Synthesis and evaluation of poly (N-vinyl caprolactam)-co-tert-butyl acrylate as kinetic hydrate inhibitor

Low dosage kinetic hydrate inhibitors(KHIs) are a kind of alternative chemical additives to high dosage thermodynamic inhibitors for preventing gas hydrate formation in oil & gas production wells and transportation pipelines.In this paper,a new KHI,poly(N-vinyl caprolactam)-co-tert-butyl acrylate(PVCapco-TBA),was successfully synthesized with N-vinyl caprolactam(NVCap) and tert-butyl acrylate.The kinetic inhibition performances of PVCap-co-TBA on the formations of both structure Ⅰ methane hy...     

Crystal growth inhibition of tetrahydrofuran hydrate with poly(N-vinyl piperidone) and other poly(N-vinyl lactam) homopolymers

Poly(N-vinyl pyrrolidone) (PVP) containing the 5-ring lactam and poly(N-vinyl caprolactam) (PVCap) containing the 7-ring lactam are well-known kinetic hydrate inhibitors (KHIs). For the first time we have synthesised and studied the performance of poly(N-vinyl piperidone) (PVPip), containing the 6-ring lactam, as a kinetic hydrate inhibitor. In the first part of the study we have investigated the ability of PVPip to inhibit the growth of tetrahydrofuran SII hydrate crystals. The results are compared to those of PVP and PVCap. Various polymer molecular weights have been investigated at varying subcoolings. PVPip shows an intermediate growth inhibition performance compared to PVP and PVCap at similar polymer molecular weights. In addition, the weight percentage concentration of polymer needed to achieve complete THF hydrate crystal growth inhibition increases as the polymer molecular weight decreases.     

Miscibility and interactions in poly(methylthiomethyl methacrylate)/poly(vinyl alcohol) blends

Poly(methylthiomethyl methacrylate) (PMTMA) is miscible with poly(vinyl alcohol) (PVA) over the whole composition range as shown by the existence of a single glass transition temperature in each blend. The interaction between PMTMA and PVA was examined by Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The interactions mainly involve the hydroxyl groups of PVA and the thioether sulfur atoms of PMTMA, and the involvement of the carbonyl groups of PMTMA in interactions is not significant. The measurements of proton spin-lattice relaxation time reveal that PMTMA and PVA do not mix intimately on a scale of 1-3 nm, but are miscible on a scale of 20-30 nm. In comparison, we have previously found that PMTMA is miscible with poly(p-vinylphenol) and the two polymers mix intimately on a scale of 1-3 nm.     

An investigation into the laboratory method for the evaluation of the performance of kinetic hydrate inhibitors using superheated gas hydrates

Kinetic hydrate inhibitors (KHIs) are used to prevent gas hydrate formation in gas and oilfield operations. Recently, a new KHI test method was reported in which hydrates are formed and re-melted just above the equilibrium temperature, before the fluids are re-cooled and the performance of the chemical as a KHI is determined. The method, which we have called the superheated hydrate test method, is claimed to be more reliable for KHI ranking in small equipment, giving less scattering in the hold time data due to avoiding the stochastic nature of the first hydrate formation. We have independently investigated this superheated hydrate test method in steel and sapphire autoclave tests using a gas mixture forming Structure II hydrates and a liquid hydrocarbon phase, which was necessary for satisfactory results. Our results indicate that hold times are shorter than using non-superheated hydrate test methods, but they are more reproducible with less scattering. The reduced scattering occurs in isothermal or slow ramping experiments even when the hydrates are melted at more than 10 °C above the equilibrium temperature (T_eq). However, if a rapid cooling method is used, the improved reproducibility is retained when melting hydrate at 2.4 °C above T_eq but lost when warming to 8.4 °C above T_eq. Using the ramping test method, most, but not all the KHIs tested agreed with the same performance ranking obtained using traditional non-superheated hydrate test methods. This may be related to the variation in the dissociation temperature of gas hydrates with different KHIs and different KHI inhibition mechanisms. Results also varied between different size autoclave equipments.     

