Synthesis and characterization of flexible polyoxadiazole films through cyclodehydration of polyhydrazides

Aiming to produce flexible films of poly(4,4′-diphenylether-1,3,4-oxadiazole), POD-DPE, the synthesis of POD-DPE through thermal cyclodehydration of polyhydrazide in solutions of poly(phosphoric acid), PPA, and in film form is studied here. It was observed that POD-DPE polymer samples obtained when the cyclodehydration of polyhydrazide is performed in solutions of PPA are insoluble in the solvents normally used for film preparation. On the other hand, the cyclodehydration of polyhydrazide in film form can lead to brittle POD-DPE films due to the high temperatures required for reaction to occur. In order to obtain flexible POD-DPE films with high conversion through cyclodehydration of polyhydrazide films, it is shown here that it is very important to adjust the cyclodehydration temperature (T_c) as a function of the glass transition temperature (T_g) and the weight average molecular weight (M_w) of the polyhydrazide. In all cases analyzed, polyhydrazides were synthesized by low temperature solution polycondensation reactions and were characterized by intrinsic viscosity measurements, size exclusion chromatograpy, nuclear magnetic resonance, infrared spectroscopy and thermal analysis. Polyhydrazides with weight average molecular weights up to 74,100 g/mol were obtained. The POD-DPE films obtained were characterized by infrared spectroscopy and nuclear magnetic resonance, showing that the production of POD-DPE films is indeed possible from cyclodehydration of polyhydrazide films.     

Synthesis and properties of novel fully conjugated polymers containing bithiazole rings

Two novel fully conjugated polymers containing bithiazole rings (PDDBTz and PDABTz) were first synthesized by polycondensation of 2,7-dimethyl-2,4,6-octatriene-1,8-dial with 2,2′-bis(diethylphosphinatyl methyl)-4,4′-bithizole or 2,2′-diamino-4,4′-bithiazole (DABT). The structure of the polymers was determined by IR, ¹H NMR and elemental analysis. PDDBTz is soluble in trifluoroacetic acid and DMSO, whereas PDABTz is soluble in common solvent such as THF, DMSO, DMF. Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions. Their lanthanide metal complexes were prepared. The magnetic behavior of these polymeric complexes was measured as a function of magnetic field strength (0-60 kOe) at 4 K and as a function of temperature (4-300 K) at magnetic field strength of 30 kOe. The results show that they all exhibit features of soft ferromagnet.     

Synthesis of highly conjugated poly(3,9-carbazolyleneethynylenearylene)s emitting variously colored fluorescence

Novel conjugated polymers P1–P7 containing 3,9-linked carbazole units in the main chain were synthesized by the polycondensation of 3-ethynyl-9-(4-ethynylphenyl)carbazole (EEPCz) and dihaloarenes, and their optical and electrical properties were studied. Polymers with weight-average molecular weights of 4100–48,000 were obtained in 24–92% yields by the Sonogashira coupling polycondensation in tetrahydrofuran (THF)/Et₃N at 30 or 50 °C for 48 h. All the polymers absorbed light around 350 nm. The polymers with electron-accepter units exhibited absorption bands originating from charge transfer. The polymers except the one containing azobenzenes emitted variously colored fluorescence with moderate quantum yields upon excitation at the absorption maxima. P1–P3 were oxidized around 0.6 V, and then reduced around 0.5 V. The conductivity of P3 was 1.1 × 10⁻¹⁴ S/cm at 10³ V/cm.     

Synthesis and properties of chiral helical polymers based on optically active polybinaphthyls

