Thiophene‐cored 2,2‐bis(methylol)propionic acid dendrimers for optical‐power‐limiting applications

The synthesis and characterization of dendron‐coated 2,5‐bis(phenylethynyl)thiophene chromophores are described. The dendrimers were grown divergently on the arylthiophene core with the versatile anhydride of 2,2‐bis(methylol)propionic acid. The arylthiophene core was synthesized with Sonogashira coupling reactions. Structurally well‐defined dendrimers up to the fourth generation were grown, as confirmed by size exclusion chromatography, NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight analysis. The different dendritic substitution did not influence the absorption spectra of the compounds in or near the visible region. Solutions of arylthiophenes had good transparency at wavelengths greater than 400 nm. The dendritic thiophenes exhibited an optical‐power limit at the laser wavelength of 532 nm. However, the magnitude of the optical‐power limit of these compounds was slightly lower than that of a nondendritic arylthiophene with n‐pentyl substituents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1177–1187, 2005     

Thermal and X‐ray powder diffraction studies of aliphatic polyester dendrimers

The syntheses and thermal and X‐ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2‐bis(hydroxymethyl)propionic acid as a repeating unit and 2,2‐dimethyl‐1,3‐propanediol, 1,5‐pentanediol, and 1,1,1‐tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250 °C for the hydroxyl‐ended dendrimers and around 150 °C for the acetonide‐protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X‐ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first‐generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass‐transition temperatures were observed in subsequent heating scans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5574–5586, 2004     

Dendronized polymers with tailored surface groups

A series of polymers tethered with bis‐MPA dendrons was synthesized by a combination of divergent growth and atom transfer radical polymerization (ATRP). Macromonomers of first and second generation were synthesized utilizing the acetonide protected anhydride of bis‐MPA as the generic esterfication agent. The macromonomers were polymerized in a controlled fashion by ATRP utilizing Cu(I)/Cu(II) and N‐propyl‐2‐pyridylmethanamine as the halogen/ligand system. The end‐groups of these polymers were further tailored to achieve hydroxyl, acetate, and aliphatic hexadecyl functionality. With this approach all polymers will emanate from the same backbone, enabling for an evaluation of both the generation and end‐group dependent properties. Furthermore, a dendronized tri‐block copolymer was synthesized. All materials were analyzed by ¹H and ¹³C NMR, as well as size‐exclusion chromatography (SEC). The SEC analysis revealed that the molecular weights of the divergently grown dendronized polymers increased with increasing generation while the polydispersity (PDI) was kept low. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3852–3867, 2005     

Synthesis and characterization of a bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine monomer and its polymer for light‐emitting applications

This study focuses on the preparation, polymerization, characterization, and optical properties of a new bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine monomer. This is the first nitrogen‐containing monomer having nitrogen atoms as bridges between phenyl rings, and it was synthesized in three steps. The polymerization was carried out through the Ni(0)‐catalyzed homocoupling reaction of the bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine compound. The resulting polymer, polybis(paraphenyl)phenylamine, emitted an intense blue color (where λ = 415 nm) upon irradiation by ultraviolet light. The photoluminescence quantum yield was found to be 36% with a long excited‐state lifetime of 3.3 ns. Electrical conductivity data for an HCl‐doped film of the polymer were also examined. This novel polymer is of interest as an organic emitting material for electroluminescent devices. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1860–1867, 2007     

Preparation and characterization of fluorine‐containing aromatic condensation polymers. VII. Aromatic polyacetals and copolyacetals from 2,2‐bis(4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane and/or 2,2‐bis(4‐hydroxyphenyl)propane and 2‐(trifluoromethyl)benzal chloride

