Synthesis and Polymerization of Fused‐Ring Thienodipyrrole Monomers

The synthesis and polymerization of fused‐ring 1,7‐didodecyl‐1,7‐dihydrothieno[3,2‐b:4,5‐b′]dipyrrole monomer are reported. The FeCl₃‐mediated oxidative polymerization and Stille coupling polymerization of the thienodipyrrole monomer were employed to generate homopolymers and an alternating copolymer with thiophene. The synthesized polymers have molecular weights ranging from 1600 to 6500 g mol^?1 and display the absorption maxima at ≈355 nm.     

Hyperbranched Polyalkoxysiloxanes via AB3‐Type Monomers

We have synthesized polyethoxysiloxanes starting from the AB₃‐type monomers triethoxysilanol and acetoxytriethoxysilane. The polymers are liquid and soluble in organic solvents. ²⁹Si NMR spectroscopy and MALDI‐ToF mass spectrometry analyses show that the polymers have a hyperbranched structure with additional internal cyclization. ²⁹Si NMR spectroscopy indicates that the polymer synthesized from acetoxytriethoxysilane is less branched than the polymer synthesized from triethoxysilanol. Analysis of the molar mass and mass distribution of the polymers via size exclusion chromatography (calibrated via MALDI‐ToF MS and viscosimetry) yields a molar mass of M _n ≈ 2 kg · mol^?1 and M _w ≈ 8 kg · mol^?1 for polymers synthesized from triethoxysilanol. The molar mass of the polymers synthesized from acetoxytriethoxysilane can be controlled by variation of the polymerization time in the range of M _n ≈ 1.8–12 kg · mol^?1 and M _w ≈ 2.1–2 200 kg · mol^?1.

Photograph of a vial containing polyethoxysiloxane obtained from triethoxysilanol and a schematic drawing of the proposed molecular structure of the polymer.     

Role of High‐Molecular‐Weight Homopolymers on Block Copolymer Self‐Assembly: From Morphology Modifier to Template

For block copolymer (BCP)/homopolymer self‐assembly systems, the molecular weight of homopolymers is usually lower than that of BCPs. Herein, the cooperative self‐assembly of polystyrene‐b‐poly(ethylene glycol) (PS‐b‐PEG) BCPs with high‐molecular‐weight polystyrene (PS) homopolymers is reported. The molecular weight of PS homopolymers is 3–63 times that of the PS blocks. Typically, a spherical micelle–vesicle–large sphere morphology transition is observed by increasing the weight fraction of PS homopolymers in the polymer mixtures (f _HP). Dynamic process studies reveal that with adding water to the solution of polymer mixtures in organic solvent, the homopolymers first collapse into globules, and their size increases with f _HP and the molecular weight. Then these PS globules cooperatively self‐assemble with the PS‐b‐PEG BCPs. Depending on their size, these PS globules play different roles in the self‐assembly process. Small PS globules act as morphology modifiers inducing the micelle–vesicle transition, while large PS globules serve as self‐assembly templates for PS‐b‐PEG resulting in large spheres.     

Copolymerization of N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide with Arylacetylenes into Fluorescent Polyacetylene‐Type Conjugated Polymers

N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide (PNPr), i.e., the monomer with a terminal ethynyl group and 1,8‐naphthalimide fluorophore, has been successfully copolymerized with a series of monoethynylarenes into well‐soluble high‐molecular‐weight (M_w up to 210 000) linear polyacetylene‐type copolymers containing from 14 to 51 mol% units derived from PNPr. The copolymerization of PNPr with bifunctional 4,4′‐diethynylbiphenyl provides polyacetylene‐type micro/mesoporous fluorescent network containing 8 mol% PNPr units and exhibiting the Brunauer–Emmett–Teller surface of ≈1000 m² g^?1. The copolymerizations (catalyzed with acetylacetonato(norborna‐2,5‐diene)rhodium complex, [Rh(nbd)acac]) proceed smoothly despite the fact that the homopolymerization of PNPr fails. The fluorescence of PNPr (emission at ≈ 510 nm) has been retained after the incorporation of PNPr into the copolymers. The fluorescence of the copolymers can be induced by a direct excitation of PNPr units or via an energy transfer mechanism. In the latter case, the comonomeric units with aromatic hydrocarbon fluorophores (e.g., of the biphenyl‐type) emitting at 380–400 nm (after irradiation with 300 nm UV radiation) serve as energy donors for fluorescent PNPr acceptors. The difference between the wavelengths of the primary absorbed radiation and the finally emitted radiation is 210 nm.

