Chain coherence length of rigid‐rod poly(p‐phenylene benzobisthiazole) and derivatives

Chain coherence length of rigid‐rod poly(p‐phenylene benzobisthiazole) (PBZT) and its derivatives in the solid state was determined from the wide‐angle X‐ray diffraction patterns of axially disordered crystal. The degree of the PBZT main chain extension was estimated from the coherence lengths and was compared to investigate the effects of side chain, orientation, heat treatment, and polymer solution concentration. Extremely small coherence length obtained from both highly oriented fibers and powder or bulk PBZT homopolymer suggested that a chain conformation deviated from the fully extended conceptual rigid‐rod, supporting the ribbon‐like conformation, as was previously predicted by molecular dynamic simulation. The deviation was also found to be highly dependent on the processing conditions. Fibers stretched during spinning exhibited much greater chain extension than the isotropic powder, the bulk, and fibers spun without tension. The chain extension was also dependent on the solution concentration prior to the processing. The PBZT produced from solution above the critical concentration exhibited higher chain extension than those from below the critical concentration. However, side chain attachment to the PBZT main chain or post‐heat treatments showed a minimal effect on the extension of the PBZT backbone. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 661–666, 1999     

End‐group modification of poly(2,6‐dimethyl‐1,4‐phenylene ether) and in situ synthesis of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer

The preparation of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer was performed by the reaction of the 2‐hydroxyethyl modified poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE‐EtOH) with poly(ethylene terephthalate) (PET) by an in situ process, during the synthesis of the polyester. The yield of the reaction of the 2‐hydroxyethyl functionalized PPE‐EtOH with PET was close to 100%. A significant proportion of the PET‐b‐PPE‐EtOH block copolymer was found to have short PET block. Nevertheless, the copolymer structured in the shape of micelles (20 nm diameter) and very small domains with 50–200 nm diameter, whereas unmodified PPE formed much larger domains (1.5 μm) containing copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3985–3991, 2008     

Synthesis of new thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing epoxide pendant groups

A new class of thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing pendant epoxide groups were synthesized and characterized. These new epoxy polymers were prepared through the bromination of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in halogenated aromatic hydrocarbons followed by a Wittig reaction to yield vinyl‐substituted polymer derivatives. The treatment of the vinyl‐substituted polymers with m‐chloroperbenzoic acid led to the formation of epoxidized poly(2,6‐dimethyl‐1,4‐phenylene oxide) with variable pendant ratios, and the structures and properties were studied with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The ratios of pendant functional groups were tailored for the polymer properties, and the results showed that the glass‐transition temperatures increased as the benzylic protons were replaced by bromo‐, vinyl‐, or epoxide‐functional groups, whereas the thermal stability decreased in comparison with the original polymer. Within a molar fraction of 20–50%, the degree of functionalization had little effect on the glass‐transition temperature; however, it correlated inversely with the thermal stability of each functionalized polymer. The thermal curing behavior of the epoxide‐functionalized polymer was enhanced by the increment of the pendant functionality, which resulted in a significant increase in the glass‐transition temperature as well as the thermal stability after the curing reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5875–5886, 2006     

Studies on molecular composite. I. Processing of molecular composites using a precursor polymer for poly(p‐phenylene benzobisthiazole)

The blending of a precursor polymer for poly(p‐phenylene benzobisthiazole) (PBZT) with various matrix polymers was attempted, followed by heat conversion of the PBZT precursor polymer to obtain molecular composites consisting of PBZT and the matrix polymers. A higher concentration of mixed solution using organic solvent and milder conditions to remove the solvent could be applied to blend the polymers using the precursor polymer in place of rodlike PBZT. The dispersibility of PBZT in the matrix polymer in the blended materials obtained depended on the ability to form intermolecular hydrogen bridges between the PBZT precursor and the matrix polymer. In particular, the blended material, obtained using a nonthermoplastic aromatic polyamide as the matrix polymer having a molecular structure similar to that of the PBZT prepolymer, was transparent and showed excellent reinforcing efficiency of PBZT. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 189–197, 1999     

