Showing papers on "Methacrylic acid published in 2002"

Layered, erasable polymer multilayers formed by hydrogen-bonded sequential self-assembly

Abstract: Robust multilayers can be formed on solid surfaces, and subsequently destroyed by changing the environmental conditions, by the layer-by-layer sequential assembly of monomolecular films of a polyacid and polybase from aqueous solution. Interlayer hydrogen bonding produces stable multilayers up to the point where altered pH or other environmental stimulus introduces an unacceptably large electrical charge within them. This is demonstrated for the polyacids poly(acrylic acid), PAA, and poly(methacrylic acid), PMAA, and for the polybases poly(vinylpyrrolidone), PVPON, and poly(ethylene oxide), PEO, in D2O. The adsorption was quantified by Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The ratio between suppressed ionization of the carboxylic groups within the film and their ionization in solution, as directly measured by FTIR-ATR, was used to estimate the fraction of hydrogen-bonded carboxylic groups; this was ∼0.5 in PVPON/PMAA but only ∼0.1 in the PEO/PMAA system, though...

ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives

Abstract: The direct preparation of amphiphilic graft copolymers from commercial poly(vinylidene fluoride) (PVDF) using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary fluorinated site of PVDF facilitates grafting of the hydrophilic comonomer. Amphiphilic comb copolymer derivatives of PVDF having poly(methacrylic acid) side chains (PVDF-g-PMAA) and poly(oxyethylene methacrylate) side chains (PVDF-g-POEM) are prepared using this method. Surface segregation of PVDF-g-POEM additives in PVDF is examined as a route to wettable, foul-resistant surfaces on PVDF filtration membranes. Because of surface segregation during the standard immersion precipitation process for membrane fabrication, a PVDF/5 wt % PVDF-g-POEM membrane, having a bulk POEM concentration of 3.4 wt %, exhibits a near-surface POEM concentration of 42 wt % as measured by X-ray photoelectron spectroscopy (XPS). This membrane displays substantial resistance to BSA fouling compared with pure PVDF and wets...

A basic study of some normoxic polymer gel dosimeters

Abstract: Polymer gel dosimeters offer a wide range of potential applications in the three-dimensional verification of complex dose distribution such as in intensity-modulated radiotherapy (IMRT). Until now, however, polymer gel dosimeters have not been widely used in the clinic. One of the reasons is that they are difficult to manufacture. As the polymerization in polymer gels is inhibited by oxygen, all free oxygen has to be removed from the gels. For several years this was achieved by bubbling nitrogen through the gel solutions and by filling the phantoms in a glove box that is perfused with nitrogen. Recently another gel formulation was proposed in which oxygen is bound in a metallo-organic complex thus removing the problem of oxygen inhibition. The proposed gel consists of methacrylic acid, gelatin, ascorbic acid, hydroquinone and copper(II)sulphate and is given the acronym MAGIC gel dosimeter. These gels are fabricated under normal atmospheric conditions and are therefore called 'normoxic' gel dosimeters. In this study, a chemical analysis on the MAGIC gel was performed. The composition of the gel was varied and its radiation response was evaluated. The role of different chemicals and the reaction kinetics are discussed. It was found that ascorbic acid alone was able to bind the oxygen and can thus be used as an anti-oxidant in a polymer gel dosimeter. It was also found that the anti-oxidants N-acetyl-cysteine and tetrakis(hydroxymethyl)phosphonium were effective in scavenging the oxygen. However, the rate of oxygen scavenging is dependent on the anti-oxidant and its concentration with tetrakis(hydroxymethyl)phosphonium being the most reactive anti-oxidants. Potentiometric oxygen measurements in solution provide an easy way to get a first impression on the rate of oxygen scavenging. It is shown that cupper(II)sulphate operates as a catalyst in the oxidation of ascorbic acid. We, therefore, propose some new normoxic gel formulations that have a less complicated chemical formulation than the MAGIC gel.

Fluorochemical sulfonamide surfactants

Abstract: Described are fluorochemical surfactants derived from nonafluorobutanesulfonyl fluoride that contain polyalkyleneoxy side chains and may be copolymerized with acrylic acid or methacrylic acid to form polyacrylates or polymethacrylates. The surfactants surprisingly lower the surface tension of water and other liquids in the same or similar low values achieved by premier surfactants such as those derived from perfluorooctane sulfonyl fluoride.

