Akihiro Yokoyama

The palladium-mediated intramolecular biarylation of the cyclic triamide of 2-bromo-4-(isobutylamino)benzoic acid proceeded effectively by the introduction of three methyl groups and the use of tri-tert-butylphosphine as the ligand.

© 2020 Elsevier Ltd A coronene analogue containing amide linkage was synthesized from a halogenated cyclic triamide by palladium-mediated intramolecular C[sbnd]C bond formation. The cyclic triamide was formed from the condensation of 2-chloro-4-(isobutylamino)benzoic acid in the presence of dichlorotriphenylphosphorane in 1,1,2,2-tetrachloroethane. By contrast, the condensation of 2-bromo counterpart required silicon tetrachloride in pyridine. The intramolecular C[sbnd]C bond formation, which yielded the target coronene analogue, occurred during the reaction of bromo-substituted cyclic triamide with palladium(II) acetate, triphenylphosphine, and potassium carbonate in N,N-dimethylformamide.

The effect of the side chain chiral center position on the secondary structure of oligomers and polymers of N-substituted 4-aminobenzoic acid was studied. Monomer 1 was prepared from L-alanine methyl ester hydrochloride in seven steps. The poly(p-benzamide) having an α-substituted side chain at the nitrogen atom (α-Me-PA) was obtained from the polymerization of 1 with triethylsilane, CsF, and 18-crown-6 in THF. The circular dichroism (CD) studies in solution demonstrated that α-Me-PA adopted a right-handed helical conformation in protic polar solvents, such as water and methanol, and a random structure in chloroform, indicating that solvophobic interactions played an important role in the helical folding of α-Me-PA. The tetramer of (S)-4-(sec-butylamino)benzoic acid was synthesized as a model compound of α-Me-PA. The single crystal X-ray analysis of the tetramer revealed that the right- and left-handed helical molecules existed in a one-to-one ratio in the crystal, and that the screw pitch of the right-handed helix was shorter than the left-handed helix.

To synthesize ladder-type polyamides by construction of two amide bonds successively, 2,5-diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide-linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 degrees C. (C) 2017 Wiley Periodicals, Inc.

An axially chiral binaphthyl-bipyridyl cyclic dyad in which the two units are connected by short -CH2O- linkers Was synthesized. Experimental and theoretical analyses indicate that the (R)-binaphthyl unit in the dyad induces (R)-chirality in the bipyridyl unit, both in the solid state and in solution. It is shown that vibrational circular dichroism (VCD) is useful to determine the twisting pattern of 2,2'-bipyridyl compounds. The dyad shows crystallization-induced emission enhancement (CIEE).

Isopropyl-substituted tri(ethylene glycol) is used as a chiral side chain of N-substituted poly(p-benzamide) in order to increase the difference of stability between the right- and left-handed helical structures of the polymer. The target polymer is synthesized by the chain-growth condensation polymerization of the corresponding monomer with an initiator using lithium 1,1,1,3,3,3-hexamethyldisilazide as a base. A circular dichroism (CD) study of the polymer reveals that the CD signal is due to an excess of a thermodynamically controlled right-handed helical structure of the polymer, and that the replacement of the methyl group with a bulkier isopropyl group at the side chain of poly(p-benzamide) increases the abundance of right-handed helical structure in chloroform. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1623-1628