     

Synthesis and Properties of a New Poly(arylene ethynylene) Containing 1,3,5‐Triazine Units

Summary: A new photoluminescent poly(arylene ethynylene) containing 1,3,5‐triazine units was prepared by polycondensation between 2,4‐diphenyl‐6‐N,N‐bis(4‐bromophenyl)amino‐1,3,5‐triazine and 1,4‐didodecyloxy‐2,5‐diethynylbenzene using Pd(PPh₃)₄ and CuI as the catalysts in the presence of triethylamine. The polymer showed good solubility in common organic solvents and had a number average molecular weight, , of 3 400, and a weight average molecular weight, , of 8 100. In toluene the polymer exhibited an intrinsic viscosity [η] of 0.11 dL · g^?1 at 30 °C. The polymer showed photoluminescence (PL) with emission peaks at 479 nm in CHCl₃ and at 509 nm in the solid state; quantum yield of the PL in CHCl₃ was 21%. Electrochemical reduction (or n‐doping) of the polymer started at about ?2.05 V versus Ag/AgNO₃ and gave a peak at ?2.30 V versus Ag/AgNO₃.

The 1,2,3‐triazine unit‐containing poly(arylene ethynylene) (PATZ) polymer synthesized and investigated here.     

Synthesis and properties of alternating polymers containing 2,6‐diaryldithienosilole and organosilicon units

Nickel‐complex‐catalyzed dehalogenative coupling of diGrignard reagents prepared from bis(bromoaryl)disilanes or monosilane with 2,6‐dibromodithienosiloles afforded the corresponding polymers composed of alternating 2,6‐diaryldithienosilole and organosilicon units. These polymers exhibit strong UV‐vis absorption and emission bands at 422–444 and 482–541 nm, respectively. Their cyclic voltammograms display the first oxidation peaks at 0.95–1.00 V vs. SCE (saturated Calomel electrode). When the polymer films were doped with FeCl₃ vapor, the films became conducting, and their conductivities were determined to be 3.3×10^–5 – 8.7×10^–3 S/cm using the four probe method. Electron‐ and hole‐transporting properties of the polymers were also studied by evaluating the performance of electroluminescent (EL) devices based on these polymers.     

Fiber‐Like Micelles from the Crystallization‐Driven Self‐Assembly of Poly(3‐heptylselenophene)‐block‐Polystyrene

The crystallization‐driven self‐assembly (CDSA) of crystalline‐coil polyselenophene diblock copolymers represents a facile approach to nanofibers with distinct optoelectronic properties relative to those of their polythiophene analogs. The synthesis of an asymmetric diblock copolymer with a crystallizable, π‐conjugated poly(3‐heptylselenophene) (P3C7Se) block and an amorphous polystyrene (PS) coblock is described. CDSA was performed in solvents selective for the PS block. Based on transmission electron microscopy (TEM) analysis, P3C7Se₁₈‐b‐PS₁₂₅ formed very long (up to 5 μm), highly aggregated nanofibers in n‐butyl acetate (nBuOAc) whereas shorter (ca. 500 nm) micelles of low polydispersity were obtained in cyclohexane. The micelle core widths in both solvents determined from TEM analysis (≈ 8 nm) were commensurate with fully‐extended P3C7Se₁₈ chains (estimated length = 7.1 nm). Atomic force microscopy (AFM) analysis provided characterization of the micelle cross‐section including the PS corona (overall micelle width ≈ 60 nm). The crystallinity of the micelle cores was probed by UV–vis and photoluminescence (PL) spectroscopy and wide‐angle X‐ray scattering (WAXS).     