Poly(ethylene oxide) coated surfaces

Abstract: Methods are provided for the fabrication of hydrophilic coatings on hydrophobic surfaces. In one embodiment, a polyethylene oxide (PEO) coating is fabricated on the surface of a polymeric material by contacting the surface with a methacrylic acid or acrylic acid monomer. The monomer first is reacted, for example by irradiation with an electron beam, to polymerize and covalently attach the monomer to the surface, to improve the hydrophilicity of the polymeric material. A coating of PEO molecules is subsequently attached to the polymer surface by hydrogen bond complexation. The PEO coating then may be covalently grafted onto the surface, for example, by irradiation grafting with an electron beam. The covalent grafting of a coating of the methacrylic or acrylic monomers to the surface greatly improves the wettability of the surface, and facilitates the covalent or non-covalent attachment of a coating of PEO to the polymer surface. Thus, hydrophilic PEO coatings can be fabricated on hydrophobic polymer surfaces, to improve the biocompatibility and other properties of the polymer surfaces.

Synthesis and swelling behavior of a weak polyacid brush

Abstract: We describe the synthesis and the swelling behavior of a weak polyacid brush attached to a solid surface. Monolayers of poly methacrylic acid are generated by using self-assembled monolayers of an azo initiator and radical chain polymerization of methacrylic acid monomer at the surface of a planar substrate in situ. The thickness of the resulting surface-attached polyelectrolyte brush can be adjusted between 5 and 400 nm in the dry, collapsed state. The swelling behavior in water as a function of pH and salt concentration is investigated by multiple-angle null-ellipsometry. At high salt concentrations the brush thickness decreases due to electrostatic screening. At low concentration, however, an increase of thickness with ion concentration is found.

Molecularly imprinted polymer nanospheres as synthetic affinity receptors obtained by miniemulsion polymerisation

Abstract: Highly crosslinked polymer nanospheres composed of poly[(methacrylic acid)-co-(ethylene glycol dimethacrylate)] and poly(EGDMA) have been synthesised by miniemulsion polymerisation in presence of a chiral molecular template, L- or D-Boc-phenylalanine anilid. The miniemulsions and the resulting microgels were characterised by surface tension measurements, gravimetric analysis, dynamic light scattering, transmission electron microscopy, 1 H and 13 C CP-MAS NMR, and Brunauer-Emmett-Teller gas adsorption measurements. The efficiency of the non-covalent molecular imprinting was examined by binding experiments and quantified by UV absorption. The miniemulsions were converted to coagulate-free and stable latexes with a conversion of 98±2% and an apparent hydrodynamic particle diameter of 200 ± 20 nm. Molecular imprinting was most effective when a miniemulsion of molar imprinting was most effective when a miniemulsion of molar ration n MAA /n EGDMA = 0.25:1 was used for the microgel preparation. Enantioselective binding of the templates to the particles was observed. Binding of the L-enantiomer was four times greater in the L-imprinted polymer than in the non-imprinted polymer and 10 times than binding of the D-enantiomer in the L-imprinted microgels. This new method allows for a one-stage preparation of fully synthetic affinity receptors with a defined spherical shape and a high specific surface area due to their nanoscopic dimension.

Molecularly imprinted composite materials via iniferter-modified supports

Abstract: Wide pore silica (DP = 100 nm) and gel-type or macroporous (12% nominal crosslinking density) Merrifield resins were modified with iniferter groups for grafting of crosslinked molecularly imprinted or non-imprinted polymer layers through quasi-living polymerisation. Prior to iniferter coupling, the silica supports were premodified by silanisation with p-(chloromethyl)phenyl trimethoxysilane. The iniferter groups were then introduced by reacting the resin-bound chloromethyl groups with sodium N,N-diethyldithiocarbamate. It was shown that the coupling yield, measured as the conversion of the chloromethyl groups, could be varied between 5 and 85% through kinetic control, with the fastest conversions observed for the macroporous resins. This allows the density of radical generating groups to be finely adjusted. Ultraviolet light-initiated copolymerisations of ethyleneglycol dimethacrylate and methacrylic acid in toluene resulted in grafting of 0.2–1.9 g of polymer per gram of support, where the grafted amount increased with reaction time, iniferter content and monomer concentration. The dry-state texture of the composite beads prepared from the gel-type resin depended strongly on the amount of grafted polymer. According to the scanning electron micrographs, the beads with the lower grafted amounts (0.4 g polymer per g support) were deformed exhibiting a peculiar folded structure, whereas the beads containing more grafted polymer (1.6 g polymer per g support) were spherical, with an appearance similar to the precursor particles. None of these materials exhibited permanent porosity. Only the composites obtained from the porous precursor particles also exhibited porosity after grafting. Among these, the silica-based composites also showed recognition for their templates when assessed in the chromatographic mode, whereas no imprinting effects could be demonstrated for the polystyrene-supported materials.