The chiral polymer P-1 was synthesized by the polymerization of (R)-6,6′-dibutyl-3,3′-diiodo-2,2′-bisoctoxy-1,1′-binaphthyl (R-M-1) with 5,5′-divinyl-2,2′-bipyridine (M-1)via Pd-catalyzed Heck reaction. P-2 and P-2′ were prepared by Wittig-Horner reaction of (R)-6,6′-dibutyl-2,2′-bisoctoxy-1,1′-binaphthyl-3,3′-dicarbaldehyde (R-M-2) with 5,5′-bis (diethylphosphonomethyl)-2,2′-bipyridine (M-2) in the presence of EtONa or NaH, respectively. P-3 was synthesized by Wittig-Horner reaction of (R)-6,6′-di(4-trifluoromethylphenyl)-2,2′-bisoctoxy-1,1′-binaphthyl-3,3′-dicarbaldehyde (R-M-3) with M-2 using NaH as a base. The four polymers have strong blue-green fluorescence due to the extended π-electronic structure between the chiral model compounds (R)-6,6′-dibutyl-/di(4-trifluoromethylphenyl)-2,2′-bisoctoxy-1,1′-binaphthyl (R-1 or R-2) and the conjugated linker 2,2′-bipyridyl group via vinylene bridge. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and circular dichroism (CD) spectroscopy. Based on the great differences of specific rotation values and CD spectra, P-1 and P-2 may adopt a zigzag chain configuration, while P-2′ and P-3 may adopt a helical configuration. The responsive optical properties of the two chiral helical polymers P-2′ and P-3 on transition metal ions were investigated by fluorescence, UV-vis and CD spectra. The results show that Ag⁺ and Ni²⁺ lead to nearly complete fluorescence quenching of P-2′ and P-3, Cu²⁺ and Fe²⁺ can cause obvious fluorescence quenching, but Zn²⁺ and Cd²⁺ can only produce slight fluorescence quenching. Ag⁺, Ni²⁺, Cu²⁺ and Fe²⁺ can also lead to the obvious changes of UV-vis spectra of P-2′ and P-3. On the contrary, Zn²⁺ and Cd²⁺ cause little changes. Most importantly, the CD intensities and wavelengths of the chiral helical polymers P-2′ and P-3 exhibit the pronounced changes upon addition of Ag⁺ and Ni²⁺.     

Synthesis and properties of carbazole-based hyperbranched conjugated polymers

Carbazole-based novel hyperbranched conjugated polymers linked with triphenylamine and benzene moieties were synthesized by Sonogashira coupling polycondensation of N-octadecyl- and N-octyl-3,6-diethynylcarbazoles with tris(4-iodophenyl)amine and 1,3,5-tribromobenzene. Solvent-soluble polymers with number-average molecular weights in the range of 3500-21,000 were obtained in 48-66% yields. The UV-vis absorption bands of the polymers were red-shifted compared to that of carbazole, indicating the extension of conjugation length. The polymers emitted blue-green fluorescence with high quantum yields up to 67% in CHCl₃. Poly(1/3) containing triphenylamine units emits visible light and shows unique solvatochromism. The polymers were electrochemically redox-active.     

Hg detection by aniline-based conjugated copolymers with high selectivity

Conjugated polymers (P1, P1L and P2-P5) constructed by alkynyl-substituted aniline and substituted arene analogs could be synthesized through Pd-catalyzed Sonogashira coupling. The responsive optical properties of poly(2-ethynyl aniline) (P1 and P1L for different molecular weights, P1L with longer chains on average) toward various metal ions (including Ni²⁺, Ag⁺, Cu²⁺, Zn²⁺, Fe³⁺, Fe²⁺, Mn²⁺, Na⁺, Ca²⁺, Pb²⁺, K⁺, Cr³⁺, Al³⁺, Cd²⁺, Pt²⁺, Au³⁺ and Tl³⁺) were investigated. Hg²⁺ exhibited the most pronounced fluorescence response of both P1 and P1L without interference from those coexistent ions due to aniline in the polymer backbone as the metal binding ligand, while other metal ions does not cause obvious change of fluorescence. Compared with P1, P1L exhibits better sensitivity toward Hg²⁺. Introducing pyridyl, thienyl or phenyl groups into the polymer backbone would weaken the quenching responses to Hg²⁺ compared with P1. The results indicated P1 and P1L could be used as a selective fluorescence sensor toward Hg²⁺.     

Synthesis and ion responsiveness of optically active polyacetylenes containing salicylidene Schiff-base moieties

Acetylenic monomers containing salicylidene Schiff-base groups (1a and 1b) as well as Schiff-base and hydroxy groups (1c) were synthesized and polymerized with [(nbd)RhCl]₂/Et₃N catalyst to afford the corresponding polymers 2a–c with high molecular weights (M_n = 2.6–7.2 × 10⁵) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO₄⁻, whereas these polymers did not exhibit responsiveness to other anions, such as F⁻, Cl⁻, and Br⁻.     

Synthesis of hydroxyphenylglycine-derived novel poly(silylenevinylenephenyleneethynylene)s

The hydrosilylation polymerization of d-(−)-p-hydroxyphenylglycine-derived diethynyl monomers 1p and 1m with dihydrosilanes Si1 and Si2 was carried out using RhI(PPh₃)₃ as a catalyst to give optically active novel poly(silylenevinylenephenyleneethynylene)s [(E)-poly(1p-Si1), (E)-poly(1p-Si2), (E)-poly(1m-Si1), (E)-poly(1m-Si2), and (Z)-poly(1p-Si1)] with number-average molecular weights ranging from 2800 to 17,000 in 41-92% yields. Polymers having (E)- and (Z)-olefin moieties were obtained, wherein the (E)-/(Z)-ratios depended on the reaction conditions. The UV-vis absorption edge of (E)-poly(1p-Si1) was positioned at a wavelength longer than that of (Z)-poly(1p-Si1), indicating that (E)-vinylene-linkage extends the conjugation more largely than the (Z)-counterpart. This was also confirmed by fluorescence spectroscopy. Alkaline hydrolysis of ester moieties of these polymers gave the corresponding polymers having carboxy groups. The (E)-polymers showed different solubility in hydrophobic solvents before and after hydrolysis, but the non-hydrolyzed and hydrolyzed (Z)-polymers exhibited the same solubility.     

