Showing papers on "Methacrylic acid published in 2007"
TL;DR: The resulting nanocomposites exhibited improved elastic properties and have potential application in dental composites and bone cements.
Abstract: Inorganic−polymer nanocomposites are of significant interest for emerging materials due to their improved properties and unique combination of properties. Methacrylic acid (MA), a functionalization agent that can chemically link TiO2 nanomaterials (n-TiO2) and polymer matrix, was used to modify the surface of n-TiO2 using a Ti−carboxylic coordination bond. Then, the double bond in MA was copolymerized with methyl methacrylate (MMA) to form a n-TiO2−PMMA nanocomposite. The resulting n-TiO2−PMMA nanocomposite materials were characterized by using thermal analysis, electron microscopy, and elemental analysis. The dynamic mechanical properties (Young's and shear modulus) were measured using an ultrasonic pulse technique. The electron microscopy results showed a good distribution of the nanofillers in the polymer matrix. The glass transition temperature, thermal degradation temperature, and dynamic elastic moduli of the nanocomposites were shown to increase with an increase in the weight percentage of nanofibe...
208 citations
TL;DR: In this paper, the authors examined four specific materials (ionomers and non-ionomer copolymers) to determine if ionic interactions are responsible for puncture reversal, and concluded that ionic content is not necessary for the healing response.
Abstract: Several poly(ethylene-co-methacrylic acid) copolymers have shown the unique ability to self-heal following projectile puncture, with the punctured site subsequently holding pressures in excess of 3 MPa. Four specific materials (ionomers and non-ionomer copolymers) were examined to determine if ionic interactions are responsible for puncture reversal. A range of novel experiments including peel, projectile, and quantitative post-puncture testing were used to determine that ionic content is not necessary for the healing response. Mechanistically, it was concluded that healing occurs through at least a two-stage process of melt elastic recovery followed by sealing and polymer chain interdiffusion at the damaged site.
198 citations
TL;DR: Water filtration studies revealed that the grafted ENM had a better flux throughput than the HVLP membrane, suggesting that ENMs can be successfully engineered through surface modification to achieve smaller pores while retaining their high flux performance.
Abstract: Electrospun nanofibrous membranes (ENM) which have a porous structure have a huge potential for various liquid filtration applications. In this paper, we explore the viability of using plasma-induced graft copolymerization to reduce the pore sizes of ENMs. Poly(vinylidene) fluoride (PVDF) was electrospun to produce a nonwoven membrane, comprised of nanofibers with diameters in the range of 200-600 nm. The surface of the ENM was exposed to argon plasma and subsequently graft-copolymerized with methacrylic acid. The effect of plasma exposure time on grafting was studied for both the ENM and a commercial hydrophobic PVDF (HVHP) membrane. The grafting density was quantitatively measured with toluidine blue-O. The degree of grafting increased steeply with an increase in plasma exposure time for the ENM, attaining a maximum of 180 nmol/mg after 120 s of plasma treatment. However, the increase in the grafting density on the surface of the HVHP membrane was not as drastic, reaching a plateau of 65 nmol/mg after 60 s. The liquid entry permeation of water dropped extensively for both membranes, indicating a change in surface properties. Field emission scanning electron microscopy micrographs revealed an alteration in the surface pore structure for both membranes after grafting. Bubble point measurements of the ENM reduced from 3.6 to 0.9 um after grafting. The pore-size distribution obtained using the capillary flow porometer for the grafted ENM revealed that it had a similar profile to that of a commercial hydrophilic commercial PVDF (HVLP) membrane. More significantly, water filtration studies revealed that the grafted ENM had a better flux throughput than the HVLP membrane. This suggests that ENMs can be successfully engineered through surface modification to achieve smaller pores while retaining their high flux performance.
170 citations
TL;DR: It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.
Abstract: A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (∼2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. “Multidentate” thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful co...
154 citations
TL;DR: In this paper, a series of pH-responsive silver nanoparticles/poly(2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methyl ether methacyl (PEGMA)-methacrylic acid (MAA)) composite hydrogels were successfully prepared by in situ reducing Ag + ions anchored in the hydrogel by the deprotonized carboxyl acid groups.