Inorganic-organic hybrid polymers by polymerization of methacrylate- or acrylate-substituted oxotitanium clusters with methyl methacrylate or methacrylic acid

Abstract: Inorganic−organic hybrid polymers were prepared by radical polymerization of methacrylic acid or methyl methacrylate with 0.5−2 mol % of the (meth)acrylate-substituted oxotitanium clusters Ti6O4(OEt)8(OMc)8 (OMc = methacrylate), Ti6O4(OPr)8(OAcr)8 (OAcr = acrylate), and the new clusters Ti4O2(OPri)6(OOCR)6 (OOCR = methacrylate or acrylate). A small cluster proportion is sufficient for an efficient cross-linking of the polymers. Glassy (PMMA) or powdery polymers (PMA) were obtained. With an increasing proportion of cluster, the surface area of the PMA powders increased considerably. The obtained hybrid polymers exhibit a higher thermal stability than the parent polymers because the thermal depolymerization is inhibited or at least retarded. The swelling index of cluster-cross-linked PMMA in organic solvents correlates with the cluster proportion. Small-angle scattering investigations showed that Ti6O4(OPr)8(OAcr)8 in PMMA and PMA and Ti4O2(OPri)6(OMc)6 in PMA is more evenly distributed than Ti4O2(OPri)6(OM...

Ion Hopping in Ethylene−Methacrylic Acid Ionomer Melts As Probed by Rheometry and Cation Diffusion Measurements

Abstract: The dynamics of chain and ionic group motion were investigated in a series of ethylene−methacrylic acid (E/MAA) ionomers of varying cation type and neutralization level, all formed from the same E/MAA copolymer. Low-shear-rate rheological measurements were utilized to determine the terminal relaxation time (td) of the polymer chains. The much faster ion-hopping time (τ) was measured through the use of cation diffusion studies, in which a finite slab of one ionomer diffuses into a matrix of a second ionomer. For the Mg/Ca, Mg/Li, Na/Ca, and Na/Li diffusion couples studied, the diffusion coefficient follows inversely with melt viscosity, though τ extracted from the diffusion coefficients depends more weakly on cation type than does td obtained from melt rheometry. For the highly neutralized E/MAA ionomers, τ is 4 orders of magnitude shorter than td, but the two relaxation mechanisms have a similar dependence upon temperature, in agreement with current theories of ionomer dynamics.

Behavior of Poly(N-vinylcaprolactam-co-methacrylic acid) Macromolecules in Aqueous Solution: Interplay between Coulombic and Hydrophobic Interaction

Abstract: Dynamic light scattering measurements have been performed for aqueous solutions of linear copolymer of N-vinylcaprolactam (VCa) and methacrylic acid (MA) with variable composition (i.e., charge degree of polymer chain). The swelling behavior of macromolecules was investigated as a function of both the solution pH value and fraction of methacrylic acid groups. It was shown that these copolymers are thermosensitive, and intermacromolecular aggregation takes place at the temperature increase. They exhibit compositionally dependent swelling behavior as a function of both pH and temperature. The behavior of studied copolymer was explained by the partial formation of ion pairs. The dependence of hydrodynamic diameter on pH of the solution is nonmonotonic. In acidic media at room temperatures we observed the intermolecular aggregation of copolymers accompanied by a sharp increase of the light scattering intensity. In alkaline media intermacromolecular aggregation is observed at higher temperatures. The effect of...

Morphology of poly(methacrylic acid)/poly(N-isopropyl acrylamide) interpenetrating polymeric networks

Abstract: The morphology of interpenetrating polymeric networks (IPNs) composed of the temperature-sensitive poly(N-isopropyl acrylamide) (PNIPAAm) and the pH-sensitive poly(methacrylic acid) (PMAA) were investigated by scanning electron microscopy (SEM). The IPN hydrogels were prepared by a sequential UV polymerization method. SEM studies were conducted on IPN hydrogel samples dried by different methods, and the influence on the IPN structure was discussed. The environmental conditions induced morphological changes for these dual sensitive IPN hydrogels which were studied by cryogenic SEM, when the gels were analyzed in their wet state. The results showed that the porous size in the IPN was strongly influenced by the environmental pH and temperature. Decrease in pH and increase in temperature resulted in significant pore size decrease for the swollen IPNs hydrogels.

