Chain-growth Condensation Polymerization Research Articles

Synthesis of Well-Defined, Water-Soluble Hyperbranched Polyamides by Chain-Growth Condensation Polymerization of AB2 Monomer

Condensation polymerization of 5-aminoisophthalic acid methyl ester 1 bearing a N-tri(ethylene glycol) methyl ester (TEG) chain as an AB2 monomer was conducted and the properties of the resulting hyperbranched polyamides (HBPA) were investigated. When the polymerization of 1 was carried out with N-methyl core initiator 2b at various feed ratios of 1 to 2b ([1]0/[2b]0) in the presence of LiHMDS and LiCl at −10 °C, the Mn values of the obtained HBPA increased in proportion to the [1]0/[2b]0 ratio from 7 to 46 (Mn = 3810–18600), retaining a narrow molecular weight distribution (Mw/Mn = 1.11–1.19). The HBPA was soluble in water, and a 0.25 wt.−% aqueous solution of the HBPA exhibited a lower critical solution temperature (LCST). The cloud point was 21–23 °C, which is about 30 °C lower than that of the corresponding poly(m-benzamide) with the N-TEG unit.

Synthesis of linear and cyclic aromatic peptides with fixed conformation owing to intramolecular hydrogen bonding by condensation polymerization method

Chain-growth condensation polymerization of 3-(4-octyloxybenzylamino)benzoic acid esters bearing an alkoxy group on the benzene ring was investigated for the synthesis of polyamides having a specific conformation owing to intramolecular hydrogen bonding of CONH⋯OR. The 4-octyloxybenzyl group on the nitrogen of the amide linkage was easily removed with trifluoroacetic acid after polymerization to afford the desired polyamides, which had lower solubility than expected. Furthermore, we found that a cyclic triamide was selectively obtained by slow addition of the base to a solution of the monomer.

Synthesis and Properties of a Variety of Well-Defined Hyperbranched N-Alkyl and N-H Polyamides by Chain-Growth Condensation Polymerization of AB2 Monomers

Well-defined hyperbranched polyamides (HBPAs) were synthesized by means of chain-growth condensation polymerization of AB2 monomers from core molecules, making use of the change of substituent effects between the monomer and the polymer. Polymerization of 5-(methylamino)isophthalic acid ethyl ester 1c as an AB2 monomer with core 3b was carried out in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) and LiCl in THF at −30 °C to yield HBPA with low polydispersity (Mw/Mn ≤ 1.13) and well-defined molecular weight (Mn = 2370–39300) depending on the feed ratio of the monomer to the core (from 7 to 200). The matrix-assisted laser desorption ionization time-of-flight (MALDI–TOF) mass spectra showed that the obtained HBPA included the core unit, indicating that the polymerization proceeds by selective reaction of the monomer with the core and the polymer ends, without side reactions. Polymerization of other AB2 monomers with N-ethyl, octyl, and 4-octyloxybenzyl (OOB) groups afforded the corresponding well-defined HBPAs. HBPA with the N-OOB group was converted to unsubstituted N-H HBPA with low polydispersity by treatment with trifluoroacetic acid (TFA). The solubility of HBPAs depended upon the nature of the N-alkyl groups and the terminal ester moieties. The glass transition temperature (Tg) and 10% weight-loss temperature (Td10) of HBPAs depended upon the molecular weight, as well as the nature of the N-alkyl groups and terminal ester moieties.

Synthesis of poly(naphthalenecarboxamide)s with low polydispersity by chain‐growth condensation polymerization

AbstractCondensation polymerization of 6‐(N‐substituted‐amino)‐2‐naphthoic acid esters (1) was investigated as an extension of chain‐growth condensation polymerization (CGCP). Methyl 6‐(3,7‐dimethyloctylamino)‐2‐naphthoate (1b) was polymerized at −10 °C in the presence of phenyl 4‐methylbenzoate (2) as an initiator and lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. When the feed ratio [1a]0/[2]0 was 10 or 20, poly(naphthalenecarboxamide) with defined molecular weight and low polydispersity was obtained, together with a small amount of cyclic trimer. However, polymer was precipitated during polymerization under similar conditions in [1a]0/[2]0 = 34. To increase the solubility of the polymer, monomers 1c and 1d with a tri(ethylene glycol) (TEG) monomethyl ether side chain instead of the 3,7‐dimethyloctyl side chain were synthesized. Polymerization of the methyl ester monomer 1c did not proceed well, affording only oligomer and unreacted 1c, whereas polymerization of the phenyl ester monomer 1d afforded well‐defined poly(naphthalenecarboxamide) together with small amounts of cyclic oligomers in [1d]0/[2]0 = 10 and 29. The polymerization at high feed ratio ([1d]0/[2]0 = 32.6) was accompanied with self‐condensation to give polyamide with a lower molecular weight than the calculated value. Such undesirable self‐condensation would result from insufficient deactivation of the electrophilic ester moiety by the electron‐donating resonance effect of the amide anion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Efficient Low-Temperature Atom Transfer Radical Coupling and Its Application to Synthesis of Well-Defined Symmetrical Polybenzamides

