Thermomechanical Synergisms from Ionic Liquid Doping of Poly(methyl methacrylate).

A synergism between methyl methacrylate and an amphiphilic ionic liquid acrylate 1-(11-acryloyloxyundecyl)-3-methyl imidazolium bromide (IL) not only increases the apparent thermal stability (kinetic retardation of thermal decomposition) of poly(MMA-co-IL) copolymers by 50 °C at relatively low doping levels of 0.5 mol %, but also increases the storage (∼10%) and loss (15-25%) moduli over 0-75 °C (increasing the elasticity). Moderate to high doping levels provide plasticization without the risk of leaching or plasticizer contamination.

Triblock copolymer based on poly(propylene oxide) and poly(1-[11-acryloylundecyl]-3-methyl-imidazolium bromide).

The controlled atom transfer radical polymerization of an ionic liquid, 1-(11-acryloylundecyl)-3-methyl imidazolium bromide (ILBr), from both ends of a telechelic poly(propylene oxide) (PPO) macroinitiator, end-functionalized with bromoisobutyryloyl is reported. The resulting highly water-soluble triblock, poly(ILBr-b-PO-b-ILBr) is multistimuli responsive. This new class of triblocks exhibits classical surface activity in lowering surface tension at the air-water interface and in modifying wetting in waterborne coatings. It also immunizes model colloids against coagulation induced by Debye-Hückel (indifferent electrolyte) electrostatic screening. Further, sol-gel thermoreversibility is unexpectedly found as an additional form of stimuli responsiveness.

Polymer dewetting via stimuli responsive structural relaxation-contact angle analysis.

Thin films of a stimuli-responsive homopolymer dewet as a stimulus response after anion exchange of the imidazolium's counter anion. Contact angle analysis and interfacial energy considerations indicate dewetting goes counter to increasing spreading coefficient. Intrafilm stress arising from structural relaxation drives the dewetting.

Stimuli responsive poly(1-[11-acryloylundecyl]-3-methyl-imidazolium bromide): dewetting and nanoparticle condensation phenomena.

A stimuli-responsive homopolymer poly(ILBr) is fabricated via a "two-phase" atom transfer radical polymerization (ATRP) process, where ILBr stands for the reactive ionic liquid surfactant, 1-[11-acryloylundecyl]-3-methyl-imidazolium bromide. An extraordinarily wide molecular weight distribution (PDI = 6.0) was obtained by introducing the initiator (4-bromomethyl methyl benzoate) in a heterogeneous two-phase process. The molecular weight distribution of poly(ILBr) was characterized by size-exclusion chromatography (SEC). The resulting homopolymer was found to be surface active and stimuli responsive. Poly(ILBr) films coated on quartz exhibit stimuli-responsive dewetting after ion exchange of Br(-) by PF(6)(-). This dewetting phenomenon can be understood in chain segmental terms as a stimuli-induced structural relaxation and appears to be the first such reported stimuli-responsive polymeric dewetting. Titrating aqueous poly(ILBr) with aqueous bis(2-ethylhexyl)sulfosuccinate induces nanophase separation and results in the condensation of nanoparticles 30-60 nm in diameter.

Organic solvent-dispersed TiO(2) nanoparticle characterization.

Anatase titanium dioxide nanoparticles are derivatized with the polymerizable reagent (3-methacryloxypropyl)trimethoxysilane to provide dispersions in organic solvent. The titania core particles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The organic component structures and thickness are elucidated using nuclear magnetic resonance (NMR), quasielastic light scattering (QELS), and size-exclusion chromatography (SEC). Thin, high-refractive-index coatings prepared from the organic dispersions are characterized by atomic force microscopy (AFM). The combination of microscopies, spectroscopy, light scattering, and separation techniques provides unique information on the structure, thickness, morphology, and size distributions of the surface-treated nanoparticles that is difficult to obtain by any single technique. The findings indicate titania platelets with a modal diameter of 9.8 nm and a thickness of approximately 1.5 nm. The particles are coated with a 1.5-1.9 nm thick organic ligand layer, and a substantial population of 2 nm siloxane oligomers is detected. The analytical methodology presented may also be useful for characterizing other anisotropic organic-inorganic nanoparticles and their dispersions.

Characterizing property distributions of polymeric nanogels by size-exclusion chromatography.

