)propionyl ethyleneimine] or poly(3,5-dinitrobenzoylethylenimine) blocks (A block) and poly (ethyleneglycoladipate) blocks (B block) have been synthesized.

Préparation et etude de copolymères triséquencés isoprène et méthacrylate de méthyle

AbstractA convenient method is described for the synthesis of ABA triblock copolymers having a high vinyl polyisoprene as center block and poly(methyl methacrylate) as end blocks. Dynamic mechanical properties of these copolymers as a function of temperature are compared for different compositions (100%, 85%, 70%, 60%, 50%, and 30% of rubber) using solvent‐casting methods. Since the morphology is dependent on the method of preparation of the samples, five solvents of different solubility parameters were tested for the same copolymer (i.e., 70% polyisoprene by weight) to show their influence on mechanical behavior.