Synthesis of conjugated poly(acrylene)s with 1,2‐type (η4‐cyclobutadiene)cobalt moieties in the main chain

The synthesis of polymers containing 1,2‐type (η⁴‐cyclobutadiene)cobalt moieties in the main chain (i. e., poly(cyclobutadienecobalt‐1,2‐diyl‐alt‐biphenyl‐4,4′‐diyl)s) is described. Dichloride monomers with (cyclobutadiene)cobalt moieties (i. e., (cyclopentadienyl)[1, 2‐bis(4‐chlorophenyl)‐3, 4‐bis(4‐alkoxyphenyl)]cyclobutadiene cobalts were obtained by the reaction of (4‐chlorophenyl)(4′‐hydroxyphenyl)acetylene with (η⁵‐cyclopentadienyl)bis(triphenylphosphine)cobalt(I) and chromatographic separation over silica gel of a pure 1,2‐isomer followed by the alkylation of the hydroxy groups. The Ni(0)‐mediated dehalogenative polycondensation of the 1,2‐type monomer was carried out at 80°C in benzene under nitrogen to yield polymers which are soluble in common organic solvents. The number average molecular weights (M_n) of the resulting 1,2‐type organocobalt polyarylenes were 8 000–13 600. The polymers with appropriate lateral alkyl chains were found to show a thermotropic liquid crystalline phase in the range of 58–184°C determined by differential scanning calorimetry and the optical measurement using the crossed polarizers.     

New polymer syntheses, 47. Synthesis of aromatic polyethers from silylated diphenols and activated dichloro-substituted aromatics

Bis(trimethylsilyl)bisphenol-A was condensed with 4,4′-dichlorodiphenyl sulfone under various reaction conditions. Satisfactory yields and molecular weights of the resulting poly(ethersulfone)s were only obtained when the condensation was conducted in amide solvents (e. g., N-methyl-2-pyrrolidone) in the presence of equimolar amounts of K₂CO₃. The purity of the solvent plays an important role for the molecular weights. By light scattering, weight-average molecular weights (M _w's) up to 130000 were found. Further polycondensations were conducted with 2,6-dichlorobenzonitrile, 2,6-dichloropyridine or 3,6-dichloropyridazine. For polyethers derived from 2,6-dichlorobenzonitrile M _w's up to 106000 were found and for copoly(pyridine-ether-sulfone)s M _w's up to 220 000. The corresponding difluoroaromatics gave similar results. In contrast to the polycondensation of free diphenols with dihaloaromatics under alkaline conditions, no water is formed when silylated diphenols are used.     

Electroinitiated cationic polymerization of ethyl and i-butyl vinyl ethers

The electroinitiated cationic polymerization of ethyl and i-butyl vinyl ethers has been studied under various experimental conditions using NaB(C₆H₅)₄ as background electrolyte. Differring from other electrolytes with higher oxidation potentials, the NaB(C₆H₅)₄ allows appreciable current intensities and the polymerizations can occur at moderate rates. The monomer to polymer conversion presents a slightly sigmoidal shape as a function of the quantity of electricity and at a fixed quantity of electricity is independent from the current intensities. The molecular weights of the polymers are substantially controlled by chain transfer to monomers and solvents: the relative chain transfer constants are reported. The reaction temperature affects remarkably the molecular weights while the influence of dielectric constant of the reaction medium is negligible. An interpretation is given of the effect of NaB(C₆H₅)₄ electrolyte on the initiation mechanism and on the resulting conditions of polymerization.     

Anionic polymerization of monomers containing functional groups, 11. Anionic polymerizations of alkynyl methacrylates

Anionic polymerization of 2-propynyl methacrylate ( 1 ), 3-trimethylsilyl-2-propynyl methacrylate ( 2 ), 2-butynyl methacrylate ( 3 ), and 3-pentynyl methacrylate ( 4 ) was carried out in tetrahydrofuran at −78°C for 1 h. The employed initiator systems were (diphenylmethyl)potassium/diethylzinc (Et₂Zn) and 1,1-bis(4′-trimethylsilyphenyl)-3-methylpentyllithium/lithium chloride (LiCl). Although poly( 1 ) was obtained quantitatively with each initiator system, the observed molecular weights were always higher than the predicted values and the molecular weight distributions were rather broad (M̄_w/M̄_n > 1.3), indicating a side reaction at the acidic acetylenic proton. On the other hand, the polymerization of 2–4 , i.e., methacrylate monomers having no terminal acetylenic protons in the ester moieties, proceeded quantitatively under similar conditions. The resulting poly( 2–4 )s were found to possess the predicted molecular weights and narrow molecular weight distributions (M̄_w/M̄_n < 1.1), indicating the living character of the polymerization systems. The trimethylsilyl protecting group of poly( 2 ) was completely removed to form a poly( 1 ) having well-defined chain structures by treating it with potassium carbonate in a mixed solvent of THF and methanol at room temperature for 1 h.     

