A block copolymer containing P3HT and C60 is synthesized and subjected to single‐molecule spectroscopy (SMS) and AFM studies to investigate the impact of the C60 on the P3HT chain conformation and the phase‐separation behavior upon annealing, respectively. Both the SMS and the single‐molecule polarization investigations indicate that the grafting of the C60‐containing block to the P3HT moiety does not significantly change its conformational structure. AFM studies on thin films of the block copolymer indicate that they are stable with microphase separation, while blended films of the block‐copolymer precursor (without C60) with PCBM undergo macroscale phase separation upon thermal annealing.
The synthesis, thermal, and photoluminescence properties of novel platinum metallopolyynes of electron‐deficient acridone derivatives with electronically tunable bandgaps and their molecular model complexes are described. Polymer P2 has an optical bandgap (Eg) of 2.10 eV which is much lowered than that of P1 (2.60 eV). The incorporation of electron‐accepting dicyanomethylene units on the acridone ring in the main chain creates a strong π‐conjugated system that features unique donor‐acceptor interactions and intramolecular charge‐transfer states.
Oriented films of miscible polymer blends of poly(vinylidene fluoride) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] were prepared using a flow‐orientation technique. The lamellar structure and crystal orientation depended upon composition and flow temperature (Tflow). An interlamellar exclusion structure was induced in the blend flow‐oriented below 150 °C, whereas an interlamellar inclusion structure was developed above 150 °C. The crystal orientation of PHBHV was affected by the lamellar structures because the PHBHV chains crystallized in the pre‐existing crystalline morphology of PVDF. Crystallization of PHBHV was markedly restricted at lower PHBHV contents.
An alternating copolymer (PBDTC10DBT) of benzo[1,2‐b:3,4‐b′]dithiophene (BDT) as donor and 4,7‐di(3‐decylthiophen‐2‐yl)‐2,1,3‐benzothiadiazole (C10DBT) as acceptor is designed and synthesized. In order to investigate the effect of the 1,8‐diiodooctane (DIO) additive on the morphology and photovoltaic performance, polymer solar cells (PSCs) based on PBDTC10DBT:[6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) are fabricated. The morphology of blend films and the interpenetrating network between the donor and the acceptor is examined using atomic force microscopy and scanning electron microscopy. This work shows that the PBDTC10DBT:PC61BM blend films with added DIO (3%, v/v) have improved absorption and controlled phase separation. Morphology with a domain size of 20–30 nm that forms in the DIO system is proposed to facilitate charge transport and minimize charge carrier recombination, which are the main reasons why the power conversion efficiency of the PSCs is improved from 1.93% (without DIO) to 2.23% (with DIO).
Reactive species in SiO2‐supported, zirconocene‐based olefin‐polymerization catalysts have been characterized by comparison of their UV‐vis spectra with those of related, NMR‐spectroscopically identified catalyst species in homogeneous solution. Neutral zirconocene dihydride complexes are found to arise in hydrocarbon solutions as well as on SiO2 supports when catalyst systems that contain rac‐Me2Si(ind)2ZrCl2 and methylaluminoxane (MAO) are modified by addition of diisobutylaluminum hydride or triisobutylaluminum. These complexes, tentatively formulated as adducts with Lewis‐acidic alkylaluminum species AlR2X, rac‐Me2Si(ind)2ZrH2 · {nAlR2X}, are reconverted into the initial reactive zirconocene cations upon addition of isobutene to these reaction systems.
Temperature‐ and pH‐sensitive diblock copolymers PAANa75‐b‐PNIPAMm are prepared by a combination of reverse and normal ATRP in aqueous solution at room temperature. The block copolymer is also stimuli‐sensitive with respect to salt in the aqueous solution, and forms spherical star‐like micelles with a PNIPAM core and an expanded PAANa shell for PAANa75‐b‐PNIPAM76 as well as spherical crew‐out micelles with a PNIPAM core for PAANa75‐b‐PNIPAM5110, as indicated by a fluorescence probe technique and TEM. A three‐stage model mechanism of phase transition driven by small molecule salt is proposed.
