Biobased Polyethers via Acyclic Diene Metathesis Polymerization of α,ω-Diene Furanics

Controlled synthesis of azobenzene-containing block copolymers both in the main- and side-chain from SET-LRP polymers via ADMET polymerization

A novel synthetic methodology for 9-alkylidene-9H-fluorenes by the palladiumcatalyzed cascade reaction of aryl iodides and internal alkynes has been developed. This methodology has been extended to a number of aryl iodides and internal alkynes. The synthesis of a 9-alkylidene-9H-fluorene has also been achieved from a vinylic iodide. It has been demonstrated that this unusual cascade migration/coupling process also provides an efficient synthetic route to polycyclic aromatic hydrocarbons. We have also investigated the palladium-catalyzed reaction of internal alkynes and (2-iodophenyl)acetonitrile or 2-iodobenzonitrile. (2-Iodophenyl)acetonitrile reacts with diphenylacetylene in the presence of a palladium catalyst to afford 2-amino-3.4diphenylnaphthalene in 83% yield. This is the first example of a cyano group actually participating in an organopalladium addition reaction. An unusual product 2-amino-3-{(£')l-propenyl }-4-propylnaphthalene has been obtained as the sole product in the reaction of 4octyne. The formation of this unusual product has been rationalized by a mechanism similar to the palladium-catalyzed cyclization of enynes. The reaction of 2-iodobenzonitrile and diphenylacetylene affords 2.3-diphenylindenone in 30% yield. The acyclic diene metathesis (ADMET) polymerization of soybean oil has been studied in this thesis. The polymerization of ethylene glycol dioleate afforded the isomerized E,£-dioleate (27%), dimer (18%), trimer (13%), tetramer (7%), pentamer (5%), hexamer (4%), heptamer (4%) and 9-octadecene (21%). Only a trace amount of the intramolecular cyclized compound (0.1 %) was formed in the reaction. Under the same conditions, glyceryl trioleate undergoes ADMET polymerization to produce dimer, trimer. tetramer, pentamer and monocyclic oligomers, with monocyclic oligomers predominating. A variety of materials, from sticky oils to mbbers, have been prepared from the ADMET

Three- and four-arm star shaped polymers, as well as diblock copolymers, are synthesized via acyclic diene metathesis (ADMET) polymerization. This is accomplished by using an asymmetric α,ω-diene containing a terminal double bond and an acrylate, which is polymerized in the presence of multifunctional acrylates as selective and irreversible chain transfer agents using Hoveyda-Grubbs second generation catalyst. High cross-metathesis selectivities are achieved at low temperatures enabling good control over molecular weights. Furthermore, additional polyethyleneglycol (PEG) blocks are attached to these polymers via Heck coupling of the acrylate end-groups of these polymers with aryl iodide functionalized PEG, obtaining three- and four-arm star shaped di- and triblock copolymers with molecular weights up to 31 kDa.

Sequence‐regulated vinyl polymers with functional groups, such as aliphatic, aromatic, hydroxy, amino, and carboxylic acid groups, as found in natural macromolecules such as proteins, are one of the ultimate targets in synthetic polymers. This study is directed toward the synthesis of periodically functionalized sequence‐regulated vinyl polymers using a series of reactions consisting of iterative atom transfer radical additions (ATRAs) of vinyl monomers, allylation, functionalization, protection, acyclic diene metathesis (ADMET) polymerization, hydrogenation, and deprotection. The functionalized sequence‐regulated telechelic diene oligomers, possessing protected hydroxy, carboxylic acid, and amino groups in the pendant of the acrylate unit between two styrene units, are prepared by iterative ATRAs of two styrene molecules to methyl dichloroacetate followed by allylation of both C–Cl termini and substitution of methyl ester with the protected functionalized groups. The protected functionalized sequence‐regulated telechelic diene oligomers are then polymerized by ADMET polymerization to afford polymers with main‐chain internal olefins and protected functionalized side chains in the acryl units between the two styrene units. The subsequent hydrogenation and deprotection reactions produce a series of sequence‐regulated vinyl polymers with periodic polar functional groups such as –OH, –CO2H, and –NH3+Cl–. These functional groups affect the thermal properties and solubility of the polymers.

