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Synthesis of ring-opening metathesis polymerization (ROMP)-derived highly conjugated chromophore functional hyperbranched polymers opens up new possibilities for obtaining functional conjugated macromolecules with novel photophysical and morphological properties.

Synthesis of cycloolefin-based polymers via metathesis-accompanied cyclopolymerization and tandem Ring-Opening/Ring-Closing Metathesis (RO/RCM) polymerization are undergoing exciting developments and emerging as an area of great interest in the field of polymer synthesis. Among the conventional polymerization techniques, both cyclopolymerization and tandem polymerization give access to highly functional cycloolefin ring-based polymers. This review provides an overview of the synthesis of such cycloolefin-based conjugated and non-conjugated polymers following cyclopolymerization and tandem RO/RCM polymerization methodologies.

Novel methods to synthesize electron-deficient π-conjugated polymers utilizing transition-metal-free coupling reactions for the use of nonfunctionalized monomers are attractive due to their improved atom economy and environmental prospective. Herein we describe the use of iPrMgCl·LiCl complex to afford thiazole-based conjugated polymers in the absence of any transition metal catalyst, that enables access to well-defined polymers with good molecular weights. The mechanistically distinct polymerizations proceeded via nucleophilic aromatic substitution (SNAr) reaction supported by density functional theory (DFT) calculations. This work demonstrates the first example of fully conjugated thiazole-based aromatic homopolymers without the need of any transition metal catalyst.

Polyisobutylene (PIB)-bound ruthenium bipyridine [Ru(PIB-bpy)

The synthesis and characterization of asymmetric alkoxy- are reported, fluoro-benzothiadiazole (BT) acceptor core derivatized with a series of six different heterocycles (selenophene, thiophene, furan, 5-thiazole, 2-thiazole and 2-oxazole). The effect of the flanked-heterocycles containing different chalcogen atoms of the six homopolymers (HPX) is studied using optical, thermal, electrochemical, and computational analysis. Computational calculations indicate a strong relationship between the most stable conformation for each homopolymer and their bearing heterocycle, thus homopolymers HPSe', HPTp', HPFu', and HPTzC5, adopted the syn-syn and syn-anti conformations due to their noncovalent interactions with shorter distances, while HPTzC2' and HPOx' demonstrate preference for the anti-anti conformation. Optical property studies of the homopolymers reveal a strong red-shift in solution and film upon exchanging the chalcogen atom from OxygenSulfurSelenium in HPFu, HPTp, and HPSe, respectively. In addition, deeper highest occupied molecular orbital (HOMO) energy levels are observed when the donor-acceptor moieties (HPSe, HPTp, and HPFu) are substituted for the acceptor-acceptor systems such as HPTzC5, HPTzC2, and HPOx. Improved packing and morphology are exhibited for the donor-acceptor homopolymers. Thus, having a flanked heterocycle containing different chalcogen-atoms in polymeric systems is one way of tuning the physicochemical properties of conjugated materials for optoelectronic applications.

Carbon monoxide (CO) is an important biological gasotransmitter in living cells. Precise spatial and temporal control over release of CO is a major requirement for clinical application. To date, the most reported carbon monoxide releasing materials use expensive fabrication methods and require harmful and poorly designed tissue-penetrating UV irradiation to initiate the CO release precisely at infected sites. Herein, we report the first example of utilizing a green light-responsive CO-releasing polymer P synthesized via ring-opening metathesis polymerization. Both monomer M and polymer P were very stable under dark conditions and CO release was effectively triggered using minimal power and low energy wavelength irradiation (550 nm, ?28 mW). Time-dependent density functional theory (TD-DFT) calculations were carried out to simulate the electronic transition and insight into the nature of the excitations for both L and M. TD-DFT calculations indicate that the absorption peak of M is mainly due to the excitation of the seventh singlet excited state, S7. Furthermore, stretchable materials using polytetrafluoroethylene (PTFE) strips based on P were fabricated to afford P-PTFE, which can be used as a simple, inexpensive, and portable CO storage bandage. Insignificant cytotoxicity as well as cell permeability was found for M and P against human embryonic kidney cells. Copyright - 2019 American Chemical Society. The authors gratefully acknowledge the support of this work from the Qatar National Research Fund project number: NPRP X-095-1-024. Scopus

TPEN is an amino chelator of transition metals that is effective at the cellular and whole organism levels. Although TPEN of often used as a selective zinc chelators, it has affinity for copper and iron and has been shown to chelate both biologically. We have previously shown that TPEN selectively kills colon cancer cells based on its ability to chelate copper, which is highly enriched in colon cancer cells. The TPEN-copper complex is redox active thus allowing for increased ROS production in cancer cells and as such cellular toxicity. Here we generate TPEN derivatives with the goal of increasing its selectivity for copper while minimizing zinc chelation to reduce potential side effects. We show that one of these derivatives, TPEEN despite the fact that it exhibits reduced affinity for transition metals, is effective at inducing cell death in breast cancer cells, and exhibits less toxicity to normal breast cells. The toxicity effect of the both chelators coupled to the metal content of the different cell types reveals that they exhibit their toxicity through chelating redox active metals (iron and copper). As such TPEEN is an important novel chelators that can be exploited in anti-cancer therapies.