A series of fluorine‐containing aromatic homopolyacetals and copolyacetals with a wide range of unit ratios were synthesized by the solution polycondensation of 2,2‐bis(4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane (bisphenol AF), 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol A), or both with 2‐(trifluoromethyl)benzal chloride, and the effect of fluorine substitution on the properties of these polymers is discussed in relation to the fluorine contents. High molecular weight polyacetals with reduced viscosities of 0.43–0.97 dL/g were obtained in high yields with potassium hydroxide as a base, 18‐crown 6‐ether as a catalyst, and N‐methyl‐2‐pyrrolidinone as a medium at 100 °C for 3 h. Regardless of the fluorine contents, these polymers all were highly soluble in various solvents, including benzene, chloroform, ethyl acetate, and tetrahydrofuran, and afforded colorless, transparent, and tough films by solution casting. The temperatures of 5% weight loss and 10% weight loss under nitrogen both increased significantly and monotonously with increasing fluorine content, whereas the glass‐transition temperatures were scarcely affected by fluorine substitution. The dielectric constant at 1 MHz of the bisphenol AF‐based homopolyacetal was 2.43, which was remarkably lower than the value of the bisphenol A‐based homopolyacetal, 2.68. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1873–1879, 2000     

Preparation and characterization of cyclic polystyrene with short poly(2‐tert‐butylbutadiene) sequences

A polystyrene‐block‐oligo(2‐tert‐butylbutadiene)‐block‐polystyrene triblock copolymer was prepared and cyclized by end‐to‐end ring closure. Ring‐shaped polystyrene‐block‐oligo(2‐tert‐butylbutadiene) was isolated from the coupling product via gel permeation chromatography (GPC) fractionation. The ring polymer was ozonized for decomposition of the oligo(2‐tert‐butylbutadiene) sequences selectively referring to the linear molecule. From GPC analysis of the decomposed products by ozonolysis, it was quantitatively confirmed that the fractionated product was 86% ring molecules. Single chain dimensions of the ring and linear molecules in a good solvent, benzene, and in a θ solvent, cyclohexane, were measured with small‐angle neutron scattering. The ratios of the radii of gyration, R_g(ring)/R_g(linear), were 0.780 in benzene and 0.789 in cyclohexane. These were compared with theoretically predicted values. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1582–1589, 2002     

Synthesis and characterization of new highly organosoluble poly(etherimide)s derived from 1,1‐bis{4‐[4‐(3,4‐dicarboxyphenoxy)phenyl]‐4‐phenylcyclohexane} dianhydride

A new bulky pendent bis(ether anhydride), 1,1‐bis[4‐(4‐dicarboxyphenoxy)phenyl]‐4‐phenylcyclohexane dianhydride, was prepared in three steps, starting from the nitrodisplacement of 1,1‐bis(4‐hydroxyphenyl)‐4‐phenylcyclohexane with 4‐nitrophthalonitrile to form bis(ether dinitrile), followed by alkaline hydrolysis of the bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). A series of new poly(ether imide)s were prepared from the bis(ether anhydride) with various diamines by a conventional two‐stage synthesis including polyaddition and subsequent chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.50–0.73 dL g^?1. The gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 57,000 and 130,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility in comparison with the other polyimides derived from adamantane, norbornane, cyclododecane, and methanohexahydroindane and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. These polymers had glass‐transition temperatures of 226–255 °C. Most of the polymers could be dissolved in chloroform in as high as a 30 wt % concentration. Thermogravimetric analysis showed that all polymers were stable up to 450 °C, with 10% weight losses recorded from 458 to 497 °C in nitrogen. These transparent, tough, and flexible polymer films could be obtained by solution casting from DMAc solutions. These polymer films had tensile strengths of 79–103 MPa and tensile moduli of 1.5–2.1 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2066–2074, 2002     

Electrochemical Reduction of 4,4′‐(2,2,2‐Trichloroethane‐1,1‐diyl)‐ bis(chlorobenzene) (DDT) and 4,4′‐(2,2‐Dichloroethane‐1,1‐diyl)‐ bis(chlorobenzene) (DDD) at Carbon Cathodes in Dimethylformamide