A series of polyethylenes containing 21-carbon alkyl branches have been synthesized by acyclic diene metathesis (ADMET) polymerization. These 21-carbon alkyl branches are precisely placed on every 15th, 19th, 21st, 23rd, and 39th carbon along the polymer backbone. Precision of primary structures of all polymers is verified by 1H and 13C NMR spectroscopy. All polymers present well-defined melting profiles, even at a high branch incorporation (13.3% mol). The melting temperature increases as the branch frequency decreases, similar to what we observed for short-chain branched polyethylenes. These observations together with a good linear relationship derived from Flory's theory suggest the exclusion of 21-carbon side chains from polyethylene crystal units.

Efficient and sustainable transformation of biomass-derived chemicals to materials with the potential to replace conventional fossil-derived polymers is considered a major challenge. In this work, we disclose the synthesis of a novel furan-based α,ω-diene monomer following a facile, green, and energy-efficient process from fully renewable starting materials. The multifunctional monomer was produced by the base-catalyzed cross-aldol condensation of 10-undecenal (UA) and 2,5-diformylfuran (DFF) under mild conditions, providing the desired product in good yields. By employing the new monomer, fully biobased polymers were prepared in good molecular weights (<i>M</i> _n up to 31 kg/mol) by acyclic diene metathesis (ADMET) polymerization using Grubb's second-generation catalysts. The structure-property investigation of the polymers revealed <i>T</i> _g in the range of -16 to 5 °C, high thermal stability, good hydrophobicity, and photoactive properties. Owning to the presence of amenable functional groups, the resultant polymer was also subjected to postpolymerization modifications. The effect of these modifications on the polymer properties showed enhanced crystallization attributed to hydrogen bonding interactions. This work demonstrates a scalable and environmentally benign approach to access structurally novel and versatile materials exhibiting interesting properties from 100% biobased resources.

Amorphous, hydrophobic telechelic hydrocarbon diols were synthesized using acyclic diene metathesis (ADMET) polymerization. These diols can be used in hydrolysis and UV resistant polyurethanes. The hydrocarbon backbone is based on a mimic of an ethylene/isobutylene polymer, made by the ADMET polymerization of a gem‐dimethyl substituted α,ω‐diene followed by hydrogenation of the polymer's repeat unit unsaturation. Chain termination reactants (CTR's) having one, three, and nine methylene “spacers,” respectively, between their olefin and alcohol precursor group were used to cap the polymer chain ends to yield 2.0 functional telechelics. Use of the medium length CTR in a polymerization–depolymerization scheme, resulted in amorphous (Tg = −56 °C) telechelic diols with good molecular weight control.magnified image

Acyclic diene metathesis (ADMET) polymerization is a unique strategy for achieving polymers with precise control over the primary structure. This precision is obtained by specific monomer design and carefully controlled polymerization conditions. Over time, this approach has produced an array of sophisticated architectures ranging from precise polyethylenes, to hyperbranched polymers, to rotaxanes. image

Acyclic diene metathesis (ADMET) polymerization has been used in the synthesis of telechelic materials using alkoxy-functionalized carbosiloxane or oligo(oxyethylene)-based polymers, varying from internal to terminal cured materials or the combination of them. Previous investigations demonstrated that introduction of chain-end crosslinking improves the stress–strain behavior of such materials. A series of saturated and unsaturated carbosiloxane and oligo(oxyethylene)-based polymers were synthesized by ADMET polymerization using silacyclobutane as chain-end, thermally induced crosslinker. The carbosiloxane derivatives presented pure amorphous behavior, whereas the oligo(oxyethylene) polymers were semicrystalline. The thermal curing process was monitored by differential scanning calorimetry via the exotherm between 160 and 210 °C. Mechanical properties on thermoset polymers were measured, where cured polymers showed moduli from 0.6 to 9.3 MPa, tensile strengths from 0.3 to 1.0 MPa, and elongations from 12 to 76%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The research presented in this thesis focuses on the preparation of functionalized polymers using olefin metathesis polymerization methods. A portion of this research is also devoted to the development of applications for metathesis-derived polymers. Three distinct types of olefin metathesis polymerizations can be recognized within this work. Ring-opening metathesis polymerization (ROMP) is the most prevalent type, followed by acyclic diene metathesis (ADMET) polymerization and a hybrid of the ROMP and ADMET mechanisms known as ring-opening-insertion metathesis polymerization (ROIMP). Many of the concepts that appear throughout this thesis are introduced in Chapter 1. Olefin metathesis occupies a central role in each of the subsequent chapters; detailed descriptions of the mechanism and important olefin metathesis catalysts are provided. The chapter also includes background information regarding polymers, polymer properties and the application of ROMP in the construction of electronic devices. Although the utility of ADMET does not yet seem to match that of ROMP, valuable information can be obtained from ADMET polymerizations. In an effort to elucidate catalytic activity, Chapter 2 details a comparison of the ADMET polymerizations of terminal and non-terminal dienes. Experimental investigations involving ROIMP, a novel method for the production of A,B-alternating copolymers, is presented in Appendix A. The mechanism of ROIMP is conceptually very different from the mechanisms of either step growth or chain growth polymerizations. Efforts toward understanding the mechanism of ROIMP using a mathematical model are discussed in Chapter 3. Polymeric chain transfer agents (PCTAs) suitable for ROMP reactions are polymers that contain a single, metathesis-active olefin. These polymers are the focus of Chapter 4 and can be used in the preparation of novel block copolymers. As an example, Appendix B presents the preparation of block copolymers consisting of polyacetylene and various commodity polymers. Finally, the development of applications for surface-initiated ROMP (SI-ROMP) is discussed in Chapter 5 and Appendix C. Polymer films prepared using SI-ROMP are shown to be viable dielectric layers in thin-film transistors, and research is presented involving microcontact printing and dip pen nanolithography as methods for forming patterned SI-ROMP polymer films.