Cross-Linked Poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) Microspheres and Microgels Prepared by Precipitation Polymerization: A Morphology Study

Abstract: We applied the concept of precipitation polymerization in organic solvents to the polar and hydrogen-bonding monomers methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMM), with ethylene dimethacrylate (EDMA) as cross-linker. Soluble copolymers, swellable microgels, microspheres, macrogels, and coagulum were observed after copolymerization in mixtures of methyl ethyl ketone and heptane. Increasing the amount of covalent cross-linker or decreasing the solvency of the reaction medium caused a change of morphology from microgels to microspheres. The ratio of acid to ethylene oxide groups present in the comonomers also dramatically changed the polymer−polymer interactions and hence the morphology. Three types of cross-linking are proposed to exist in this system: covalent cross-linking by EDMA and hydrogen-bonding cross-linking between two acid units as well as between acid and ethylene oxide groups. The size of the particles increased with decreasing solvency, decreasing EDMA co...

NMR Studies of the Structure and Dynamics of Polymer Gels Based on N-Isopropylacrylamide (NiPAAm) and Methacrylic Acid (MAA)

Abstract: A series of copolymer gels and interpenetrating networks (IPN) based on N-isopropylacrylamide (NiPAAm) and methacrylic acid (MAA) were synthesized and subsequently investigated by magic angle spinning 1H MAS, cross polarization 13C CP-MAS and pulse-saturation transfer 13C PST-MAS NMR. The structure of the interpenetrating networks is compared to that of the copolymer gels with the same composition. The study of the proton lines reveals low mobility of the chains in the copolymer gels and IPN with higher concentration of MAA, whereas those which are predominantly N iPAAm show higher mobility and therefore narrower proton lines. 13C CP-MAS revealed an interaction between the components of the IPNs. The PST-MAS technique was utilized to study the structure of the polymers in the gel phase. Copolymer gels exhibit some additional peaks in the carbonyl region due to the new chemical environment in the stereoregular sequences. In order to assure assignment, uncrosslinked copolymers with similar compositions as the copolymer gels were synthesized for comparative purposes and examined by conventional solution-state 13C NMR. A linear homopolymer of N iPAAm was synthesized inside of a P(MAA) gel. The polymer was extracted after the completion of the reaction and characterized by solution 13C NMR. About 24% of this P(N iPAAm) homopolymer could not be extracted presumably because of a strong hydrogen bonding or partial topological constrains. In the 13C NMR spectrum a new signal appeared in the carbonyl region due to MAA monomeric units. It may correspond to the methacrylic carbonyls interacting by hydrogen bonds with the amide groups.

Thermal properties of cross-linked poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], their random copolymers [P(N-iPAAm-co-MAA)], and sequential interpenetrating polymer networks (IPNs)

Abstract: The thermal behavior of cross-linked poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], their random copolymers and their sequential interpenetrating polymer networks (IPNs) has been investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The state of the water has been studied on the basis of DSC traces of swollen samples. Several types of water have been found depending on water concentration and polymer structure. The lower critical solution temperature (LCST) as studied by DSC only occurs in the high N-iPAAm containing hydrogels. For the low water concentration regime, LCST seems to depend on the Tg value. TGA analysis of the dry samples indicates that the copolymers having higher content in N-iPAAm monomer have a lower thermal stability than that of the component homopolymers. On the contrary, sequential IPN samples degrade at higher temperature than their component homopolymers and copolymers with similar composition, indicating that inte...

Synthesis of Conjugated-Acidic Block Copolymers by Atom Transfer Radical Polymerization

Abstract: A novel series of well-defined amphiphilic triblock copolymers containing conjugated polyfluorene (PF) and coillike poly(methacrylic acid) (PMAA) were successfully synthesized by vacuum thermolysis of the precursor block copolymers, poly(2-tetrahydropyranyl methacrylate)−PF−poly(2-tetrahydropyranyl methacrylate) (PTHPMA−PF−PTHPMA) prepared by using atom transfer radical polymerization (ATRP) with a 2-bromoisobutyrate end-capped PF as the macroinitiator. Both the linear first-order kinetic plot and the linear dependence of the Mn vs conversion indicate the controlled nature of the polymerization of THPMA. The polydispersity indices of the PTHPMA−PF−PTHPMA triblock copolymers were essentially less than 1.3, demonstrating the well-defined structures of the obtained block copolymers. The chemical structures of the PTHPMA−PF−PTHPMA block copolymers were confirmed by 1H NMR, 13C NMR, and FTIR studies. Decomposition of the precursors at about 145 °C afforded the PMAA−PF−PMAA block copolymers, and the anhydride f...