In dimethylformamide containing tetramethylammonium tetrafluoroborate, cyclic voltammograms for reduction of 4,4′‐(2,2,2‐trichloroethane‐1,1‐diyl)bis(chlorobenzene) (DDT) at a glassy carbon cathode exhibit five waves, whereas three waves are observed for the reduction of 4,4′‐(2,2‐dichloroethane‐1,1‐diyl)bis(chlorobenzene) (DDD). Bulk electrolyses of DDT and DDD afford 4,4′‐(ethene‐1,1‐diyl)bis(chlorobenzene) (DDNU) as principal product (67–94%), together with 4,4′‐(2‐chloroethene‐1,1‐diyl)bis(chlorobenzene) (DDMU), 1‐chloro‐4‐styrylbenzene, and traces of both 1,1‐diphenylethane and 4,4′‐(ethane‐1,1‐diyl)bis(chlorobenzene) (DDO). For electrolyses of DDT and DDD, the coulometric n values are essentially 4 and 2, respectively. When DDT is reduced in the presence of a large excess of D₂O, the resulting DDNU and DDMU are almost fully deuterated, indicating that reductive cleavage of the carbon–chlorine bonds of DDT is a two‐electron process that involves carbanion intermediates. A mechanistic scheme is proposed to account for the formation of the various products.     

Highly active methyl methacrylate polymerization catalysts obtained from bis(3,5‐dinitro‐salicylaldiminate)nickel(II) complexes and methylaluminoxane

The homopolymerization of methyl methacrylate was investigated with bis(salicylaldiminate)nickel(II) complexes, such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)salicylaldiminate]nickel(II) ( IIIa ) and bis[3,5‐dinitro‐N(phenyl)salicylaldiminate]nickel(II) ( IIIb ), and with methylaluminoxane (MAO) as an activator. In particular, the effect of the Al/Ni molar ratio on the catalytic activity and on the properties of the resulting poly(methyl methacrylate) (PMMA) was checked. The maximum activity was ascertained when an Al/Ni molar ratio equal to about 100 was used. However, the productivity of the catalytic systems was rather low. When the IIIa /MAO catalytic system was prepared under an ethylene atmosphere, an extremely high activity was observed, a productivity value of up to around 150,000 g of PMMA/(mol of Ni × h) being obtained, the highest ever found with nickel‐based catalysts. No appreciable presence of ethylene counits in the polymeric products was also ascertained. When the IIIb /MAO system was used, similar results were found, and high molecular weight PMMAs were obtained, despite the absence of bulky isopropyl substituents in positions ortho and ortho′ to the N‐aryl moiety of the salicylaldiminate ligand. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2117–2124, 2003     

Synthesis of polyphosphonates containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with phosphonic dichlorides

The polyaddition of 4,4′‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]biphenyl (4,4′‐BEOBP) and phenylphosphonic dichloride (PPDC) with quaternary onium salts as catalysts proceeded under mild reaction conditions to afford a polymer containing phosphorous atoms in its main chain. A polyphosphonate with a high number‐average molecular weight (10,300) was obtained by the reaction of 4,4′‐BEOBP and PPDC in the presence of tetraphenylphosphonium chloride (TPPC) in o‐dichlorobenzene at 130 °C for 24 h. The structure of the resulting polymer was confirmed with IR, ¹H NMR, and ³¹P NMR spectroscopy. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with phosphonic dichlorides proceeded smoothly to give corresponding polyphosphonates with TPPC as the catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3835–3846, 2002     

Synthesis of polyacrylonitrile mediated by manganese(III) acetylacetonate (Mn(acac)3) and 2‐cyanoprop‐2‐yl dithionaphthalenoate

