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Articles 1 - 14 of 14
Full-Text Articles in Engineering
The Effect Of The Core On The Thermotropic Behavior Of Three-Arm Star Poly [11-(4-Cyanophenyl-4-Phenoxy) Undecyl Acrylate] S Synthesized By Atom Transfer Radical Polymerization, Coleen Pugh, Andrea Kasko, Steven Grunwald
The Effect Of The Core On The Thermotropic Behavior Of Three-Arm Star Poly [11-(4-Cyanophenyl-4-Phenoxy) Undecyl Acrylate] S Synthesized By Atom Transfer Radical Polymerization, Coleen Pugh, Andrea Kasko, Steven Grunwald
Coleen Pugh
“Three-arm star” poly[11-(4′-cyanophenyl-4′′-phenoxy)undecyl acrylate]s were synthesized by atom transfer radical polymerization (ATRP) of 11-(4′-cyanophenyl-4′′-phenoxy)undecyl acrylate using two new trifunctional initiators: 1,3,5-tri- (methyl 2-bromopropionate)benzene and 2,4,6-tri[4′-methyl(2′′-bromopropionate)phenoxymethyl]mesitylene. The polymers synthesized with 1,3,5-tri(methyl 2-bromopropionate)benzene (series II) contained 14–127 repeat units according to gel permeation chromatography relative to linear polystyrene (GPCPSt) and 13–271 repeat units according to GPC with a light scattering detector (GPCLS). Those synthesized with 2,4,6-tri[4′-methyl(2′′-bromopropionate)phenoxymethyl]mesitylene (series III) contained 14–87 repeat units according to GPCPSt and 10–120 repeat units according to GPCLS. The absolute molecular weight, size, and shape of both series of polymers were characterized by light scattering in CH2Cl2, and …
Characterization Of Linear And Branched Polyacrylates By Tandem Mass Spectrometry, Kittisak Chaicharoen, Michael Polce, Anirudha Singh, Coleen Pugh, Chrys Wesdemiotis
Characterization Of Linear And Branched Polyacrylates By Tandem Mass Spectrometry, Kittisak Chaicharoen, Michael Polce, Anirudha Singh, Coleen Pugh, Chrys Wesdemiotis
Coleen Pugh
The unimolecular degradation of alkali-metal cationized polyacrylates with the repeat unit CH(2)CH(COOR) and a variety of ester pendants has been examined by tandem mass spectrometry. The fragmentation patterns resulting from collisionally activated dissociation depend sensitively on the size of the ester alkyl substituent (R). With small alkyl groups, as in poly(methyl acrylate), lithiated or sodiated oligomers (M) decompose via free-radical chemistry, initiated by random homolytic C-C bond cleavages along the polymer chain. The radical ions formed this way dissociate further by backbiting rearrangements and beta scissions to yield a distribution of terminal fragments with one of the original end groups …
Synthesis, Isolation, And Thermal Behavior Of Polybutadiene Grafted With Poly (2, 3, 4, 5, 6-Pentafluorostyrene), Marta Paz-Pazos, Coleen Pugh
Synthesis, Isolation, And Thermal Behavior Of Polybutadiene Grafted With Poly (2, 3, 4, 5, 6-Pentafluorostyrene), Marta Paz-Pazos, Coleen Pugh
Coleen Pugh
2,3,4,5,6-Pentafluorostyrene (PFS) was copolymerized with polybutadiene (PB) in tetrahydrofuran using benzoyl peroxide as the initiator at 50, 60, and 80 °C. The copolymerizations follow typical radical polymerization kinetics and behavior. The grafting parameters were evaluated as a function of monomer conversion, initiator concentration, and/or temperature by gel permeation chromatography of directly injected copolymerization mixtures. The grafting efficiencies and grafting ratios are most consistent with a system that terminates by combination and whose graft sites are generated by hydrogen abstraction of allylic radicals by primary initiator radicals. Pure graft copolymers were isolated by extracting unreacted PB into hexanes and PPFS homopolymer …
Measurement Of Chain Transfer Constants To Polymer Using Oligomers And Model Compounds: Chain Transfer To Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] In Radical Polymerization, Coleen Pugh, Guangyu Fan, Andrea Kasko
Measurement Of Chain Transfer Constants To Polymer Using Oligomers And Model Compounds: Chain Transfer To Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] In Radical Polymerization, Coleen Pugh, Guangyu Fan, Andrea Kasko
Coleen Pugh
The chain transfer constant to polymer (CP) for poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate] was measured directly by the Mayo method by following the decrease in molecular weight at low monomer conversion by gel permeation chromatography of poly(methyl acrylate) generated in the presence of increasing amounts of 11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl propionate (CP = (6.62 ± 0.476) × 10-3) and 11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl isobutyrate (CP = (4.27 ± 0.858) × 10-3) as model compounds that mimic one repeat unit of the polymer and oligo[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate] with nine repeat units (CP = (5.54 ± 0.608) × 10-3) synthesized by atom transfer radical polymerization. The mean chain …
Synthesis Of Hyperbranched Polyacrylates By A Chloroinimer Approach, Coleen Pugh, Anirudha Singh, Reichel Samuel, Karla Bernal Ramos