Apparatus and process for the high yield production of methyl methacrylate or methacrylic acid

Abstract: A high yield process for the production of methyl methacrylate or methacrylic acid and an apparatus for increasing the yield in a process for the production of methyl methacrylate or methacrylic acid are disclosed

Synthesis of amphiphilic block copolymers based on tert-butyl methacrylate and 2-(N-methylperfluorobutanesulfonamido)ethyl methacrylate and its behavior in water

Abstract: Di- and triblock copolymers of tert-butyl methacrylate (tBMA) and 2-(N-methylperfluorobutanesulfonamido)ethyl methacrylate (FMA) were synthesized by sequential anionic polymerization. These polymers were characterized by size-exclusion chromatography and 1 H and 19 F NMR spectroscopy. The microphase separation of bulk samples was studied by atomic force microscopy and small-angle X-ray scattering. Thermal annealing of the block copolymers at 200 °C yielded inter- and intramolecular anhydrides due to the splitting of the ester having tert-butyl groups connected with isobutene formation. This conversion was followed by time-resolved Fourier transform infrared (FT-IR) spectroscopy. The anhydrides can be transformed into the sodium salt of methacrylic acid units in 1 N NaOH under reflux. The thermal ester splitting of the tBMA block at 200 °C did not influence the FMA block. The obtained block copolymers were soluble in water when the FMA content was less than 10 mol %. The behavior of these solutions was studied by various experimental methods. The critical micelle concentration was obtained by surface tension measurements. The micelle dimensions were determined by dynamic light scattering. The size and inner structure of the micelles were investigated by small-angle X-ray scattering and could also be observed by transmission electron microscopy after transfer of the diluted solutions onto carbon films. Typical polyelectrolyte effects were observed by viscosity measurements for PtBMA only. For block copolymers the aggregation behavior is dominating even at very low concentrations.

Synthesis and Characterization of Double-Hydrophilic Model Networks Based on Cross-linked Star Polymers of Poly(ethylene glycol) Methacrylate and Methacrylic Acid

Abstract: A series of model networks based on cross-linked star polymers of poly(ethylene glycol) methacrylate (PEGMA) and tetrahydropyranyl methacrylate (THPMA), a protected form of methacrylic acid (MAA), were synthesized by group transfer polymerization (GTP), covering various compositions (homopolymers and copolymers), arm architectures (homopolymer, block and statistical copolymers), and star architectures (heteroarm and star block). The synthesis took place in tetrahydrofuran (THF) using tetrabutylammonium bibenzoate (TBABB) as the catalyst and 1-methoxy-1-(trimethylsiloxy)-2-methylpropene (MTS) as the initiator, and comprised a four- or six-step procedure: first, the formation of linear polymer chains upon the GTP of the monomer(s); next, the interconnection of the linear segments to star polymers (“arm-first” stars) by the in situ polymerization of the ethylene glycol dimethacrylate (EGDMA) cross-linker, followed by the addition of monomer(s) for a second time to grow new chains from the cores of the stars...

Polymeric dispersants used for aqueous pigmented inks for ink-jet printing

Abstract: The present invention relates to graft copolymers, useful as dispersants in ink jet ink compositions, which comprise two structurally distinct segments: a hydrophilic segment and a hydrophobic segment. The preferred hydrophilic segment is comprised preferably of a methacrylic acid polymer, or a copolymer thereof with another monomer, such as styrene sulfonic acid. The preferred hydrophobic segment comprises a polymer or copolymer containing electron rich functional groups comprised of a plurality of methacrylate derivatized monomers, preferably a methacrylate ester monomer, or a substituted methacrylate ester monomer (a methacrylate ester where the alkyl group is replaced with a siloxyl substituent, an oligomeric siloxane). The present invention also relates to aqueous ink compositions which include the polymeric dispersants of the present invention. A further embodiment of the present invention comprises a polymer comprising a monomeric hydrophobic head and a polymeric tail. In a preferred embodiment, the monomeric hydrophobic head is (ethylene glycol) 2,4,6-tris-(1-phenylethyl)phenyl ether.