Chain-Growth Polycondensation for Nonbiological Polyamides of Defined Architecture

Abstract

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...

Synthesis of controlled rod–coil block copolymers by a macroinitiator method: Chain‐growth polycondensation for an aromatic polyamide from a polystyrene macroinitiator

“…Consequently, MI-1 served as an initiator for the polymerization of 1 despite the steric hindrance of the polystyrene backbone, and the block copolymer of polystyrene and poly1 was synthesized in a controlled fashion. Then, N-octyl-N-triethylsilylaniline (3), 4 which generates a stronger base than triethylsilane in the presence of fluoride ions, was used instead of triethylsilane to yield the block copolymer (entry 5), whose GPC elution curve was unimodal without shoulders [ Fig. 1(d)].…”

“…4 This polymerization shows the feature of living polymerization. Thus, we have demonstrated that a sequential monomer addition method gives block copolyamides having different aminoalkyl side chains.…”

“…A solution of an MI (0.05 mmol), 1 (0.326 g, 1.0 mmol), and 3 (0.320 g, 1.0 mmol) or triethylsilane (0.116 g, 1.0 mmol) in dry THF (4 mL) was added to the flask under a nitrogen flow. A solution of 18-crown-6 (0.530 g, 2.0 mmol) in dry THF (1 mL) was added to the mixture at room temperature, and the whole was stirred at room temperature for 39 h. The reaction mixture was quenched with saturated aqueous NH 4 Cl and extracted with CH 2 Cl 2 . The combined organic layer was washed with saturated aqueous NaHCO 3 and water and dried over anhydrous MgSO 4 .…”

“…A solution of 18-crown-6 (0.530 g, 2.0 mmol) in dry THF (1 mL) was added to the mixture at room temperature, and the whole was stirred at room temperature for 39 h. The reaction mixture was quenched with saturated aqueous NH 4 Cl and extracted with CH 2 Cl 2 . The combined organic layer was washed with saturated aqueous NaHCO 3 and water and dried over anhydrous MgSO 4 . After concentration in vacuo, the block copolymer and N-octylaniline in the residue were separated by preparative high-performance liquid chromatography (HPLC; eluent: CHCl 3 ) with the use of polystyrene gel columns to afford the block copolymer.…”

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

“…18-Crown-6 (TCI) was used after drying overnight under reduced pressure at 50 C. N-Octyl-N-triethylsilylaniline (2) was prepared as described previously. 6 …”