Development of novel processable electron accepting conjugated polymers containing fluoranthene units in the main chain

Considerable interest exists in the development of novel n-type conjugated polymers, since many currently available polymer systems have insufficient electron mobility and/or electron affinity. In this work, a universal synthesis route is presented towards a new class of n-type conjugated polymers, i.e. poly(p-fluoranthene vinylene) (PFV) and its derivatives. This route is illustrated with three examples, i.e. unsubstituted PFV and functionalized hexyl-PFV and dodecyl-PFV. All polymers have been synthesized via the dithiocarbamate precursor route. Solubility was introduced by incorporation of alkyl side chains, which leads to a significantly enhanced purity and processability as compared to unsubstituted PFV. Under the applied electrochemical conditions PFV-type polymers demonstrate typical n-type behavior. Additional CELIV mobility measurements on dodecyl-PFV reveal an excellent electron mobility, μ_e = 1.4 × 10⁻⁴ cm²/Vs. Hence, poly(p-fluoranthene vinylene) and its derivatives are promising n-type materials for organic optoelectronic applications.     

Synthesis of graft copolymers based on polyphenylene xylylene and fullerene grafted polystyrene

Graft copolymers containing poly(phenylene xylyene) (PPX) backbone and polystyrene fullerene (PSFu) grafting chains (PPX‐g‐PSFu) were prepared by using a purposed synthetic route comprising a combination of reaction mechanisms namely the modified Wessling route, an iniferter polymerization, and an atom transfer radical addition (ATRA). The monomer was first prepared by reacting dichloroxylene with tetrahydrothiophene. After that the monomer was polymerized in a sodium hydroxide solution to provide a polymer precursor. Subsequently, the polymer precursor was modified by reacting it with a dithiocarbamate (DTC) compound. The macroiniferter was obtained and then copolymerized with styrene and chloromethylstyrene via an iniferter polymerization. Finally, the graft copolymer was reacted with fullerene through an ATRA technique to attach the C60 groups onto the graft copolymer molecule. The products obtained from each of the steps were characterized by using various techniques including Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, UV–visible spectroscopy, and thermal gravimetric analysis. The aforementioned results suggest that the graft copolymers were prepared. The grafting yield and grafting efficiency were found to increase with the monomers concentration and the amount of DTC used. Some homopolymer contaminants also occurred but those could be minimized and subsequently removed by extraction with selective solvents. These graft copolymer products might be used for the development of a bulk heterojunction polymer solar cell. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The thermal conversion reaction of sulphonyl substituted poly(para-xylylene): evidence for the formation of PPV structures

The thermal elimination of the n-octyl-sulphonyl group from poly[1,4 phenylene (1-n-octyl-sulphonyl)-1,2-ethylene] and the phenyl-sulphonyl group from poly[1,4 phenylene (1-phenyl-sulphonyl)-1,2-ethylene] is evaluated by different analytical techniques: thermal gravimetric analysis, direct insert probe mass spectrometry, in situ ultraviolet-visible spectroscopy and in situ Fourier transform infra red spectroscopy. This thermal treatment yields PPV with improved optical properties compared to the conventional PPV concerning UV-absorption and photoluminescence efficiencies. The results obtained are consistent with the formation of a PPV with a more or less restricted conjugation length compared to the PPV material obtained from the conversion of a sulphinyl precursor polymer.     

A simple route to functionalize siloxane polymers for DMMP sensing

Hexafluoroisopropanol (HFIP) was the most widely used functional group for nerve agents detection. However, to incorporate HFIP group into a polymer backbone, highly toxic hexafluoroacetone gas was needed in a conventional synthetic route. In this article, a new route with low toxicity was proposed to synthesize a strong hydrogen‐bond acidic (HBA) siloxane polymer by using 2‐vinylhexfluoroisopropanol as the raw material in the hydrosilylation reaction. The synthesized fluoroalcoholic linear polysiloxane (LSFA) was characterized by FT‐IR, confirming its molecular structure was much similar to SXFA, a well‐established HBA polymer synthesized by the conventional route. TGA data verified the adduct's thermal stability. The dimethyl methylphosphonate (DMMP) sensing properties of LSFA and SXFA, along with PLF, were compared basing on the surface acoustic wave (SAW) platform. The results demonstrated that the conventional synthetic route was somewhat difficult to handle and control, while the new route was simpler, easier and was an effective and promising alternative. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4516–4520, 2013     