Phase‐separated,conducting composites from polyaniline and benzobisthiazole rigid‐rod polymer

As an alternative method for processing polyaniline (PANI) from its conducting (protonated) state, vacuum casting of PANI from a methanesulfonic acid (MSA) solution provided films with electrical conductivity values of about 130–150 S/cm. In addition, we similarly prepared blended films of PANI · MSA and poly(p‐phenylene benzobisthiazole) (PBZT). This process eliminated the need for a subsequent protonation step and had the additional advantage that the conjugated PBZT may provide alternative conducting pathways. Conductivity values of the composite films ranged from 100 pS/cm to 124 S/cm, and the films displayed critical concentration behavior with a PANI threshold concentration of 2.75% and a critical exponent of 4. Transmission electron micrographs displayed phase‐separated regions with PANI forming a continuous network at high concentrations. Thermogravimetric analysis results demonstrated the thermal and thermooxidative stability advantage of the blends due to the PBZT component. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2539–2548, 2001     

Studies on molecular composite. II. Processing of molecular composites using copolymers consisting of a precursor of poly(p‐phenylene benzobisthiazole) and aromatic polyamide

The copolymerization of a precursor of poly(p‐phenylene benzobisthiazole) (PBZT) with aromatic polyamides was attempted. Two types of copolymers, randomlike and blocklike, which have different properties, were synthesized according to the copolymerization process. The copolymers were suitable for use as the reinforcing polymer in molecular composite because of the improved intermolecular hydrogen bridges between the matrix polymers, such as aromatic polyamides, and then could be converted to the PBZT copolymers by heat treatment of the molecular composite. In particular, the possibility that the fine phase structure of the molecular composite was maintained was shown, even after heat treatment at above the melting temperature of the thermoplastic matrix polymer, due to the use of a PBZT copolymer as the reinforcing polymer, introduced a fragment which had the same molecular structure as in the matrix polyamides. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 199–207, 1999     

Studies on molecular composite. III. Nano composites consisting of poly(p‐phenylene benzobisthiazole) and thermoplastic polyamide

A bulk sample of a nano composite consisting of poly(p‐phenylene benzobisthiazole) (PBZT) and a thermoplastic matrix polymer was obtained by polymer blending of a matrix polymer of thermoplastic aromatic polyamide and a reinforcing polymer of a copolymer consisting of a precursor of PBZT and a fragment in common with the matrix polymer, using organic solvent, followed by molding. The phase structure of obtained specimens was varied by controlling the molding process conditions. In particular, the mechanical properties, heat resistance, and chemical resistance of the matrix polymer of a bulk specimen which has a three‐dimensional network structure of PBZT were improved drastically, even when only a small amount of the reinforcing material was added. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 209–218, 1999     

Yellow‐light‐emitting cyano‐substituted poly[(1,3‐phenylene vinylene)‐alt‐(1,4‐phenylene vinylene)] derivative: Its synthesis and optical properties

A soluble cyano‐substituted poly[(1,3‐phenylene vinylene)‐alt‐(1,4‐phenylene vinylene)] derivative ( 9 ) was synthesized and characterized. Comparison between 9 and its model compound ( 10 ) showed that the chromophore in 9 remained to be well defined as a result of a π‐conjugation interruption at adjacent m‐phenylene units. The attachment of a cyano substituent only at the β position of the vinylene allowed the maximum electronic impact of the cyano group on the optical properties of the poly(p‐phenylene vinylene) material. At a low temperature (?108 or ?198 °C), the vibronic structures of 9 and 10 were partially resolved. The absorption and emission spectra of a film of 9 were less temperature‐dependent than those of a film of 10 , indicating that the former had a lower tendency to aggregate. A light‐emitting diode (LED) based on 9 emitted yellow light (λ_max ≈ 578 nm) with an external quantum efficiency of 0.03%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3149–3158, 2003     