Application of chain-growth condensation polymerization (CGCP) to obtain well-defined polybenzoxazole (PBO) was examined. CGCP of both phenyl 3-{(2-methoxyethoxy)methoxy (MEM-oxy)}-4-(octylamino)benzoate (1b) (para-substituted monomer) and phenyl 4-MEM-oxy-3-(octylamino)benzoate (3b) (meta-substituted monomer) was examined in the presence of metal disilazide base and phenyl 4-nitro- or methylbenzoate 2 as an initiator. Polymerization of the latter monomer, but not the former, afforded polymer with controlled molecular weight based on the feed ratio of monomer to initiator and with a narrow molecular weight distribution. Accordingly, monomer 3c, in which the octyl group on the amino nitrogen of 3b was replaced with a 4-(octyloxy)benzyl (OOB) group, was polymerized in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS), phenyl 4-methylbenzoate (2b), and LiCl in THF at 0 degrees C to yield poly3c with well-defined molecular weight (M-n = 4520-9080) and low polydispersity (M-w/M-n 1.11). Treatment of poly3c with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly(o-hydroxyamide) (poly4) without scission of the amide linkages. Cyclodehydration of poly4 proceeded at 350 degrees C to yield PBO (poly5), which was insoluble in organic solvents and acids. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1730-1736

Well-defined poly(3-alkyl-4-benzamide) was synthesized by means of chain-growth condensation polymerization of phenyl 3-octyl-4-(4-octyloxybenzyl(OOB)amino)benzoate (1c) from initiator 2, followed by removal of the OOB groups on amide nitrogen of poly1c. Polymerization of 1c with phenyl 4-(trifluoromethyl)benzoate (2b) in the presence of 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) and LiCl in THF at -10 degrees C gave poly1c with a narrow molecular weight distribution (M-w/M-n 1.08) and a well-defined molecular weight (M-n = 4480-12,700) determined by the feed ratio of monomer to initiator (from 10 to 30). The OOB groups of poly1c were removed with H2SO4 to give the corresponding N-unsubstituted poly(p-benzamide) (poly1c) with low polydispersity. The solublity of poly1c in polar organic solvents was dramatically higher than that of poly(p-benzamide), demonstrating that introduction of an alkyl group on the aromatic ring is very effective for improving the solubility of poly(p-benzamide). (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 360-365

As new and chiral macrocyclophanes with unique structures, variously sized Pn and Mn (n=2-7=number of 'rod' segments) with D-2-D-7 symmetry were constructed by alternating connection of axially chiral binaphthyls and linear biphenyls via -CH2O- moieties, so that the macrocycle consists of multiple rod-like naphthalene biphenyl naphthalene units linked together at the binaphthyl bonds. The dihedral angle of the two naphthalene rings of binaphthyl is restricted to around 90 degrees, and the calculated values of strain energy difference per naphthalene biphenyl unit in P2-P7 are almost independent of the macrocycle size, presumably owing to the flexibility of the -CH2O- connectors. (C) 2013 Elsevier Ltd. All rights reserved.

To successively construct two amide bonds between two benzene rings, the reaction of methyl N-alkylanthranilate and N-alkylisatoic anhydride in the presence of a base was studied. When the reaction was carried out with lithium hexamethyldisilazide and N,N,N',N'-tetramethylethylenediamine in THE at 70 degrees C under reduced pressure, a cyclic diamide was obtained in high yield.

Thermosetting resins and rubbers are widely used in commercial coatings and composites, but these materials are more difficult to recycle than soluble, linear polymers, and hence chemical recycling of crosslinked materials has received considerable attention. Reversible covalent bonding has also recently been utilized for crosslinking, based on the concept of dynamic covalent chemistry in supramolecular chemistry. Although hydrogen bonds are weaker than covalent bonds, crosslinking via hydrogen bonding can be strengthened by employing organized multiple hydrogen bonds. Furthermore, crosslinked polymers based on hydrogen bonding can be cast conveniently from a solution of the polymer in a solvent that breaks hydrogen bonds. Thus, such a crosslinked polymer should be recyclable by treatment with a hydrogen-bond-breaking solvent.

Quinoxaline derivatives having bis(fluoromethyl), bis(chloromethyl), or bis(iodomethyl) groups at the 2- and 3-positions, and various electron-donating/withdrawing substituents at the 6- and/or 7-positions, were synthesized. Their antibacterial and antifungal activities were evaluated by means of minimum inhibitory concentration assays. The relationships between the substituents and the antimicrobial activities of the quinoxaline derivatives indicate that the electrophilicity of the halomethyl units plays an important role in generating the antimicrobial activity.