Low-temperature synthetic route for boron carbide

Boron carbide is one of the hardest materials with diamond-like mechanical properties, and is already used for a variety of applications including armor plating, blasting nozzles, and mechanical seal faces, as well as for grinding and cutting tools. It is produced on an industrial scale by classical carbothermal reduction of boric oxides at high temperatures, but the formation of pure boron carbide in processed forms, such as films and fibers, is difficult. As an alternative to high-temperature powder techniques, there is recently great interest in the development of polymer precursors to produce ceramic materials. The aim of the present work is to develop a cost effective and low-temperature manufacturing process to synthesize boron carbide from cheap and easily available raw materials. The initial objective of our research is the design and synthesis of a new type of boron–carbon polymer, which would serve as precursor for boron carbide. The polymeric precursor is synthesized by the reaction of boric acid and polyvinyl alcohol that after pyrolysis at 400 °C and 800 °C gives boron carbide. The polymeric precursor and its pyrolyzed products are characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). X-ray diffraction shows that boron carbide (B₄C) obtained from this method has an orthorhombic crystal structure. It is a unique low-temperature (∼400 °C) synthetic route for boron carbide.     

Synthesis and characterization of poly-(allylbenzene p-sulphonate) films incorporating electrolessly deposited Ni–P

The preparation of a novel electrode material is described. The ionic exchange properties of polymer films electrochemically prepared from the allyl ether of the p-benzenessulphonic acid monomer were explored with an incorporated ion of metallic crystallites in the polymeric matrix. The autocatalytic activity of the pristine and modified polymer for the electroless deposition of Ni–P from a hypophosphite containing solution was analyzed and conditions for the use of the deposition method to modify the nature and the size of the metal particles established. The performance of typical electrodes prepared by this route, e.g., polymer/Cu/Ni–P, towards the proton reduction reaction in buffer solution, when contrasted to polymer/Ni, revealed promising electrocatalytic activity. This behaviour, along with the simplicity of the preparation route makes these modified electrodes strong candidates to replace other systems for electrohydrogenation purposes.     

Proton abstraction as a route to electrically conductive polymers

Proton abstraction with a strong base from relatively acidic doubly allylic and/or benzylic methylene moieties spaced along an otherwise all-conjugated polymer chain has been demonstrated as an alternative route to electrically conductive polymers. Poly(p-phenylene pentadienylene) and its model compound 1,5-diphenylpentadiene, have been prepared via a Wittig reaction sequence. Proton abstraction from the methylene moiety of the model compound to form the delocalized carbanion has been achieved through reaction with n-BuLi and has been confirmed by reaction with methyl iodide. Proton abstraction from poly(p-phenylene pentadienylene) oligomers has been achieved by treatment with n-BuLi to yield a blue-black solid. Preliminary results indicate a conductivity of 10⁻¹−10⁰ S cm⁻¹ for a pressed pellet of the blue-black solid.     

Poly(p-tert-butoxycarbonyloxystyrene): a convenient precursor to p-hydroxystyrene resins

An efficient synthetic route to pure, high molecular weight poly(p-hydroxystyrene) is reported. The route involves synthesis of a new monomer, p-tert-butoxycarbonyloxystyrene, polymerization by radical initiation or by cationic initiation in liquid SO₂, followed by thermolysis or acidolysis of the tert-butoxycarbonyl protecting group. Porous, crosslinked resin beads containing the nucleophilic, phenol pendant group have been prepared in a similar fashion from the precursor terpolymer of p-tert-butoxycarbonyloxystyrene, styrene and divinylbenzene. The utility of this resin for solid-phase synthesis has been demonstrated.     

Processing route dramatically influencing the nanostructure of carbon-rich SiCN and SiBCN polymer-derived ceramics. Part I: Low temperature thermal transformation

In this study, the significant effect of the processing route on the nanostructure evaluation of carbon-rich SiCN and SiBCN polymer-derived ceramics is reported. For the first time, bulk carbon-rich SiCN and SiBCN ceramics are successfully produced by warm pressing of polyphenylvinylsilylcarbodiimide and polyborophenylsilylcarbodiimide. The bulk samples were compared with their analogous powder samples with respect to the developed nanostructure. Representative temperatures of 1100 and 1400 °C were chosen in order to investigate the effect of processing route used on the crystallization behavior of those samples. As the solid-state structure of polymer-derived ceramics (PDCs) is highly sensitive to the molecular structure of the precursor, the variation of processing route and pyrolysis temperature during the polymer to ceramic transformation and decomposition enables to alter the nanostructure of PDCs. It was found that the bulk carbon-rich SiCN and SiBCN ceramics show an improved thermal stability against crystallization as compared to their powder analogues.     