A series of 11 novel fluorinated and non-fluorinated di(thiazolyl)benzenes have been synthesized via microwave assisted Stille coupling and characterized using X-ray crystallography. A comparative analysis of nonbonding interactions in bis-heteroaryl-phenylene derivatives depending on the heterocycle structure and degree of fluorination of the central aromatic unit has been reported. We have systematically studied the effect of fluorination on the intramolecular interactions, π–π stacking, CH⋯F and S⋯F non-covalent interactions. Axial conformations of the biaryl system A is regulated by thermodynamic fluctuations and steric repulsions. On the other hand 2-phenyl thiophene B consists of only one H,H-repulsion interaction with a possibility of having a weak noncovalent CH⋯S interaction, hence, the combination of these factors results in the decrease in the energetics of the eclipsed conformation. When replacing the thiophene moiety with the thiazol-2-yl substituent C this allow us to eliminate the H,H-repulsions and results in CH⋯N hydrogen bonding and CH⋯S interactions. S⋯F non-covalent interactions can be used for pre-orientation of organic conjugated materials in a quasi-planar conformation.

The synthesis, characterisation and photovoltaic performance of an indacenodithiophene (IDT)-based organic dye in DSSCs has been presented. The dye was designed with a novel A-D-A system, which combines the advantages of a large, pi-extended donor core, flanked with double acceptor/anchoring groups. The studies presented herein illustrate the utility of the IDT core as an efficient energy-level mediator, and fluorescence resonance energy-transfer module operating via intramolecular charge transfer (ITC). in contrast to the current dyes used for DSCCs, the excitation in the IDT moiety occurs symmetrically along the long axis of the molecule, representing a new pathway of development of DSSCs. This compact system when fabricated into a metal free dye sensitized solar cell achieves promising power conversion efficiency of up to 4.2%, with a high short-circuit current density (J(sc)) of 11.69 mA cm(-2) and open-circuit voltage (V-oc) of 0.6 V and fill factor (FF) of 0.6 under AM 1.5 irradiation (100 mW cm(2))., Qatar National Research Fund (QNRF); National Priorities Research Program [NPRP 12S-0304-190227], This work was supported by the Qatar National Research Fund (QNRF) and the National Priorities Research Program, project number NPRP 12S-0304-190227. The numerical calculations reported here were performed in part at the TUBITAK ULAKBIM, High Performance and Grid Computing Centre (TRUBA resources).

There a few reports of rhodamine-based fluorescent sensors for selective detection of only Al3+, due to the challenge of identifying a suitable ligand for binding Al3+ ion. The use of fluorophore moieties appended to a polymer backbone for sensing applications is far from mature. Here, we report a new fluorescent probe/monomer 4 and its ROMP derived polymer P for specific detection of Al3+ ions. Both monomer 4 and its polymer P exhibit high selectivity toward only Al3+ with no interference from other metal ions, having a limit detection of 0.5 and 2.1 µM, respectively. The reversible recognition of monomer 4 and P for Al3+ was also proved in presence of Na2EDTA by both UV–Vis and fluorometric titration. The experimental data indicates the behavior of 4 and P toward Al3+ is pH independent in medium conditions. In addition, the switch-on luminescence response of 4 at acidic pH (0

Tandem metathesis polymerization of terminal alkynes with a small functional ring-size cycloalkene remains a challenge. A series of 1-propargyl-1′-carboxylate ester monomers M1-M4 derived from 3-cyclopentene initiated by ruthenium-alkylidene complexes have been investigated via tandem polymerization. Detailed DFT calculations and end-group analysis using 1H NMR experiments provided us with a deeper insight into the proposed polymerization mechanism. The energy profile obtained from DFT analysis provides two pathways for the polymerization of monomers having both cycloalkene and alkyne functionalities. The most stable coordination of M was found to be via a π-coordination to the triple bond, which is oriented perpendicularly to the ruthenium-alkylidene bond. Both cycloalkene- and alkyne-initiated polymerizations were found to be feasible pathways. However, the alkyne-initiated polymerization mechanism was found to be the preferred pathway due to the higher stability of the alkyne coordination to the monomer and the slightly lower rate-determining step barrier. In addition, the synthesis of the model MC compound supported our proposed polymerization mechanism as well as the position of the styrene end-group on the polymer chain.

We report the synthesis and characterization of four novel small bandgap copolymers incorporating the electron-deficient thieno[2,3-d:5,4-d′]bisthiazole and selenopheno[2,3-d:5,4-d′]bisthiazole building blocks with a series of electron-deficient diketopyrrolopyrole units. The four resultant copolymers were synthesized via palladium Stille cross-coupling reaction, and their optical, thermal stability, electrochemical, and field-effect charge transport properties were investigated. All copolymers showed low optical bandgaps (1.53–1.56 eV); in addition, X-ray diffraction on solution-cast films revealed that the selenium-containing copolymers exhibit higher crystallinity compared to their thiophene counterparts.

Ring opening metathesis polymerization (ROMP) of a series of low-strain cyclic olefins and their hydroxyl derivatives using second generation Hoveyda–Grubbs catalyst has been investigated. Additionally, density functional theory (DFT) calculations were performed to evaluate the ring strain energies of the cyclic olefins and their hydroxyl derivatives, coupled with kinetic studies for the ROMP reactions. It was found that among different ring size monomers, Cy8 having a relatively moderate ring strain energy in comparison with the other cyclic olefins, exhibited the highest monomer conversion. The effect of temperature (0, 10, 15, and 25 °C) and monomer concentration (1 M; 2.5 M and 5 M for Cy5; and 1 M and 5 M for Cy7) for the cyclic olefins Cy5 and Cy7 were investigated. In general, the experimental results for the kinetic ROMP studies obtained using complex HG2 correlate really well with the DFT calculations determined for the ring strain energies of the cyclic olefins. For comparison, DFT calculations predicted the following trend for the ring strain energies Cy8 > Cy5 > Cy7 > Cy6, and the polymerizations carried out experimentally followed the same trend in terms of monomer conversion, with the exception of Cy5 and Cy7 at lower concentrations, which followed this trend Cy8 > Cy7 > Cy5 > Cy6. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3137–3145