Synthesis of poly(p-phenylene vinylene) and derivatives via a new precursor route, the dithiocarbamate route

A new synthetic route towards poly(para-phenylene vinylene) (PPV) and its derivatives has been investigated. In this route, a bis-dithiocarbamate monomer is polymerized towards a dithiocarbamate precursor polymer by the addition of a strong base (LDA). The corresponding conjugated polymer is obtained via a heat treatment of the precursor polymer. This dithiocarbamate (DTC) precursor route strikes an optimal balance between several straightforward but sometimes troublesome precursor routes and the more complex sulphinyl precursor route yielding superior purity materials. The novelty lies in the fact that the monomer synthesis is not as difficult as compared to the sulphinyl route and this without losing the quality and accessibility of the precursor polymer. In the paper, the mechanism of the polymerization process is discussed and strong indications for radical as well as anionic mechanisms are presented.     

Polymer conformation-assisted wrapping of single-walled carbon nanotube: The impact of cis-vinylene linkage

A soluble π-conjugated polymer cis-PmPV is found to be twice as effective as its trans-PmPV isomer in dispersing SWNTs into organic solvents. The improved efficiency is related to the specific conformation of cis-vinylene-enriched PmPV, which facilitates a planar π-π interaction with SWNT surface and leads to improved nanotube dispersion. ¹H NMR spectra indicate that the cis-CHCH bonds are partially converted to the trans-CHCH, thereby providing necessary conformational cavity for SWNT wrapping. Irradiation triggers a precipitation from SWNT dispersion, providing a purified SWNT/conjugated polymer composite.     

Synthesis and characterization of some novel conjugated polyoxadiazoles with Schiff base structure

Some novel conjugated polyoxadiazoles with Schiff base structure were efficiently synthesized through polycondensation of 4,4′-(1,3,4-oxadiazole-2,5-diyl)dianiline with some dialdehydes. The polymers were characterized by IR, ¹H NMR, ultraviolet spectroscopy, fluorescence spectroscopy, gel permeation chromatography and thermal analyses. All polymers have high thermal stability with decomposition temperature higher than 260 °C. Some polymers have good solubility in common organic solvents. They also have strong absorptions at 294–345 nm, and strong emissions at 405–432 nm.     

Synthesis and Characterization of Polyacetylene with Side-chain Thiophene Functionality

A new polyacetylene derivative with electroactive thiophene substituent, namely poly(2-methylbut-2-enyl thiophene-3-carboxylate) was synthesized and characterized. For this purpose, novel acetylene monomer was synthesized by the reaction of 3-thiophenecarboxylic acid with propargyl bromide and polymerized with a Rh catalyst to give the corresponding polymer. The chemical structure of the polymer was characterized to comprise the conjugated backbone and electroactive thiophene side group. UV spectral changes of the polymer with temperature were also studied. The polymer exhibited better thermal stability than the unsubstituted polyacetylenes.     

Electrochemical synthesis and characterization of novel bile acid functionalized polypyrroles

A new series of pyrroles bearing bile acid moieties were synthesized and electrochemically polymerized in acetonitrile with tetrabutylammonium hexafluorophosphate (TBAFP₆) as the supporting electrolyte. It is found that these functionalized monomers could form polypyrrole films, but their electrochemical properties and the stability of the films are strongly dependent on the length of the alkyl spacer between pyrrole ring and the pendant bile acid moiety. Each of the resulting polymers with different bile acid groups shows a distinctive behaviour in terms of its microstructure of surface, as well as electrochemical and optical properties. Compared to other analogous polypyrroles, the optical property of the cholic acid functionalized polymer is sensitive to the polarity of the used solvents, exhibiting solvatochromic behaviour. This phenomenon is probably derived from its unique facial amphiphilic structure.     