Radical coupling reactions have been widely used for preparation of symmetrical macromolecules. In previous studies of atom transfer radical coupling (ATRC), coupling efficiency above 90% has been generally attained at high temperature (T = 70–110 °C) by using Mn < 5000 precursors. From the mechanistic viewpoint, we designed a strategy for styrene-assisted ATRC from methacrylic macroradicals at low temperature (St/PMMA–Br/CuIBr/Cu0/Me6TREN). Analysis of the products (1H NMR, H–H COSY, MALDI–TOF mass spectra and gel permeation chromatography) indicated that this provides an efficient “convergent” or coupling approach, if a high degree of chain-end functionality is preserved. We then applied this concept in combination with chain-growth condensation polymerization (CGCP), which usually affords quantitative chain-end functionality. Couplings of high-molecular-weight AB-type diblock polybenzamide, 2-bromoisobutyryl-terminated poly(N-octyloxybenzyl-m-benzamide)-block-poly(N-octyl-m-benzamide) (Mn = 9300, Mw/Mn...

Well-Defined Star-Shaped Rod−Coil Diblock Copolymers as a New Class of Unimolecular Micelles: Encapsulation of Guests and Thermoresponsive Phase Transition

A series of star-shaped rod−coil diblock copolymers composed of poly(arylene ether sulfone) (PAES) as a core, and poly[2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate] [poly(MEO2MA-co-OEGMA)] as a shell was synthesized by combination of chain-growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP). In the presence of 4-arm initiator (1), CGCP of 4-fluoro-4′-hydroxydiphenyl sulfone potassium salt (2) via nucleophilic aromatic substitution (SNAr) reaction yielded a well-defined star-shaped polymer with four fluorine end groups (C5−F and C8−F). Transformation of the fluorine groups into ATRP initiating sites produced a macroinitiator having four bromine groups (C5−Br and C8−Br). In the presence of the macroinitiator, random copolymerization of MEO2MA and OEGMA via ATRP formed thermoresponsive shell blocks to produce a desired star-shaped PAES-b-poly(MEO2MA-co-OEGMA) block copolymer with various block lengths. Dynamic light scattering (DLS) of the...

Synthesis of polybenzamide‐b‐polystyrene block copolymer via combination of chain‐growth condensation polymerization and atom transfer radical polymerization

We present an efficient and easy approach using chain-growth condensation polymerization (CGCP) followed by atom-transfer radical polymerization (ATRP) to synthesize well-defined polybenzamide-b-polystyrene diblock copolymers with ππ interactions of aromatic rings, as well as strong intermolecular multiple hydrogen bonding between amide linkages after removal of the protecting group on amide nitrogen.

Synthesis of Core Cross-Linked Star Polymers Consisting of Well-Defined Aromatic Polyamide Arms

Homopolymer-arm, block-arm, and miktoarm star polymers consisting of poly(N-octyl-m-benzamide) and poly(N-H-m-benzamide) were synthesized by means of a core cross-linking method. Macromonomers (MM) with the styryl terminal moiety were synthesized by chain-growth condensation polymerization of 3-(alkylamino)benzoic acid esters 1 in the presence of phenyl 4-vinylbenzoate as an initiator, and copolymerization with N,N′-methylenebis(acrylamide) as a divinyl monomer in the presence of 2,2′-azobis(isobutyronitrile) at 60 °C yielded the corresponding star polymers. In the synthesis of star polymers containing poly(N-H-m-benzamide) arms, the 4-(octyloxy)benzyl group on the amide nitrogen of the obtained star polymers was removed with trifluoroacetic acid. The number of arms per molecule, determined by multiangle laser light scattering, varied in the range of 36−100 depending on the N-alkyl group of 1 and the molecular weight of MM. The 1H NMR spectra of the star polymers in dimethyl sulfoxide revealed that the po...