Single-source precursor route to carbon nanotubes at mild temperature

Carbon nanotubes were synthesized via a single-source precursor route at 500 °C, using iron carbonyl both as carbon source and catalyst. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Transmission electron microscope (TEM) images of the sample reveal carbon nanotubes with an average inner (outer) diameter of 30 nm (60 nm). High-resolution TEM indicates that fabrication of the carbon nanotube walls was composed of ca. 40 graphene layers. The Raman spectrum shows two strong peaks at 1587 and 1346 cm⁻¹, corresponding to the typical Raman peaks of graphitized carbon nanotubes. This method avoids the separation of raw material from solvent and simplifies the operation process. At the same time, the research provides a new route to large-scale synthesis of carbon nanotubes.     

Reversible addition-fragmentation chain transfer polymerization of 7-(4-(acryloyloxy)butoxy)coumarin

The light sensitive vinyl monomer with coumarin unit, 7-(4-(acryloyloxy)butoxy)coumarin (7AC), was synthesized. The reversible addition-fragmentation chain transfer (RAFT) polymerization of 7AC, initiated by 2,2′-azobisisobutyronitrile (AIBN), was carried out using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as a RAFT agent in N,N-dimethylformamide (DMF) solution. The kinetics exhibited first-order relationship with respect to the monomer concentration. The molecular weight of the polymer increased linearly with the monomer conversion. The chain extension of poly(7-(4-(acryloyloxy)butoxy)coumarin) (P7AC) using styrene (St) as the second monomer demonstrated that the obtained polymers were almost “living”. The fluorescence intensity of P7AC increased with the molecular weight of P7AC and was stronger than that of the monomer. The obtained polymer had strong ultraviolet (UV) absorption at 322 nm. The molecular weights of the polymer had no effect on its ultraviolet absorption intensity. The coumarin structure existing in P7AC underwent [2 + 2] cycloaddition reaction (photodimerization) under UV irradiation in tetrahydrofuran (THF) solution, which can be further used to prepare small particles from the single polymer.     

Structural control in radical polymerization with 1,1-diphenylethylene. Part 3. Aqueous heterophase polymerization

Results on aqueous heterophase polymerization in the presence of either 1,1-diphenylethylene or water-soluble precursor polymers containing an α,p-dimer unit of 1,1-diphenylethylene are reported. The precursor polymers are bound covalently to the particles due to a special kind of chain transfer reaction showing on the one hand some features of controlled radical polymerization and leading on the other hand to the formation of block copolymers. Moreover, the covalently bound precursor molecules act as very efficient colloidal stabilizers of the final dispersion and thus, they can be considered as reactive surfactant with the additional ability to control radical polymerization (controlsurf). Under optimum conditions the precursor polymer molecules are almost completely covalently attached to polymer particles. Results are presented regarding block copolymer yields, solids content, and particle diameter in dependence on the polymerization conditions, particularly the precursor polymer concentration, the monomer as well as the initiator concentration, and the initiator type. Under optimum conditions the attainable block copolymer yields and the solids content of the final latexes can be above 95 and about 40%, respectively. Based on experimental results the mechanism of this special kind of controlled radical polymerization under the peculiarities of aqueous heterophase polymerization is discussed.     

Electrochromic performance and ion sensitivity of a terthienyl based fluorescent polymer

A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents directly attached to the 3,4-positions of the central thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(3,4-ethylenedioxythiophen-2-yl)thiophene-3,4-dicarboxylate. The corresponding polymer was characterized by cyclic voltammetry, FT-IR and UV–vis spectroscopy. The polymer has a well-defined redox process (E_p,1/2 = 0.74 V) and demonstrates a reversible electrochromic behavior; lilac in the neutral state and transparent sky blue in the oxidized state. Also, the polymer had low band gap (E_g = 1.82 eV) and high redox stability (retaining 94.0% of its electro-activity after 500th switch). Moreover, the sensitivity of both the monomer and its polymer towards metal cations was investigated by monitoring the change in the fluorescence intensity. Among various common ions both the monomer and its polymer were found to be selective towards Cu²⁺ and Cu⁺ ions by quenching the fluorescence efficiency with a Stern–Volmer constant (K_sv) of (1.4–1.6 × 10³ M^?1) and (1.5–1.8 × 10² M^?1) for monomer and polymer solutions, respectively.     

