Units In Main Chain Research Articles

Conjugated polymers containing electron‐transporting, hole‐transporting, and light‐emitting units in the polymer main chain

AbstractConjugated polymers containing electron‐transporting, hole‐transporting, and blue light‐emitting units were synthesized by Suzuki polycondensation. These copolymers exhibited excellent thermal and optical stability. Optical investigation indicated that the incorporation of the spirobifluorene units in the polymer main chain could markedly increase the effective conjugation length of polymers. Electrochemical studies showed that the incorporation of spirobifluorene unit could raise the electrochemical stability and improve the electron‐ and hole‐injecting abilities. The electroluminescent results also showed that the introducing of spirobifluorene units could significantly improve the device performance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1349–1356, 2008

高分子半導体の合成とナノ構造制御

This article describes the synthesis of hole transporting polymers containing triphenylamine (TPA) unit either in side chain or main chain for electroluminescent devices, and photorefractive applications. Radically polymerized polyacrylate having tetraphenyldiaminobiphenyl (TPD) unit showed higher drift mobility compared with conventional poly(N-vinylcarbozole) (PVK). TPA derivatives were reacted with paraformaldehyde or benzaldehyde in the presence of p-toluenesulfonic acid to yield polymers soluble in common organic solvents. Acid catalyzed Friedel-Crafts reactions between TPA derivatives and divinylbenzene were also applied to prepare the main chain polymers. TPA derivatives were oxidatively coupled to afford polymers with well-defined structure. Resulting polymer sensitized with fullerene showed much higher photoconductivity than PVK. Electron transporting polymers having oxadiazole, fluorene, or thioxanthene unit are also introduced. For the further improvement of device performance, molecular design for multifunctional and multiphased materials including block copolymers and rod-coil type polymers is described.

High-efficiency red and green light-emitting polymers based on a novel wide bandgap poly(2,7-silafluorene)

A new type of high-efficiency red and green light-emitting polymer was synthesized via the Suzuki coupling reaction by incorporating narrow bandgap (NBG) comonomers 4,7-di(4-hexyl-2-thienyl)-2,1,3-benzothiadiazole (DHTBT) and 2,1,3-benzothiadiazole (BT), respectively, into the backbone of poly(2,7-silafluorene) (PSiF). The thermal, photophysical, electrochemical and electroluminescent properties of the PSiF copolymers were investigated and compared with those of the corresponding polyfluorene (PF)-based polymers. The advantages of polymers with PSiF as the main chain over PFs were confirmed by comparison of the electroluminescent performances of PSiF-DHTBT10 and PSiF-BT10 with those of the PF-based copolymers with the same NBG content. Preliminary results showed that the device efficiencies of the emitters containing the same NBG units in the PSiF main chain are higher than those based on PFs. The devices with the configuration of ITO/PEDOT : PSS/PVK/polymer/Ba/Al showed the maximum external quantum efficiency (EQE) of 2.89% and current efficiency (CE) of 2.0 cd A−1 with CIE coordinates of (0.67, 0.33) for PSiF-DHTBT10 and the maximum EQE of 3.81% and CE of 10.6 cd A−1 with CIE coordinates of (0.38, 0.57) for PSiF-BT10, respectively, which are among the best results of fluorescent red or green light-emitting polymers reported so far, indicating PSiF derivatives are a promising class of light-emitting polymers.

Comb macromolecules with attracting functional groups in side chains

The conformational behavior of a single comb-shaped macromolecule with associating groups in side chains was studied by means of Monte Carlo simulation. The side chains contain two types of units, type A representing nonfunctional units (main chain units are likewise classified with type A) and type B representing functional (attracting) units. As a result of an increase in attraction energy between associating groups, the transition of the macromolecule from coil to the globule state takes place. The coil-globule transition is accompanied by segregation of unlike units; as a result, the globule has a complex structure: the core of the globule is formed by attracting groups of side chains, and the envelope is formed from soluble units of both main and side chains. The dependence of the size and shape of the macromolecule on its structural parameters, such as the length of main and side chains and the graft density of side chains, and on the position of the functional groups in side chains was examined. Along with the single globule, conformations in which the attracting units of side chains formed several bead globules were observed.