Acyclic diene metathesis (ADMET) polymerization of divinyltetramethyldisiloxane in the presence of rhodium [RhCl(COD)]2 and ruthenium RuCl2(PPh3)3 catalysts led predominantly to linear oligomers [M n=1815,M w/M n=1.16] if the rhodium catalyst was used or to mixtures of dimeric and trimeric oligomers if the ruthenium complex was applied. The rhodium complex appeared to be the first effective catalyst for ADMET polymerization of divinyldisubstituted organosilicon compounds.

The exclusive synthesis of a series of end-functionalizedconjugatedpolymers, poly­(9,9′-di-n-octylfluorene-2,7-vinylene)­s(EF-PFVs) containing different end groups (chromophores), enabledby adopting acyclic diene metathesis (ADMET) polymerization usinga molybdenum catalyst, Mo­(CHCMe2Ph)­(N-2,6-Me2C6H3)­[OC­(CH3)­(CF3)2], followed by termination, treating with various aldehydesthrough Wittig-type cleavage, has been demonstrated. The formationof the EF-PFVs containing different end groups was further confirmedby the analysis of their photophysical properties through steady-stateand time-resolved fluorescence studies for PFVs containing one ortwo terthiophene units. These EF-PFVs exhibit multicolored emissions.The EF-PFVs containing coumarin and F-BODIPY as end groups, expressedas Coumarin-PFV-F-BODIPY, showed white light emission with high efficiency(ΦPL = 71–75%). The emission properties (CIEcoordinates and fluorescence spectra) of the EF-PFVs containing chromophoreswere strongly affected by the end groups and the PFV chain lengthsemployed.

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Tandem acyclic diene metathesis (ADMET) polymerization/catalytic hydrogenation has been exploited to synthesize copolymers modeling ethylene/vinyl acetate (EVA) materials. A series of four sequence-ordered ethylene-co-vinyl acetate copolymers were prepared possessing precisely defined ethylene run lengths from 18 to 26 carbons. Use of the well-defined ADMET reaction in combination with a quantitative olefin−hydrogen technique generates well-defined EVA's, all of which are semicrystalline with a linear relationship between ethylene run length and melting temperature. All polymers except that with the lowest ethylene run length are film and fiber forming.

A novel cyclodextrin-based hyperbranched polymer (HBP) was synthetized via acyclic diene metathesis (ADMET) polymerization in homogeneous water/organic mixtures. A modified α-cyclodextrin (α-CD) molecule with one electron-rich terminal alkene and many electron-poor acrylates was first prepared through the esterification reaction, and then utilized as an ABn-type monomer for subsequent ADMET polymerization between alkene and acrylate using the second generation Hoveyda-Grubbs catalyst, yielding HBP with the reaction time prolonged. The chemical structures of monomer and HBP were characterized by elemental analysis, IR, gel permeation chromatography with multiangle laser light scattering, and NMR measurements. The degree of branching was determined by using 1H NMR spectroscopy and the values ranged from 0.51 to 0.42. Influence of the molecular weight on the properties (thermal stability and solubility) was also investigated. The resulting HBPs showed the good thermal stability, and higher molecular weight resulted in higher decomposition temperature from 361 °C to 383 °C. These thermally stable HBPs also displayed the excellent solubility in aprotic polar solvents.