New low band gap copolymers P1–P4, based on thienylenevinylene (TV) and pyrrolo[3,2-d:4,5-d′]bisthiazole (PBTz) units composed of different alkyl side chains, such as 2-octyldodecyl (OD), n-hexadecyl (HD), 2-ethylhexyl (EH), and 9-heptadecyl (HD) groups, respectively, have been synthesized and characterized. Electrochemical and optical studies of the copolymers indicated low energy band gaps in the range of 1.40–1.47 eV. Moreover, theoretical calculation with density functional theory (DFT) and time-dependent DFT calculations demonstrated that the energy band gaps, HOMO energy levels and maximum absorption values in the copolymers were in good agreement with the experimental results. The decomposition temperature of all copolymers was measured to be above 340 °C by thermogravimetric analysis (TGA), which indicates high thermal stability. Thermally annealed OTFT devices based on P1–P4 thin films demonstrated a range of hole mobilities; thus, the P2 based OTFT device exhibited the highest hole mobility of 0.062 cm2 V−1 s−1.

Ruthenium catalyzed ring closing metathesis (RCM) and ring opening metathesis polymerization (ROMP) reactions using a supported bis(arylimino)acenaphthene N-heterocyclic carbene (BIAN-NHC) complex have been reported. The BIAN-NHC Ru-complex exhibits excellent catalytic activity and tolerates a wide range of substrates at low catalyst loadings. DFT calculations were also carried out on some selected key intermediates in the reaction mechanism to study the effect of having the conjugated aromatic moiety (BIAN-NHC) in the backbone of the complex. The newly synthesized BIAN-NHC Ru-complex shows comparable catalytic activities to the commercially available second generation Ru catalyst HG2. The recycled complex was reused for up to eight reaction cycles for the RCM of N,N-diallyl tosylamine affording a high average isolated yield, with lower levels of Ru contamination in the final product.

A series of four donor-acceptor conjugated copolymers P1-P4 with linear and branched side chains based on a ladder-type indacenodithiazole (IDTz) moiety containing an electron-deficient thiazole unit are copolymerized with di-2-thienyl-2,1,3-benzothiadiazole (DTBT) and 4,7-di(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazole (DTBTff) as building blocks. Their optical, electrochemical, and thermal properties and charge transport behavior in organic field-effect transistors (OFETs) are studied. All copolymers exhibit nearly identical features in solution with good solubility. In the solid state, P1 does not exhibit a significant shift, while P3 shows a 27 nm red shift, thus illustrating the influence of the side chain. In the case of copolymers P1 and P2 having linear side chains, there is a clear effect of fluorination on the film morphology, while it is less pronounced in the case of polymers P3 and P4 having branched side chains. All copolymers P1-P4 have similar highest occupied molecular orbitals regardless of fluorination, while fluorinated polymers P2 and P4 result in an increase in the lowest unoccupied molecular orbital. In addition, density functional theory calculations reveal that the energy levels of IDTz are down-shifted in comparison to its IDT counterpart containing an electron-rich thiophene unit. OFETs based on all copolymers exhibit ambipolar behavior; among the four copolymers, P2 having a linear dodecyl side chain exhibits remarkable transport properties with saturated hole mobility as high as 0.87 cm2 V-1 s-1, while P3 exhibits the highest electron mobility of up to 0.50 cm2 V-1 s-1. Our results set an interesting path to further utilize the electron-deficient thiazole block in semiconducting materials. Copyright - 2019 American Chemical Society. This work was supported by the Qatar National Research Fund (QNRF) and the National Priorities Research Program, project number NPRP 8-245-1-059. Scopus

Ring-opening metathesis polymerization (ROMP) of thioether-derived oxanorbornene imide (M1) and its copolymerization with various cycloolefin comonomers such as cyclopentene (M2), cyclopent-3-en-1-ol (M3), cycloheptene (M4), and cyclooctene (M5) using Hoveyda�Grubbs second generation catalyst has been investigated. Polymerizations were performed at two different temperatures (0 and 25?�C) and the obtained functional poly(olefin)s were characterized by nuclear magnetic resonance 1H and 13C (NMR), and infrared spectroscopy as well as size exclusion chromatography, differential scanning calorimetry, and thermogravimetric analysis analyses. Additionally, the dependence of the polymer composition on the reaction temperature and monomer feed was studied with time-dependent 1H NMR experiments. Copolymerization of M1 with a five-membered cycloolefin monomer M2 showed relatively low ROMP reactivity irrespective of the reaction conditions in comparison to M3, M4, and M5 monomers. In general, the degree of monomer incorporation into poly(olefin)s were determined in the order of M5 > M3 > M4 > M2, and that sheds light on the effect of cycloolefin ring strain energies in the ruthenium-alkylidene initiated ROMP. - 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1741�1747. - 2019 Wiley Periodicals, Inc. The authors gratefully acknowledge the support of this work from the Qatar National Research Fund project number: NPRP X-095-1-024. Scopus

Ethanedithiol-functionalized polyisobutylene was prepared in one step by a photoinitiated thiol-ene &ldquo, click&rdquo, reaction starting from ethanedithiol and polyisobutylene (PIB). The functionalized oligomer product was then used as a soluble sequestrant for transition metals. This PIB-bound thioether-thiol ligand is phase selectively soluble in alkanes and it quantitatively sequesters common transition metals like Cu2+ and Pd2+ into an alkane phase, separating them from polar solvents in a biphasic liquid/liquid separation. The chelating thioether-thiol ligand was also successfully used to remove Cu and Pd transition metal catalyst residues from products in crude reaction mixtures in both azide/alkyne click reactions and cross-coupling reactions using a liquid/liquid extraction. Separation efficiencies exceeding 95% and in many cases 99% were achieved.