Synthesis and crystallization behavior of acetal copolymer/silica nanocomposite by in situ cationic ring‐opening copolymerization of trioxane and 1,3‐dioxolane

AbstractThe acetal copolymer/silica nanocomposite was prepared by in situ bulk cationic copolymerization of trioxane and 1,3‐dioxolane in the presence of nanosilica. The crystallization behavior of acetal copolymer/silica nanocomposite was studied by AFM, DSC, XRD, and CPOM, and the macromolecular structure of acetal copolymer/silica nanocomposite was characterized by FTIR and 1H‐NMR. The 1H‐NMR results showed that the macromolecular chain of acetal copolymer had more than two consecutive 1,3‐dioxolane units in an oxymethylene main chain, while that of acetal copolymer/silica nanocomposite had only one 1,3‐dioxolane unit in an oxymethylene main chain. There existed interaction between the macromolecular chains and nanoparticles (such as hydrogen bonds and coordination). On one hand, nanoparticles acted as nucleation center, which accelerated the crystallization rate but reduced the crystallinity. The spherulite sizes also decreased with addition of nanoparticles attributed to the nucleation effect. On the other hand, the presence of nanoparticles interrupted the spherical symmetry of the crystallite. In conclusion, the high surface energy and small scale of nanoparticles have a prominent impact on the polymerization mechanism and crystallization behavior of nanocomposite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A high-viscosity glycoglucuronomannan from the gum exudate of Vochysia thyrsoidea: Comparison with those of other Vochysia spp.

The polysaccharide (VTh) extracted with water from the gum exudate of the trunk Vochysia thyrsoidea gave a solution of high viscosity and was homogeneous, with M w 92.5 × 10 3 and d n/d c = 0.212. Partial hydrolysis gave a main chain of →4)-β- d-Glc pA-(1 → 2)-α- d-Man p-(1→ repeating groups. Since VTh contained 24% GlcA, neither its monosaccharide ratio (GC–MS of alditol acetates) nor methylation results were accurate. It was therefore carbodiimide-reduced to CR 3VTh, which contained Ara, Xyl, Man, Gal, and Glc in a molar ratio of 28:4:29:19:25: methylation analysis showed mainly nonreducing end-units of Ara f (25%), Ara p (8%), and Gal p (8%) and side-chain units of 3- O- (6%) and 3,4-di- O-subst. Gal p (12%). Main-chain units of Man p were 2,3-di- O-substituted (17%), showing that they were substituted at O-3 by side chains, but there was less side-chain substitution of Glc p units, which were mainly 4- O-substituted (12%). Most Ara f units in VTh and CR 3VTh were single nonreducing end-units, and were present in groups of α- l-Ara f-(1 → 3)- d-Man p and α- l-Ara f-(1 → 3)-[α- l-Ara f-(1 → 4)]-β- d-Gal p-(1 → 3)-α- d-Man p. Other degradation products derived from VTh agreed with this structure. The degree of side-chain substitution of the same main chain was greatest with the gum exudate polysaccharide of V. tucanorum, and progressively less with those of V. thyrsoidea, and V. lehmannii. High-viscosity aqueous solutions were formed by the gum of V. thyrsoidea, in contrast with those of V. lehmannii and V. tucanorum.

Synthesis and Properties of Thermotropic Main-Chain Type Liquid Crystalline Polyurethanes Containing Biphenyl Mesogen

A new type of thermotropic main-chain liquid crystalline polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4′-Bis(8-hydroxyoctoxy)biphenyl (BP8). The structure of the monomer and the corresponding polymers were confirmed using FT-IR and 1H-NMR spectroscopic methods. BP8 exhibited a smectic type mesophase, however, nematic phases were found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP8 based polyurethane. For example, polyurethane 2,5-TDI/BP8 exhibited monotropic liquid crystallinity in the temperature ranging from 172 to 160 °C on the cooling stage. Properties of these polyurethanes were studied by differential scanning calorimetry (DSC), and optical polarizing microscopy. The FT-IR study indicated that the hydrogen bonding among urethane linkages attributed to the mesomorphism.