THF hydrate crystal growth inhibition with small anionic organic compounds and their synergistic properties with the kinetic hydrate inhibitor poly(N-vinylcaprolactam)

Small, cationic tetraalkylammonium ions (particularly for alkyl=butyl or pentyl) are known to inhibit tetrahydrofuran (THF) and natural gas hydrate crystal growth and have been used as synergists for commercial kinetic hydrate inhibitor polymers (KHIs), such as N-vinylcaprolactam polymers, for a number of years. The ability for small, organic anionic molecules to inhibit (THF) hydrate crystal growth and their potential as KHI synergists in blends with poly(N-vinylcaprolactam) have been investigated. Several series of sodium alkyl carboxylates, sulphates and sulphonates were synthesised. It was found that none of these molecules were capable of inhibiting THF hydrate crystal growth as well as the best tetraalkylammonium salts. Alkyl carboxylates appeared to be more effective as inhibitors than the sulphonates or sulphates. The most effective anionic THF hydrate crystal growth inhibitors had butyl or pentyl groups, with alkyl branching at the tail (i.e. iso- rather than n-isomers) being advantageous. Anionic carboxylate molecules, particularly with isopentyl or isobutyl groups, showed some kinetic inhibition synergy with poly(N-vinylcaprolactam) lowering the onset and catastrophic hydrate formation temperatures in high pressure (78 bar) constant cooling experiments with Structure II hydrates by 1–2 °C when dosed at 2500 ppm compared with using 2500 ppm polymer alone. This synergism was however less than the best tetraalkylammonium salts (alkyl=n-butyl or n-pentyl) at the same test conditions. Sodium butyl sulphonate and sodium 4-methylpentanoate did not prevent hydrate agglomeration with 3.6% brine and decane at 25% water cut in stirred sapphire cells when dosed at 20,000 ppm based on the aqueous phase, whereas 10,000–20,000 ppm active material of several commercially available anti-agglomerants gave fine transportable slurries and no hydrate deposits at the same conditions.     

Mechanical properties evaluation of new composites with protein biofibers reinforcing poly(methyl methacrylate)

Poly(methyl methacrylate) composites reinforced with natural protein biofibers from chicken feathers were prepared and evaluated through a series of tensile tests. Afterward, the samples were analyzed by optical and scanning electron microscopy studies, to obtain a clear picture of the tensile-induced damages.The hydrophobic nature of keratin fiber produces an excellent compatibility between fibers and PMMA matrix. This fact is reflected in the good dispersion of protein fibers achieved without use of coupling agents. The normally rigid behavior of PMMA may be modified by using keratin fibers as were demonstrated by tensile test; while at the same time, Young's modulus of composite material is also increased. The microscopic studies realized at the corresponding fracture surface level show good adherence between fibers and matrix. These results demonstrate that feather fibers could be a new source of natural high structure fibers useful to create new materials provided with satisfactory properties.     

Phase continuity and inversion in polystyrene/poly(methyl methacrylate) blends

Dual-phase continuity and phase inversion of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends processed in a twin-screw extruder was investigated using a selective extraction technique and scanning electron microscopy. Emphasis was placed on investigating the effects of viscosity ratio, blend composition, processing variables (mixing time and annealing) and diblock copolymer addition on the formation of bi-continuous phase structure (BPS) in PS/PMMA blends. The experimental results were compared with the volume fraction of phase inversion calculated with various semi-empirical models. The results showed that the formation of a BPS strongly depends on the blend composition and the viscosity ratio of the constituent components. Furthermore, BPS was found in a wide volume fraction interval. Increasing the mixing time and the addition of diblock copolymer, both led to a narrowing range of volume fraction in which BPS exists. Quiescent annealing coarsened the structure but indicated no qualitative changes. Some model predictions for phase inversion could predict qualitative aspects of the observed windows of co-continuity but none of the models could account quantitatively for the observed data.     

