Helix formation in synthetic polymers by hydrogen bonding with native saccharides in protic media

Water-soluble poly(m-ethynylpyridine)s were designed to realize saccharide recognition in protic media. UV/Vis, 1H NMR, and fluorescence measurements revealed that the polymer forms a helical higher order structure by solvophobic interactions between the ethynylpyridine units in the protic medium. The resulting pore in the helix behaves like a binding pocket in proteins, by taking advantage of inwardly directed hydrogen-bonding functional groups of the polymers. Molecular recognition of native saccharides by the polymers was investigated by circular dichroism (CD). The chirality of the saccharide was transferred to the helical sense of the polymers, accompanied by the appearance of induced CDs (ICDs) in the absorptive region of the polymers. In MeOH/water (10/1), mannose and allose showed intense ICDs, and the apparent association constant between the polymer and D-mannose was 14 M(-1).     

Aroxydihydro pyrans

The vinyl ether of o-fluorophenol by diene condensation with acrolein forms an adduct and this with a higher yield than the vinyl ethers of chloro- and bromophenols. Eight 2-halogenaroxy-3, 4-dihydropyrans were synthesized. New halogen-containing acetals and polymers of the tetrahydropyran series were obtained.For part VI, see [1].     

Trends in geometric and electronic properties of thiophene- and cyclopentadiene-based polymers

In this work, we present theoretical evidence illustrating that cyano derivatives of conducting polymers such as polythiophene, polycyclopentadiene, and polyfulvene have smaller intrinsic band gaps than those of their parent polymers. The geometric and electronic properties of the parent and the derivative polymers were studied with the use of two methodologies: (1) the pseudo-one-dimensional band-structure calculations performed using the semi-empirical molecular orbital theory (MNDO, AM1) and (2) oligomer calculations performed using the ab initio molecular orbital theory both at the Hartree–Fock and configuration interaction levels. In particular, we found that an organic polymer, poly(dicyanomethylene cyclopentadifulvene) (PCNFv), has a comparable (possibly lower) band gap to the one observed in poly(dicyanomethylene cyclopentadithiophene) (PCNTH) (which has a band gap of 0.8 eV). The precursor of PCNFv is poly(dicyanomethylene cyclopentadicyclopentadiene) (PCNCY) in which two cyclopentadiene rings are connected by a dicyanomethylene group. The additional bond conjugation (in contrast to PCNCY) perpendicular to the chain axis makes PCNFv very rigid and fully planar. Trends in structural properties indicate that the lower band gaps in the cyano-substituted polymers, in comparison to their parent polymers, are accompanied by a decrease in bond alternations in the aromatic or trans–cisoid forms and by an increase in bond alternations in the quinoid or cis–transoid forms. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 229–240, 1998     

Synthesis and photochromism of polymer-bound phenoxyquinone derivatives

Acrylate- and styrene-derived polymers having pendant phenoxyquinones for photochromism were prepared by 2,2′-azoisobutyronitrile (AIBN)-initiated radical polymerization. Synthesis of the monomers were straightforward and the polymers were obtained in high yields in spite of the quinone moieties presented in the monomers, which usually can function as radical scavengers and/or catalysts poison. Photo-induced rearrangement from the “trans”-quinone forms to the “ana”-quinone forms readily occurred when the polymer films were irradiated with UV light.     

Bis-ureidodeazapterin (Bis-DeAP) as a general route to supramolecular star polymers

Supramolecular recognition unit Bis-DeAP, 1, containing two high affinity hydrogen-bonding acceptor-acceptor-donor-donor (AADD) arrays was designed to self-assemble into cyclic assemblies. It was prepared through a highly scalable synthesis and was further functionalized with 2-bromo-2-methylpropanoyl bromide and used to initiate the polymerization of methylmethacrylate (MMA). Bis-DeAP-PMMA polymers quantitatively self-assembled into star polymers in toluene. In DMF Bis-DeAP-PMMA forms a mixture of star polymers and unassembled polymers. Bis-DeAP was also functionalized with polyethylene glycol (PEG) polymers. The Bis-DeAP-PEG polymers formed star polymers in DMF; however, higher molecular weight polymeric assembles that varied with concentration were observed in water. Mixing studies in toluene indicated that the self-assembled star polymers are kinetically stable and resist mixing even at elevated temperatures. In DMF, kinetically controlled structures are initially observed, however, mixing occurs at a faster rate and assembled star polymers show a decrease in polydispersity index (PDI) over time. In addition, Bis-DeAP functionalized PS and PMMA were mixed in DMF to generate a star copolymer through self-assembly.     

