Unsaturated alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s: Synthesis and chemical–physical characterization

A new series of alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s modified by the insertion of small percentages of various comonomers were synthesized through the precursor polyhydrazides. The comonomers used contained trans double bonds or meta‐alkoxy‐substituted aromatic rings to improve the solubility of the final polymers. The synthesized copolymers were chemically characterized by ¹H NMR and Fourier transform infrared spectroscopy. In some cases, the copolymers really showed improved solubility in organic solvents. The ¹⁵N solid‐state NMR technique was applied to examine the degree of conversion from the precursor polyhydrazides to the final polymers, which determined the effective conjugated length in the target polyoxadiazoles. Thermal stability and structural characteristics of all the polymers as well as a preliminary investigation on the optical properties of polyoxadiazoles are also reported. The copolymers retained high absorbance in the UV region and high transmission in the whole telecommunication range. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3916–3928, 2003     

Synthesis of poly(p‐phenylene sulfide) from bis(4‐bromophenyl) disulfide

Improved reaction conditions for the preparation of poly(p‐phenylene sulfide) (PPS) directly from bis(4‐bromophenyl) disulfide (BBD) have been established. Heating BBD with magnesium metal afforded only a low molecular weight polymer. PPS with a melting temperature around 280 °C was obtained from BBD in the presence of sodium carbonate or zinc metal. The best results were obtained with the addition of a catalytic amount of KI to the zinc–BBD mixture. Polymers prepared by the above methods are semicrystalline and dissolve in 1‐chloronaphthalene and have properties comparable to commercial PPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 900–904, 2006     

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     

Synthesis of poly(p‐phenylene vinylene)‐ and poly(phenylene ethynylene)‐based polymers containing p‐terphenyl in the main chain with alkoxyphenyl side groups

Starting from the pyrylium salt and following a facile synthetic route, we synthesized and polymerized 4,4″‐diiodo‐2′,6′‐di[4‐(2′‐ethylhexyl)oxy]phenyl‐p‐terphenyl with p‐divinylbenzene or p‐diethynylbenzene. The resulting polymers had moderate molecular weights, were amorphous, and dissolved in tetrahydrofuran and chloroform, with glass‐transition temperatures of 120–131 °C. The polymers behaved as violet‐blue‐emitting materials with photoluminescence maxima around 420 and 450 nm in solution and in thin films, respectively. They possessed well‐defined chromophores resulting from steric interactions in the polymer chain. The photoluminescence quantum yields were up to 0.29. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2591–2600, 2002     

Dynamics of poly(p‐phenylene) ladder polymers in solution

Photon correlation spectroscopy in both polarized and depolarized geometry was employed to investigate the dynamics of a ribbon‐type polymer exhibiting good solubility. In dilute solution, the translational diffusion for all examined molecular weights has confirmed the picture of wormlike chains with rather short (∼ 7 nm) persistence length (Macromolecules 1997, 30, 273). In the semidilute regime, the total concentration fluctuations display, besides the fast dominant cooperative diffusion, a second slower diffusive process that exhibits weak concentration dependence and is not related to the self‐diffusion measured by pulse‐field‐gradient NMR. The concentration dependence of the cooperative and the self‐diffusion coefficient as well as of the zero‐shear viscosity cannot be consistently described by neither flexible nor stiff chain models. Presence of aggregates was revealed at high concentrations. Owing to the short persistence length, the rotational diffusion is too fast to be adequately investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2211–2220, 1999     

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     

Vibrational spectroscopic investigation of poly(p‐phenylene sulfide)

Poly(p‐phenylene sulfide) (PPS) is an important polymer of engineering interest particularly useful in the electronics and automotive industries. Normal mode analysis including phonon dispersion has been performed to understand completely the vibrational spectra of this polymer. Various characteristic features of the dispersion curves have been reported. Crossing/Repulsion between various pairs of modes at certain phase values have been explained as arising due to internal symmetry in the energy momentum space. The heat capacity is calculated as a function of temperature via density‐of‐states in the range 220–360 K. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2353–2367, 2009     