Homo‐ and Co‐Polymers of Norbornene Containing Aryl‐ and Hetaryl‐Azo Dyes; Synthesis and Sensing Properties

A series of polynorbornene homo‐ and copolymers containing aryl‐ and/or hetaryl‐azo dyes were prepared through ring‐opening metathesis polymerization (ROMP). Thermal studies indicated that the polymers were thermally stable up to 250 °C, and possessed glass transition temperatures ranging from 93 to 133 °C. In THF solutions, the aryl‐azo dye containing homopolymers, displayed λ_max = 417 nm while the hetaryl‐azo dye containing homopolymers displayed λ_max = 495 nm. The copolymers displayed a λ_max that encompassed both the aryl‐ and hetaryl‐azo dye range. The monomers and polymers showed bathochromic shifts in solution when acidified. The polymers were cast into films that changed colour in the presence of both aqueous 1.2 M HCl or HCl_(g). The colour change reverses when exposed to aqueous 1.2 M NaOH or NH_3(g). This process was repeated several times without disintegration of the polymer film, indicating that these polymers may be useful as reusable acid sensors.

     

Polyphenylenes and Poly(phenyleneethynylene)s with 9,10‐Anthrylene Subunits

Summary: Light‐emitting conjugated polyphenylenes and poly(phenyleneethynylene)s have been synthesized, which comprise of 9,10‐linked anthracene repeat units with branched alkyl side‐chains (2‐octyldecyl) at the 2,6‐positions with p‐terphenyl ( P1 ), p‐diethynylbenzene ( P2 ), and diphenylacetylene ( P3 ) units. Both Sonogashira‐Hagihara and Suzuki‐Miyaura‐type cross‐coupling reactions under palladium catalysis were used as polycondensation methods. The branched alkyl side chains not only improve the solubility of the resulting copolymers but also prevent stacking in the solid state as evident from the almost identical PL spectra in solution and film. The copolymers P1 and P3 display pure blue emission while P2 exhibits green emission due to the extended π‐system along the polymer backbone. All polymers possess high thermal stability and P1 shows the best solubility and film‐forming ability among the three copolymers investigated. Furthermore, the enhanced color stability of this material is demonstrated by the almost identical PL spectra obtained on annealing at 200 °C.

Alternating copolymers P1 , P2 , and P3 .     

Synthesis and Photovoltaic Characterization of Dithieno[3,2‐b:2′,3′‐d]thiophene‐Derived Narrow‐Bandgap Polymers

Three novel dithieno[3,2‐b:2′,3′‐d]thiophene‐based low‐bandgap polymers are synthesized by a Suzuki–Miyaura coupling reaction or by direct arylation polycondensation. The polymers present a high molecular weight (26–32 kDa) and narrow polydiversity (1.3–1.7). With a highest occupied molecular orbital (HOMO) energy level around ?5.20 eV, these polymers exhibit a narrow bandgap of 1.75–1.87 eV. All the polymers display strong absorption in the range of 350–700 nm. Bulk‐heterojunction (BHJ) solar cells are further fabricated by blending the as‐prepared polymer with (6,6)‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) at different weight ratios. The best devices contribute a power conversion efficiency (PCE) of 0.73% under AM 1.5 (100 mW cm^?2).

     

cis‐Specific Living Polymerization of 1,3‐Butadiene with CoCl2 and Methylaluminoxane

The polymerization of 1,3‐butadiene was conducted by CoCl₂ combined with methylaluminoxane (MAO) as a cocatalyst at 0 and 18°C. The uni‐modal molecular weight distribution curves of the resulting polymers shifted toward higher molecular weight regions and became narrower when increasing the polymerization time. The number‐average molecular weight increased linearly with polymerization time, while the polymer yield increased exponentially in the initial stage. As a consequence, the number of polymer chains, calculated from the polymer yield and M̄_n, increased gradually with polymerization time to reach a plateau value. These phenomena was interpreted based on a slow initiation system without any termination and chain transfer reaction. The microstructure of the polymer was determined by ¹H NMR and ¹³C NMR spectroscopy to be a cis‐1,4 structure in a 98–99% purity.     