Synthesis of beta-O-4-type artificial lignin polymers and their analysis by NMR spectroscopy

We describe the synthesis and NMR spectroscopic analysis of three artificial lignin polymers containing only the beta-O-4 substructure: syringyl-type homopolymer, p-hydroxyphenyl-type homopolymer and guaiacyl/syringyl-type heteropolymer. Using gel permeation chromatography, the weight-average degree of polymerization (DP(w)) of the three polymers was determined as 19.2, 38.6, and 13.9, respectively. The polymers were prepared based on the synthetic methodology of guaiacyl-type homopolymer, and were fully characterized using (1)H-, (13)C-, and (1)H-(13)C NMR spectroscopy of the acetylated and non-acetylated forms. The spectra of guaiacyl/syringyl-type heteropolymers were in good agreement with those of the beta-O-4 substructure of milled wood lignin obtained from the hardwood of Japanese white birch.     

Synthetic analogues of polynucleotides—XIII: The resolution of dl-β-(thymin-1-yl)alanine and polymerisation of the β-(thymin-1-yl)alanines

dl-β-(Thymin-1-yl)alanine has been resolved into d(+) and l(?) forms. The pure d(+) form was obtained by fractional crystallisation of the (+)α-methylphenylethylamine salts of the α-N-formyl derivatives. The pure l(?) isomer was obtained on a small scale by chromatography of the same salts. The optically active amino acids and the dl-mixture were polymerised by the mixed anhydride procedure to give polymers which showed no evidence of base stacking or of interaction with polyadenylic acid. The molecular weights of the polymers were in the range 2–4 × 10³. These were determined by end group assay which involved the synthesis of α-N-(2,4-dinitrophenyl)-dl-β-(thymin-1-yl)alanine as a standard.     

Coenzyme models. 19. Oxidation of furoin by a flavin immobilized in cationic polyelectrolytes: A flavoenzyme model

The rate constants for the oxidation of furoin by a flavin (vitamin B₂ analog) immobilized in cationic polymers were evaluated under anaerobic conditions, and the influence of reaction environments was discussed in connection with the enzymatic reactivity. It was found that (1) proton abstraction from furoin which forms the carbanionic intermediate is rate determining in the initial stage of the reaction and is facilitated by the environment of cationic polymers, (2) proton abstraction is efficiently accelerated by added cationic surfactant (CTAB), and (3) N-dodecylbenzohydroxamic acid in aqueous CTAB acts as an excellent proton-abstracting reagent. The polymers with high dodecyl group content served, in all cases, as better oxidizing reagents. As a summary of these conclusions, the importance of hydrophobic environments in flavin-mediated oxidation was emphasized.     

Soluble narrow band gap and blue propylenedioxythiophene-cyanovinylene polymers as multifunctional materials for photovoltaic and electrochromic applications

A family of soluble narrow band gap donor-acceptor conjugated polymers based on dioxythiophenes and cyanovinylenes is reported. The polymers were synthesized using Knoevenagel polycondensation or Yamamoto coupling polymerizations to yield polymers with molecular weights on the order of 10 000-20 000 g/mol, which possess solubility in common organic solvents. Thin film optical measurements revealed narrow band gaps of 1.5-1.8 eV, which gives the polymers a strong overlap of the solar spectrum. The energetic positions of the band edges were determined by cyclic voltammetry and differential pulse voltammetry and demonstrate that the polymers are both air stable and show a strong propensity for photoinduced charge transfer to fullerene acceptors. Such measurements also suggest that the polymers can be both p- and n-type doped, which is supported by spectroelectrochemical results. These polymers have been investigated as electron donors in photovoltaic devices in combination with PCBM ([6,6]-phenyl C(61)-butyric acid methyl ester) as an electron acceptor based on the near ideal band structures designed into the polymers. Efficiencies as high as 0.2% (AM1.5) with short circuit current densities as high as 1.2-1.3 mA/cm(2) have been observed in polymer/PCBM (1:4 by weight) devices and external quantum efficiencies of more than 10% have been observed at wavelengths longer than 600 nm. The electrochromic properties of the narrow band gap polymers are also of interest as the polymers show three accessible color states changing from an absorptive blue or purple in the neutral state to a transmissive sky-blue or gray in the oxidized and reduced forms. The wide electrochemical range of electrochromic activity coupled with the strong observed changes in transmissivity between oxidation states makes these materials potentially interesting for application to electrochromic displays.     

Stereoregular condensation polymers. I. Synthesis and comparison of optically active and inactive polycamphorates and polycamphoramides

Optically active and inactive polycamphorates and polycamphoramides were prepared by polycondensation of d- and dl-camphoryl dichloride with 1,4-butanediol, bisphenol A, and piperazine. The higher melting and more crystalline properties of optically active stereoregular condensation polymers compared to inactive atactic forms appear consistent with results from optically active isotactic and inactive atactic addition polymers.     