Poly(p‐phenylene methylene)‐based block copolymers by mechanistic transformation

The synthesis of poly(p‐phenylene methylene) (PPM)‐based block copolymers such as poly(p‐phenylene methylene)‐b‐poly(ε‐caprolactone) and poly(p‐phenylene methylene)‐b‐polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid‐catalyzed polymerization of tribenzylborate at 16 °C. Then, this polymer was used as macroinitiators in either ring‐opening polymerization of ε‐caprolactone or cationic ring‐opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and ¹H NMR investigations. The composition of block copolymers as determined by ¹H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Water‐soluble poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) copolymer: Synthesis and characterization

Water‐soluble and photoluminescent block copolymers [poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) (PEO‐b‐PPV)] were synthesized, in two steps, by the addition of α‐halo‐α′‐alkylsulfinyl‐p‐xylene from activated poly(ethylene oxide) (PEO) chains in tetrahydrofuran at 25 °C. This copolymerization, which was derived from the Vanderzande poly(p‐phenylene vinylene) (PPV) synthesis, led to partly converted PEO‐b‐PPV block copolymers mixed with unreacted PEO chains. The yield, length, and composition of these added sequences depended on the experimental conditions, namely, the order of reagent addition, the nature of the monomers, and the addition of an extra base. The addition of lithium tert‐butoxide increased the length of the PPV precursor sequence and reduced spontaneous conversion. The conversion into PPV could be achieved in a second step by a thermal treatment. A spectral analysis of the reactive medium and the composition of the resulting polymers revealed new evidence for an anionic mechanism of the copolymerization process under our experimental conditions. Moreover, the photoluminescence yields were strongly dependant on the conjugation length and on the solvent, with a maximum (70%) in tetrahydrofuran and a minimum (<1%) in water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4337–4350, 2005     

Glass‐formation kinetics of miscible blends of atactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

We present a detailed investigation of the kinetics associated with the glass transitions of miscible blends composed of atactic polystyrene (a‐PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). According to both dynamic mechanical analysis and differential scanning calorimetry, relaxation times displayed an enhanced temperature dependence (i.e., more fragile or more cooperative behavior) for the blends compared with additive behavior based on the responses of neat a‐PS and PPO. This is consistent with the notion that specific interactions between the blend components heighten the intermolecular cooperativity. The compositional dependence of fragility provided insight into physical aging results for the properties of volume and enthalpy. The combination of our research and a previously reported pressure–volume–temperature study by Zoller and Hoehn (J Polym Sci Polym Phys Ed 1982, 20, 1385) provided evidence that the observation of increased glassy densities for the blends compared with those of the pure polymers was kinetic in origin and was not a feature of the thermodynamics of miscibility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2118–2129, 2001     

Photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide): A reinvestigation

Reinvestigation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) photodegradation at wavelengths > 290 nm shows that both methyl groups and aromatic rings are sites of oxidation with their relative rates dependent on exposure conditions, based on infrared spectroscopy. The methyl group loss is linear with exposure and apparently proceeds by direct abstraction of a benzylic hydrogen by oxygen. The aromatic ring loss and carbonyl growth in the IR spectra appear to be auto‐accelerating and seem to proceed by electron transfer to oxygen, either sensitized or through a direct reaction with oxygen, and recombination of the polymer radical cation and superoxide to result in oxygen addition to the ring. Molecular weight loss in solution occurs to a significant degree only in the presence of oxygen, even in the presence of a hydrogen‐donating solvent, indicating that aryl ether photolysis is not a major pathway. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2318–2331     

Synthesis and nuclear magnetic resonance analysis of starch‐g‐poly(1,4‐dioxan‐2‐one) copolymers

A new biodegradable starch graft copolymer, starch‐g‐poly(1,4‐dioxan‐2‐one), was synthesized through the ring‐opening graft polymerization of 1,4‐dioxan‐2‐one onto a starch backbone. The grafting reactions were conducted with various 1,4‐dioxan‐2‐one/starch feed ratios to obtain starch‐g‐poly(1,4‐dioxan‐2‐one) copolymers with various poly(1,4‐dioxan‐2‐one) graft structures. The microstructure of starch‐g‐poly(1,4‐dioxan‐2‐one) was characterized in detail with one‐ and two‐dimensional NMR spectroscopy. The effect of the feed composition on the resulting microstructure of starch‐g‐poly(1,4‐dioxan‐2‐one) was investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3417–3422, 2004     