Condensation reaction of poly(ethylene glycol) (PEG) with a carboxyl group at one chain end and hyperbranched polyamide (HBPA) with a hydroxyl group at the focal point was performed in the presence of condensation agent at ambient temperature, yielding PEG-b-HBPAs with defined molecular weight and very narrow molecular weight distribution. PEG-b-HBPA formed micelles in water. © 2013 Wiley Periodicals, Inc.

Kumada-Tamao coupling polymerization of 6-bromo-3-chloromagnesio-2-(3-(2-methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki-Miyaura coupling polymerization of boronic ester monomer 2, which has the same substituted pyridine structure, with tBu3PPd(o-tolyl)Br were investigated for the synthesis of a well-defined n-type p-conjugated polymer. We first carried out a model reaction of 2,5-dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl2 and then observed exclusive formation of 2,5-diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada-Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head-to-tail poly(pyridine-2,5-diyl), poly(3-(2-(2-(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix-assisted laser desorption ionization time-of-flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst-transfer polymerization is accompanied with disproportionation. Suzuki-Miyaura polymerization of 2 with tBu3PPd(o-tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl-ended polymer was a major product, again indicating the occurrence of disproportionation. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Well-defined (AB)3 type star block copolymer consisting of aromatic polyether arms as the A segment and polystyrene (PSt) arms as the B segment was prepared using atom transfer radical polymerization (ATRP), chain-growth condensation polymerization (CGCP), and click reaction. ATRP of styrene was carried out in the presence of 2,4,6-tris(bromomethyl)mesitylene as a trifunctional initiator, and then the terminal bromines of the polymer were transformed to azide groups with NaN3. The azide groups were converted to 4-fluorobenzophenone moieties as CGCP initiator units by click reaction. However, when CGCP was attempted, a small amount of unreacted initiator units remained. Therefore, the azide-terminated PSt was then used for click reaction with alkyne-terminated aromatic polyether, obtained by CGCP with an initiator bearing an acetylene unit. Excess alkyne-terminated aromatic polyether was removed from the crude product by means of preparative high performance liquid chromatography (HPLC) to yield the (AB)3 type star block copolymer (Mn = 9910, Mw/Mn = 1.10). This star block copolymer, which contains aromatic polyether segments with low solubility in the shell unit, exhibited lower solubility than A2B or AB2 type miktoarm star copolymers. In addition, the obtained star block copolymer self-assembled to form spherical aggregates in solution and plate-like structures in film. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Condensation polymerization of 5-aminoisophthalic acid methyl ester 1 bearing a N-tri(ethylene glycol) methyl ester (TEG) chain as an AB(2) 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 degrees C, the M-n values of the obtained HBPA increased in proportion to the [1](0)/[2b](0) ratio from 7 to 46 (M-n = 3810-18600), retaining a narrow molecular weight distribution (M-w/M-n = 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 degrees C, which is about 30 degrees C lower than that of the corresponding poly(m-benzamide) with the N-TEG unit.

Vanadium complexes with quinoline ligands (1b-g) and pyridinone ligands (2b-d) were synthesized, and the effect of the length and shape of alkyl chains on the antiproliferative activity toward U937 cells was studied. For the synthesis of the vanadium complexes, quinoline and pyridinone ligands were prepared and then treated with VOSO4 or VO(acac)(2). The vanadyl(IV) complexes were characterized by IR, ESR, and UV-vis spectroscopy and elemental analyses. The antiproliferative activity of 1a-g toward U937 cells showed little dependence on the length and shape of the alkyl chain. In contrast, a good correlation was found between the IC50 values and partition coefficients (logP) values of 2a-c. Among them, 2c showed the highest inhibitory activity, and its IC50 value was smaller than that of cisplatin. The apoptosis-inducing ability of 2b and 2c was supported by annexin V-propidium iodide staining experiments and agarose gel electrophoresis analysis. Inhibitors of caspase-3, -8, and -9 did not affect the antiproliferative activity of 2c, indicating that the apoptosis induced by 2c was via a caspase-independent pathway. (C) 2012 Elsevier Ltd. All rights reserved.