Molecular Engineering in Symmetric End-Substituted Oligothiophene Derivatives: Analysis of Condensed-Phase Photoemission Spectra Using Semiempirical Hartree−Fock Calculations

The electronic structures of two series of end-capped thiophene oligomers, one set containing the electron-deficient dimesitylboryl end-cap and one containing the electron-rich triaryl amine end-cap, have been modeled using semiempirical quantum chemical calculations and the results used to assign features in the photoemission spectra of the materials in the condensed phase. For the thiophene oligomers end-capped with the electron-deficient dimesitylboryl moieties, the energy of the occupied frontier orbitals is largely governed by pi-type orbitals of the thiophene repeat units in the oligothiophene main chain. Conversely, in oligomers end-capped with electron-rich triarylamine moieties, the occupied frontier orbital energies are largely governed by orbital states of heavily mixed character associated with thiophene pi-type systems and the low-lying nitrogen lone pairs of end capping groups.

Stimuli-responsive polymers. 9. Photo-regulation of optical rotations in chiral polyesters: Altering responsive outputs with conformationally flexible backbone elements

Conformationally restricted polyesters comprising alternating azobenzene and chiral binaphthylene main-chain units undergo photo-induced oscillations in optical rotatory power when stimulated with sequential intervals of ultraviolet and visible light exposure. The incorporation of flexible (oligo)ethylene oxide backbone segments into these constructs has resulted in a new family of materials having vastly altered photo-responsive chiroptical properties. Light-regulated outputs were found to be strongly dependent upon the length of the flexible backbone segments employed and on their specific locations of placement within the polyester chain. Most notably, the insertion of flexible oligo(ethylene oxide) spacer elements between neighboring binaphthylene and azobenzene main-chain units had a pronounced damping effect on the photo-dynamic behavior exhibited by these chiral systems. Similar results were noted for a related series of oligomeric model compounds that were specifically designed to mimic local monomer sequences present within the larger polyester structures.

Synthesis of the Optically Active Polymer Consisting of Chiral Phosphorus Atoms and p-Phenylene-ethynylene Units

We successfully synthesized optically active polymer 4 by using chiral bisphosphine, (S,S)-1,2-bis(boranato(t-butyl)methylphosphino)ethane (S,S)-1, as a key building block. The structure of the polymer was characterized by 1H, 13C, and 31P NMR spectra. According to the CD spectra, the p-phenylene-ethynylene unit in the polymer main chain exhibited Cotton signals around the area of π-π* transition band.

Chain Growth of Polymers with Fluorescent Main-Chain Units

There are few chain-growth polymerizations that directly place electronic elements into the backbone. This polymerization can be conducted under radical conditions and the authors have skillfully shown molecular-weight control with polydispersity indexes ranging from 1.14-1.66 using what is known as a RAFT (reversible addition-fragmentation chain transfer) polymerization. The polymers are fluorescent and have potential applications in emerging electronic polymer technologies.

Thermal Properties of a Liquid-Crystalline Polyurethanes Containing Biphenyl Mesogen

A new type of thermotropic main-chain liquid crystalline polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4′-Bis(11-hydroxyundeyloxy)biphenyl (BP11). The structure of the monomer and the corresponding polymers were confirmed FT-IR and 1H NMR spectroscopic methods. BP11 exhibited a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP11 based polyurethane. For example, polyurethane 2,5-TDI/BP11 exhibited monotropic liquid crystallinity in the temperature ranges from 173 to 156 °C on the cooling stage.