Synthesis of well‐defined rod‐coil block copolymers containing trifluoromethylated poly(phenylene oxide)s by chain‐growth condensation polymerization and atom transfer radical polymerization

Well‐defined trifluoromethylated poly(phenylene oxide)s were synthesized via nucleophilic aromatic substitution (S_NAr) reaction by a chain‐growth polymerization manner. Polymerization of potassium 4‐fluoro‐3‐(trifluoromethyl)phenolate in the presence of an appropriate initiator yielded polymers with molecular weights of ～4000 and polydispersity indices of <1.2, which were characterized by ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography. Initiating sites for atom transfer radical polymerization (ATRP) were introduced at the either side of chain ends of the poly(phenylene oxide), and used for ATRP of styrene and methyl methacrylate, yielding well‐defined rod‐coil block copolymers. Differential scanning calorimetry study indicated that the well‐defined trifluoromethylated poly(phenylene oxide)s showed high crystallinity and were immiscible with polystyrene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1049–1057, 2010     

A Novel Approach to the Preparation of Nanoblends of Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/Polyamide 6

Summary: A novel approach of in situ polymerization and in situ compatibilization was adopted to prepare poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and polyamide 6 (PA6) nanoblends. Anionic ring‐opening polymerization of ε‐caprolactam was carried out in the presence of PPO, the chain of which bore p‐methoxyphenylpropionate (MPAA), acting as macroactivator to initiate PA6 chain growth from the PPO chain and form a graft copolymer of PPO and PA6 and pure PA6 simultaneously. The nanostructured PA6 dispersed phase in the PPO matrix could be achieved.

A TEM image of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 nanoparticles obtained from in situ polymerization and in situ compatibilization.     

Electrospinning of polystyrene/poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene) blends

Ultrafine polystyrene (PS)/poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene) (MEH‐PPV) fibers were successfully prepared by electrospinning of PS/MEH‐PPV solutions in chloroform, 1,2‐dichloroethane, and tetrahydrofuran (THF). Three concentrations of the solutions were prepared: 8.5, 16, and 23.5% (w/v), with the compositional weight ratios between PS and MEH‐PPV being 7.5:1, 15:1, and 22.5:1, respectively. Smooth fibers only observed from 23.5% (w/v) PS/MEH‐PPV solution in chloroform. Improvement in the electrospinnability of 8.5% (w/v) PS/MEH‐PPV solution in chloroform was achieved by addition of an organic salt, pyridinium formate (PF), or by addition of a minor solvent with a high dielectric constant value. The average diameters of the as‐spun PS/MEH‐PPV fibers were between 0.30 and 5.11 μm. Last, photoluminescence of 8.5% (w/v) solutions of PS/MEH‐PPV in a mixed solvent system of chloroform and 1,2‐dichloroethane of various volumetric compositions and the resulting as‐spun fibers was investigated and compared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1881–1891, 2005     

Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS‐graft‐PET copolymer on morphology and crystallization behavior

The morphology and crystallization behavior of poly(phenylene sulfide) (PPS) and poly(ethylene terephthalate) (PET) blends compatibilized with graft copolymers were investigated. PPS‐blend‐PET compositions were prepared in which the viscosity of the PPS phase was varied to assess the morphological implications. The dispersed‐phase particle size was influenced by the combined effects of the ratio of dispersed‐phase viscosity to continuous‐phase viscosity and reduced interfacial tension due to the addition of PPS‐graft‐PET copolymers to the blends. In the absence of graft copolymer, the finest dispersion of PET in a continuous phase of PPS was achieved when the viscosity ratio between blend components was nearly equal. As expected, PET particle sizes increased as the viscosity ratio diverged from unity. When graft copolymers were added to the blends, fine dispersions of PET were achieved despite large differences in the viscosities of PPS and PET homopolymers. The interfacial activity of the PPS‐graft‐PET copolymer appeared to be related to the molecular weight ratio of the PPS homopolymer to the PPS segment of the graft copolymer (M_H/M_A). With increasing solubilization of the PPS graft copolymer segment by the PPS homopolymer, the particle size of the PET dispersed phase decreased. In crystallization studies, the presence of the PPS phase increased the crystallization temperature of PET. The magnitude of the increase in the PET crystallization temperature coincided with the viscosity ratio and extent of the PPS homopolymer solubilization in the graft copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 599–610, 2000     