We synthesized 12 derivatives of 2,3-bis(bromomethyl) quinoxaline with substituents at the 6-and/or 7-positions, and evaluated their activities against bacteria and fungi. Of the 12 compounds, nine (1a-h, 1j, and 1k) showed antibacterial activity. The derivative 1g, which bears a trifluoromethyl group at the 6-position, showed the highest activity against Gram-positive bacteria, while 1c, which has a fluoro-group at the 6-position, showed the widest antifungal activity spectrum. However, only the derivative with an ethyl ester substitution, 1k showed activity against Gram-negative bacteria. (C) 2012 Elsevier Inc. All rights reserved.

Vanadium complexes with different ligands were synthesized and evaluated for antiproliferative activity on U937 cells. The alkyl chain length of the ligands affected the antiproliferative activity, and two complexes-3b and 4-exhibited strong activities with IC50 values of 6.02 and 3.90 mu M respectively. Annexin V staining and DNA ladder formation indicated that these complexes induced apoptosis in U937 cells.

A new regioregular head-to-tail (HT)-type polypyridine with methoxyethoxyethoxy (MEEO) side chains, HT-PMEEOPy, was synthesized by means of Kumada-Tamao coupling polymerization of a Grignard monomer with a Ni catalyst. Although the polymer was precipitated in THF during polymerization, multiangle laser light scattering (MALLS) analysis indicated that the weight-average molecular weight (Mw) was about 25,000. The HT content in the polymer was 95%. A solution of HT-PMEEOPy in CHCl3 was found to emit a strong blue light when the solution was irradiated with UV light; the UV-vis absorption maximum (?max) and photoluminescence maximum (?max em) were at 392 and 460 nm, respectively. To clarify the effect of regioregularity of PMEEOPy on the photoluminescence, head-to-head (HH) PMEEOPy was synthesized by means of Yamamoto coupling polymerization. The photoluminescence of HH-PMEEOPy (?max = 330 nm, ?max em = 414 nm) was weaker than that of HT-PMEEOPy. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Ni-catalyzed Kumada-Tamao coupling polymerization of S-bromo-3-chloromagnesio-2-(2-(2-methoxyethoxy)ethoxy)pyridine (1) was investigated. Monomer 1, which was obtained quantitatively by treatment of the corresponding bromoiodopyridine 3 with 1.0 equiv of (PrMgCl)-Pr-i at 0 degrees C, was polymerized with Ni(dppp)Cl-2 (dppp = 1,3-bis(diphenylphospino)propane)) in the presence of 2.0 equiv of LiCl in THF at room temperature to yield poly(2-(2-(2-methoxyethoxy)ethoxy)pyridine-3,5-diyl) (m-PMEEOPy) with narrow polydispersity. The M-n value was controlled by the feed ratio of the monomer precursor 3 to Ni(dppp)Cl-2. MALDI-TOF mass spectra showed that m-PMEEOPy uniformly had a bromine atom at one end and a hydrogen atom at the other. Both end groups could be converted to aryl groups by addition of an excess of aryl magnesium chloride to the reaction mixture after completion of the polymerization. These results indicate that the polymerization of 1 with Ni(dppp)Cl-2 involves the intramolecular catalyst-transfer polymerization mechanism.

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 center dot center dot center dot 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. (C) 2011 Elsevier Ltd. All rights reserved.

Well-defined hyperbranched polyamides (HBPAs) were synthesized by means of chain-growth condensation polymerization of AB(2) 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 AB(2) 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 degrees C to yield HBPA with low polydispersity (M-w/M-n <= 1.13) and well-defined molecular weight (M-n = 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 AB(2) 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 (T-g) and 10% weight-loss temperature (T-d(10)) of HBPAs depended upon the molecular weight, as well as the nature of the N-alkyl groups and terminal ester moieties.