Isoindigo (IID)‐Based Semiconductor with F⋯S Interaction Locked Conformation for High‐Performance Ambipolar Bottom‐Gate Top‐Contact Field‐Effect Transistors

The development of high‐performance ambipolar polymer semiconductors is critical to organic electronics. Herein, isoindigo (IID)‐based copolymers PIIDDTBT and PIIDDTffBT are synthesized and characterized. Both polymers have suitable highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels for hole and electron injection. Density functional theory calculation reveals F?S intramolecular interactions are formed in PIIDDTffBT , which locks the molecular conformation and leads to a more planar backbone. Thin film transistor characterization shows both polymers display ambipolar charge carrier transport behavior. The hole/electron mobilities are 0.29/0.1 cm² V^?1 s^?1 for PIIDDTffBT and 0.053/0.013 cm² V^?1 s^?1 for PIIDDTBT in the bottom‐gate/top‐contact (BGTC) device structures. The hole/electron mobilities of PIIDDTffBT are one of the highest values for IID‐based ambipolar polymer transistors in BGTC device structure. Atomic force microscopy and X‐ray diffraction results reveal PIIDDTffBT films have higher film quality, crystallinity, and more ordered microstructures, being ascribed to the F?S interactions locked backbone. These results demonstrate that the introduction of F?S interactions is an effective strategy to design high‐performance ambipolar polymer semiconductors.     

Synthesis and Properties of Soluble,Strongly Fluorescent Poly(m‐Phenylene)s with Pendant Stilbene‐Based Chromophores

The nickel‐catalyzed dehalogenative coupling of substituted m‐dichlorobenzenes afforded a new series of poly(m‐phenylene)s with pendant 2,6‐bisstilbenyl‐N‐alkylpyridinium tetrafluoroborate groups. Characterization of polymers was accomplished by viscosimetry, GPC, FT‐IR, NMR, X‐ray, differential scanning calorimetry, thermomechanical analysis, UV‐vis, and luminescence spectroscopy. The polymers were amorphous and showed an excellent solubility being readily soluble at room temperature in THF, chloroform, and chlorobenzene. Their T_g values ranged from 96 to 148°C. The polymers with pendant stilbene‐based chromophores were strongly fluorescent both in solution and in solid state. Their photoluminescence (PL) spectra showed maxima at 391–410 nm and 445–532 nm in solution and in thin film, respectively. The structure of the alkyl attached to the pyridinium nitrogen influenced remarkably the PL quantum yield of polymers. The most efficient fluorescent polymers obtained were those bearing long chain aliphatic group on this nitrogen. Their PL quantum yield in THF solution was up to 0.65.     

Synthesis and Characterization of Poly(3‐alkylthiophene)s for Light‐Emitting Diodes

A serial of poly(3‐alkylthiophene)s with different alkyl chains substituted at 3‐position (3‐C_n‐PTs) was synthesized. The long‐chain alkyl group would enhance not only the processability but also the luminescence efficiency. The synthesized polymers were highly soluble in common organic solvents. The weight‐average molecular weights of the resulting polymers were in the range of 7 900–100 300 g/mol with molecular polydispersity indexes in the range of 1.88–8.70. The decomposition temperatures were in the range of 357.8–450.6°C determined by thermogravimetry analysis. A quasi‐reversible and stable electrochemical behavior for these polymers was observed in the oxidation process. The highest occupied molecular orbital, lowest unoccupied molecular orbital energy levels and band gaps were estimated by electrochemical as well as optical measurements. The UV‐Vis absorption spectra of the present polymers showed absorption bands around 400–427.5 nm in solution and 430–490 nm as thin solid films. The photoluminescence spectra showed strong light emission at ˜520 nm in chloroform and at ˜560–580 nm as thin solid film. Yellow‐orange light emission from the light‐emitting diodes with the structure of Indium‐tin oxide/poly(N‐vinylcarbazole)/3‐C_n‐PTs/Al using the polymers as the active emissive layers was achieved.     