Synthesis of soluble poly(para‐phenylene) with a long polymer chain: Characteristics of regioregular poly(1,4‐phenylene)

Soluble poly(para‐phenylene) having a long polymer chain (more than six repeat units) was synthesized with a tert‐butyl end‐group (t‐PPP) and was found to have improved solubility and excellent optical properties. Poly(1,3‐cyclohexadiene) (PCHD) consisting of only 1,4‐cyclohexadiene (1,4‐CHD) units was synthesized with a tert‐butyl end‐group (t‐PCHD), and completely dehydrogenated to obtain t‐PPP. This end‐group effectively prevented the crystallization of t‐PPP, and polymers containing up to 16 repeat units were soluble in tetrahydrofuran. Soluble t‐PPP obtained had an ability to form a tough thin film prepared by spin‐coating method. Optical analyses of t‐PPP provided strong evidence for a linear polymer chain structure. A block copolymer of t‐PPP and a soluble polyphenylene (PPH) was then synthesized, and the excellent optical properties were retained by this block copolymer along with its solubility. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5223–5231, 2008     

Negative‐type photosensitive poly(phenylene ether) based on poly(2,6‐dimethyl‐1,4‐phenylene ether), a crosslinker,and a photoacid generator

A negative‐type photosensitive poly(phenylene ether) (PSPPE) based on poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE), a novel crosslinker 4,4′‐methylene‐bis [2,6‐bis(methoxymethyl)phenol] (MBMP) having good compatibility with PPE, and diphenylidonium 9,10‐dimethoxy anthracene‐2‐sulfonate (DIAS) as a photoacid generator (PAG) has been developed. This resist consisting of PPE (73 wt %), MBMP (20 wt %) and DIAS (7 wt %) showed a high sensitivity (D_0.5) of 58 mJ/cm² and a contrast (γ_0.5) of 9.5 when it was exposed to i‐line (365 nm wavelength light), postexposure baked at 145 °C for 10 min, and developed with toluene at 25 °C. A fine negative image featuring 6 μm line‐and‐space pattern was obtained on the film exposed to 300 mJ/cm² of i‐line by a contact‐printed mode. The resulting polymer film cured at 300 °C for 1 h under nitrogen had a low dielectric constant (ε = 2.46) comparable to that of PPE and a higher T_g than that of PPE. In addition, the cured PSPPE film was pretty low water absorption (<0.05%) as same as PPE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4949–4958, 2008     

Resonance raman spectra of poly‐(p‐phenylenebenzobisoxazole), poly‐(p‐phenylenebenzobisthiazole), and poly(pyridobisimidazole)

Resonance Raman spectra of poly(p‐phenylenebenzobisoxazole) (PBO), poly(p‐phenylenebenzobisthazole) (PBZT), and poly(pyridobisimidazole) (PIPD) were measured. In the case of PBO, no large dependence on wavelength of excited laser can be observed, whereas in the cases of PBZT and PIPD, the spectra depends on wavelength of excited laser. This difference may be attributed to the colors of the samples: PBO is gold, and PBZT and PIPD are metallic blue, which show the different conjugated states. The spectra of PBO are rather simpler than those of PBZT and PIPD. This is considered to be reflected by the fact that only a chain passes through the unit cell of PBO, while two chains pass through the unit cell of PBZT and PIPD. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1791–1793, 2001