Condensation 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 degrees 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. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3020-3029, 2011

(t)Bu(3) PPd(Ph)Br (1)-catalyzed Suzuki-Miyaura coupling polymerization of 2-(4-hexyl-5-iodo-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2) was investigated. Monomer 2 was polymerized with 1 at 0 degrees C in the presence of CsF and 18-crown-6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head-to-tail regioregularity. The (M) over bar (n) values increased up to 11 400 g.mol(-1) in proportion to the feed ratio of 2 to 1. The MALDI-TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. Successive 1-catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well-defined block copolymer of polyfluorene and P3HT.

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 degrees C) by using M(n) < 5000 precursors. From the mechanistic viewpoint, we designed a strategy for styrene-assisted ATRC from methacrylic macroradicals at low temperature (St/PMMA-Br/Cu(I)Br/Cu(0)/Me(6)TREN). Analysis of the products ((1)H 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) (M(n) = 9300, M(w)/M(n) = 1.09), were conducted to yield ABA-type triblock polybenzamides with high coupling efficiency (>94%). The molecular weight (M(n) similar to 18000) was doubled and a narrow molecular weight distribution (M(w)/M(n) < 1.18) was maintained. Selective removal of the octyloxybenzyl groups was achieved, resulting in a poly(N-H-m-benzamide) segment (i.e., A block). Thermal transitions of the diblock and triblock polybenzamides were examined by DSC. In the case of triblock polybenzamides, the T(g) value shifted from 45 to 62 degrees C after removal of the octyloxybenzyl groups; this might be ascribed to a confinement effect of the segments at the extremities via strong intermolecular hydrogen-bonding interaction.

Random copolymers of poly(p-benzamide)s having a methyl-substituted tri(ethylene glycol) unit as a chiral side chain and a nonsubstituted tri(ethylene glycol) or branching alkyl unit as an achiral side chain were synthesized by copolymerization of N-substituted 4-aminobenzoic acid ester monomers with a base in the presence of an initiator. Copoly-merizations of the chiral (S)-monomer with N-tri(ethylene glycol) achiral monomer and with the racemic monomer were carried out by the addition of a mixture of two monomers and an initiator to a solution of a base all at once, affording the corresponding random copolymers. On the other hand, random copolymerization of the chiral monomer with monomer having an achiral branching alkyl side chain required dropwise addition of the achiral monomer to a mixture of the chiral monomer, the initiator, and the base. These copolymers formed helical structures, but analysis of the CD spectra indicated the absence of cooperativity between the monomer units along the copolymers. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1387-1395,2011

A variety of well-defined tetra-armed star-shaped poly(N-substituted p-benzamide)s, including block poly(p-benzamide)s with different N-substituents, and poly(N-substituted m-benzamide)s, were synthesized by using porphyrin-cored tetra-functional initiator 2 under optimized polymerization conditions. The initiator 2 allowed discrimination of the target star polymer from concomitantly formed linear polymer by-product; by means of GPC with UV detection, and the polymerization conditions were easily optimized for selective synthesis of the star polybenzamides. Star-shaped poly(p-benzamide) with tri(ethylene glycol) monomethyl ether (TEG) side chain was selectively obtained by polymerization of phenyl 4-{2-[2-(2-ME hoxyethoxy)ethoxy]ethylaminolbenzoate (1b') with 2 at -10 degrees C in the case of [1b'](0)/[2](0) = 40 and at 0 degrees C in the case of [1b(0)](0)/[2](0) = 80. Star-shaped poly(p-benzamide) with 4-(octyloxy)benzyl (OOB) substituent was obtained only when methyl 4-[4-(octyloxy)benzylamino]benzoate (1c) was polymerized at 25 degrees C at [1c](0)/[2](0) = 20. On the other hand, star-shaped poly(m-benzamide)s with N-butyl, N-octyl, and N-TEG side chains were able to be synthesized by polymerization of the corresponding meta-substituted aminobenzoic acid alkyl ester monomers 3 at 0 degrees C until the ratio of [3](0)/[2](0) reached 80. However, star-shaped poly(m-benzamide)s with the 008 group were contaminated with linear polymer even when the feed ratio of the monomer 3d to 2 was 20. The UV-visible spectrum of an aqueous solution of star-shaped poly(p-benzamide) with TEG side chain indicated that the hydrophobic porphyrin core was aggregated. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 986-994, 2011