Synthesis of multiwalled carbon nanotube/fluorine‐containing poly(p‐phenylene benzoxazole) composites exhibiting greatly enhanced dielectric constants

A series of high‐performance polymer/carbon nanotube (CNT) composites with different nanotube contents have been prepared via condensation of N‐silylated diamino terminated precursor of the polymer with acid chloride‐functionalized CNTs and subsequent thermal cyclodehydration. The composites have been fully characterized by infrared and Raman spectroscopy, electron microscopy, and thermal analysis. Various interesting morphologic features including helical structures have been observed in the composites as a result of covalent attachment of the polymer. The composites exhibit excellent thermal stability and a significant improvement in the dielectric constant and mechanical strength with the inclusion of CNTs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Novel route to poly(p‐phenylene vinylene) polymers

Poly(p‐phenylene vinylene) (PPV), poly(2,5‐dioctyl‐p‐phenylene vinylene) (PDOPPV), and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene] (MEHPPV) were synthesized by a liquid–solid two‐phase reaction. The liquid phase was tetrahydrofuran containing 1,4‐bis(bromomethyl)benzene, 1,4‐bis(chloromethyl)‐2,5‐dioctylbenzene, or 1,4‐bis(chloromethyl)‐2‐methoxyl‐5‐(2′‐ethylhexyloxy)benzene as the monomer and a certain amount of tetrabutylammonium bromide as a phase‐transfer catalyst. The solid phase consisted of potassium hydroxide particles with diameters smaller than 2 mm. The experimental results demonstrated that the reaction conversions of PPV and PDOPPV were fairly high (～65%), but the conversion of MEHPPV was only 45%. Moreover, gelation was found in the polymerization processes. As a result, PPV was insoluble and PDOPPV and MEHPPV were partially soluble in the usual organic solvents, such as tetrahydrofuran and chloroform. Soluble PDOPPV and MEHPPV were obtained with chloromethylbenzene or bromomethylbenzene as a retardant regent. The molar mass of soluble PDOPPV was measured to be 2 × 10⁴ g mol^?1, and that of MEHPPV was 6 × 10⁴ g mol^?1. A thin, compact film of MEHPPV was formed via spin coating, and it emitted a yellow light. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 449–455, 2003     

Graft copolymers from star‐shaped and hyperbranched polystyrene macromonomers

Branched polystyrene macromonomers were synthesized by the slow addition of a stoichiometric amount of either 4‐(chlorodimethylsilyl)styrene or vinylbenzyl chloride as a coupling agent to living polystyryllithium. Star‐shaped macromonomers were produced by the addition of the coupling agent alone, and hyperbranched macromonomers resulted from the addition of the coupling agent along with styrene monomer. Star and hyperbranched graft copolymers were produced by the copolymerization of the macromonomers with styrene and methyl methacrylate. The copolymers were characterized by gel permeation chromatography coupled with multi‐angle laser light scattering, ¹H NMR spectroscopy, and Soxhlet extraction to determine that the macromonomers were incorporated in high yields into the copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3547–3555, 2001     

Ionic poly(p‐phenylene terephthalamide)s: Preparation and characterization

The preparation and characterization of two types of ionic poly(p‐phenylene terephthalamide) (PPTA) is described. A sufficient number of ionic groups were added to render modified PPTA soluble in dimethylsulfoxide (DMSO). In one type, a hydrogen atom of the amide group was replaced by an ionic propanesulfonate group. In the other type, one of the hydrogen atoms on the phenylene ring was replaced by an ionic sulfonate group. The ionic PPTAs in DMSO showed an upturn in viscosity at very low concentrations that was characteristic of the polyelectrolyte behavior. Fourier transform infrared spectra of these samples were also studied. When the ionic group was attached at the end of the short propane side chain, the intensity of both the free and hydrogen‐bonded N? H stretching mode was reduced compared with that of PPTA. Depending on the location of the ionic group, there were some changes in the intensity and wave number of the asymmetric and symmetric vibrations of the ionic SO group and the stretching mode of the carbonyl group. In both ionic PPTAs, there was an upward shift in the frequency of the symmetric vibrations of the sulfonate ion when the counterion, having been monovalent, became divalent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2653–2663, 2001     

Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006     

Synthesis of poly(p‐phenylene)‐poly(4‐diphenylaminostyrene) bipolar block copolymers with a well‐controlled and defined polymer chain structure

A poly(p‐phenylene) (PPP)‐poly(4‐diphenylaminostyrene) (PDAS) bipolar block copolymer was synthesized for the first time. A prerequisite prepolymer, poly(1,3‐cyclohexadiene) (PCHD)‐PDAS binary block copolymer, in which the PCHD block consisted solely of 1,4‐cyclohexadiene (1,4‐CHD) units, was synthesized by living anionic block copolymerization of 1,3‐cyclohexadiene and 4‐diphenylaminostyrene. To obtain the PPP‐PDAS bipolar block copolymer, the dehydrogenation of this prepolymer with quinones was examined, and tetrachloro‐1,2‐(o)‐benzoquinone was found to be an appropriate dehydrogenation reagent. This dehydrogenation reaction was remarkably accelerated by ultrasonic irradiation, effectively yielding the target PPP‐PDAS bipolar block copolymer. The hole and electron drift mobilities for PPP‐PDAS bipolar block copolymer were both on the order of 10^?3 to 10^?4 cm²/V·s, with a negative slope when plotted against the square root of the applied field. Therefore, this bipolar block copolymer was found to act as a bipolar semi‐conducting copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and Characterization of Cross‐Linked Poly(p‐phenylene ethynylene)s

Summary: Conjugated poly(p‐phenylene ethynylene) networks with interesting optoelectronic properties were synthesized by the palladium‐catalyzed polycondensation of 2,5‐diiodo‐4‐[(2‐ethylhexyl)oxy]methoxybenzene, and 1,4‐diethynyl‐2,5‐bis‐(octyloxy)benzene, with 1,2,4‐tribromobenzene as cross‐linker. The cross‐linker concentration was varied and materials with different cross‐link densities were prepared. The materials were processed into films by simultaneous polymerization and shaping. An alternative approach is to synthesize these cross‐linked polymers in the form of spherical particles, which can be processed from dispersions.

Schematic representation of the cross‐linking process.     

Synthesis of macromonomers of acrylic acid by telomerization: Application to the synthesis of polystyrene‐g‐poly(acrylic acid) copolymers

The synthesis of macromonomers of acrylic acid was performed by telomerization in a three‐step process. The first step was the telomerization of tert‐butyl acrylate in the presence of thioglycolic acid. Different molecular weights were obtained with different ratios of the monomer to the transfer agent. Good control of the molecular weights and architectures of the oligomers (e.g., the presence of an acid function on the chain end) was observed. The transfer constant of tert‐butyl acrylate with thioglycolic acid was assessed (chain‐transfer constant = 0.6). In the second step, the terminal unsaturation of the oligomers was obtained by the reaction of the terminal acid groups with 2‐isocyanatoethyl methacrylate to yield the macromonomers of tert‐butyl acrylate. In the last step, the tert‐butyl acrylate groups were hydrolyzed in the presence of trifluoroacetic acid at room temperature. The macromonomers were copolymerized with styrene to obtain graft copolymers, and the reactivity ratios were evaluated. Finally, the copolymers were characterized with surface electron microscopy and atom force microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 395–415, 2007     

Dicarboxylic imide‐substituted poly(p‐phenylene vinylenes) with high electron affinity