Low-viscosity poly(α-olefin)s (PAOs) either alone or with functional hydrocarbon oligomer cosolvents are nontoxic, nonvolatile, recyclable solvent systems that effectively and efficiently sequester trace amounts of nonpolar organic compounds such as benzene and halogenated organics from water. More polar compounds including perfluorooctanoic acid and nitrobenzene or water-miscible compounds such as THF and triethylamine can also be sequestered if the PAO phase contains an H-bonding PAO-anchored cosolvent.

This study describes the use of polyisobutylene (PIB) to phase-anchor pyridine ligands that form a phase-separable Grubbs third-generation catalyst. We further show that this complex is useful in ring-opening metathesis polymerization (ROMP) reactions. These PIB-bound pyridine-ligated Grubbs catalysts provide the same benefits of control over polymer chain growth and polydispersity of the product as their low-molecular-weight analogs and reduce Ru leaching in ROMP products from approximately 16% (820 ppm residues) as seen with a similar pyridine-ligated catalyst to a value of approximately 3% (160 ppm residues). These labile ligands are shown to be as effective at generating separable metal complexes as less labile PIB-functionalized N-heterocyclic carbene catalyst ligands that are typically used for immobilization but that require a multistep synthesis.

Linear trans-polypentenamers are highly desired materials among synthetic tire additives due to their comparable physical properties to natural rubber. trans-Polypentenamer can be prepared by equilibrium ring-opening metathesis polymerization (ROMP) using well-defined ruthenium catalyst systems. This unique feature of the equilibrium polymerization reaction opens a way for the synthesis of durable, environmentally benign elastomers where polymers including synthetic tire additives can be synthesized and readily recycled using the same transition metal catalyst system. The addition of silica fillers significantly improves the physical properties of the composite materials in comparison to the use of polymeric material. It is also known that the structural effects and the polymer–filler surface interaction are of prime importance. Herein, we report on the synthesis of silica filler compatible recyclable polypentenamer copolymers via equilibrium ROMP of cyclopentene 1 and 4-(triethoxy)siloxy cyclopentene 11....

In the past decade, numerous examples of chemical technologies based on olefin metathesis have been developed to make olefin metathesis increasingly dominant in several sustainable and green chemical processes. In spite of the wide application profile, conjugated olefin metathesis, especially conjugated polyene metathesis, is an area of great interest with little exploration. The metathesis of conjugated polyenes is often cumbersome and requires a high catalyst loading, most probably because of the formation of poorly active or inactive ruthenium η3-vinylcarbene intermediates. A mechanistic understanding and the development of a new highly active catalytic system for olefin metathesis will open new areas for exploration, such as the utilisation of cyclopentadiene and other petrochemical by-products or a new way to use butadiene, isoprene and conjugated electron systems that contain natural products such as terpenes and polyunsaturated fatty acids. An understanding of the mechanism of ruthenium η1–η3-vinylcarbene interconversion may open the way to the development of a new generation of Ru-based latent metathesis catalyst systems. This review summarises the most relevant pioneering work focused on the metathesis of conjugated polyenes to open new ideas for the development of forthcoming latent metathesis catalysts and to explore different applications.

This study evaluates the potential of selected ionic polymers to act as pavement subgrade binders. Investigations were based on their relative performance with a Qatari soil which was selected as typical of a pavement subgrade to be found in the Middle East and North African region. The polymeric binders chosen were three synthetic ionic variations of polyacrylamide: cationic poly(acrylamidopropyl trimethyl ammonium chloride) (designated PAMTAC), anionic hydrolysed poly(acrylamide) (HPAM) and the ampholitic terpolymer poly(acrylamide-co-sodiumacrylate-co-(3-acrylamidopropyl) trimethylammonium chloride) (TPAM). The polymers were characterised by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic spectroscopy (1H-NMR and 13C-NMR). The comparative performance of the polymer-treated soil was judged on the basis of results obtained from selected standard mechanical test data: specifically, the unconfined compressed strength, the stiffness modulus and the toughness. It is concluded tha...

Perfluorocarbons (PFCs) are a promising class of molecules for medical applications: they are detectable through 19F nuclear magnetic resonance (NMR) and they assemble separately from water or lipophilic phases, thus bringing unique supramolecular interactions into nanostructures. We report the ready insertion of PFCs into nucleic acids, as well as non-natural polymers in a sequence-defined fashion. This is achieved via an automated and efficient synthetic pathway using phosphoramidite chemistry. Modulating the PFC tail length of “DNA–Teflon” block copolymers resulted in micelles that are almost monodisperse, have a low critical micelle concentration (CMC), are traceable by 19F NMR and are responsive to external stimuli. Strong fluorine–fluorine interactions in DNA duplexes allowed remarkable melting temperature increases and provided nuclease resistance. Finally, PFC insertion into siRNA was achieved, and the conjugates were efficient for gene silencing, outlining that these modifications are highly suitable for oligonucleotide therapeutics and bioimaging tools.