Well‐defined star‐shaped poly(p‐benzamide) via chain‐growth condensation polymerization: Use of tetra‐functional porphyrin initiator to optimize star polymer formation

Most star polymers with controlled molecular weight and low polydispersity are synthesized by living polymerization, in which only initiation and propagation reactions, but not chain transfer reaction, take place. Accordingly, the obtained star polymers are generally not contaminated with linear polymers. Recently, we have developed chain-growth condensation polymerization, a kind of living polymerization yielding condensation polymers with controlled molecular weight and narrow molecular weight distribution. However, synthesis of star-shaped poly(p-benzamide)s through this method, using multifunctional initiators, afforded not only the desired star-shaped poly(p-benzamide) via chain-growth polymerization, but also a linear poly(pbenzamide) via self-polycondensation of the monomer when the amount of the initiator was decreased. This contamination with linear polymer was more liable to occur as compared to the case of chain-growth condensation polymerization with a monofunctional initiator under the same conditions. In addition, separation of the products by means of high-performance liquid chromatography (HPLC) was necessary to confirm which product was the star polymer and which the linear polymer. However, by using an initiator containing porphyrin, the absorption maximum of which is around 430 nm and quite different from that of poly(p-benzamide), we could easily differentiate the star polymer bearing the porphyrin initiator unit from the linear polymer without this initiator unit by means of GPC with a variable-wavelength UV detector, and thus we could optimize the polymerization conditions for selective synthesis of star aromatic polyamides. Furthermore, there are rather few reports on the synthesis of porphyrin-cored star polymers with rigid arms, as compared with star polymers with flexible-coil polymer arms. For example, porphyrin-cored star polyfluorene was synthesized by Suzuki coupling polycondensation of bromofluorene boronic ester in the presence of a porphyrin having four iodofluorene moieties. In this polymerization, the length of the arms was not controlled and the molecular weight distribution was broad. Therefore, not only the synthesis, but also the properties of porphyrin-cored star polymers with well-defined rigid or semirigid arms remain to be fully established. In this article, we investigated the chain-growth condensation polymerization of 4-(octylamino)benzoic acid esters 1 with porphyrin-cored tetra-functional initiator 3 under various conditions and optimized the conditions for selective synthesis of star-shaped poly(p-benzamide)s with suppression of the formation of linear selfcondensed polyamides (Scheme 1).

Chain-Growth Condensation Polymerization for the Synthesis of Well-Defined Condensation Polymers and π-Conjugated Polymers

Chain-Growth Condensation Polymerization for the Synthesis of Well-Defined Condensation Polymers and π-Conjugated Polymers

Synthesis of Well‐Defined Polybenzamide‐block‐Polystyrene by Combination of Chain‐Growth Condensation Polymerization and RAFT Polymerization

Well-defined diblock copolymers composed of poly(N-octylbenzamide) and polystyrene were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene with a polyamide chain transfer agent (CTA) prepared via chain-growth condensation polymerization. Synthesis of a dithioester-type macro-CTA possessing the polyamide segment as an activating group was unsatisfactory due to side reactions and incomplete introduction of the benzyl dithiocarbonyl unit. On the other hand, a dithiobenzoate-CTA containing poly(N-octylbenzamide) as a radical leaving group was easily synthesized, and the RAFT polymerization of styrene with this CTA afforded poly(N-octylbenzamide)-block-polystyrene with controlled molecular weight and narrow polydispersity.

Synthesis of Well-Defined Miktoarm Star Copolymers of Aromatic Polyether and Polystyrene by Chain-Growth Condensation Polymerization and Atom Transfer Radical Polymerization

Well-defined AB2 and A2B type miktoarm star copolymers consisting of aromatic polyether arms as the A segment and polystyrene arms as the B segment were synthesized from trifunctional initiators. Atom transfer radical polymerization (ATRP) of styrene was carried out in the presence of 3,5-bis(1-bromoethyl)-4′-fluorobenzophenone as a trifunctional initiator, and then the terminal C−Br bond of the polymer was reduced with Bu3SnH. The obtained polystyrene macroinitiators were used for aromatic polyether segment construction via chain-growth condensation polymerization (CGCP). The GPC trace showed a clear shift toward the higher-molecular-weight region with retention of low polydispersity, and no peak was detected in the lower-molecular-weight region. Accordingly, the target AB2 type miktoarm star copolymers were synthesized without step-growth polycondensation. The synthesis of A2B type miktoarm star copolymers was carried out similarly using 1-bromomethyl-3,5-bis(4-fluorobenzoyl)benzene as a trifunctional i...

Synthesis via Chain-Growth Condensation Polymerization and Gelating Properties of a Variety of Block Copolymers of Meta- and Para-Substituted Aromatic Polyamides

Well-defined diblock copolymers consisting of poly(m-benzamide)s with different N-alkyl groups and of poly(m-benzamide)s and poly(p-benzamide)s with different N-alkyl groups were synthesized by means of sequential chain-growth condensation polymerization. The polymerization of 3-(alkylamino)benzoic acid alkyl ester 1 was carried out with phenyl 4-methylbenzoate (3) as an initiator in the presence of 2.2 equiv of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base, followed by addition of another kind of 1 or 4-(alkylamino)benzoic acid alkyl ester 2 to the reaction mixture to yield the block copolymer. The 4-octyloxybenzyl groups on the amide nitrogen in the obtained block copolymers were removed with trifluoroacetic acid (TFA) to give block copolymers containing an N−H polyamide segment. These block copolymers showed gelating properties at low concentration in various solvents ranging from aromatic to aprotic polar solvents. Scanning electron microscopic (SEM) images of the CH2Cl2 gel revealed tha...