Catalyst-transfer Suzuki-Miyaura coupling polymerization of 2,5-bis(hexyloxy)-4-iodophenylboronic acid (1b) with Bu(3)PPd(Ph)Br (2) was investigated. When 1b was polymerized with 2 at 0 degrees C in the presence of 4 equiv of CsF, 8 equiv of 18-crown-6, and a small amount of water (to dissolve CsF), poly-(p-phenylene) (poly1b) with a narrow molecular weight distribution was obtained. The conversion-number average molecular weight (M(n)) and feed ratio-M(n) relationships indicate that this polymerization proceeded in a chain-growth polymerization manner. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that poly1b with moderate molecular weight uniformly had a phenyl group, derived from 2, at one end of each polymer chain and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. However, the molecular weight distribution of the polymer gradually became broader with increase of the feed ratio of 1b to 2, and polymer chains with other end groups were formed. Successive catalyst-transfer Suzuki-Miyaura coupling polymerization of 2-(7-bromo-9,9-dioctyl-9H-fluoren-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3) and then 1b yielded a well-defined block copolymer of polyfluorene and poly(p-phenylene).

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 degrees 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 (1)H NMR spectra of the star polymers in dimethyl sulfoxide revealed that the poly(N-octyl-m-benzamide) segments and arms of the block-arm and miktoarm star polymers, respectively, were compactly packed at room temperature and became extended at higher temperatures.

Chain-growth condensation polymerization of p-aminobenzoic acid esters 1 bearing a tri(ethylene glycol) monomethyl ether side chain on the nitrogen atom was investigated by using lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base. The methyl ester monomer la afforded polymer with low molecular weight and a broad molecular weight distribution, whereas the polymerization of the phenyl ester monomer 1b at -20 degrees C yielded polymer with controlled molecular weight (M(n) = 2800-13,400) and low polydispersity (M(w)/M(n) = 1.10-1.15). Block copolymerization of 1b and 4-(octylamino)benzoic acid methyl ester (2) was further investigated. We found that block copolymer of poly1b and poly2 with defined molecular weight and low polydispersity was obtained when the polymerization of 1b was initiated with equimolar LiHMDS at -20 degrees C and continued at -50 degrees C, followed by addition of 2 and equimolar LiHMDS at -10 degrees C. Spherical aggregates were formed when a solution of poly1b in THF was dropped on a glass plate and dried at room temperature, although the block copolymer of poly1b and poly2 did not afford similar aggregates under the same conditions. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1357-1363, 2010

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.

Well-defined AB(2) and A(2)B 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 Bu(3)SnH. 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 AB(2) type miktoarm star copolymers were synthesized without step-growth polycondensation. The synthesis of A(2)B type miktoarm star copolymers was carried out similarly using 1-bromomethyl-3,5-bis(4-fluorobenzoyl)benzene as a trifunctional initiator. The A(2)B type miktoarm star copolymers, which contained two arms of aromatic polyether units with high crystallinity, exhibited higher solubility than AB type diblock copolymer or AB(2) type miktoarm star copolymers. As in the case of the AB type diblock copolymer, the AB(2) and A(2)B type miktoarm star copolymers self-assembled to form spheres of 150-600 urn diameter when a THF solution of the copolymers was allowed to dry on a glass plate. Similar spherical aggregates were obtained from a THF-methanol solution of the A(2)B type miktoarm star copolymer, whereas the AB(2) type afforded fiber-like structures under the same conditions.