The fluorous alkenes H2CCHRfn (Rfn = (CF2)n−1CF3; n = 8, 10) undergo the Mizoroki–Heck reaction with a variety of aromatic monobromides and polybromides such as 1,3- and 1,4-C6H4Br2, 1,3,5-C6H3Br3, 1,3,5-C6H3Br2Cl, 1,4-XC6H4Br (X = CF3, Rf8, COCH3, CN, 1,4-OC6H4Br), 1,2-O2NC6H4Br, 5-bromoisoquinoline, 5-bromopyrimidine, 3-bromo-5-methoxypyridine, and 3,5-dibromopyridine (sixteen examples, 78% average isolated yield). Typically, 1.2–2.4 equiv. of alkene are employed per Ar–Br bond, together with Pd(OAc)2 catalyst (4–5 mol%/Ar–Br bond), n-Bu4N+ Br− (0.8–1.0 equiv./Ar–Br bond), NaOAc (1.2–2.4 equiv./Ar–Br bond), and 3 : 1 w/w DMF/THF as solvent (120 °C). No effort is necessary to exclude air or moisture, and reactions may be conducted on >10 g scales. Only E isomers of the products Ar(CHCHRfn)m are detected. Thirteen representative examples are hydrogenated (Pd/C, balloon pressure H2), giving Ar(CH2CH2Rfn)m (92% average isolated yield).

Functionalization of polyolefins, in particular polyisobutylene, remains a relatively unexplored application for the Michael reaction. This work evaluates the potential of polyisobutylene acrylate (PIBA) chain-end modification via organocatalyzed thiol-Michael and aza-Michael additions. A series of chain-end functional polyisobutylene oligomers are prepared using "click" reactions of thiols or amines to PIBA in the presence of 0.02 equivalents of organocatalyst. Reaction kinetics and chain-end transformations are monitored using NMR spectroscopy and the macromolecular products are characterized by size exclusion chromatography. Further potential of this synthetic strategy is illustrated by thiol-Michael addition of thiols formed in situ via nucleophilic thiolactone ring opening. The obtained results provide an efficient method for the preparation of functional polyisobutylene oligomers that can be utilized in a broad range of potential applications.

Sequence-defined polymers with customizable sequences, monodispersity, substantial length, and large chemical diversity are of great interest to mimic the efficiency and selectivity of biopolymers. We report an efficient, facile, and scalable synthetic route to introduce many chemical functionalities, such as amino acids and sugars in nucleic acids and sequence-controlled oligophosphodiesters. Through achiral tertiary amine molecules that are perfectly compatible with automated DNA synthesis, readily available amines or azides can be turned into phosphoramidites in two steps only. Individual attachment yields on nucleic acids and artificial oligophosphodiesters using automated solid-phase synthesis (SPS) were >90% in almost all cases. Using this method, multiple water-soluble sequence-defined oligomers bearing a range of functional groups in precise sequences could be synthesized and purified in high yields. The method described herein significantly expands the library of available functionalities for nucleic acids and sequence-controlled polymers.