Nanogels are highly branched, swellable polymer structures with average diameters between 1 and 100nm. Size-exclusion chromatography (SEC) fractionates materials in this size range, and it is commonly used to measure nanogel molar mass distributions. For many nanogel applications, it may be more important to calculate the particle size distribution from the SEC data than it is to calculate the molar mass distribution. Other useful nanogel property distributions include particle shape, area, and volume, as well as polymer volume fraction per particle. All can be obtained from multi-detector SEC data with proper calibration and data analysis methods. This work develops the basic equations for calculating several of these differential and cumulative property distributions and applies them to SEC data from the analysis of polymeric nanogels. The methods are analogous to those used to calculate the more familiar SEC molar mass distributions. Calibration methods and characteristics of the distributions are discussed, and the effects of detector noise and mismatched concentration and molar mass sensitive detector signals are examined.

Importance of solubility in the sample preparation of poly(ethylene terephthalate) for MALDI TOFMS.

The role of solubility in the sample preparation process for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is demonstrated for oligomeric and medium molar mass poly(ethylene terephthalate) (PET). For low molar mass oligomers (PET-1), minor discrimination effects were observed when the sample was not completely in solution. MALDI spectra of medium molar mass PET, representative of the entire molar mass distribution, were obtained only when a good solvent for PET was used, such as 1,1,1,3,3,3-hexafluoro-2-propanol (commonly referred to as HFIP), as the sample preparation solvent and dithranol as the matrix. The azeotropic composition of 70:30 CH(2)Cl(2)/HFIP better solubilizes the more nonpolar matrixes, which enables more latitude in selecting sample preparation conditions than pure HFIP. Segregation effects were observed when the azeotrope mixture was diluted with tetrahydrofuran, resulting in large molar mass distribution discrimination effects in the MALDI spectra. Dilution with CH(2)Cl(2) resulted in a significant decrease in the overall signal intensity for the entire polymer distribution. With each attempt to dilute the azeotrope, the sample after solvent evaporation was visibly heterogeneous, which resulted in shot-to-shot variability. Both examples demonstrate the importance of constant solvent composition during solvent evaporation. The compatibility of matrix and polymer was explored using relative HPLC retention times. Consistent with previous work in our laboratories, it was found that the matrix/polymer combination that has the closest match of retention time resulted in the best MALDI signal intensity.

Polymerizable bis(2-ethylhexyl)sulfosuccinate: application in microemulsion polymerization.

A hygroscopic and polymerizable salt ([2-methacryloyloxy]ethyl trimethylammonium chloride) is used to ion exchange the sodium ion in AOT (bis[2-ethylhexyl]sulfosuccinate, sodium salt) to produce a polymerizable form of AOT, MDOS ([2-methacryloyloxy]ethyl trimethylammonium bis[2-ethylhexyl]sulfosuccinate). A partial ternary phase diagram of water, MDOS, and methyl methacrylate (MMA) was determined at room temperature (22 +/- 1 degrees C). A relatively large L2 domain is obtained, but this domain is smaller than that obtained with AOT. Microemulsion polymerization in this domain at 70 degrees C, using AIBN (azoisobutyronitrile) as an initiator, produces an optically clear copolymer solid domain nearly as large as the L2 domain. This interesting behavior contrasts with similar studies of Pavel and Mackay [Langmuir 2000, 16, 8528] using a polymerizable surfactant DDAMA (didecyldimethylammonium methacrylate) that produced a much larger L2 domain than MDOS but yielded a much smaller optically clear domain after thermally initiated polymerization. Thermogravimetric analysis indicates that optically clear composites obtained at an MDOS/MMA weight ratio of 1:4 and containing 5% water (w/w; weight % water in microemulsion) released the water in a transition commencing around 160 degrees C and continuing to 250 degrees C. Thereafter, the thermal decomposition was substantially impeded relative to poly(methyl methacrylate) as a control, which was due to the fire-resistant nature of the MDOS monomer. Molecular weight measurements indicate MDOS/MMA copolymers form substantially higher molecular weights as the proportion of MDOS increases. At a given radius of gyration, higher MDOS-containing copolymers exhibit higher molecular weights, suggesting a more compact structure with increasing MDOS.

Size-exclusion chromatography in 1,1,1,3,3,3-hexafluoro-2-propanol.

1,1,1,3,3,3-Hexafluoroisopropanol is re-examined as an eluent for size-exclusion chromatography (SEC) of polyesters, nylons, and other polar polymers. It is shown that anomalous SEC behavior reported in previous literature can be eliminated by adding 0.01 M tetraethylammonium nitrate to the eluent. The eluent modifier does not affect the solution viscosity or root-mean-square radii of moderately polar polymers such as polyesters and nylons, but it does decrease these quantities for more polar polymers such as poly(ethylene oxide) and poly(2-vinylpyridine). More important, this salt appears to minimize repulsive interactions with styrene-divinylbenzene column packings that have contributed to non-ideal size-exclusion behavior. As a result, conditions are established that satisfy universal calibration.