Synthesis Of Hyperbranched Polyacrylates By A Chloroinimer Approach, Coleen Pugh, Anirudha Singh, Reichel Samuel, Karla Bernal Ramos
Coleen Pugh
(2-Chloro-2-alkoxycarbonyl)ethyl acrylates with methyl, dodecyl, perfluoroalkyl, siloxane, oligooxyethylene, and mesogenic ester substituents were synthesized as inimers for self-condensing vinyl polymerization (SCVP) to produce hyperbranched polyacrylates. The inimers were polymerized by atom transfer radical polymerization under a variety of conditions to produce soluble polymers with broad polydispersities (up to PDI = 5.24) characteristic of hyperbranched polymers, although the isolated polymers had narrower polydispersities. The molecular weight distribution was followed as a function of time and inimer conversion for the polymerization of the mesogenic inimer. The first-order inimer conversion was linear with time. The buildup of a hyperbranched structure during the SCVP …
Synthesis And Mass Spectrometry Studies Of An Amphiphilic Polyether-Based Rotaxane That Lacks An Enthalpic Driving Force For Threading, Kathleen Wollyung, Kaitian Xu, Michael Cochran, Andrea Kasko, Wayne Mattice, Chrys Wesdemiotis, Coleen Pugh
Synthesis And Mass Spectrometry Studies Of An Amphiphilic Polyether-Based Rotaxane That Lacks An Enthalpic Driving Force For Threading, Kathleen Wollyung, Kaitian Xu, Michael Cochran, Andrea Kasko, Wayne Mattice, Chrys Wesdemiotis, Coleen Pugh
Coleen Pugh
A pure amphiphilic macrocrown ether (MC-12) was obtained by removing linear oligomers and larger macrocycles at the macrocyclization step, before proceeding with an established synthetic procedure. This pure MC-12 was used to synthesize a rotaxane composed of one MC-12 ring threaded with one end-capped poly(tetrahydrofuran) (PTHF) oligomer by equilibrating half an equivalent of the thread with an organized solution of MC-12 and end-capping the threads with excess 2-p-[tris(p-tert-butylphenyl)methyl]phenoxymethyl-4,4-dimethylazlactone. The rotaxane was positively identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry (MS), although the spectra showed a low abundance of the rotaxane ions and high abundances of unthreaded MC-12 and …
Architectural Effects In Side-Chain Liquid Crystalline Polymers: Hyperbranched Sclcps, Coleen Pugh, Anirudha Singh
Architectural Effects In Side-Chain Liquid Crystalline Polymers: Hyperbranched Sclcps, Coleen Pugh, Anirudha Singh
Coleen Pugh
No abstract provided.
Elucidating The Structure Of Hyperbranched Side-Chain Liquid Crystalline Polyacrylates, Anirudha Singh, Coleen Pugh
Elucidating The Structure Of Hyperbranched Side-Chain Liquid Crystalline Polyacrylates, Anirudha Singh, Coleen Pugh
Coleen Pugh
Side-chain liquid crystalline polymers (SCLCPs) prepared by non-living polymerizations generally exhibit very broad phase transitions, in contrast to low molar mass liquid crystals. The broad phase transitions were immediately dismissed in the SCLCP literature as being due to polydispersity in molecular weight. For example, when poly[11-(4'-cyanophenyl-4"-phenoxy)undecyl acrylate] was prepared by a conventional radical polymerization and then fractionated,1 each of the fractions underwent a narrower smectic A to isotropic transition (full widths at half maximum peak intensity (fwhm) = 6.25 – 10.71 o C) than the unfractionated polymer (fwhm = 17.0 o C).2 However, we have provided evidence that the broad …
Solution Behavior Of Topological Isomers Of Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] S Prepared By Atom Transfer And Conventional Radical Polymerizations, Andrea Kasko, Coleen Pugh
Solution Behavior Of Topological Isomers Of Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] S Prepared By Atom Transfer And Conventional Radical Polymerizations, Andrea Kasko, Coleen Pugh
Coleen Pugh
The solution behavior of linear, three-arm star, and comb poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate]s previously synthesized by atom transfer radical polymerization was investigated by gel permeation chromatography (GPCPSt) and light scattering measurements in CH2Cl2, THF, and CHCl3 in order to correlate their size and shape with their molecular architecture and in order to investigate the extent of branching in the corresponding polymer prepared by conventional radical polymerization. The inaccuracy of the GPCPSt molecular weights increases as the polymers become more branched: linear < three-arm star < comb; the discrepancy between the GPCPSt and absolute molecular weights of polymers fractionated from the conventional radical polymerization is between those of the three-arm star and comb polymers in all three solvents. Light scattering studies demonstrate that CH2Cl2 is the best solvent for all of the polymers, resulting in either no aggregation or an insignificant amount of aggregation, whereas all of the topologies except the comb polymers tend to aggregate in THF and CHCl3; nevertheless, the extent of aggregation is not great enough to be detected by variations in the average GPCLS-determined molecular weights measured in any of these solvents. The tendency to aggregate in all of the solvents and the radius of gyration in CH2Cl2 decrease as the branching increases: linear > three-arm star > comb, with the polymer prepared by conventional radical polymerization being similar to the branched polymers. The scaling coefficients …