Accessing New DPP‐Based Copolymers by Direct Heteroarylation Polymerization

A diketopyrrolopyrrole derivative was copolymerized with different electron‐withdrawing units [i.e., thieno[3,4‐c]pyrrole‐4,6‐dione ( TPD ), bis(thieno[3,4‐c]pyrrole‐4,6‐dione) ( BTPD ), and 3,4‐dicyanothiophene ( DCT )] using direct heteroarylation polymerization (DHAP) methodology. Alternating copolymers with low‐lying frontier orbitals suitable for n‐type semiconducting behavior were obtained. Under optimized conditions, polymerization reactions were reproducible and high number‐average molecular weights (M _n) were achieved. Density functional theory (DFT) calculations indicated that the structures with the lowest conformational energy had planar backbones. Preliminary results showed that these new low‐bandgap materials exhibit good n‐type behavior.     

Micro‐ and Macrophase Separation in Phenolic Resol Resin/PEO‐PPO‐PEO Block Copolymer Blends: Effect of Hydrogen‐Bonded PEO Length

We demonstrate microphase‐separated thermosets based on blends of phenolic resol resin and poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐PPO‐PEO), i. e., so‐called Pluronics. Three triblock copolymers are used (PE 9200, PE 10300 and PE 9400) where the molecular weights of the PPO blocks are nearly equal and the weight fractions of the PEO blocks f_PEO are 0.20, 0.30 and, 0.40, respectively. The blends are prepared in a particularly straightforward way using aqueous solutions and thermal crosslinking. Structure formation is characterized using transmission electron microscopy and small‐angle X‐ray scattering. PPO turns out to be sufficiently repulsive to allow microphase separation in the bulk crosslinked phase and the tendency for macrophase separation upon curing is reduced due to the hydrogen bonding between the PEO and resol. The weight fraction of PEO‐PPO‐PEO in the present blends has been limited to a relatively small value, i. e., 20 wt.‐%, and spherical microphase‐separated structure is observed for f_PEO = 0.40 with a long period of the order 120 Å. Macrophase separation manifests upon curing if the weight fraction of the PEO blocks is smaller, i. e., f_PEO = 0.30 or f_PEO = 0.20. In addition, in order to prevent macrophase separation, the molecular weights of PEO blocks and resol resin before curing are of the same order. In that respect, the system behaves qualitatively similar to the corresponding thermoplastic homopolymer/block copolymer blends.     

Substituted and branched polychalcones, 2. Polymeric and solubility properties of the polychalcones

The polymeric and solubility properties of polychalcones 2a, b prepared by Friedel-Crafts acetylation of vanillin ( 3a ) and p-hydroxybenzaldehyde ( 3b ) were investigated. The polymers had limited solubility, and only polychalcones obtained from vanillin were completely soluble in dimethyl sulfoxide (DMSO); the others swelled in this solvent. Approximate values for the average molecular weights between cross-links, M _c, were calculated from the swelling in DMSO using the Flory-Rehner equation. Average molecular weights (M _w and M _n) and molecular weight distributions of the soluble fraction were determined by gel permeation chromatography on Sephadex G gels in DMSO. M _n corresponded to the molecular weights of the polymers in ethanol and of the acetylated materials in chloroform obtained with a vapour pressure osmometer.     

Role of cyclization in the synthesis of hyperbranched aliphatic polyesters

The intramolecular cyclization in hyperbranching polycondensation reactions of the type AB₂/B_f was investigated both theoretically and experimentally. Hyperbranched aliphatic polyesters prepared from 2,2‐bis(hydroxymethyl)propionic acid (BisMPA) and 1,1,1‐tris(hydroxymethyl)propane (TMP) as B₃ core molecule as well as commercially available samples with ethoxylated pentaerythrol as B₄ core (Perstorp, Boltorn^®) have been investigated with a combination of methods (NMR, vapor pressure osmometry (VPO), size exclusion chromatography (SEC), MALDI‐TOF‐MS) with respect to the formation of intramolecular cycles during polymerization. Absolute molecular weights were determined for the first time and found to be in the range of 632 (G2) to 1046 g/mol (G5) and 827 (PG2) to 1974 g/mol (PG5) for the commercial samples, respectively, i. e. considerably lower than reported previously. Theoretical considerations as well as experimental data clearly demonstrate cyclization to be an important reaction regardless of the presence of a core. The fraction if cyclized molecules was found to increase with molecular weights from 32% to 48%, limiting molecular weights drastically. In summary, previously reported results could not be confirmed. Incremental addition of the BisMPA monomer to the TMP‐core did not permit to control molecular weights and the term “pseudogeneration” is inappropriate for the low molecular weight materials formed.     