Novel low band gap polymers based on pyrrolo[3,2-d:4,5-d′]bisthiazole (PBTz) and thienylenevinylene (TV) For Organic Electronic Applications Dhananjaya Patra?,1 Hassan S. Bazzi,1 Lei Fang¬2 and Mohammed Al-Hashimi1 1Department of Chemistry, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar 2Department of Chemistry and Department of Materials Science and Engineering, Texas A&M University, College Station, TX. Corresponding author: dhananjaya.patra@qatar.tamu.edu π-Conjugated organic polymers have been intensively studied over the past two decades due to their potential applications in areas such as organic light-emitting diodes (OLEDs),1 organic thin-film transistors (OTFTs), organic photovoltaics (OPV), and organic laser devices. In addition, they possess excellent properties that enable them to be solution processed offering a path-way for fabrication on large-area printable and cost-effective flexible electronic devices. Several donor-acceptor (D-A) conjugated polymers and small molecules are reported recently with photovoltaic performance over 12%.2-4 Recently significant development has been made in the design and synthesis of high performance polymers with mobilities now easily surpassing μ > 1 cm2 V-1 s-1.5 Among the various conjugated electron-donating building blocks, thienylenevinylene (TV) unit has attracted much interest owing to its coplanarity and extended π-conjugation which are induced by the presence of a vinylene spacer between the two thiophene units. As a result this enhanced interchain interaction the polymers exhibit a higher hole mobility and reduced energy band gaps.4 Recently, the incorporation of vinylene unit into several electron-rich (i.e., donor) and electron deficient (i.e., acceptor) units has been widely studied, especially, targeting at the device application for n-channel and ambipolar OTFTs with promising device performance. Among these units are diketopyrrolopyrrole (DPP), benzoselenadiazole (BSe), phthalimide (PhI), naphthalenediimide (NDI), benzothiadiazole (BT), dithienothiophene (DTT), thienopyrroledione (TPD), and isoindigo (iI) as depicted in Figure 1. For instance, Yoo et al. reported the synthesis of various polymers based on DPP and (E)-2-(2-(thiophen-2-yl)-vinyl)thiophene units by altering the number of thiophene in the repeat unit to induce strong π–π stacking and favorable molecular conformation. By replacing the thiophene unit with the selenophene vinylene selenophene Kang et al. reported an enhanced mobility. Several DPP and TV based polymers reported by Oh and Kim et al. via various side-chain engineering on the DDP units, obtained remarkable mobilities from 8.74 to 17.8 cm2 V − 1 s − 1.5 Reichmanis and co-workers also reported the synthesis of a series of BT oligothiophene and oligo-TV donor-acceptor (D − A) copolymers exhibiting mobilities of up to 0.75 cm2 V − 1 s − 1. Kim and co-workers reported the synthesis and characterization of highly soluble poly(thienylenevinylene) exhibiting carrier mobility of 1 cm2 V − 1 s − 1.6 Al-Hashimi, Heeney and co-workers systematically investigated the role of modifying the heteroatom, by synthesizing a series of vinylene copolymers containing 3-dodecylthiophene, selenophene and tellurophene.7,8 Figure 1. Structures of thiophene (Th), thiazole (Tz) diketopyrrolopyrrole (DPP), benzoselenadiazole (BSe), phthalimide (PhI), naphthalenediimide (NDI), benzothiadiazole (BT), dithienothiophene (DTT), thienopyrroledione (TPD), and isoindigo (iI). Another particularly promising class of building block for the development of high performing polymeric semiconductors for OTFTs is the electron-deficient pyrrolo[3,2-d:4,5-d′]bisthiazole (PBTz)-based heterocycle. In comparison to dithienothiophene (Figure 1), PBTz-unit is a weak acceptor having an electronegative nitrogen atom, which lowers the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies. Therefore, it is expected that the large polarity of the thiazole ring can enhance the intermolecular interaction. In addition, the bridging nitrogen (N) of PBTz offers the opportunity to include an additional solubilizing sidechain, which is not present in the analogous DTT. This potentially offer improved solubility and processability of the polymers. Nonetheless, to the best of our knowledge, there is no single report on the synthesis, polymer characterization, and charge carrier transport properties employing the fused PBTz containing TV units. In this work, we report the synthesis and characterization of a series of four PBTz-TV-based copolymers P1-P4 (Scheme 2) with various alkyl side chains for OTFT applications. Particularly, we have selected a dodecyl alkyl side chain on the thienylenevinylene unit, three branched alkyl side chains such as 2-octyldodecyl (OD), 9-heptadecyl (HD) and 2-ethylhexyl (EH), and a long straight n-hexadecyl (HD) chain on the nitrogen of the pyrrolobisthiazole unit, thus, for improving polymer solubility and effectively to promote π − π interchain interactions. The electrochemical redox properties and related electronic structures (HOMO/LUMO energy levels) were systematically investigated by cyclic voltammetry (CV). In addition, the microstructure and morphology of the polymer thin films were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). Finally, the PBTZ-copolymers show band gaps in the range of 1.40 − 1.46 eV and mobilities in the range of 0.002-0.062 cm2 V − 1 s − 1 in bottom-gate/top-contact OTFTs.9 References. 1. Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.; Friend, R. H.; Burn, P. L.; Holmes, A. B. Nature, 1990, 347, 539. 2. Sekitani, T.; Zschieschang, U.; Klauk, H.; Someya, T. Nat. Mater.,2010, 9, 1015.3. Zhao, W.; Li, S.; Yao, H.; Zhang, S.; Zhang, Y.; Yang, B.; Hou, J. J. Am. Chem. Soc., 2017, 139, 7148. 4. Li, N.; Baran, D.; Forberich, K.; Machui, F.; Ameri, T.; Turbiez, M.; Carrasco-O., M.; Drees, M.; Facchetti, A.; Krebse, F.C.; Brabec, C. J. Energy Environ. Sci., 2013, 6, 3407. 5. Kim, J.; Lim, B.; Baeg, K. J.; Noh, Y. Y.; Khim, D.; Jeong, H. G.; Yun, J. M.; Kim, D. Y. Chem. Mater.,2011, 23, 4663. 6. Fu, B. Y.; Baltazar, J.; Hu, Z. K.; Chien, A. T.; Kumar, S.; Henderson, C. L.; Collard, D. M.; Reichmanis, E. Chem. Mater.,2012, 24, 4123 7.Al-Hashimi, M.; Han, Y.; Smith, J.; Bazzi, H. S.; Alqaradawi, S. Y. A.; Watkins, S. E.; Anthopoulos, T. D.; Heeney, M. Chem. Sci.,2016, 7, 1093. 8. Al-Hashimi, M.; Baklar, M. A.; Colleaux, F.; Watkins, S. E.; Anthopoulos, T. D.; Stingelin, N.; Heeney, M. Macromolecules, 2011, 44, 5194. 9. Patra, D.; Lee, J.; Lee, J.; Sredojevic, D. N.; White, A.J.P.; Bazzi, H. S.; Brothers, E. N.; Heeney, M.; Fang, L.; Yoon. M.-H.; Al-Hashimi, M. J. Mater. Chem. C., 2017, 5, 2247.

Equilibrium ring-opening metathesis polymerization (ROMP) of cyclic olefins using a soluble supported second-generation Ru complex has been investigated. Cycloolefin homo- and copolymers are of great academic and industrial importance owing to their interesting applications as packaging materials, adhesives in coatings, and optoelectronics. The supported complex exhibits good chemical stability and was effective in ROMP of strained cyclic olefins. In addition, the complex is easily phase separated from the product, resulting in lower residual ruthenium in the final polymer product compared with the homogeneous complex.

With metal-based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L'n M-L) to activate the catalyst. The resulting coordinatively unsaturated active species (L'n M) can either back react with the ligand in a k-1 step, or combine with the substrate in a k2 step. When dissociation is not rate determining and k-1 [L] is greater than or comparable to k2 [substrate], this slows the rate of reaction. By introducing a phase label onto the ligand L and providing a suitable orthogonal liquid or solid phase, dramatic rate accelerations can be achieved. This phenomenon is termed "phase-transfer activation". In this Concept, some historical antecedents are reviewed, followed by successful applications involving fluorous/organic and aqueous/organic liquid/liquid biphasic catalysis, and liquid/solid biphasic catalysis. Variants that include a chemical trap for the phase-labeled ligands are also described.

Polyethylene oligomers (PEOlig) can be used as cosolvents and sometimes soluble catalyst supports in ring-opening metathesis polymerization (ROMP) reactions. As a catalyst support, this polyolefin serves as an N-heterocyclic carbene ligand for a ROMP catalyst, making it soluble at 70 °C and insoluble at room temperature. As a cosolvent, unfunctionalized PE oligomers facilitate quantitative separation of PEOlig-bound Ru-catalyst residues from polymer products. In these cases, the insolubility of the unfunctionalized polyethylene (Polywax) and its entrapment of the PEOlig-supported Ru residue in the product phase at room temperature afford ROMP products with Ru contamination lower than other procedures that use soluble catalysts. These separations require only physical processes to separate the product and catalyst residues—no additional solvents are necessary. Control experiments suggest that most (ca. 90%) of the Ru leaching that is seen results from Ru byproducts formed in the vinyl ether quenching step ...