Tacticity effects on the miscibility behavior of poly(methyl methacrylate)/poly(ethylene oxide-b-dimethylsiloxane-b-ethylene oxide) blends

The miscibility of a triblock copolymer poly(ethylene oxide)-poly(dimethylsiloxane)-poly(ethylene oxide) with syndiotactic and isotactic poly(methylmethacrylate) wasstudied. Although isotactic poly(methyl methacrylate) (PMMA) was miscible with poly(ethylene oxide) (PEO) in the pure state, it was immiscible with the PEO end blocks in the copolymer. In comparison, the syndiotactic poly(methyl methacrylate) (sPMMA) was miscible with the PEO blocks as indicated by melting point depression, decrease in crystallinity, and slower rate of spherulite growth of PEO. When blends of the triblock copolymer were cooled to low temperatures, the poly(dimethylsiloxane) (PDMS) middle block which resided in the interlamellar region of PEO spherulites also crystallized; the development of PDMS crystals was clearly suppressed at high sPMMA contents.On leave from Union Chemical Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan     

Hot-drawing of poly(methyl methacrylate) and simulation using a glass-rubber constitutive model

The large-deformation three-dimensional glass-rubber constitutive model for isotropic, amorphous, linear polymers near the glass transition, previously proposed, has been extended to include a spectrum of network relaxations. In addition, an experimental programme of uniaxial tension and compression tests was carried out on high molecular weight cast sheets of poly(methyl methacrylate) (PMMA), with varying strain-rate and temperature across the range from 114 to 190 °C, encompassing the thermoforming range of practical importance. The extended model was found to fit successfully the data for PMMA, provided a doublet network relaxation spectrum was employed. The original model, with only a single network relaxation, was found to be grossly inadequate when there was significant network relaxation by entanglement slippage. Parameters of the model for PMMA, obtained by fitting to the new data, were compared with values obtained by other routes.     

Effect of physical aging on nano- and macroscopic properties of poly(methyl methacrylate) glass

Physical aging of amorphous poly(methyl methacrylate) has been studied by low frequency Raman scattering, broad-band dielectric spectroscopy, low frequency high resolution mechanical spectroscopy and differential scanning calorimetry. The material was subjected to different thermal histories by isothermal aging. A consistent relationship between the changes caused by the physical aging in nanostructure and molecular dynamics has been found. The aging makes the structure more homogeneous at a scale of few nanometers, bringing it to a structural state of lower energy. These structural changes affect mainly the -relaxation, however, some increase in the relaxation strength as well as an increase in the activation energy of the β-relaxation is also observed.     

Preparation of gold nanoparticles on poly(methyl methacrylate) nanospheres with surface-grafted poly(allylamine)

A facile method for in situ anchoring of gold nanoparticles onto the surface of polymer nanospheres was successfully developed in this study. As polymer nanospheres, amphiphilic poly(methyl methacrylate) (PMMA)/poly(allylamine) (PAA) nanospheres were prepared by graft copolymerization of methyl methacrylate from PAA. The gold nanoparticles anchored were spherically symmetric and the average sizes were ∼12 nm for all samples. It was found that surface-grafted PAA effectively anchored and stabilized gold nanoparticles for a long period of time.     

Synthesis of poly(methyl methacrylate)-silica nanocomposites using methacrylate-functionalized silica nanoparticles and RAFT polymerization

Well-defined poly(methyl methacrylate)-silica nanocomposites were produced by “grafting through” using reversible addition-fragmentation chain transfer (RAFT) polymerization. The surface of silica nanoparticle was modified covalently by attaching methacryl group to the surface using 3-methacryloxypropyldimethylchlorosilane. Polymerization of methyl methacrylate (MMA) using the 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid RAFT agent, produced the PMMA-SiO₂ nanocomposites. Characterization of these well-defined nanocomposites included FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), transmission electron microscopy (TEM) and dynamic mechanical analysis. These results show that the T_g values are higher and the mechanical strength of the PMMA-SiO₂ nanocomposites is slightly improved when compared to bulk PMMA. Further, the molecular weight of the PMMA (up to M_n = 100,000) is controlled and the SiO₂ are well dispersed in the PMMA matrix.     