Copolymerization of propylene and disubstituted diallylsilanes involving intramolecular cyclization with stereoselective zirconocene catalysts

AbstractThe copolymerization of propylene and disubstituted diallylsilanes [(CH2 CHCH2)2R2Si (R = CH3 or C6H5)] was investigated with isoselective and syndioselective zirconocene catalysts with methylaluminoxane as a cocatalyst. The syndioselective catalyst showed a higher reactivity for disubstituted diallylsilanes than the isoselective catalysts. Diallyldimethylsilane was incorporated into the polymer chain via cyclization insertion preferentially and formed 3,5‐disubstituted dimethylsilacyclohexane units in the polypropylene main chain. In the copolymerization with diallyldiphenylsilane, diallyldiphenylsilane was copolymerized via both cyclization insertion and 1,2‐insertion, which formed a pendant allyl group. The structures of isolated silacyclohexane units, determined by 13C NMR and distortionless enhancement by polarization transfer spectroscopy, proved that the 1,2‐insertion of diallylsilanes proceeded with enantiomorphic site control; however, the diastereoselectivity of the cyclization reaction was independent of the stereoselectivity of the catalysts used, and cis‐silacyclohexane units were mainly formed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6083–6093, 2006

Hydrogen‐Assisted Unique Incorporation of 1,4‐Divinylbenzene in Copolymerization with Propylene Using an Isospecific Zirconocene Catalyst

AbstractSummary: Propylene was copolymerized with 1,4‐divinylbenzene (1,4‐DVB) using rac‐Me2Si(2‐Me‐4‐Ph‐Ind)2ZrCl2 and MAO in the presence of hydrogen. 1H NMR spectra of the obtained copolymer confirmed the successful incorporation of 1,4‐DVB. 13C NMR analysis revealed a unique copolymer structure with the incorporated 1,4‐DVB units predominantly forming 1,4‐substituted phenyl repeating units in the polymer main chain. A plausible mechanism involving spontaneous insertion of terminal styryl into Zr‐H species was proposed to rationalize the unique incorporation of 1,4‐DVB.Copolymerization of propylene with 1,4‐divinylbenzene in the presence of hydrogen.imageCopolymerization of propylene with 1,4‐divinylbenzene in the presence of hydrogen.

Synthesis of Polyolefins Containing Silacycloalkane Units in the Main Chain, 1

AbstractSummary: Copolymerizations of ethylene and disubstituted diallylsilanes (CH2CHCH2)2R2Si (R = CH3, C6H5) have been investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged stereospecific catalysts showed a higher reactivity for disubstituted diallylsilanes than the non‐bridged aspecific catalysts. Disubstituted diallylsilanes were incorporated into the polymer chain via cyclization insertion preferentially, and formed 3,5‐disubstituted silacyclohexane units in the polyethylene main chain. A zirconocene catalyst, dimethylsilylenebis(indenyl)zirconium dichloride, produced a copolymer containing pendant allyl groups derived from the 1,2‐insertion of diallyldiphenylsilane without cyclization. magnified image

DSC studies on thermally induced structural transformation of hydrogen-bonded amphoteric molecular assemblage

Thermally induced structural transformation of fibrous hydrogen-bonded molecular assemblage formed from an amphoteric pyridinecarboxylic acid of 6-[2-propyl- 4-(4-pyridylazo)phenoxy]hexanoic acid (C5PR) was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetry (TG). The organized fibrous morphology formed in an aqueous solution was stable at temperatures below 150°C. The ordered crystalline solid phase (K1) of the original fibrous material altered to a disordered crystalline solid phase (K2) at 150°C and subsequently to an isotropic phase (I) at 172°C. In the isotropic state, the C5PR molecule was slowly decomposed by decarboxylation. Once the molecular assemblage was subjected to the mesophase by heating, another ordered crystalline solid phase (K3) appeared reversibly at 17°C. The heat budget analyses by DSC indicated that a conformational entropy change such as the side-chain propyl group and the main-chain pentamethylene unit in the hydrogen-bonded molecular assemblage took place between the two ordered crystalline solid phases K1 and K3.