Soluble,well-defined copper(I) and silver(I) coordination polymers from 4,4″-bis((9-aryl)-2-o-phenanthrolinyl)-2′,5′-dihexyl-p-terphenyl

A novel synthetic concept is presented which allows, for the first time, the preparation of soluble, constitutionally well-defined transition-metal coordination polymers of considerable molecular weights from kinetically unstable, pseudotetrahedral copper(I)- and silver(I)-phenanthroline complexes. It is demonstrated that rigorous exclusion of all molecules that might act as competitive ligands for the metal ions of the polymer constitutes the central requirement for obtaining solutions of “proper” coordination polymers, i.e., polymers having a constant number of repeating units per individual chain. Tetrachloroethane was found to be an appropriate solvent for this purpose. Solubility of the copper(I) and silver(I) coordination polymers – which are polyelectrolytes – in this rather apolar solvent was achieved by the attachment of two hexyl side chains to each polymer repeating unit. It was thus possible to prove the defect-free constitution of the obtained coordination polymers and to show their excellent stability in solution with the aid of ¹H and ¹³C NMR spectroscopy. Moreover, formation of coordination polymers of considerable chain lengths is supported by the complete disappearance of end-group absorptions in the ¹H NMR spectra and the results of viscosimetric investigations.     

Alkyne–Azide Click Polymerization Catalyzed by Magnetically Recyclable Fe3O4/SiO2/Cu2O Nanoparticles

The Cu(I)‐catalyzed click polymerization fully meets the trend of developing powerful and economic tools for facile synthesis of functional polymers. However, the use of Cu(I) catalyst generally results in polymers with high copper residuals, which complicate the polymer purification and limit their applications. Moreover, these catalysts can only be used one time. Inspired by the report that Fe₃O₄‐based nanoparticles can be used as magnetically recyclable catalysts, these magnetic nanoparticles are used to produce Fe₃O₄/SiO₂/Cu₂O catalysts. These magnetic nanoparticles can efficiently catalyze the azide–alkyne click polymerization under mild reaction conditions, producing 1,4‐regioregular polytriazoles with high molecular weights in excellent yields. The copper residuals in the polymer products are much lower than those catalyzed by the conventional Cu(I) catalysts. Moreover, the Fe₃O₄/SiO₂/Cu₂O can be recycled and reused for at least 12 times. Introducing aggregation‐induced emission (AIE)‐active tetraphenylethylene unit into the polymer main‐chains endows the resultant polymer with AIE feature, too. Thus, this work not only simplifies the polymer purification procedures, but also provides a general strategy to reduce the copper residues in the polymers.     

Preparation and Thermoresponsive Properties of UCST‐Type Polypeptide Bearing p‐Tolyl Pendants and 3‐Methyl‐1,2,3‐triazolium Linkages in Methanol or Ethanol/Water Solvent Mixtures

A series of ionic polypeptides bearing p‐tolyl pendants and 3‐methyl‐1,2,3‐triazolium linkages is synthesized by N‐alkylation and subsequent ion‐exchange reaction. ¹H NMR and Fourier transform infrared (FTIR) analysis verify their molecular structures and reveal quantitative conversions. The nonionic polypeptides bearing p‐tolyl pendants and 1,2,3‐triazole linkages show no thermoresponsiveness in various solvents. The resulting ionic polypeptides (i.e., P2) are able to show reversible upper critical solution temperature (UCST)‐type phase behaviors both in methanol and ethanol/water binary solvent mixtures by incorporation with proper counteranions (i.e., iodide). FTIR analysis reveals that P2 may have interacted with solvent molecules via the van der Waals interaction, H‐bonding, and dipolar–dipolar interactions. Variable‐temperature UV–vis spectroscopy reveals that the UCST‐type phase transition temperatures (T _pts) of P2 are in the range of about 26–37 °C in MeOH and in the range of about 11–46 °C in EtOH/H₂O solvent mixtures depending on the main‐chain length, polymer concentration, and the weight percentage of ethanol (f _w).