Monodisperse macroporous poly(glycidyl methacrylate) microspheres coated with silica: Design,preparation and characterization

Monosized macroporous poly(glycidyl methacrylate) (PGMA) microspheres that were 9.3 μm in size were synthesized by multistep swelling polymerization using a modified Ugelstad technique. The PGMA microspheres and their hydrolyzed analogs derived from poly(2,3-dihydroxypropyl methacrylate) (PDHPMA) were coated by silanization with tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES), respectively. The particles were characterized by elemental and thermogravimetric (TGA) analysis, scanning and transmission electron microscopy (SEM and TEM) coupled with an energy dispersive X-ray analysis (EDAX) and FT-IR spectroscopy to determine the SiO₂ content, morphology, particle size, polydispersity and structure. These types of particles are expected to have improved biocompatibility relative to their starting polymers.     

Electrospinning of cyclodextrin functionalized poly(methyl methacrylate) (PMMA) nanofibers

Cyclodextrin functionalized PMMA nanofibers (PMMA/CD) were successfully produced by electrospinning technique with the goal to develop functional nanowebs. Bead-free uniform electrospun PMMA/CD nanofibers were obtained from a homogeneous solution of CDs and PMMA in dimethylformamide (DMF) using three different types of CDs, α-CD, β-CD and γ-CD. The electrospinning conditions were optimized in order to form bead-free PMMA/CD nanofibers by varying the concentrations of PMMA and CDs in the solutions. The concentration of CDs was varied from 5% up to 50% w/w, with respect to the PMMA matrix. We find that the presence of the CDs in the PMMA solutions facilitates the electrospinning of bead-free nanofibers from the lower polymer concentrations and this behavior is attributed to the high conductivity and viscosity of the PMMA/CD solutions. The X-ray diffraction (XRD) spectra of PMMA/CD nanowebs did not show any significant diffraction peaks indicating that the CD molecules are homogeneously distributed within the PMMA matrix and does not form any phase separated crystalline aggregates. Furthermore, attenuated total reflection Fourier transform infrared (ATR-FTIR) studies elucidate that some CD molecules are located on the surface of the nanowebs. This suggests that these CD functionalized nanowebs may have the potential to be used as molecular filters and/or nanofilters for waste treatment purposes.     

Solid-state NMR studies on phase behavior and motional mobility in binary blends of polystyrene and poly(cyclohexyl methacrylate)

The phase behavior and motional mobility in binary blends of polystyrene (PS) and poly(cyclohexyl methacrylate) (PCHMA) have been investigated by solid state ¹³C NMR techniques. The blend miscibility has been studied by examining the ¹H spin-relaxation times in the laboratory frame (T₁^H) and in the rotating frame (T_1ρ^H) for the PCHMA/PS blends with various compositions and pure components. The T_1ρ^H results show that PCHMA and PS are intimately mixed at the molecular level within the blends at all compositions. In addition, according to the results of carbon T_1ρ relaxation time measurements, we conclude that mixing is intimate enough to cause a reduction in local chain mobility for PS, but an increase in side chain mobility for PCHMA.     

Viscous and elastic properties of poly(methyl methacrylate) melts filled with silica nanoparticles

In this paper it is shown that elastic properties of a poly(methyl methacrylate) melt in the linear range of deformation are more significantly influenced by the addition of silica nanoparticles than viscous ones. The effect is the strongest in the steady-state which is reached at several thousand seconds. That is the reason why the often used dynamic-mechanical experiments are not a very suitable method for investigations of that kind. Therefore, creep and creep-recovery tests were applied for the characterisation of the filled materials. The linear steady-state recoverable compliances following from the recovery experiments increase by a factor of 6 at the highest measured volume content of 2.1%. This finding is explained by the existence of long retardation times in the filled materials resulting from interactions between the fillers and matrix molecules attached to their surfaces which reduce their molecular mobility. Retardation spectra calculated from the recovery curves quantify these assumptions. The model is supported by the experimental finding that the recoverable compliance becomes smaller above a certain stress applied and approaches that of the matrix as such a behaviour could be explained by a detachment of the molecules from the particle surface. The paper demonstrates that investigations of elastic properties of nanoparticle filled polymers in the molten state at long experimental times are a very sensitive tool to get an insight into interactions between particles and macromolecules of such systems.     