Water-soluble conjugated polyelectrolyte with pendant glycocluster: Synthesis and its interaction with heparin

A novel fluorescent conjugated polyelectrolyte with pendant glucosamine hydrochloride clusters was prepared through Cu(I)-catalyzed azide/alkyne “click” ligation and Suzuki coupling polymerization. Compared with monosugar-functionalized conjugated polymer, the water-solubility and fluorescence quantum yield of the glycocluster-containing polymer (P-3) were significantly improved. As a glucosamine-containing cationic fluorescent polyelectrolyte, the water-soluble fluorescent polymer can interact with heparin through electrostatic bindings, which induce great fluorescence quenching of P-3 due to the polymer aggregation. Furthermore, upon treatment of the P-3-heparin ensemble with protamine, the fluorescence emission of P-3 recovered since the protamine possesses a competitively strong binding affinity to the heparin and thus results in the release of the fluorescent glycopolymer P-3 from the P-3-heparin ensemble.     

Synthesis of terpyridine-functionalized poly(phenylenevinylene)s: The role of meta-phenylene linkage on the Cu and Zn chemosensors

A meta-phenylene-containing poly(phenylenevinylene) (PPV) with pendant terdentate terpyridine ligand 2b was synthesized and its fluorescence properties were compared with its isomeric PPV. The meta-phenylene bridge interrupts the resonance connection between the PPV backbone and the metal-chelation sites, while jointing the structurally defined chromophores together. The fluorescence of the polymer, with emission λ_em = 460 nm and ?_fl ≈ 0.45, is found to be selectively quenched by Cu²⁺ ion with interference from Co²⁺ and Ni²⁺ ions. The nature of the quenching process in 2b is probed by using Stern-Volmer analysis, revealing that the quenching results from both dynamic collision and metal chelation. Addition of Zn²⁺ and Cd²⁺ ions only induces partial fluorescence quenching, accompanied with a broad new emission band occurring at ∼560 nm. With the aid of a model compound study, the new emission band at 560 nm is attributed to the complex formation with terpyridine to Zn ratio of 1:1. The study finds that the polymer has the potential for Cu²⁺ and Zn²⁺ sensors.     

L-精氨酸衍生物的合成及其性质研究

以L-精氨酸(L-Arginine)和香兰素(Vanillin)为原料,首先合成新型的具有手性的希夫碱配体L(C_(14)H_(14)KN_3O_4),其次配体L分别与金属盐(CH_3COO)_2Ni·2H_2O、BaCl_2、(CH_3COO)_2Zn·2H_2O进行配位反应,得到3种新型的金属配合物(C_(16)H_(19)ZnKN_3O_7、C_(14)H_(14)BaClKN_3O_4和C_(18)H_(20)KN_3NiO_8),目标产物用IR、荧光分光光度计和元素分析仪等表征其结构,并用紫外漫反射光谱在可见光照射下,考察了配体L和3种新型的金属配位化合物的催化性能。实验结果推测配体L和L金属配合物均具有光催化性质,L金属配合物的催化性能更强。     

Multicolor emission and thin film transistor properties of 1,8-diethynylcarbazole-based conjugated copolymers

1,8-Carbazole-based conjugated copolymers are synthesized by the Sonogashira polycondensation between the 1,8-diethynylcarbazole derivative and dibromo comonomers. The resulting polymers are fully characterized by GPC, and ¹H NMR and IR spectroscopies, and their high thermal stability with the 5% decomposition temperature exceeding 350 °C by thermogravimetric analyses. The optical properties of the carbazole polymers reveal that the comonomer structures significantly affect the absorption and emission spectra. For example, a bathochromic shift of the spectra is achieved when electron-accepting comonomers are selected, finally leading to the production of additive primaries. The mixtures of three carbazole polymers with red, green, and blue emission colors provide a white light emission both in solutions and in thin solid films. In addition, the thin film transistor properties of the carbazole polymers are investigated. The 1,8-carbazole-based polymers display an intermediate mobility between the 2,7-carbazole and 3,6-carbazole-based counter polymers. All these results suggest the potential application possibilities of the 1,8-carbazole-based conjugated polymers in optoelectronic devices.     

Triphenylamine-based fluorescent conjugated glycopolymers: Synthesis, characterization and interactions with lectins

Two well-defined triphenylamine-based fluorescent conjugated glycopolymers were easily synthesized through Suzuki coupling polymerization of peracetylated galactopyranosyl-carrying monomer and consequent efficient deacetylation under Zemplén condition. Their structures were characterized using ¹H NMR, IR, and UV-vis spectroscopies. The preliminary insight into carbohydrate-lectin interactions was revealed by the titration of peanut agglutinin (PNA) to one of the final polymers, d-galactose-bearing poly(fluorene-alt-triphenylamine) copolymer (P-2), resulting in a significant fluorescence quenching of the polymer with a Stern-Volmer quenching constant of 1.56 × 10⁵ M⁻¹. Whereas no distinct change in the fluorescent properties of P-2 was observed when concanavalin A (Con A) was employed.