A single component photoimaging system with styrene copolymers having t-BOC-protected quinizarin dye precursors and photoacid generating groups in a single polymer chain

A styrene monomer tBQSt, having a tert-butyloxycarbonyloxy (t-BOC)-protected quinizarin dye precursor as a pendent, has been copolymerized with N-(tosyloxy)maleimide (TsOMI) to obtain a dual functional polymer P(tBQSt/TsOMI). The polymer P(tBQSt/TsOMI), as a single component photoimaging system without using an external photoacid generator (PAG), was applied for fluorescent photopatterning by dry process based on the chemical amplification (CA) process. The TsOMI units in the polymer chains were responsible for photochemical generation of p-toluenesulfonic acid by UV exposure and the acid generated in the solution cast polymer film induced the catalytic deprotection of acid labile t-BOC groups of the quinizarin dye precursors. Accordingly, the quinizarin moieties were regenerated in the polymer chains by the CA process, thereby recovering the original color and fluorescence of the quinizarin dye. Fluorescent patterns were readily delineated on the thin polymer films by imagewise UV exposure even without a wet development process.     

Propylene polymerisations with novel heterogeneous combination metallocene catalyst systems

Propylene was polymerised with novel combination metallocene catalyst systems prepared by an emulsion-based heterogenisation method in liquid monomer conditions. The catalyst combinations investigated were rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]zirconium dichloride/methylaluminoxane (MAO) (1 + 2) and rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-dimethylsilanylbis(2-isopropyl-4-[3,5-dimethylphenyl]indenyl)zirconium dichloride/MAO (1 + 3). The effects of polymerisation temperature and hydrogen on catalyst performance and polymer properties, as well as copolymerisation with hexene and ethylene were investigated. Depending on the polymerisation conditions, M_w of polypropylene varied from 144 to 286 kg/mol for 1 + 2 and from 200 to 390 kg/mol for 1 + 3. Combination 1 + 2 produced broader molecular weight distribution (MWD) than 1 + 3, and a bimodal MWD with clearly separated low- and high-M_w polymer fractions was observed with 1 + 2. The two catalyst systems showed similar hydrogen and hexene responses. Each metallocene precursor showed individual response towards the polymerisation conditions, especially polymerisation temperature, suggesting that interaction between the catalyst active sites was negligible in the studied systems.     

Interfacial coarsening of ternary polymer blends with partial and complete wetting structures

The coarsening of polymer mixtures is an important route towards major morphology modification in multiphase polymer systems. To date however the coarsening of ternary systems has not been significantly examined. In this study the phase coarsening mechanism via annealing for partial wetting, and complete wetting morphologies in ternary polymer blends is characterized. This is a route towards the examination of interfacial coarsening in polymer blends since ternary partially wet systems involve the presence of interfacial droplets while completely wet ternary systems are comprised of a complete interfacial layer. A partial wetting type of morphology is obtained for polybutylene succinate (PBS)/poly(lactic acid) (PLA)/polycaprolactone (PCL). Three different compositions for that system with composition ratios of ?_(PBS/PLA) = 1.5; ?_(PBS/PLA) = 3; and ?_(PBS/PLA) = 10 are prepared to show the effect of the concentration of the self-assembled PLA droplets located at the interface of PBS/PCL. As the concentration of PLA decreases, the growth rate of the PLA phase during the annealing process sharply decreases due to a significant increase of the “surface to volume ratio” of the PLA droplets required in order to cover the interface. In this case, due to the short inter-droplet distances between PLA droplets at the interface, coalescence is controlled by the drainage time. This mechanism is confirmed by the observation of a linear relationship between the third power of droplet size and annealing time. For the 37.5%PBS/12.5%PLA/50%PCL blend, the conservation of interfacial-angles confirms that the annealing time has no effect on the angle values between phases, as predicted by Harkins spreading theory.     

聚对亚苯基苯并二(噁)唑合成新路线及其制备新技术

为进一步提升聚对亚苯基苯并二噁唑（PBO）材料的性价比并促进其工业化,研究了以4,6-二硝基间苯二酚为原料,先选择还原制得4-氨基-6-硝基间苯二酚盐酸盐,进而与对甲氧羰基苯甲酰氯进行缩环合获得苯并噁唑化合物,再催化加氢合成AB型PBO新单体2-(对甲氧羰基苯基)-5-氨基-6-羟基苯并噁唑（MAB）,最后自缩聚反应制备PBO的新路线和新方法.结果表明：该方法具有原料易得、反应条件缓和、中间体稳定等新技术优势.合成的PBO树脂总收率达64%、特性黏数η>10 dl&#8226;g^-1,新单体MAB的纯度>98%,具有稳定性优异和缩聚基团完全等当比等性质,以及均缩聚时间<20 h和过程易操作等技术特点,均为4,6-二氨基间苯二酚（DAR）共缩聚路线所难以比拟的.其综合经济性优于三氯化苯经DAR共缩聚的工业化路线,有望发展成易于实施PBO产业化的一项新技术.     