Copolymer electron resists: poly(stryene-methyl methacrylate) copolymers

The factors influencing electron beam sensitivity are reviewed. The variation of electron beam sensitivity and constrast are reported for a series of random copolymers of styrene and methyl methacrylate. Data are also presented for an alternating copolymer of styrene and methyl methacrylate. This study indicates the effects which arise when a negative resist material, polystyrene, is incorporated into a positive resist material, poly(methyl methacrylate).     

Morphology and spherulitic growth kinetics in poly(ethylene oxide)/poly(n‐butyl methacrylate) blends

Results of a study concerning the morphology and the spherulite growth rates of poly(ethylene oxide) (PEO) in binary blends with poly(n‐butyl methacrylate) (PnBMA) are reported. Microscopic observations show that blending causes the spherulite structure to become coarser and less birefringent and confirms that the spherulitic growth rates of PEO were reduced by the addition of PnBMA. X‐ray diffraction studies show no change in the unit cell dimensions and a decrease in the degree of crystallinity upon blending. Analysis of the spherulite radial growth rate data by using Lauritzen–Hoffman theory indicates that crystallization in the range of 300 to 330 K occurs solely within regime III. The calculated surface free energy of folding, σ_e, for pure PEO is 57 erg cm^?2 and decreases with increasing the content of PnBMA in the blend. Copyright © 2004 Society of Chemical Industry     

Single-molecular hybrid nano-cylinders: Attaching polyhedral oligomeric silsesquioxane covalently to poly(glycidyl methacrylate) cylindrical brushes

We present the preparation of novel single-molecular hybrid nano-cylinders by covalently attaching a monothiol-functionalized polyhedral silsesquioxane (POSS-SH) to poly(glycidyl methacrylate) (PGMA) cylindrical brushes. Grafting of GMA from a long poly-initiator poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) (PBIEM) via ATRP was first carried out. Gel permeation chromatography (GPC), ¹H NMR, dynamic light scattering (DLS), static light scattering (SLS) and atomic force microscopy (AFM) measurements confirmed the well-defined worm-like structures of the PGMA brushes. Then POSS-SH was covalently linked to PGMA brushes by reaction with about 19% of the epoxy groups. The successful preparation of the PGMA-POSS hybrid brush was demonstrated by Fourier-transform infrared spectroscopy (FTIR), DLS, SLS, energy dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA) measurements. An increase of the length and diameter of the brushes was shown by AFM and non-stained transmission microscopy (TEM) measurements. Residual SiO₂ after pyrolysis of the PGMA-POSS hybrid brush in air displayed interesting cylindrical network structures.     

Structural aspects of the LCST phase behavior of poly(benzyl methacrylate) in room-temperature ionic liquid

The structure and lower critical solution temperature (LCST) phase behavior of well-defined poly(benzyl methacrylate) (PBnMA) solution using 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₂mim][NTf₂] ionic liquid (IL) as a solvent have been studied by dynamic light scattering (DLS) and small-angle neutron scattering (SANS) at various temperatures. The SANS profiles observed for fully deuterated IL ([C₂mim]-d₁₁[NTf₂]) containing PBnMA were kept practically unchanged in the temperature range between 298 and 363 K, while they suddenly changed at 363 K. This indicates that the LCST behavior of PBnMA-IL solution is a first-order phase transition, which is consistent with the DLS results. The SANS profiles below 363 K were well represented by the theoretical Debye scattering function with inter-molecular interaction and the radius of gyration, R_g was estimated to be almost constant, i.e., ∼45 Å. The SANS result obtained here was compared with those in aqueous PNIPAm solutions as a typical LCST system, and some differences between IL and aqueous solution systems are pointed out. It is found that thermodynamic quantities (ΔH_demix, ΔS_demix and ΔG_demix) from the homogeneous solution to the phase separation states strongly depend on the solvation of the PBnMA polymer by the IL ([C₂mim] cation and [NTf₂] anion). We propose an LCST phase separation mechanism in the polymer-IL solution.