The self‐assembly of PVPh‐b‐PS in different solvents was studied. Upon replacing toluene by THF as the solvent, the morphology of the resulting aggregates change from core‐shell spheres, rod‐like micelles and vesicles to onion‐like aggregates. With increasing block copolymer concentration, morphologies such as honeycomb‐like films, surfaces of aggregated large porous spheres, or pincushion‐like spheres with protruding tubular vesicle aggregates are observed. These surface‐patterned films show significantly enhanced hydrophobicity. The results suggest that a superhydrophobic behavior can be achieved, with a maximum contact angle of 158°, by using the pincushion‐like micellar structure.
An aqueous solution containing acryloyl‐type monomers or polymers undergoes gelation by UV irradiation in the presence of APS as UV‐photoinitiator. We investigate the mechanism of the UV‐induced gelation using LS and ESR. In LS, the dependence of the gelation time tgelation on the APS concentration CAPS is demonstrated for NIPAm solutions, and the relation between CAPS and tgelation fits a power law function, i.e., tgelation ～ C, indicating that UV‐induced gelation progresses according to a radical polymerization mechanism. On the other hand, ESR data reveal that the UV‐induced cross‐linking reaction takes place at α‐carbon atoms in acryloyl‐type monomers and polymers.
A novel conjugated oligomer, oligo(9,9′‐dioctylfluorene‐alt‐bithiophene) (OF8T2), was found to exhibit a unique phase transition between crystalline and liquid‐crystalline states, and a liquid‐crystalline glass was easily generated, offering better TFT device performance. In thin films, upon annealing the OF8T2 molecules oriented preferentially with their planes of conjugation being normal to the substrate, and both film thickness and annealing temperature were critical to the film morphology and the molecular orientation. When the OF8T2 film was deposited on a rubbed polyimide surface and annealed, the molecules aligned their long axes along the rubbing direction.
P2VN‐b‐PAA is a novel diblock copolymer which has potential as a self‐assembled nanoscale patterning material. Thin spin cast P2VN‐b‐PAA films rapidly reorganize to vertical lamellar with exposure to acetone vapor. P2VN‐b‐PAA lamellar morphology was aligned by electric field under acetone vapor at a significantly faster rate and at lower electric field strengths than other polymer systems. Observed dry etching selectivity for P2VN to PAA were comparatively high for a variety of etch gases, consistent with estimations from Ohnishi and ring parameters. Block copolymer self assembled patterns were transferred to silicon via two‐step CF4 and SF6 etching.
Nitrogen‐rich organic thin films were deposited by VUV‐assisted photochemical polymerisation of flowing C2H4/NH3 mixtures. The fundamental reaction mechanisms of these binary gas mixtures were investigated as a function of the wavelength of two almost monochromatic VUV sources. Compositions of these “UV‐PE:N” films close to the surface were determined by XPS, and the amine concentrations and selectivities were quantified via chemical derivatisation. The UV‐PE:N films were compared with plasma polymers deposited using low‐pressure glow discharges in similar gas flow mixtures, “L‐PPE:N”; it is shown that VUV photochemistry is superior to plasma chemistry in producing almost monofunctional organic thin films.
We describe results relating to the effect of halide counterion in the ROMP of a permanently cationic exo‐7‐oxanorbornene derivative. Statistical copolymerizations of exo‐benzyl‐[2‐(3,5‐dioxo‐10‐oxa‐4‐aza‐tricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)ethyl]dimethyl ammonium bromide/chloride were conducted at different molar ratios and the polymerizations evaluated with respect to their kinetic features, as well as their molecular mass profiles, as a function of conversion, and the ability to produce materials with narrow molecular mass distributions. The polymerization characteristics are rationalized in terms of the in situ formation of the mixed Grubbs' derivative RuClBr(PCy3)2CHPh and/or the dibromo analog RuBr2(PCy3)2CHPh.
Six conjugated polymers based on the indenopyrazine ( IPY) unit are designed and synthesized by copolymerization with different electron‐deficient and electron‐rich building blocks. All of the polymers show good solubility, excellent film‐forming ability, and low‐lying highest occupied molecular orbit (HOMO) energy levels. The effects of the different copolymerized units on the optical, electrochemical, and photovoltaic properties are investigated. Results indicate that their bandgaps and molecular energy levels are readily tuned by copolymerizing with electron‐deficient and electron‐rich units. Polymer solar‐cell devices are fabricated utilizing the polymers as electron donors and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) as an electron acceptor. The best power conversion efficiency of the cell based on PIPY‐DTBTA , one of the IPY‐ based polymers, reaches 0.77%, with a relatively high Voc up to 0.78 V.