153 citations
TL;DR: A novel approach to analyzing thin-film gradients with the reversed Wentzel-Kramers-Brillouin (WKB) approximation presents a powerful tool for the characterization of inhomogeneous hydrogels, which would otherwise be very difficult to capture experimentally.
Abstract: The structural features and swelling properties of responsive hydrogel films based on poly(N-isopropylacrylamide) copolymers with a photo-cross-linkable benzophenone unit were investigated by surface plasmon resonance, optical waveguide mode spectroscopy, and atomic force microscopy. The temperature-dependent swelling behavior was studied with respect to the chemical composition of the hydrogel polymers containing either sodium methacrylate or methacrylic acid moieties. In the sodium methacrylate system, a refractive index gradient was found that was not present in the free acid gel. This refractive index gradient, perpendicular to the swollen hydrogel film surface, could be analyzed in detail by application of the reversed Wentzel-Kramers-Brillouin (WKB) approximation to the optical data. This novel approach to analyzing thin-film gradients with the WKB method presents a powerful tool for the characterization of inhomogeneous hydrogels, which would otherwise be very difficult to capture experimentally. In AFM images of the hydrogel layers, a macroscopic pore structure was observed that depended on the polymer composition as well as on the swelling history. This pore structure apparently prevents the often-observed skin barrier effect and leads to a quickly responding hydrogel.
139 citations
TL;DR: Performance tests of TNT imprinted polymer beads showed that acrylamide (AA) and more pronounced also methacrylic acid (MAA) possessed an enhanced adsorption tendency for gaseous TNT.
134 citations
TL;DR: Aqueous dispersions of gold nanoparticles protected with a stimuli-sensitive diblock copolymer were studied as a function of pH and temperature and a blue shift in the SPR was observed both with decreasing pH and increasing temperature.
Abstract: Aqueous dispersions of gold nanoparticles protected with a stimuli-sensitive diblock copolymer were studied as a function of pH and temperature. Poly(methacrylic acid)−block-poly(N-isopropylacrylamide), PMAA−b-PNIPAM, copolymer was synthesized using the RAFT technique. A one-pot method utilizing the dithiobenzoate functionalized polymer was used to prepare gold nanoparticles protected with PMAA−b-PNIPAM. The gold nanoparticles coated with block copolymers, with the PNIPAM block bound to the particle surface and PMAA as an outer block form stimuli-sensitive aggregates in water. The changes in the absorption maxima of the surface plasmon resonance, SPR, of the gold particles and in the size of the aggregates were investigated as a function of pH and temperature. pH was observed to affect the size of the aggregates, whereas the effect of temperature was moderate. However, a blue shift in the SPR was observed both with decreasing pH and increasing temperature. Whereas the PMAA blocks control the colloidal sta...
110 citations
TL;DR: Measurements of the photoluminescent properties of these materials show that the ternary rare-earth/inorganic/organic polymeric hybrids present stronger luminescent intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary rare- earth/in organic polymeric hybrid hybrids.
Abstract: 2-Hydroxynicotinic acid (HNA) was grafted by 3-(triethoxysilyl)propyl isocyanate (TEPIC) to achieve the molecular precursor HNA-Si through the hydrogen-transfer nucleophilic addition reaction between the hydroxyl group of HNA and the isocyanate group of TEPIC. Then, a chemically bonded rare-earth/inorganic polymeric hybrid material (A) was constructed using HNA-Si as a bridge molecule that can both coordinate to rare-earth ions (HNA-Si-RE) and form an inorganic Si−O network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation processes. Further, three types of novel rare-earth/inorganic/organic polymeric hybrids (B−D) were assembled by the introduction of three different organic polymeric chains into the above system. First, methacrylic acid (MAA) [or methacrylic acid and acrylamide (ALM) in the molar ratio of 1:1] was mixed to polymerize (or copolymerize) with benzoyl peroxide (BPO) as the initiator to form poly(methacrylic acid) (PMAA) [or poly(methacrylic and acrylamide) (PMAALM)], a...