Comparison Of The Thermotropic And Solution Behavior Of Six-Arm Star And Comb Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] S, Andrea Kasko, Coleen Pugh
Comparison Of The Thermotropic And Solution Behavior Of Six-Arm Star And Comb Poly [11-(4'-Cyanophenyl-4''-Phenoxy) Undecyl Acrylate] S, Andrea Kasko, Coleen Pugh
Coleen Pugh
“Six-arm star” poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate]s with 13−112 (gel permeation chromatography, GPC, relative to linear polystyrene) or 23−756 (GPC using a light scattering detector) repeat units were synthesized from the hexafunctional initiator, 1,2,3,4,5,6-hexa((4‘-methyl(2‘ ‘-bromopropionate)phenoxymethyl)benzene, by atom transfer radical polymerization of 11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate, followed by fractionation to narrow the polydispersity to 1.06−1.57. The absolute molecular weight, size, and shape of these polymers were characterized by light scattering in CH2Cl2, and their thermotropic behavior was analyzed by differential scanning calorimetry; both types of properties were compared to those of the other architectures, especially the corresponding comb poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate]s with six branches. …
Monte Carlo Simulation Of Solvent Effects On The Threading Of Poly (Ethylene Oxide), Guoqiang Xu, Sagar Rane, Carin Helfer, Wayne Mattice, Coleen Pugh
Monte Carlo Simulation Of Solvent Effects On The Threading Of Poly (Ethylene Oxide), Guoqiang Xu, Sagar Rane, Carin Helfer, Wayne Mattice, Coleen Pugh
Coleen Pugh
Recently, we described a coarse-grained model of poly(ethylene oxide) (PEO) and then employed that model to study the amount of spontaneous threading of cyclic molecules by linear chains in the melt (Helfer et al Macromolecules at press). We now use that coarse-grained model to determine how the amount of threading is affected by dilution of the PEO melt with good, Θ, or poor solvents. We employ two distinctly different methods for incorporating the solvent. One method employs explicit coarse-grained solvent molecules, which have the same size as a coarse-grained bead of the polymer. Solvents of different quality are produced by …
Synthesis And Thermotropic Behavior Of Polynorbornenes With Laterally Attached 2, 5-Bis [(4'- N-Alkylthiobenzoyl) Oxy] Benzyl Mesogens, Senetta Bancroft, Matthew Thompson, Nanna Frimpong, Richard Mullins, Coleen Pugh
Synthesis And Thermotropic Behavior Of Polynorbornenes With Laterally Attached 2, 5-Bis [(4'- N-Alkylthiobenzoyl) Oxy] Benzyl Mesogens, Senetta Bancroft, Matthew Thompson, Nanna Frimpong, Richard Mullins, Coleen Pugh
Coleen Pugh
roduction Supramolecular chemistry investigates entities generated via intermolecular, non-covalent bonding such as hydrogen bonding, electrondonor-acceptor (EDA) interactions and metal ion coordination, which can be used to generate polymolecular assemblies.i In spite of maturity of the field of low molar mass liquid crystals (LMMLCs) and side-chain liquid crystalline polymers (SCLCPs) in electro-optical displays, few concepts have been developed for converting the type of mesophases exhibited by a given chemical structure. The most significant transformation is from nematic to smectic mesophases, and vice versa. Induction of a smectic mesophase in laterally attached SCLCPs (Scheme 1) is particularly challenging since this molecular architecture …
Synthesis Of Optically Active Copolymers Of 2, 3, 4, 5, 6-Pentafluorostyrene And Beta-Pinene With Low Surface Energies, Marta Paz-Pazos, Coleen Pugh
Synthesis Of Optically Active Copolymers Of 2, 3, 4, 5, 6-Pentafluorostyrene And Beta-Pinene With Low Surface Energies, Marta Paz-Pazos, Coleen Pugh
Coleen Pugh
2,3,4,5,6-Pentafluorostyrene (PFS) was copolymerized with β-pinene (PIN) in bulk using benzoyl peroxide as the initiator at 70 °C. The reactivity ratios for PFS (rPFS) and PIN (rPIN) were determined by limiting each monomer conversion to approximately 10 mol % or less during 2 h of copolymerization and then plotting the composition data according to both the Fineman–Ross (r1 = rPFS = 5.2, r2 = rPIN = 0.070) and Kelen–Tudös (r1 = rPFS = 5.0, r2 = rPIN = 0.017) methods. The copolymers exhibited a single glass transition at 60–100 °C, static water contact angles higher than 95°, and optical activity …
Correlation Of Free Radical Copolymerization Behavior And Copolymer Properties With The Strength Of Pi-Pi Stacking Interactions Between Aromatic Fluorocarbons And Aromatic Hydrocarbons: Comparison Of The Copolymerization Behavior Of 2, 3, 4, 5, 6-Pentafluorostyrene With Styrene, 1-Vinylnaphthalene And 2-Vinylnaphthalene, Coleen Pugh
Coleen Pugh
No abstract provided.