     

Protection and Polymerization of Functional Monomers, 31. Living Anionic Polymerization of Styrene Derivatives m,m′‐Disubstituted with Acetal‐Protected Monosaccharide Residues

Two new styrene derivatives m,m′‐disubstituted with acetal‐protected monosaccharide residues, 3,5‐bis(1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose‐3‐oxymethyl)styrene ( 1 ) and 3,5‐bis(1,2:3,4‐di‐O‐isopropylidene‐α‐D ‐galactopyranose‐6‐oxymethyl)styrene ( 2 ) were synthesized viahigh yielding eight reaction steps starting from isophthalic acid. Their anionic polymerizations were carried out with sec‐BuLi in THF at –78°C for 30 min. Both monomers, 1 and 2 , were found to undergo living anionic polymerization to afford quantitatively the polymers of predictable molecular weights and narrow molecular weight distributions (M̄_w/M̄_n < 1.08). Novel AB and BA diblock copolymers of 1 and styrene were also successfully synthesized. Complete deprotection of the acetal protective groups by treatment with trifluoroacetic acid was achieved to quantitatively regenerate D ‐glucose and D ‐galactose. The resulting polymers were highly water‐soluble polymers as expected.     

EPDM Synthesis by the Ziegler Catalyst Cp*TiMe3/B(C6F5)3

The utilization of the Ziegler catalyst Cp*TiMe₃/B(C₆F₅)₃ for the terpolymerization of ethylene, propylene and 5‐ethylidene‐2‐norbornene to give EPDM is investigated, and the major factors affecting yields, molecular weights, molecular weight distributions and compositional distributions of the EPDM polymers are assessed. High molecular weight polymers with narrow molecular weight distributions are obtained at ˜18°C.     

Synthesis and Characterization of α,ω‐Telechelic Polymers by Atom Transfer Radical Polymerization and Coupling Processes

Initiators for atom transfer radical polymerization (ATRP) bearing different functional groups (aldehyde, aromatic hydroxyl, dimethyl amino) were synthesized and characterized. Monotelechelics with low molecular weight were obtained by ATRP of styrene using these initiators in the presence of the CuBr/bpy catalytic complex. α,ω‐Telechelic polymers with double molecular weights with respect to the starting materials were prepared by coupling of monotelechelics under atom transfer radical generation conditions, in the absence of monomer, using CuBr as catalyst, tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand, under Cu⁰ mediated reductive conditions and with toluene as solvent. Terminal Br atoms present in monotelechelic polystyrenes (PS) as a consequence of the ATRP mechanism also offer other routes for preparing telechelic polymers. Aldehyde functionalized polymer was etherified with hydroquinone furnishing telechelic PS with a molecular weight that was two times higher. All polymers were characterized by spectral methods (NMR, IR spectroscopy) as well as by GPC.

Synthesis of initiators for atom transfer radical polymerization bearing different functional groups, for example, aldehyde, aromatic hydroxyl, dimethyl amino.     

Living cationic polymerization of styrene by 1-chloroethylbenzene/tin(IV) chloride in chloroform

Living cationic polymerization of styrene in the presence of 1-chloroethylbenzene (1-CEB)/SnCl₄ as an initiating system has been investigated in chloroform at -15 to +20°C. The best results were obtained at -15°C. Under these conditions, the number-average molecular weight (M?_n) of the products increases linearly with increasing monomer conversion. The molecular weight of the polymer produced could be further increased by adding additional monomer. The molecular weights are in good agreement with the calculated values assuming that one living polymer chain is formed per one 1-CEB molecular. The molecular weight distributions of the polymers obtained are narrow (ratio of weight- to number-average molecular weights 1,07 ≤ M?_w/M?_n ≤ 1,17). The living character of these polymerizations depends on the polarity of the solvent and on temperature.     

Synthesis and properties of (D)- and (L)-lactide stereocopolymers using the system achiral Schiff's base/aluminium methoxide as initiator

The polymerization of lactides with various D /L enantiomeric compositions using achiral Schiff's base/aluminium methoxide as initiator (SALENAlOCH₃) in dichloromethane solution at 70°C is reported. The conversion was kept below 70% in order to limit transesterification reactions. The polymers obtained after precipitation show a narrow molecular weight distribution (ratio of weight- to number-average molecular weights M _w/M _n = 1,1–1,2) and an optical rotation higher than that expected from the optical purity of the starting monomers. The examination of the thermal properties reveals that whatever their enantiomeric composition all the prepared polymers are crystalline. This unusual behavior is explained by an end-chain propagation mechanism producing stereocopolymers with long enantiomeric sequences, i.e., increased isotacticity as substantiated by an examination of the microstructure of the polymers by means of ¹³C nuclear magnetic resonance. A stereocomplex formation was observed for stereocopolymers with optical purities below 40%.     