Synthesis and Luminescent Properties of Fluorene Copolymers Bearing DCM Pendants

A series of copolymers, poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4-dicyanomethylene-2-methyl-6-[4-(diphenylamino)styryl]-4H-pyran-4‘,4‘ ‘-diyl)], were synthesized by polymerizing 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene with mixtures of 2,7-dibromo-9,9-dioctylfluorene and 4-dicyanomethylene-2-methyl-6-[bis(4‘-bromophenyl)amino]styryl]-4H-pyran (a DCM derivative) by the palladium-catalyzed Suzuki coupling reaction. The copolymers were characterized by molecular weight determination, elemental analysis, 1H NMR, FT-IR spectroscopy, DSC, TGA, UV−vis spectroscopy, and photoluminescence (PL) and electroluminescence (EL) spectroscopy. The copolymers showed two absorption peaks at 380 and 485 nm, and the long-wavelength absorption increased with increasing the fraction of the DCM comonomer. The PL spectra of copolymers in chloroform solution displayed emission from both the main chain (420 nm) and DCM units (620 nm). In the solid state, however, PL spectra of copolymers showed only the long wavelength red emission at 620 nm with no trace of emission from the main chain, which implies a facile exciton migration or energy transfer to the lower energy sites from the fluorene part to the DCM part. This results in emission of only the red light originating from the latter segments. A study on time-resolved PL rise and decay of the polymers clearly supports the energy transfer mechanism. Light-emitting diode (LED) devices were fabricated to have the configuration of ITO (indium−tin oxide)/PEDOT/polymer/Li:Al alloy. EL spectra of the devices showed only red emissions as observed in the PL spectra of the polymers' thin films. EL efficiency decreased with increasing DCM contents. When a tris(8-hydroxyquinolinato)aluminum (Alq3) layer was inserted between the emitting polymer layer and the cathode to make the ITO/PEDOT/polymer/Alq3/Li:Al alloy configuration, the device efficiencies became much higher (∼10-2%) than those (5 × 10-5−5 × 10-3%) of single-layer devices.

Low‐Band Gap Polyplatinaynes with Electron‐Accepting Silole Units

AbstractSummary: The synthesis and thermal, redox and photoluminescence properties of a soluble donor‐acceptor polyplatinayne with the electron‐accepting silole ring and its model compound are described. The polymer has an optical band gap of 2.10 eV which is much lower than that of thienyl‐ or silyl‐bridged congeners. The incorporation of electron‐accepting silole unit in the metallopolymer main chain creates a new π‐conjugated system that features unique donor‐acceptor characteristics. magnified image

Newly synthesized polybenzoxazole derivative with an adjacent hydroxyphenyl ring for optical sensing

AbstractA photoluminescent polymer with a 2‐(2′‐hydroxyphenyl)benzoxazole unit in the molecular main chain was synthesized through the deprotection reaction of a precursor polymer. The amorphous, conjugated polymer emitted green light, both in solution and as a solid, with a fluorescence emission maximum at 518 nm from an excited keto tautomer because of excited‐state intramolecular proton transfer. The polymer showed different fluorescence emission spectra in solvents with different polarities because of intramolecular hydrogen‐bond interruption. The intramolecular hydrogen‐bond‐induced emission change was successfully used as a sensitive sensing signal for metal cations as expected, the polymer acting as a fluorescence‐based chemosensor. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1397–1403, 2005

Synthesis of Graft Copolymer from Copolymerization of Styrene-terminated Poly(ethylene oxide) Macromonomer and Styrene with Ni(acac)2/Methylaluminoxane Catalyst

Copolymerization of styrene-terminated poly(ethylene oxide) (PEO) macromonomer (SEOM) and styrene (St) with Ni(acac)2/MAO catalyst was investigated. The copolymerization of SEOM and St with the Ni(acac)2/MAO catalyst proceeded to give a high molecular weight graft copolymer consisting of hydrophobic styrene units as the main chain and hydrophilic PEO units as the side chains. The numbers of graft chains were controlled by varying SEOM contents in the comonomer feed. The graft copolymer obtained from the copolymerization of SEOM and St with Ni(acac)2/MAO catalyst contained isotactic triad in a lower amount than that of poly(St) obtained with Ni(acac)2/MAO catalyst.