Synthesis of Well‐Defined Rod‐Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain‐Growth Condensation Polymerization and Atom Transfer Radical Polymerization

AbstractThe synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain‐growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well‐controlled manner to yield aromatic polyether‐block‐polyacrylonitrile (polyether‐b‐PAN) with low polydispersity. This block copolymer self‐assembled in N,N‐dimethylformamide to form bundle‐like or spherical aggregates, depending on the length of the PAN units in the block copolymer.magnified image

Catalyst-Transfer Condensation Polymerization for the Synthesis of Well-Defined Polythiophene with Hydrophilic Side Chain and of Diblock Copolythiophene with Hydrophilic and Hydrophobic Side Chains

Chain-growth condensation polymerization of 2-bromo-5-chloromagnesio-3-[2-(2-metho-xyethoxy)ethoxy]methylthiophene (2) with Ni catalysts was studied, and the block copolymer of poly2 and poly(3-hexylthiophene) was synthesized by this polymerization method. The polymerization of 2 depended on the ligands of the Ni catalyst, and poly2 with the lowest polydispersity was obtained when 1,2-bis(diphenylphosphino)ethane (dppe) was used as the ligand. The linear relationships between the conversion of 2 and Mn of the polymer and between the feed ratio of 2 to the Ni catalyst and Mn of the polymer indicate that this polymerization proceeds in a chain-growth polymerization manner via a catalyst-transfer condensation polymerization mechanism. The block copolymerization of 2 and 2-bromo-5-chloromagnesio-3-hexylthiophene (1) was then carried out in four ways by changing the order of polymerization of the two monomers and the catalysts. It turned out that the block copolymer was obtained without the formation of the homopolymers by the polymerization of 1 with Ni(dppe)Cl2 or Ni(dppp)Cl2 (dppp = 1,2-bis(diphenylphosphino)propane), followed by the postpolymerization of 2. Of the two catalysts, Ni(dppe)Cl2 resulted in narrower polydispersity of the block copolymer.

Synthesis of Well-Defined Polystyrene-b-Aromatic Polyether Using an Orthogonal Initiator for Atom Transfer Radical Polymerization and Chain-Growth Condensation Polymerization

Well-defined diblock copolymers of polystyrene and aromatic polyether were synthesized by the combination of atom transfer radical polymerization (ATRP) and chain-growth condensation polymerization (CGCP) from an orthogonal initiator. A polystyrene macroinitiator was first synthesized by the ATRP of styrene in the presence of 4-fluorobenzenesulfonyl chloride (FBS−Cl) as an orthogonal initiator, then the terminal chlorine of the polystyrene was dehalogenated with Et3SiH/Pd(OAc)2. The CGCP of potassium 5-cyano-4-fluoro-2-propylphenolate (1) was then carried out with the polystyrene macroinitiator in sulfolane at 150 °C. However, not only polystyrene-b-aromatic polyether but also macrocycles of 1 were obtained, due to transetherification of the p-sulfonylphenyl ether linkage of the macroinitiator with 1. In contrast, the CGCP of 1 from another polystyrene macroinitiator bearing a keto group, which was prepared similarly by the ATRP of styrene with 4-(1-bromoethyl)-4‘-fluorobenzophenone (FBP−Br) as an orthogo...

Converting Step-Growth to Chain-Growth Condensation Polymerization

The development and applications of chain-growth condensation polymerization are reviewed. Well-defined aromatic polyamides, polyesters, and polyethers have been synthesized via substituent effect-assisted chain-growth condensation polymerization, in which the polymer propagating ends are more reactive than the monomers due to resonance or inductive effects between the functional groups of the terminal monomer units. Chain-growth condensation polymerization for the synthesis of aromatic polyamides has been applied to the construction of well-defined block copolymers and star-shaped polymers. Nickel-catalyzed condensation polymerization of 5-metalated 2-halothiophene has been found to proceed in a chain-growth polymerization manner. Detailed investigations revealed that this polymerization is a catalyst-transfer condensation polymerization, in which the chain-growth nature is attributable to intramolecular catalyst transfer. Phase-transfer polymerization in a solid−solution biphasic system, in which the mo...