Synthesis of n‐type organic semiconductors with high electron mobilities, good environmental stability, and good processability is an urgent task in current organic electronics. This is because most of π‐conjugated materials are p‐type and prefer to transport positive hole carriers. In this article, a series of new dicarboxylic imide‐substituted poly(p‐phenylene vinylenes) (DI‐PPVs) were first synthesized. They exhibited a high electron affinity of 3.60 eV and thus are able to transport electrons. The polymers showed tunable solubility in common organic solvents and high chemical and thermal stability. They remain rigidity of the PPV backbone, and strong interchain π‐stacking was observed in thin films by X‐ray diffraction measurement. All these suggested that these polymers could serve as good candidates as n‐type semiconductors in organic electronic devices such as n‐channel field‐effect transistors and all polymer‐based solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 186–194, 2010     

Synthesis of poly(m‐phenylene) and poly(m‐phenylene)‐block‐ poly(3‐hexylthiophene) with low polydispersities

Well‐defined poly(m‐phenylene) (PMP), which is poly(1,3‐dibutoxy‐m‐phenylene), was successfully synthesized via Grignard metathesis polymerization. PMP with a reasonably high number‐average molecular weight (M_n) of 25,900 and a very low polydispersity index of 1.07 was obtained. The polymerization of a Grignard reagent monomer, 1‐bromo‐2,4‐dibutoxy‐5‐chloromagnesiobenzene, proceeded in a chain‐growth manner, probably due to the meta‐substituted design producing a short distance between the MgCl and Br groups and thereby making a smooth nickel species (? C? Ni? C? ) transfer to the intramolecular chain end (? C? Ni? Br) over a benzene ring. PMP showed a good solubility in the common organic solvents, such as tetrahydrofuran, CH₂Cl₂, and CHCl₃. Furthermore, a new block copolymer comprised of PMP and poly(3‐hexylthiophene) was also prepared. The tapping mode atomic force microscopy image of the surface of the block copolymer thin film on a mica substrate showed a nanofibril morphology with a clear contrast. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Simplified synthesis of spiro‐bridged ladder‐type poly(p‐phenylene)

In this study, a simplified route to synthesize soluble, spiro‐bridged ladder‐type poly(p‐phenylene)s (spiro‐LPPP) was developed. The new, simplified synthesis route for spiro‐LPPP involves two reaction steps: a single‐stranded precursor polymer containing diaryloylbenzene building blocks was obtained by the Suzuki reaction, followed by a subsequent twofold cyclization cascade using methanesulfonic acid to form the target spiro‐LPPP. Spiro‐LPPP shows a well‐defined chemical structure, high molecular weight (M_n of 17,500 g/mol with a polydispersity index of 2.0), excellent thermal stability (5% weight loss at 370 °C), and good solubility in common organic solvents. Spiro‐LPPP emits blue light (λ_max,em = 455 nm) with the high solution PL quantum yield (94%). The spectral properties of spiro‐LPPP in the solid state are very similar to the solution properties, thus indicating a low degree of intermolecular aggregation. After annealing a thin film of spiro‐LPPP to 120 °C in air for 3 to 24 h, its emission spectrum is unchanged, reflecting excellent thermooxidative stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5137–5143, 2009     

Synthesis of novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline)s

Novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline) (PROZO) were syn-thesized by utilizing termination of propagating species (2-oxazolinium ions) in the living polymerization of 2-alkyl-2-oxazoline (ROZO) with suitable nucleophiles. Two types of p-vinylbenzyl–type macromonomers were obtained by terminating living PROZO with sodium p-vinylbenzyl alkoxide or with sodium p-vinylbenzyl mercaptide. The synthesis of telechelics having a functional group (SH, COOH) on both ends of PROZO was achieved by using a bis(2-oxazolinium salt) initiator. The PROZO dithiol was synthesized by two methods: (1) termination of the living species on both ends with NaSH, and (2) aminolysis of PROZO bis(O-ethyldithiocarbonate) given by treatment of the living PROZO with potassium O-ethyldithiocarbonate. Termination of the living PROZO with the sodium salt of di-t-butyl malonate yielded a PROZO with di-t-butyl malonate moieties on both polymer ends, from which the PROZO dicarboxylic acid was derived via free tetracarboxylic acid. © 1995 John Wiley & Sons, Inc.