Tannic Acid‐Inspired Star‐Like Macromolecules via Temporally Controlled Multi‐Step Potential Electrolysis

Inspired by tea stains, a plant polyphenolic‐based macroinitiator is prepared for the first time by partial modification of tannic acid (TA) with 2‐bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naturally occurring star‐like polymer with a polar gallotannin core and a hydrophobic poly(n‐butyl acrylate) side arms is synthesized via a simplified electrochemically mediated ATRP (seATRP), utilizing multiple‐step potential electrolysis. To investigate the kinetics of the electrochemical catalytic process triggered by reduction of Cu(II) or Fe(III) catalytic complex in the presence of the multifunctional initiator, cyclic voltammetry measurements are conducted. The naturally derived tannin macromolecule shows narrow MWDs (? = 1.57). Moreover, solvolysis of the star polymer to cleave the side arms and characterize them indicates that all chains grow to the same length (homopolymers with M_w/M_n <1.17), which confirms the well‐controlled seATRP. The structure of the obtained TA‐based systems is characterized microscopically (AFM) and spectroscopically (¹H NMR, FT‐IR). Atomic force microscopy measurements precisely determine the diameters of the obtained star polymers (19.7 ± 3.3 nm). These new star polymers may find biomedical applications as drug delivery systems and antifouling or antimicrobial coatings.     

Syndiospecific Living Block Copolymerization of Styrenic Monomers Containing Functional Groups,and Preparation of Syndiotactic Poly{(4‐hydroxystyrene)‐block‐[(4‐methylstyrene)‐co‐(4‐hydroxystyrene)]}

At –25°C, the sequential block copolymerizations of 4‐(tert‐butyldimethylsilyloxy)styrene (TBDMSS) and 4‐methylstyrene (4MS) were investigated by using a syndiospecific living polymerization catalyst system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe₃), trioctylaluminum (AlOct₃) and tris(pentafluorophenyl)borane (B(C₆F₅)₃). The number‐average molecular weight (M̄_n) of the poly(TBDMSS)s increased linearly with increasing the polymer yield up to almost 100 wt.‐% consumption of TBDMSS used as 1^st monomer. The M̄_n value of the polymer after the second monomer (4MS) addition continued to increase proportionally to the polymer yield. The molecular weight distributions (MWDs) of the polymers remained constant at around 1.05–1.18 over the entire course of block copolymerization. It was concluded that the block copolymerizations of TBDMSS and 4MS with the Cp*TiMe₃ /B(C₆F₅)₃ /AlOct₃ catalytic system proceeded with a high block efficiency. The ¹³C NMR analysis clarified that the block copolymers obtained in this work had highly syndiotactic structure. By the deprotection reaction of silyl group with conc. hydrochloric acid (HCl), syndiotactic poly{(4‐hydroxystyrene)‐block‐[(4‐methylstyrene)‐co‐(4‐hydroxystyrene)]} (poly[HOST‐b‐(4MS‐co‐HOST)]) was successfully prepared.     

Preparation of New Hole Transport Polymers via Copolymerization of N,N ′‐Diphenyl‐N,N′‐bis(4‐alkylphenyl)benzidine (TPD) Derivatives with 1,4‐Divinylbenzene

Monomers containing N,N ′,N,N ′‐tetraphenylbenzidine (TPD) were prepared by introducing two alkyl or alkoxy substituents into the p‐position of two of the four phenyl groups in the triphenylamine unit. The monomers were copolymerized with 1,4‐divinylbenzene (DVB) in the presence of p‐toluenesulfonic acid and Lewis acids, such as SnCl₄ and BF₃. The polymerization conditions and the catalyst types showed a marked influence on yield, molecular weight and even polymer structure. ¹H NMR measurements revealed that, by using p‐toluenesulfonic acid as a catalyst, the linkage between the TPD unit and DVB occurs at the p‐position of the phenyl group and at the m‐position of the tolyl group in the TPD unit, whereas, with SnCl₄ or BF₃ catalyst, substitution occurs exclusively at the p‐position of TPD. All polymers are soluble in common organic solvents, which allows the preparation of thin films of good quality. The rigid structure of the polymeric backbone results in a high thermal stability up to 400°C. The results of ionization potential measurements and the redox behavior showed that the introduction of the TPD unit into this kind of polymer backbone does not change its electronic structure. On the basis of high electroactivity, the polymers were successfully used as hole transport layers in two‐layer electroluminescence devices.     