2‐Cyanoprop‐2‐yl dithionaphthalenoate (CPDN) was successfully used as the chain transfer agent to prepare polyacrylonitrile in combination with manganese(III) acetylacetonate (Mn(acac)₃) as the initiator. The novel polymerization exhibited well “living”/controlled characteristics. The polymerization behavior was revealed to comply with features of reversible addition–fragmentation chain transfer polymerization process. Mn(acac)₃ played a key role as the initiator rather than the radical trapping agent in polymerization and exhibited better control performance than azo‐initiator. The narrowest molecular weight distribution was 1.31 under the condition of [AN]₀:[Mn(acac)₃]₀:[CPDN]₀ = 200:1:0.025 and AN:DMF = 1:1 (V/V). Various feed ratios of Mn(acac)₃ and CPDN were also investigated in detail. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1305–1309     

Synthesis and characterization of new highly organosoluble poly(ether imide)s based on 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride

A new bis(ether anhydride), 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride ( 3 ), was prepared in three steps: the nitro displacement of 4‐nitrophthalonitrile with 2,2‐bis(4‐hydroxy‐3,5‐dimethylphenyl)propane, the alkaline hydrolysis of the intermediate bis(ether dinitrile), and the subsequent dehydration of the resulting bis(ether diacid). A series of new highly soluble poly(ether imide)s with tetramethyl and isopropylidene groups were prepared from the bis(ether anhydride) 3 with various diamines by a conventional two‐stage synthesis including polyaddition and chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.54–0.73 dL g^?1. Gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 54,000 and 124,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. Most of the polymers could be dissolved with chloroform concentrations as high as 30 wt %. These polymers had glass‐transition temperatures of 244–282 °C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight losses recorded above 463 °C in nitrogen. These transparent, tough, and flexible polymer films were obtained through solution casting from N,N‐dimethylacetamide solutions. These polymer films had tensile strengths of 81–102 MPa and tensile moduli of 1.8–2.0 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2556–2563, 2002     

Synthesis and characterization of new soluble poly(amide‐imide)s derived from 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane

A series of new soluble poly(amide‐imide)s were prepared from the diimide‐dicarboxylic acid 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane with various diamines by direct polycondensation in N‐methyl‐2‐pyrrolidinone containing CaCl₂ with triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.52–0.86 dL · g^?1. The poly(amide‐imide)s showed an amorphous nature and were readily soluble in various solvents, such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, and cyclohexanone. Tough and flexible films were obtained through casting from DMAc solutions. These polymer films had tensile strengths of 71–107 MPa and a tensile modulus range of 1.6–2.7 GPa. The glass‐transition temperatures of the polymers were determined by a differential scanning calorimetry method, and they ranged from 242 to 279 °C. These polymers were fairly stable up to a temperature around or above 400 °C, and they lost 10% of their weight from 480 to 536 °C and 486 to 537 °C in nitrogen and air, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3498–3504, 2001     

A MALDI‐TOF MS study of lanthanide(III)‐cored poly(phenylenevinylene) dendrimers

An extensive study by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry (MS) of some first‐generation and second‐generation lanthanide(III)‐cored poly(phenylenevinylene) dendrimers is described. The complexes were obtained by self‐assembly of suitably functionalized carboxylate dendrons around the lanthanide ion (La³⁺, Er³⁺). Fourier transform infrared (FT‐IR) spectroscopy gave reasonable evidence for the proposed structures. However, MS was used to ascertain unequivocally the complex formation. The most reliable results were found in the negative reflector mode, using 2‐[(2E)‐3‐(4‐tert‐butylphenyl)‐2‐methylprop‐2‐enylidene]malononitrile (DCTB) as matrix. Well‐defined and highly resolved base peaks corresponding to negative ions of [Gn₄La]^? and [Gn₄Er]^? were found in all cases, with an excellent match between the theoretical and observed isotope distributions. However, the 3 : 1 stoichiometry used in the synthesis guarantees an empirical formula Gn₃Ln for the complexes. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of soluble polyimides derived from 2′,5′‐bis(3,4‐dicarboxyphenoxy)‐p‐terphenyl dianhydride