Strategies for synthesis of more effective soluble supported ligands for phosphine-ligated Pd(0) cross coupling catalysts have been explored. Reversible addition-fragmentation chain transfer (RAFT) polymerization has been used to prepare alkane-soluble poly(4-alkylstyrene)-bound phosphine ligands. 4-tert-Butylstyrene and 4-dodecylstyrene were copolymerized with ca. 7 mol% of 4-chloromethylstyrene or a 4-diphenylphosphinestyrene monomer using RAFT chemistry to afford poly(tert-butylstyrene-co-4-dodecylstyrene) copolymers. Polymers with chloromethyl groups were allowed to react with the phenolic group of a hindered dicyclohexylbiarylphosphine ligand. This hindered polymer-bound phosphine formed reactive Pd complexes useful in haloarene amine couplings. All aryl halide amination reactions had Pd leaching that was typically

Reactions of (1) [Q]2[Fe4S4(SC(CH3)3)4] and the fluorous thiols HS(CH2)nRf8 (n = 2, 3; Rf8 = (CF2)7CF3)), or (2) [Na]2[Fe4S4(S(CH2)nRf8)4] (n = 2, 3) and [PhCH2P((CH2)3Rf6)3][Br] or [PPN][Cl] (PPN = Ph3P[horiz bar, triple dot above]N[horiz bar, triple dot above]PPh3), give the title compounds [Q]2[Fe4S4(S(CH2)nRf8)4], comprised of a fluorous dianion and in some cases fluorous cations, with (1) Q/n = Ph4P/2 (, 67%), Ph4P/3 (, 67%), Me4N/3 (69%), and Ph3P(CH2)2Rf6/2 (73%) or (2) PhCH2P((CH2)3Rf6)3/2 (, 39%), PhCH2P((CH2)3Rf6)3/3 (, 63%), and PPN/2 (36%). The educt [Ph3P(CH2)2Rf6]2[Fe4S4(SC(CH3)3)4] is in turn prepared from FeCl3, HSC(CH3)3/CH3ONa, and [Ph3P(CH2)2Rf6][I], and the educts [Na]2[Fe4S4(S(CH2)nRf8)4] from [Na]2[Fe4S4(SC(CH3)3)4] and HS(CH2)nRf8. The SCH2(1)H and (13)C NMR signals of these paramagnetic salts appear 8.7-10.3 and 32.3-34.9 ppm downfield from those of the corresponding thiols, but the chemical shifts of other signals are nearly normal. The UV-visible spectra show bands similar to those of non-fluorous analogs (290-298 nm and 406-415 nm; ε = 25 700 and 19 200 M(-1) cm(-1) for ). The singly fluorous salts are soluble in organic solvents of moderate polarity, but not in fluorous solvents. The doubly fluorous salts , are soluble in all fluorous solvents assayed, with partition coefficients of99.65 : 0.35 (CF3C6F11/toluene) and 93.2-93.1 : 6.9-6.8 (FC-72/THF). Cyclic voltammograms carried out using a platinum working microelectrode show that is 0.08 V thermodynamically easier to reduce than .

Therapeutic nucleic acids are powerful molecules for shutting down protein expression. However, their cellular uptake is poor and requires transport vectors, such as cationic polymers. Of these, poly(ethylenimine) (PEI) has been shown to be an efficient vehicle for nucleic acid transport into cells. However, cytotoxicity has been a major hurdle in the development of PEI-DNA complexes as clinically viable therapeutics. We have synthesized antisense-polymer conjugates, where the polymeric block is completely monodisperse and sequence-controlled. Depending on the polymer sequence, these can self-assemble to produce micelles of very low polydispersity. The introduction of linear poly(ethylenimine) to these micelles leads to aggregation into size-defined PEI-mediated superstructures. Subsequently, both cellular uptake and gene silencing are greatly enhanced over extended periods compared to antisense alone, while at the same time cellular cytotoxicity remains very low. In contrast, gene silencing is not enhanced with antisense polymer conjugates that are not able to self-assemble into micelles. Thus, using antisense precision micelles, we are able to achieve significant transfection and knockdown with minimal cytotoxicity at much lower concentrations of linear PEI then previously reported. Consequently, a conceptual solution to the problem of antisense or siRNA delivery is to self-assemble these molecules into 'gene-like' micelles with high local charge and increased stability, thus reducing the amount of transfection agent needed for effective gene silencing.

This paper reports the efficient synthesis of the first class of polyisobutylene(PIB)-supported palladium-PEPPSI precatalyst (PEPPSI = pyridine-enhanced precatalyst preparation, stabilization, and initiation). The new complexes are employed in Buchwald–Hartwig amination of aryl chlorides and are found to be reasonably active in the titled cross-coupling reaction. The supported catalysts are tested in polar (1,4-dioxane and 1,2-dimethoxyethane) as well as in aliphatic reaction media (toluene and n-heptane) and display superior activity in the highly lipophilic solvent (n-heptane). The catalytic efficacy of PIB-Pd-PEPPSI precatalyst is measured to be comparable to its nonsupported analog. Pd-leaching is determined by inductively coupled plasma mass spectrometry (ICP-MS) after a simple liquid/liquid extraction and is found to be 2 ppb in the product phase, translating into a recovery of ≈99.8% of the palladium.