Synthesis,Properties, and Solar Cell Performance of Poly(4‐(p‐alkoxystyryl)thiazole)s

A series of polythiazoles (PvTzs) featuring conjugated styryl sidechains equipped with different solubilizing p‐alkoxy‐groups (? OR, R = n‐octyl, n‐dodecyl, 2‐ethylhexyl, 2‐hexyldecyl) is prepared by Negishi‐coupling polycondensation. Soluble material with number‐average molecular weights of up to M_n = 8.5 kDa (polydispersity (PDI) = 1.3, degree of polymerization (DPn) ≈ 20) is obtained, with a head‐to‐tail content of the PvTzs of ≈77%, as estimated from comparison with reference polymers. The polymers exhibit optical absorption properties similar to their polythiophene analogues, while their electrochemical characterization shows a significant stabilization of their frontier orbital levels. Fluorescence measurements indicate that upon excitation of the electron rich alkoxystyryl side‐chains charge transfer onto the more electron deficient polythiazole backbone occurs. This finding is corroborated by density functional theory (DFT) calculations on oligomeric model systems, which also consistently reproduce the optical properties observed for the polymers. The potentialities of these materials for applications in organic electronics can be demonstrated by their use as donor materials in organic photovoltaic cells, which exhibit higher open circuit voltages (V_OC, up to 0.86 V) than P3HT‐ or analogous polythiophene‐based cells (V_OC = 0.5–0.6 V).     

Synthesis and Solution Processing of Nylon‐5 Ferroelectric Thin Films: The Renaissance of Odd‐Nylons?

Among odd‐nylons, nylon‐5 exhibits the highest remanent polarization and is thus a desirable material for many applications of ferroelectric polymers. However, nylon‐5 has never been used as a ferroelectric material, because the synthesis of nylon‐5 and its processing into thin films are challenging. This work revisits the synthesis of nylon‐5 via anionic ring opening polymerization (AROP) and studies the effect of reaction time and scale‐up on (i) molecular weight (M_n), (ii) melting point (T_m), (iii) yield, and (iv) ferroelectric properties. For the first time, the molecular weight of nylon‐5 is characterized via size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, as well as matrix assisted laser desorption ionization time of flight mass spectroscopy (MALDI ToF‐MS), showing M_n values of up to 12 500 g mol^‐1. Extended reaction times and the synthesis on a larger scale increase the molecular weight and yield. Nylon‐5 thin films are fabricated from a TFA:acetone (60:40 mol%) solvent mixture. Nylon‐5 thin‐film capacitors are ferroelectric and show a remanent polarization as high as 12.5 ± 0.5 μC cm^‐2, which is stable in time. The high remanent polarization values, combined with the facile solution processing, render nylon‐5 a promising candidate for future microelectronic and multi‐ferroic applications.     

Synthesis and Fluorescence Properties of Chiral Near‐Infrared Emissive Polymers Incorporating BODIPY Derivatives and (S)‐Binaphthyl

A new series of π‐conjugated chiroptical polymers consisting of styryl BODIPYs moieties and (S)‐binaphthyl units has been firstly synthesized via Sonogashira polymerization. The resulting polymers were characterized by ¹H NMR spectroscopy, gel permeation chromatography (GPC), UV–Vis absorption spectroscopy, cyclic voltammetry (CV), circular dichroism (CD), and density functional theory (DFT) calculations. The chiral polymers have moderate molecular weights, high solubility in commonly solvents and stable chiroptical conformation. And more importantly, the four chiral polymers can exhibit near‐infrared (NIR) emissive and good anisotropic fluorescence. We anticipate these chiral NIR polymers will be useful in biological measurements and cellular imaging where NIR emission is beneficial.     

Saccharide polymers, 1, Synthesis and polymerization of methyl 5-deoxy-2,3-O-iso-propylidene-ß-D-erythro-pent-4-enofuranoside

New “saccharide polymers” were synthesized. For this purpose the synthesis and the polymerization of an unsaturated sugar monomer, methyl 5-deoxy-2,3-O-isopropylidene-ß-D -erythro-pent-4-enofuranoside, briefly called “exo-ribene”, is described. All polymers, homo-and co-polymers, were synthesized under free radical conditions. The structures and compositions of the soluble “saccharide polymers” were established by elemental analysis, ¹H and ¹³C NMR, and FT-IR spectroscopy. Some characteristics e. g. molecular weights and optical rotations are reported. Depending on the comonomer reactivity and under optimized chain reaction conditions, saccharide polymers with various sugar content and high molecular weights have been obtained.