A novel bis(ether anhydride) monomer, 2′,5′‐bis(3,4‐dicarboxyphenoxy)‐p‐terphenyl dianhydride, was synthesized from the nitro displacement of 4‐nitrophthalonitrile by the phenoxide ion of 2′,5′‐dihydroxy‐p‐terphenyl, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and cyclodehydration of the resulting bis(ether diacid). A series of new poly(ether imide)s bearing laterally attached p‐terphenyl groups were prepared from the bis(ether anhydride) with various aromatic diamines via a conventional two‐stage process that included ring‐opening polyaddition to form the poly(amic acid)s followed by thermal or chemical imidization to the poly(ether imide)s. The inherent viscosities of the poly(amic acid) precursors were in the range of 0.62–1.26 dL/g. Most of the poly(ether imide)s obtained from both routes were soluble in polar organic solvents, such as N,N‐dimethylacetamide. All the poly(ether imide)s could afford transparent, flexible, and strong films with high tensile strengths. The glass‐transition temperatures of these poly(ether imide)s were recorded as between 214 and 276 °C by DSC. The softening temperatures of all the poly(ether imide) films stayed in the 207–265 °C range according to thermomechanical analysis. For all the polymers significant decomposition did not occur below 500 °C in nitrogen or air atmosphere. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1008–1017, 2004     

Synthesis and characterization of organosoluble copolyimides based on 2,2‐Bis[4‐(4‐aminophenoxy)phenyl]propane, 2,2‐Bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane and a pair of commercial aromatic dianhydrides

Organosoluble homopolyimides (PIs) and copolyimides (CoPIs) were synthesized from 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane (BAPP) or 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (6FBAPP) and six kinds of commercial aromatic dianhydrides (PMDA, II _a ; BTDA, II _b ; BPDA, II _c ; ODPA, II _d ; DSDA, II _e ; 6FDA, II _f ). Although BAPP and II _d∼f could prepare three kinds of soluble PIs ( III‐A _d∼f ), likewise 6FBAPP and II _c∼f could prepare four PIs ( III‐B _c∼f ), the insoluble PIs were synthesized from these two diamines and other dianhydrides. However, soluble CoPIs could be prepared by alternative copolycondensation from a pair of dianhydrides of soluble PIs and insoluble PIs in certain molar ratios (m₁/m₂). The ratios of m₁/m₂ of BAPP/PMDA series CoPIs ( IV _{m1(d–f)/m2a} ) ranged from 3–5, but ratios of 6FBAPP/PMDA series CoPIs ( V _{m1(c∼f)/m2a} ) decreased to 2–3. The m₁/m₂ of the BAPP/BTDA and 6FBAPP/BTDA series CoPIs were 2, while the BAPP/BPDA series were between 1–2. Composition, solubility, tensile properties and thermal properties of these CoPIs synthesized via a two‐stage thermal cyclodehydration were determined and were compared with their corresponding PIs. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3954–3961, 2000     

Influence of (1,3‐phenylene)bis(3‐methyl‐1‐phenyl pentylidene)dilithium initiator concentration on the modality of polybutadiene

The strong influence of (1,3‐phenylene)bis(3‐methyl‐1‐phenyl pentylidene)dilithium initiator (DLI) concentration on the modality of polybutadiene (PBd) in the presence of lithium s‐butoxide (s‐BuOLi) in benzene, at room temperature, has been studied. The quality of DLI has been evaluated by gas chromatography‐mass spectrometry (GC‐MS) and ¹H NMR. Keeping s‐BuOLi/C‐Li ratio (R) close to unity, at relatively high DLI concentrations (C > 7 × 10^?4 M), monomodal high 1,4‐PBds with polydispersity index less than 1.07 were obtained, whereas bimodal ones at lower concentrations (C < 6 × 10^?4 M). The effect of C‐Li concentration on the modality of PBd has been evaluated using size exclusion chromatography on samples taken during and at the end of the polymerization. Viscosity observations have also been used to further support the results. The bimodality of PBd has been attributed to partially terminated difunctional species because of the inevitable presence of protic impurities in the polymerization solution, although high vacuum technique was used, which becomes more significant at low initiator concentrations. Moreover, the strong influence of s‐BuOLi on the microstructure of PBd has been demonstrated by ¹H NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Star polymer synthesis using trithiocarbonate functional β‐cyclodextrin cores (reversible addition–fragmentation chain‐transfer polymerization)