As colloidal self-assembly increasingly approaches the complexity of natural systems, an ongoing challenge is to generate non-centrosymmetric structures. For example, patchy, Janus or living crystallization particles have significantly advanced the area of polymer assembly. It has remained difficult, however, to devise polymer particles that associate in a directional manner, with controlled valency and recognition motifs. Here, we present a method to transfer DNA patterns from a DNA cage to a polymeric nanoparticle encapsulated inside the cage in three dimensions. The resulting DNA-imprinted particles (DIPs), which are 'moulded' on the inside of the DNA cage, consist of a monodisperse crosslinked polymer core with a predetermined pattern of different DNA strands covalently 'printed' on their exterior, and further assemble with programmability and directionality. The number, orientation and sequence of DNA strands grafted onto the polymeric core can be controlled during the process, and the strands are addressable independently of each other.

Soluble poly(4-alkylstyrene) containing 4-methyl-, 4-tert-butyl, 4-dodecyl-, and 4-octadecylstyrene were formed either with monomers containing dyes-, ligands, or catalysts or with 5–10 mol% of 4-chloromethylstyrene and studied as supports for ligands or catalysts. Studies with dye-labeled polymers showed that polymers containing longer alkyl groups alone or at ca. 10 mol% loading are highly soluble in heptane can be used to separate and recycle organo- and transition metal catalysts.

Olefin metathesis is among the most powerful tools for the formation of regio- and steroselective carbon–carbon double bonds. Applying the principles of Green Chemistry to the syntheses of polymers by developing useful strategies to facilitate catalyst and polymer product separation after a polymerization is vital. In the present study, a phase selectively soluble polymer bound second generation Grubbs catalyst was successfully used to carry out ring-opening metathesis polymerization (ROMP) on norbornene and a variety of different exo-norbornene derivatives. Polymers with low ruthenium contamination levels were achieved in comparison to the non-supported Grubbs catalyst which required multiple precipitations. Furthermore, the bound catalyst exhibits similar catalytic activity to its homogenous counterpart.

Alkene metatheses catalyzed by (H2IMes)(Cy2PCH2CH2N(CH3)3+)(Cl)2Ru(CHPh) Cl−, an analog of Grubbs' second generation catalyst with an ammonium-salt containing phosphine, are dramatically accelerated when conducted in the presence of the insoluble resin PS-SO3Ag (PS = polystyrene). A mechanism involving ionic and covalent phosphine binding (PS-SO3Ag·PCy2CH2CH2N(CH3)3+ PS-SO3−) with concomitant formation of AgCl is proposed. Grubbs' second generation catalyst exhibits a modest rate enhancement, believed to reflect the generation of PS-SO3Ag·PCy3.

The reactions of the electron donor 4-benzylpiperidine (4BP) with the σ-acceptor iodine and π-acceptors 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) were studied spectrophotometrically in chloroform at room temperature. The electronic and infrared spectra of the formed molecular charge-transfer (CT) complexes were recorded. Based on the obtained data, the charge-transfer complexes were formulated as [ ( 4 BP ) I ] + I 3 - , [(4BP)(DDQ)2], and [(4BP)(TBCHD)] for the donor (4BP) and the acceptors I2, DDQ and TBCHD. In the 4BP-TCNQ reaction, a short-lived CT complex is formed followed by rapid N-substitution by TCNQ forming the final reaction product 7,7,8-tricyano-8-benzylpiperidinylquinodimethane [TCBPQDM]. These products were isolated as solids and have been characterized through electronic and infrared spectra as well as elemental and thermal analysis measurements. The formation constants (KCT), charge transfer energy (ECT), molar extinction coefficients (eCT), free energy change ΔG∘ and ionization potential IP of the formed CT-complexes [ ( 4 BP ) I ] + I 3 - , [(4BP)(DDQ)2] and [(4BP)(TBCHD)] were obtained.

Modern lubricants face the task of providing lubrication over a wide range of temperatures, and extreme engine temperatures can exceed the thermal degradation limits of many engine oils. Soft metal additives can extend the life of engine oils at very high temperatures by providing solid lubrication to contacting surfaces. We report a new silver–organic complex which contains a high metal content and minimal supporting organic ligands. This silver pyrazole–pyridine complex is evaluated as a friction-reducing and anti-wear additive in engine oil at testing temperatures which thermally degrade the base oil. Two sets of ball-on-disk tests are performed: the first at a constant temperature of 200 °C and the second while increasing the chamber temperature from 180 to 330 °C. At 200 °C, the wear is considerably reduced compared with the base oil when the silver-organic additive is present at 2.5–5.0 wt%. Furthermore, the silver-based additive at 20 wt% in oil induces a remarkable friction reduction during the temperature ramp test, so much, so that the tribological transition from the oil as the primary lubricant to its degradation, and to the silver additive as the primary lubricant, is imperceptible.

Polyisobutylene (PIB)-bound ruthenium bipyridine [Ru(PIB-bpy)3]2+ metal complexes were prepared from PIB ligands formed by alkylation of 4,4′-dimethylbipyridine with polyisobutylene bromide. The product Ru(PIB-bpy)3Cl2 complexes with at least one PIB ligand per bipyridine unit function as soluble recyclable photoredox catalysts in free radical polymerization of acrylate monomers under visible light irradiation at 25 °C with ethyl 2-bromoisobutyrate as the initiator in the presence of diisopropylethylamine. The polyacrylate products contained only about 1 ppm Ru contamination. This PIB-bound catalyst was recyclable and showed about 50-fold less Ru leaching as compared to Ru leaching in a polymerization catalyzed by the low molecular weight Ru catalyst, Ru(bpy)3(PF6)2.