Polydispersity control in ring opening metathesis polymerization of amphiphilic norbornene diblock copolymers

Ring opening metathesis polymerization (ROMP) with Grubbs's catalyst was used to synthesize narrow polydispersity (PDI)diblock copolymers of norbornene (NOR) and norbornenedicarboxylic acid (NORCOOH). Norbornene (NOR) and 5-norbornene-2,3,-dicarboxylic acid bis trimethylsilyl ester (NORCOOTMS) were used as precursor monomers for thepolymerization. [NORCOOTMS]_m/[NOR]_n was converted to [NORCOOH]_m/[NOR]_n by precipitating the polymer solution in a mixture of methanol, acetic acid, and water. The conversion to 5-norbornene-2,3-dicarboxylic acid was evidenced by ¹H NMR. By polymerizing the bulkier NORCOOTMS precursor monomer first, lower PDIs were observed for the completed [NORCOOH]_m/[NOR]_n block copolymers in comparison to copolymers where the NOR block was polymerized first. The PDI of the diblock copolymers of [NORCOOH]_m/[NOR]_n decreased with increase in block length ofthe precursor NORCOOTMS monomer. This study shows that the PDI can be controlled by selecting a monomer with appropriate functionality as the starting block of the block copolymer to control the rate of propagation, R_p, as an alternative of using additives to change the reactivity of the catalyst.     

Preparation and characterization of poly(styrene-co-butyl acrylate)-encapsulated single-walled carbon nanotubes under ultrasonic irradiation

Polymeric composite materials filled with single-walled carbon nanotubes (SWNTs) have attracted much attention, but successful applications of such composites require uniform dispersion of SWNTs in the polymeric matrix and the strong SWNTs-polymer interface interaction. In this paper, chemical modification combined with ultrasonically initiated in situ polymerization was successfully employed to prepare poly(styrene-co-butyl acrylate)/single-walled carbon nanotubes composites [P(St-BA)/SWNTs]. The whole procedure contained two steps: in the first step, 3-(trimethoxy)-propylmethacrylate-silane (silane-coupling agent, KH570), a kind of polymerizable vinyl monomer, was grafted onto the surface of SWNTs, forming KH570-g-SWNTs by reacting KH570 with hydroxyl groups on the surface of SWNTs, which was proved by combination of FTIR and XPS results. Due to the presence of polymerizable KH570 on the surface of SWNTs, this provides a basis for the next stage of polymerization to prepare polymer-encapsulated SWNTs composites. In the second step, an ultrasonically initiated in situ emulsion polymerization of monomer styrene (St) and n-butyl acrylate (BA) proceeded in the presence of KH570-g-SWNTs. Consequently, P(St-BA)/SWNTs composite emulsion was obtained. TEM confirmed that SWNTs were coated with the obtained polymer. FTIR and XPS further showed that even after 72 h of soxhlet extraction with boiling toluene, there were still unextracted polymers in P(St-BA)/SWNTs composite, indicating strong interaction between the polymer and carbon nanotubes. Finally, a mechanism for formation of polymer-encapsulated SWNTs through ultrasonically initiated in situ emulsion polymerization was proposed. This study could provide a new way to resolve the problems of the dispersion, stabilization, and compositing of SWNTs with polymer matrix and prepare polymer/SWNTs composites.     

Modified hydrothermal treatment route for high-yield preparation of nanosized ZrO2

Nanosized ZrO₂ particles are applied in high-performance thermal barrier coatings and catalyst carriers. To synthesize nanosized zirconia, precipitation from aqueous solutions followed by hydrothermal treatment is widely conducted. In this work, a modified hydrothermal treatment route is described for high-yield fabrication of well-dispersible nanosized t–ZrO₂. Zirconium oxychloride and sodium hydroxide were used as the precursor and precipitant, respectively. N, N-bis(2-hydroxyethyl) glycine (bicine) was used as surface stabilizer to inhibit the early agglomeration of nuclei, and ultrasonication was used to enhance the dispersion of ZrO₂ nanocrystals. The hydrothermal treatment was optimized for reaction temperature, time, fill fraction, and solid content. The synthesized zirconia was characterized using X-ray diffraction, dynamic light scattering, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The yield of zirconia increased to 134 g/L after hydrothermal. Tetragonal ZrO₂ obtained with hydrothermal treatment at 200 °C for 8 h at a fill fraction of 80% has a good dispersibility, with an average particle size of 20 nm and a narrow size distribution.