Preparation and Evaluation of Theophylline Sustained Release Microcapsules Using Coacervation

Preparation of sustained release dosage forms is one of the main objectives in drug formulation. Theophylline that has a narrow therapeutic index, making it a good choice to prepare a sustained release dosage form. Theophylline sustained release microcapsules were prepared by applying the coacervation method. The effect of the type and ratio of polymers, as well as the type of washing solvents, was studied on particle size, drug loading efficiency, and in vitro drug release profile. Results showed that Eudragit RS and RL could be more suitable polymers for preparation of sustained release microcapsules of theophylline when used in ratio of 1:1 and when the washing solvent was hexane.     

Tetrahedral n-type materials: efficient quenching of the excitation of p-type polymers in amorphous films

Tetrahedral naphthalenediimide compound 1 has been synthesized as an example of a new class of amorphous n-type materials, in which the nondirectionality obtained by its shape is decoupled from its optoelectronic properties. 1 forms bicontinuous films with p-type polymers and effectively quenches the excited state, yielding long-lived mobile charge carriers on pulsed illumination.     

Controlling the assembly of nanoparticle mixtures with two orthogonal polymer complexation reactions

Self-assembly from mixed dispersions of three sizes of monodisperse polystyrene nanoparticles, large (L), medium (M), and small (S), was controlled by coating each particle type with either a monofunctional or bifunctional polymer capable of participating in specific complexation reactions. The complexation reactions were (1) complexation between phenolic polymers and polyethylene glycol (PEG) containing polymers and (2) condensation of phenylboronic acid containing polymers with polyols. These complexation reactions function independently and can be "turned off" independently; phenylboronic acid complexation was reversed by lowering the pH, whereas the interactions of phenolic copolymers with PEG copolymers could be reversed by adding excess PEG homopolymer. The specificity and reversibility of the interactions was demonstrated by the formation of simple binary aggregates from mixtures. The bifunctional copolymers were poly(vinyl phenol-co-diallyldimethyl ammonium chloride), Ph-DADMAC, and poly(3-acrylamide phenylboronic acid-co-PEG methacrylate), PBA-PEG. The monofunctional polymer was polyvinylalcohol, PVA. Ph-DADMAC forms complexes with PBA-PEG (H-bonding) and with anionic surfaces or polymers (electrostatic/polyelectrolyte complexation). PBA-PEG complexes with Ph-DADMAC (H-bonding) and with PVA (boronate ester formation). PVA does not interact with Ph-DADMAC; therefore, PVA coated particles do not deposit onto Ph-DADMAC coated particles.     

Novel synthesis of photochromic polymers via ROMP

[reaction: see text] Ring-opening metathesis polymerization (ROMP) of a photochromic 1, 2-bis(3-thienyl)cyclopentene monomer generated a series of novel polymers. All polymers exhibit reversible light-activated interconversion between their colorless-open and their colored-closed forms.     

Siloxane polymers containing azo moieties synthesized by click chemistry for photo responsive and liquid crystalline applications

Three new types of siloxane‐based photoactive liquid crystalline polymers containing azo side groups were synthesized through the click chemistry route. The polymers having molecular weight range of 14,000–34,000 g mol^?1 were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and dichloromethane. The photoresponsive trans–cis photoisomerization under UV radiation and cis–trans relaxation process in dark for the polymers were studied. The isomerization rate constants were found to be 0.01–0.04 sec^?1 and 1.16*10^?4–4.67*10^?4 sec^?1, respectively. It has been noted that the polymers showed high intensity absorption for n‐π* in chloroform. Both trans and cis forms of azide monomers having azo moiety exhibited molar extinction coefficient ( ? _max) in the range of 22,000–33,000 L mol^?1 cm^?1. The thermotropic behavior of the polymers was studied by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) experiments. Polymer P1 showed liquid crystalline textures of nematic droplets, whereas P2 showed smectic focal conic texture and nematic droplets. Polymer P1 was also studied for photomechanical bending on exposure to UV radiation. The polymers showed initial degradation temperature in the range of 210–275°C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of poly-yne polymers containing transition metals,disilane, disiloxane and phosphine groups in the main chain

