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ABSTRACT 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 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2365-2372 [ABSTRACT FROM AUTHOR]

ABSTRACT 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. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1623-1628 [ABSTRACT FROM AUTHOR]

ABSTRACT 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 °C to yield poly 3c with well-defined molecular weight ( Mn = 4520-9080) and low polydispersity ( Mw/ Mn ≤ 1.11). Treatment of poly 3c with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly( o-hydroxyamide) (poly 4) without scission of the amide linkages. Cyclodehydration of poly 4 proceeded at 350 °C to yield PBO (poly 5), which was insoluble in organic solvents and acids. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1730-1736 [ABSTRACT FROM AUTHOR]

ABSTRACT 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 poly 1c. 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 °C gave poly 1c with a narrow molecular weight distribution ( Mw/ Mn ≤ 1.08) and a well-defined molecular weight ( Mn = 4480-12,700) determined by the feed ratio of monomer to initiator (from 10 to 30). The OOB groups of poly 1c were removed with H2SO4 to give the corresponding N-unsubstituted poly( p-benzamide) (poly 1c′) with low polydispersity. The solublity of poly 1c′ 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). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 360-365 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

PolystyrENe ‐ graft ‐ poly(p ‐ bENzamide) was synthesized by free radical copolymerization of poly(N ‐ octyloxybENzyl ‐ p ‐ bENzamide) macromonomer and styrENe, followed by the removal of the octyloxybENzyl groups from amide nitrogEN. The glass transition temperature (Tg) of polystyrENe ‐ graft ‐ poly(p ‐ bENzamide) increased dramatically by 50–60 °C whEN the contENt of poly(p ‐ bENzamide) exceeded a threshold of about 4%. [ABSTRACT FROM AUTHOR]

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. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

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 π-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. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

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 (λmax) and photoluminescence maximum (λmax 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 (λmax = 330 nm, λmax em = 414 nm) was weaker than that of HT-PMEEOPy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

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 °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 [ABSTRACT FROM AUTHOR]

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. Copolymerizations 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. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

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-products 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-methoxyethoxy)ethoxy]ethylamino}benzoate ( 1b′) with 2 at −10 °C in the case of [ 1b′]0/[ 2]0 = 40 and at 0 °C in the case of [ 1b′]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 °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 °C until the ratio of [ 3]0/[ 2]0 reached 80. However, star-shaped poly( m-benzamide)s with the OOB 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. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

The article presents a study on an automatic nonuniform decomposition of electric power system which aims to lessen the total data processing time taking into account the supply and demand balance in each subsystem. It discusses the effect of decomposition on the computational accuracy of transient stability. It concludes that the proposed method provides an ideal decomposition pattern without causing memory contention.

Cyclin A (A2) and cyclin A1 are members of the G2 cyclins, which are involved in the control of G2/M and G1/S transitions as well as mitosis. Human cyclin A1 was cloned as an A-type cyclin that is highly expressed in acute myeloid leukaemia (AML). The clinical significance of these cyclins in myeloid leukaemia remains to be clarified. We investigated the relative levels of these transcripts in 80 patients with de novo AML. Correlations with clinical parameters showed that the initial white blood cell count and serum lactate dehydrogenase levels were inversely associated with cyclin A (A2) mRNA levels (r = -0.276, P = 0.019) and cyclin A1 mRNA levels (r = -0.241, P = 0.042) respectively. They were independently associated with increased overall survival [P = 0.035 for cyclin A (A2) and P = 0.016 for cyclin A1]. Multivariate analysis using Cox's proportional hazard model showed that elevated cyclin A1 mRNA levels contributed significantly to the better prognosis of patients with AML. Furthermore, the analysis of survival probability showed that the group with high levels of both cyclin A (A2) and A1 survived significantly longer than the group with low expression of both these cyclins (P = 0.002). These data indicate that high expression levels of both cyclin A (A2) and A1 are associated with good prognosis in AML patients.