Well-defined diblock condensation copolymers composed of an aromatic polyamide and an aromatic polyether have been synthesized by means of successive chain-growth condensation polymerizations. Polymerization of a polyamide monomer with an orthogonally difunctional initiator is accompanied with side reactions. On the other hand, polymerization with a monofunctional initiator afforded well-defined polyamide, which has been converted into a macroinitiator by introduction of a terminal 4-fluorobenzophenone unit. Well-defined diblock copolymers are obtained by polymerization of a polyether monomer in the presence of this macroinitiator.

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-(alkylami- no)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 CH2C12 gel revealed that the block copolymers self-assembled to form three-dimensional network structures, in which the solvent was confined to afford a gel. The gelating properties were dependent on both the orientation of the monomer substituents (meta or para) and the composition ratio of the N-H poly(benzamide) segment in the block copolymers. © 2008 American Chemical Society.

Successive catalyst-transfer condensation polymerization of a Grignard-type phenylene monomer and then a thiophene monomer with a Ni catalyst yields well-defined block copolymers of poly(p-phenylene) and polythiophene, but the reverse order of polymerization results in polymers with broad molecular weight distribution.

Base-promoted self-condensation reactions of trans-stilbene and diphenylacetylene monomers bearing 4-alkylamino and 4'-methoxycarbonyl groups were investigated. Reactions of N-propyl monomers under pseudohigh-dilution conditions (a THF solution of monomer was added dropwise to a THF solution of LiHMDS) afforded the corresponding cyclic triamides in good yields. X-ray crystallographic analysis showed that these cyclic triamides possessed an almost equilateral triangle structure with a cavity surrounded by tilted benzene rings.

The 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.

We describe the development of chain-growth condensation polymerization for the synthesis of well-defined pi-conjugated polymers via a new polymerization mechanism, catalyst-transfer polymerization. We first studied the condensation polymerization of Grignard-type hexylthiophene monomer with a Ni catalyst as a part of our research on chain-growth condensation polymerization, and found that this polymerization also proceeded in a chain-growth polymerization manner. However, the polymerization mechanism involving the Ni catalyst was different from that of previous chain-growth. condensation polymerizations based on substituent effects; the Ni catalyst catalyzed the coupling reaction of the monomer with the polymer, followed by the transfer of Ni(0) to the terminal C-Br bond of the elongated molecule. This Catalyst-transfer condensation polymerization is generally applicable for the synthesis of polythiophene with an etheric side chain and poly(p-pheneylene), as well as for the synthesis of polyfluorene via the Pd-catalyzed Suzuki-Miyaura coupling reaction. (C) 2007 Wiley Periodicals, Inc.

Polymerization of diphenyl acetylene and trans-stilbene monomers bearing 4-alkylamino and 4'-phenoxy- or 4'-alkoxycarbonyl groups was carried out with an initiator in the presence of lithium 1,1,1,3,3,3-hexamethyidisilazide. Chain-growth polymerization afforded corresponding polyamides, whereas step-growth polymerization resulted in the formation of cyclic oligoamides.

Recent progress in the reaction control of condensation polymerization is described. In the past, the reactions in condensation polymerization had been improved for the purpose of production of high molecular weight polymer with more convenient methods. In recent years, chemoselective, regioselective, and stereoselective condensation polymerizations have been developed. Furthermore, it has been revealed that most condensation polymerizations possess the fundamental tendency to yield cyclic polymers as stable end products when the reactions are optimized for quantitative reaction. When the reactivity of a functional group of a monomer was enhanced after the other functional group of the monomer was reacted, condensation polymerization of AA and BB monomers afforded polymer with high molecular weight, even under nonstoichiometric conditions, and condensation polymerization of AB monomer involved a chain-growth polymerization mechanism to yield polymer with narrow molecular weight distribution.