Ethylene/4‐methyl‐1‐pentene (E/4M1P) copolymers were synthesized by [Me2Si(η5‐Me4C5)‐(η1‐N‐tBu)TiCl2] and methylalumoxane (MAO) catalyst ( CG ) and analyzed by 13C NMR. The low regio‐ and stereoregularity of CG leads to spectral multiplicities which can be ascribed not only to differences in comonomer sequences but also to the presence of regio‐ and stereoirregularities. The tendency of CG to give a nearly random comonomer distribution gives rise to so far undetectable alternating sequences. The complete set of assignments proposed allows a satisfactory characterization of variously microstructured E/4M1P copolymers and the evaluation of the amount of regioirregular sequences in addition to the full determination of dyad and triad copolymer composition.
New polydimethylsiloxanes with p‐substituted azobenzene side‐groups were synthesized. Thin films and solutions exhibit a photochemical trans‐cis isomerization of the azobenzene groups, followed by their cis‐trans thermal relaxation in the dark. In films, relaxation rates were found to be 100–1 000 times slower than the rates of photoisomerization, the former being very sensitive to the electron‐acceptor character of the substituents. in solution, the rates of cis‐trans relaxation are lower than those obtained for the solid state. This is ascribed to the dipolar intramolecular interactions between cis chromophores, which are favored in solution.
The effects of binding ligand variation on the externally initiated Ni catalyzed polymerization of P3HT were investigated using a novel methodology allowing facile screening of ligands. P3HT was synthesized with >80% initiator incorporation for both mono‐ and bidentate phosphine ligands. Variation of the initiating aryl group demonstrated vastly superior results for o‐tolyl over p‐tolyl substituents.
A novel approach to amphiphilic polymeric Janus micelles based on the protonation/deprotonation process of poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (P2VP‐b‐PEO) diblock copolymers in THF is presented. It is found that addition of HCl to the micelles solution of P2VP‐b‐PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl4 precursors, composite Janus particles containing gold in P2VP blocks are obtained.
The synthesis and phase behaviour of PB32 is reported. The results indicate that PB32 develops a low‐ordered smectic mesophase of the type SmCalt. The slow formation of such a mesophase allows the quenching of the isotropic melt into an amorphous state so that both amorphous glass and smectic glass can be obtained, which exhibit different glass‐transition temperatures. Mechanical tests indicate that the macromolecular chains in the mesophase of PB32 can be oriented either parallel or perpendicularly in relation to the streching direction, depending on the deformation conditions. Solid‐state 13C NMR spectroscopy results show that the mobility of the chains is rather similar in both phases.
We report on the controlled synthesis of amphiphilic and double‐hydrophilic block copolymers having poly(vinyl amine) segments by the reversible addition–fragmentation chain transfer (RAFT) polymerization of N‐vinylphthalimide (NVPI), followed by deprotection. The block copolymer poly(NVPI)‐b‐poly(N‐isopropylacrylamide) with a controlled molecular weight and low molecular mass distribution was obtained by the polymerization of N‐isopropylacrylamide (NIPAAm) using dithiocarbamate‐terminated poly(NVPI). The chain extension from the dithiocarbamate‐terminated polystyrene to NVPI could be controlled well under suitable conditions, and provided the block copolymer, polystyrene‐b‐poly(NVPI). We also investigated the thermoresponsive and optoelectronic properties and the aggregation behavior of double hydrophilic and amphiphilic block copolymers obtained after deprotection.
A newly established catalyst system for oxygen‐oxidative polymerization of diphenyl disulfide is reported. Combination of vanadyl compounds (e.g., VO(acac)2) and triphenylmethylium tetrakis(pentafluorophenyl)borate (TrB(C6F5)4) proceeds the polymerization to give poly(1,4‐phenylene sulfide) (PPS) at 100 °C. When triphenylmethylium tetrafluoroborate (TrBF4) is applied with vanadyl tetraphenylporphyrin (VO(TPP)) or N,N′‐(ethylenebis(salicylideneaminato))oxovanadium (VO(salen)), PPS is also given via polymerization under conditions near 160 °C. Combination of the vanadyl complex and the borate affords the first protic‐acid‐free catalytic system for the polymerization of the disulfide, suggesting the overall reaction to produce PPS and H2O from O2 and protons that are eliminated from the monomer.