Polystyrene stars were synthesized with reversible addition–fragmentation chain‐transfer (RAFT) polymerization. The core of the stars comprised a trithiocarbonate heptafunctional β‐cyclodextrin ring. Polymerizations were performed at 100 and 120 °C in the absence of an extraneous initiator and at 60 °C in the presence of a radical initiator. Monofunctional trithiocarbonate was also synthesized and used to make linear polystyrene to allow direct a comparison with the star synthesis. In all cases, the polymerization kinetics conformed to pseudo‐first‐order behavior. The measured molecular weights of the stars were found to deviate from those predicted on the basis of the monomer/trithiocarbonate group ratio. The extent of this deviation was dependent on the polymerization temperature, RAFT agent concentration, and conversion. Despite the low radical concentrations, termination reactions are suggested to play a significant role in the seven‐arm polystyrene star syntheses. The synthetic method was found to be suitable for generating star block structures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4498–4512, 2002     

Synthesis and properties of new polyamides derived from 2,2‐bis[4‐[2‐(4‐aminophenoxy)ethoxy]phenyl]sulfone by direct polycondensation

A series of new polyamides containing both sulfone and oxyethylene moieties in the polymer chain was prepared by the direct polycondensation of the diamine monomer 2,2‐bis[4‐[2‐(4‐aminophenoxy)ethoxy]phenyl]sulfone (BAEPS) and various aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. Polymers were produced with inherent viscosities of 0.30–0.60 dl/g and identified by elemental analysis, and infrared and nuclear magnetic resonance spectra. Most of the polymers were readily dissolved in polar solvents such as NMP, dimethylsulfoxide, N,N‐dimethylacetamide, N,N‐dimethylformamide and m‐cresol at room temperature. Polymers containing rigid and symmetric p‐phenylene, naphthalene and p‐biphenylene moieties revealed a crystalline nature and showed no solubility in organic solvents. These polyamides had 10% weight loss temperatures ranging between 423 and 465 °C in nitrogen atmosphere and glass transition temperatures between 170 and 305 °C. The polymers with crystallinity nature exhibited melting endotherms (T_m) below 386 °C in differential scanning calorimetry trace. Copyright © 1999 John Wiley & Sons, Ltd.     

Synthesis of novel ladder polymers of poly(3,4‐dihydro‐2H‐pyran‐2‐methanol)

Polydi(3,4‐dihydro‐2H‐pyran‐2‐methyl) esters of oxalic, adipic, and phthalic acids were prepared at different temperatures in the presence of different cationic initiators, namely, the boron trifluoride/diethyl ether complex system, anhydrous ferric chloride, and p‐toluene sulfonic acid. The obtained polymers were hydrolyzed under basic conditions, and the polydispersity indices of these polymers were determined before and after hydrolysis. The results are discussed to shed some light on the ability to use this analysis to investigate the precise structure of the obtained polymers and to predict the ability of these polymers to form ladder or semiladder polymers. Characteristics of such polymers were dependent, to some extent, on the type of crosslinks and the cationic initiators used for polymerization as well as the reaction temperature. It seems possible to optimize the conditions leading to formation of ladder or semiladder polydi(3,4‐dihydro‐2H‐pyran‐2‐methyl) esters of oxalic acid and adipic acid, respectively. The ladder structure was confirmed through determination of the polydispersity index before and after hydrolysis of the polymer formed at different temperatures and through computer‐aided molecular modeling. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3909–3915, 2002