The synthesis and characterization of metal poly-yne polymers containing disilane, disiloxane and phosphine groups in the main chain are described. The platinum and palladium poly-yne polymers were synthesized by polycondensation reactions between a metal chloride and an α, ω-bisethynyl complex in amines in the presence of cuprous iodide as a catalyst. The nickel poly-yne polymers were synthesized by an alkynyl ligand exchange reaction between a nickel acetylide and an α, ω-bisethynyl complex in diethylamine in the presence of cuprous iodide as a catalyst. The reaction of the platinum poly-yne polymer, containing disiloxane groups in the main chain, with copper (I) salts afforded adducts of η-²-bonded σ-acetylide polymer complexes. The reactions of the palladium poly-yne polymer, containing phosphine groups in the main chain, with transition-metal carbonyl complexes afforded polymer complexes which have phosphorus in the main chain-transition-metal bonds. A concentrated solution of the platinum poly-yne polymer containing disiloxane groups in the main chain forms a lyotropic liquid crystal in dichloromethane or 1, 2-dichloroethane.     

Thallium(I) supramolecular compounds: Structural and properties consideration

During the last two decades, supramolecular compounds and especially coordination polymers have received great attention and the number of their synthesized compounds is still growing, which is mainly due to their potential application in various fields such as microelectronics, nonlinear optics, ion exchange, catalysis, gas storage, separation and luminescence. Formation of polymers with main group metal ions such as thallium(I) is disproportionately sparse when compared with those of other metals. Because of the interest structures, properties and applications of thallium polymers, it is necessary to understand thallium's ability to bind donors and form supramolecular compounds. This review tries to give an overview of all supramolecular compounds which were reported from thallium(I) after 1990 and to investigate their properties and applications. Thallium(I) usually forms neutral species and exhibits greater tendency to forming one-dimensional supramolecular compounds. Thallium(I) also favors secondary interactions on its coordination sphere (especially with unsaturated carbon atoms forms organometallic polymers) with stereochemically active lone pair and hemidirected coordination sphere around it.     

Mesogen-jacketed Liquid Crystal Polymers With Mesogens of Aromatic Amide Structure

The synthesis and property of a new series of "mesogen-jacketed liquid crystal polymers" are reported. These polymers have aromatic amide structures as the mesogenic groups and are represented by poly-2,5-bis(4-methoxy- benzamido)styrene. The preliminary study on properties shows that the polymers have very high glass transition temperatures as well as very low critical concentrations for the formation of the lyotropic liquid crystal phase. The results indicate a high degree of chain rigidity. However, the liquid crystalline order of molecular organization in bulk samples disappears upon heating to the glass transition temperature as revealed by polarizing microscopy and by X-ray diffractometer. Therefore, the liquid crystalline order of these polymers forms only through solution but not through heating. This behavior is different from that of the previously studied poly-2,5-bis[(4-methoxybenzoyl)oxy]styrene and its homologs. The latter polymers are liquid crystals both lyotropically and thermotropically. © 1997 John Wiley & Sons, Ltd.     

Polytypism, homochirality, interpenetration, and hydrogen-bonding in transition metal (Mn(II), Ni(II), Cu(II), Zn(II)) 5-hydroxyisophthalate coordination polymers containing 4,4'-bipyridyl

We report the synthesis of five coordination polymers of divalent transition metals combined with 5-hydroxyisophthalic acid (HIP) and 4,4'-bipyridyl (bipy). Mn forms two polytypic two-dimensional coordination polymers, Mn(HIP)(bipy).3H(2)O and Mn(HIP)(bipy).(1/4)bipy.2H(2)O (I and II, with ABAB and ABC stacking sequences, respectively); Ni forms a chiral hexagonal three-dimensional coordination polymer with two interpenetrating trigonal sublattices exhibiting the "dual quartz" topology, Ni(HIP)(bipy)(H(2)O) (III); Cu forms a one-dimensional coordination polymer containing arrays of infinite hydrogen-bonded molecular ribbons, Cu(HIP)(2)(bipy) (IV); and Zn forms a two-dimensional coordination polymer with a stair-stepped layered structure, Zn(2)(HIP)(2)(bipy)(H(2)O)(2).H(2)O (V). The M-HIP-M connections are perpendicular to the M-bipy-M connections in all structures where they are present.     

Synthesis and some properties of poly-(2,5-trimethylene benzimidazole) and poly-(2,5-trimethylene benzimidazole hydrochloride)

A polymer, poly(2,5-trimethylene benzimidazole), the first of a new family of nonsymmetrical polymers, was synthesized via an eight-step synthetic route. The polymer, obtained by melt polymerization, is amorphous and in its neutral form behaves as a moderate insulator. It forms 1 : 1 HCl adducts. When cast from formic acid solution, it forms 1 : 1 formic acid adducts. The acid adducts are semiconductors with resistivities in the 10⁶–10⁸ ohm-cm range. Space-charge effects are generated in the adducts as carrier mobility rises.