Many natural polymeric materials are perfect monodisperse macromolecules and are produced by the successive condensation of monomers with polymer end groups that are activated by enzymes. [1][2][3][4] Although these syntheses proceed via many complicated and tightly controlled processes, the overall process could be regarded as a kind of chain-growth polycondensation. In the polycondensation of artificial monomers, however, macromolecules with a wide range of molecular weights have been synthesized, because there is little difference of reactivity between monomers and polymer end groups, and step-growth polymerization occurs. If the polymer end groups become more reactive than monomers and the reaction of monomers with each other is prevented, chain-growth polycondensation would take place to yield artificial condensation polymers having well-defined molecular weights and narrow molecular weight distributions (MWD). Kinetic studies showed that some polycondensations involve more reactive polymer end groups than monomers, but the MWD of polymers were not evaluated. 5 The synthesis of poly-(2,6-dimethyl-1,4-phenylene oxide) by oxidative polymerization of 2,6-dimethylphenol 6 and by phase transfer catalyzed polycondensation of 4-bromo-2,6-dimethylphenynol 7 also involved the reactive polymer end groups and did not show the behavior of a classic polycondensation. Percec conducted this polycondensation in the presence of chain initiators and obtained well-defined polyphenylene oxides. 7 However, the molecular weight values were much higher than the calculated values based on the [monomer]/[initiator] ratios, and polymers having a narrow MWD were obtained after precipitation; the crude polymerization mixture had a broad MWD. In the polycondensations of bifunctional nucleophilic monomers with bifunctional electrophilic monomers, polymers having a low polydispersity (M w /M n < 1.3) were also prepared by phase transfer catalyst (PTC) techniques when polymer end groups were more reactive than monomers. 8-10 This type of polycondensation, however, could not control the molecular weight.Our previous work has shown that the Pd-catalyzed polycondensation of 4-bromo-2-octylphenol and carbon monoxide underwent chain-growth polycondensation from an initiator in the initial stage. 11 Another approach to chain-growth polycondensation was the polycondensation of solid monomer with PTC in organic solvent containing an initiator, where the reaction of monomers with each other was prevented. 12 The molecular weight was controlled but the MWD was a little broad (M w /M n < 1.3). We now report the successful chain-growth polycondensation of phenyl 4-aminobenzoate derivatives 1 for aromatic polyamides having precisely controlled molecular weights and quite narrow MWD (M w /M n < 1.12), where all of the experimental criteria of a living polymerization are exhibited even in polycondensation.The expected course of polymerization of silylated 1a with CsF in the presence of a small amount of reactive initiator 2 bearing an electron-withdrawin...

Poly(p-benzamide) with a defined molecular weight and a low polydispersity and a block copolymer containing this well-defined aramide was synthesized. Phenyl 4-aminobenzoate, which would yield poly(p-benzamide), did not polymerize under the conditions of chain-growth polycondensation. However, phenyl 4-(4-octyloxybenzylamino)benzoate (1b) polymerized at room temperature in the presence of base and phenyl 4-nitrobenzoate (2) as an initiator in a chain-growth polycondensation manner to give well-defined aromatic polyamides having the 4-octyloxybenzyl groups as a protecting group on nitrogen in an amide. It was confirmed by a model reaction that deprotection of this protecting group proceeded completely with trifluoroacetic acid (TFA) without breaking the amide linkage. The utility of this approach to poly(p-benzamide) with a low polydispersity was demonstrated by the synthesis of block copolymers. Thus, phenyl 4-(octylamino)benzoate (1a) polymerized in the presence of 2 and base, followed by addition of 1b and base to the reaction mixture of the prepolymer to yield the block copolymer of 1a and 1b with a controlled molecular weight and a low polydispersity. The block copolymer was treated with TFA, resulting in a soluble block copolymer of poly(N-octyl-p-benzamide) and poly(p-benzamide). The SEM images of the supramolecular assemblies of the block copolymer showed mum-sized bundles and aggregates of flake structures.

Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m-benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 8C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c-i with a variety of N-alkyl groups was then carried out under the established conditions to yield well-defined poly(m-benzamide)s, which showed higher solubility than those of the corresponding poly(p-benzamide)s. Furthermore, the 4-octyloxybenzyl group on the amide nitrogen in poly1i was removed by treatment with trifluoroacetic acid (TFA) to give N-unsubstituted poly(m-benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4990-5003, 2006The methyl ester monomer 1a was first polymerized with various bases in the presence of Scheme 1. Inductive effect-assisted chain-growth polycondensation of 1.POLY(m-BENZAMIDE)S WITH LOW POLYDISPERSITIES

Summary: For the convenient synthesis of well‐defined poly(N‐octyl‐p‐benzamide)s with low polydispersities, the polycondensation of methyl 4‐octylaminobenzoate (1) was investigated. Methyl ester monomer 1 polymerized with lithium 1,1,1,3,3,3‐hexamethyldisilazide (LHMDS) in the presence of an initiator in tetrahydrofuran at −10 °C. The highly pure polyamide with a defined molecular weight and a low polydispersity is obtained after simple treatment of the reaction mixture with aqueous NaOH solution, followed by evaporation.The chain‐growth polycondensation of 4‐octylaminobenzoic acid methyl ester (1) with lithium 1,1,1,3,3,3‐hexamethyldisilazide (LHMDS) to yield poly(N‐octyl‐p‐benzamide).magnified imageThe chain‐growth polycondensation of 4‐octylaminobenzoic acid methyl ester (1) with lithium 1,1,1,3,3,3‐hexamethyldisilazide (LHMDS) to yield poly(N‐octyl‐p‐benzamide).