π‐Conjugated Polymers Consisting of Isothianaphthene and Dialkoxy‐p‐phenylene Units: Synthesis,Self‐Assembly,and Chemical and Physical Properties

A series of π‐conjugated alternating copolymers consisting of Th‐ITN‐Th and p‐C₆H₂(OR)₂ units were synthesized. XRD indicated that the copolymers assume an interdigitation packing mode, and UV‐Vis spectra revealed a strong tendency for self‐assembly. Upon molecular assembly of the copolymer, the UV‐Vis absorption shifted by about 100 nm to a longer wavelength from that of the single molecule. The copolymers underwent electrochemical oxidation (or p‐doping) and reduction (or n‐doping) at 0.2 and ?2.0 V versus Ag⁺/Ag, respectively. A p‐doped copolymer film showed an electrical conductivity of 182 S · cm^?1, and the temperature dependence of electrical conductivity was measured. The copolymer showed piezochromism and served as a p‐channel material for a field‐effect transistor.

     

N‐Isopropylacrylamide/2‐Hydroxyethyl Methacrylate Star Diblock Copolymers: Synthesis and Thermoresponsive Behavior

Summary: Tri‐arm star diblock copolymers, poly(2‐hydroxyethyl methacrylate)‐block‐poly(N‐isopropylacrylamide) [P(HEMA‐b‐NIPAAm)] with PHEMA and PNIPAAm as separate inner and outer blocks were synthesized via a two‐step ATRP at room temperature. The formation, molecular weight and distribution of polymers were examined, and the kinetics of the reaction was monitored. The PDI of PHEMA was shown to be lower, indicating well‐controlled polymerization of trifunctional macro‐initiator and resultant star copolymers. The thermoresponsive behavior of diblock copolymer aqueous solution were studied by DSC, phase diagrams, temperature‐variable ¹H NMR, TEM and DLS. The results revealed that introducing a higher ratio of HEMA into copolymers could facilitate the formation of micelles and the occurrence of phase transition at lower temperatures. TEM images showed that I‐(HEMA₄₀‐NIPAAm₃₂₀)₃ solutions developed into core‐shell micelles with diameters of approximately 100 nm. I‐(HEMA₄₀‐NIPAAm₃₂₀)₃ was used as a representative example to elucidate the mechanism underlying temperature‐induced phase transition of copolymer solution. In this study we proposed a three‐stage transition process: (1) separately dispersed micelles state at ≈17–22 °C; (2) aggregation and fusion of micelles at ≈22–29 °C; (3) sol‐gel transition of PNIPAAm segments at ≈29–35 °C, and serious syneresis of shell layers.

Molecular architecture of Poly(HEMA‐b‐NIPAAm).     

Self‐Assembly and Responsive Behavior of Poly(peptide)‐Based Copolymers

Well‐defined copolymers synthesized by combining poly(ethylene glycol) (PEG) and amino acid based building blocks are investigated with regard to their helical rigidity and self‐assembly. Optical active block copolymers reported here are designed to have a pendant amino acid and polymerizable group, that is, isonitrile in order to induce helix formation and reduce the mobility of polymer chains by forming a hydrogen bond network so that a helix with reasonable rigidity can be obtained. Due to the amphiphilicity and a relatively shorter PEG as a coil, these polymers form micelles as observed under transmission electron microscopy in which copolymers PEG₁₀₈‐b‐PPIC₇₆₄ and PEG₁₀₈‐b‐PPIC₁₀₂₀ appear to be evolving into nanoparticles with a size distribution of 100–200 nm. Circular dichroism spectroscopy is employed to study the nature of the helix and its rigidity. The folding and unfolding of polymer helix as a result of the ability of a selective solvent to form/disrupt hydrogen bonds with the peptide linkage is also discussed to highlight the responsive nature of the polymer.