108 citations
Patent•
01 Jun 2007
TL;DR: In this article, a cell which has been genetically modified by comparison with its wild type in such a way that it is able to form more, by comparison to its wild kind, 3-hydroxyisobutyric acid via methylmalonate semialdehyde or 3hydroxybutyryl-coenzyme A as precursors.
Abstract: The present invention relates to a cell which has been genetically modified by comparison with its wild type in such a way that it is able to form more, by comparison with its wild type, 3-hydroxyisobutyric acid or polyhydroxyalkanoates based on 3-hydroxyisobutyric acid via methylmalonate semialdehyde or 3-hydroxybutyryl-coenzyme A as precursors. The invention also relates to a method for producing a genetically modified cell, to the genetically modified cell obtainable by this method, to a method for producing 3-hydroxyisobutyric acid or polyhydroxyalkanoates based on 3-hydroxyisobutyric acid, to a method for producing methacrylic acid or methacrylic esters, and to a method for producing polymethacrylic acid or polymethacrylic esters. The present invention further relates to an isolated DNA, to a vector, to the use of this vector for transforming a cell, to a transformed cell, and to a polypeptide.
95 citations
TL;DR: Equilibrium adsorption data are more consistent with the Langmuir isotherm equation than with the Freundlich equation, which clearly exceeds the 60mg/g of Fuller's earth and the 90mg/ g of activated carbon, which are the most commonly used binding agents for paraquat.
TL;DR: In this paper, the synthesis of poly(methacrylic acid) (PMAA) brushes via surface-initiated atom transfer radical polymerization (ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate was described.
Abstract: This manuscript describes the synthesis of poly(methacrylic acid) (PMAA) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate. A CuBr/CuBr2/bipyridine catalyst system in aqueous solution at room temperature allowed the synthesis of brushes with thicknesses of up to 300 nm. Using substrates modified with mixtures of an ATRP-initiator modified trimethoxysilane and an "inert" pivaloyl-modified trimethoxysilane to initiate the ATRP of NaMA, a series of brushes with varying chain density could be prepared. Subsequent mineralization experiments revealed that, while low-density brushes promoted the formation of calcite crystals, high-density brushes were covered with a thin layer of amorphous CaCO3 (ACC). This is of interest because ACC can serve as a metastable precursor for different crystalline CaCO3 polymorphs and offers attractive perspectives for the bottom-up fabrication of well-defined CaCO3 crystal architectures. © 2007 American Chemical Society.
TL;DR: In this article, a distillation-precipitation polymerization in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator was used to synthesize monodisperse poly(methacrylic acid) microspheres with spherical shape and smooth surface.
TL;DR: In this article, the propagation rate coefficients for free-radical polymerization of methacrylic acid, MAA, in aqueous solution are presented, and the underlying k P values are from two independent sources, which both used the IUPAC-recommended technique of pulsed-laser-initiated polymerization (PLP) in conjunction with molar mass distribution (MMD) analysis of the resulting polymer by size-exclusion chromatography (SEC).
Abstract: Critically evaluated propagation rate coefficients, k p , for free-radical polymerization of methacrylic acid, MAA, in aqueous solution are presented. The underlying k P values are from two independent sources, which both used the IUPAC-recommended technique of pulsed-laser-initiated polymerization (PLP) in conjunction with molar mass distribution (MMD) analysis of the resulting polymer by size-exclusion chromatography (SEC). Different methods of measuring the MMD of the poly(MAA) samples have, however, been used: (i) direct analysis via aqueous-phase SEC and (ii) standard SEC with tetrahydrofuran as the eluent carried out on poly(methyl methacrylate) samples obtained by methylation of the poly(MAA) samples from PLP. Benchmark k p values for aqueous solutions containing 15 mass % MAA are presented for temperatures between 18 and 89 °C. The Arrhenius pre-exponential and activation energy of k p at 15 mass % MAA are 1.54 x 10 6 L mol -1 s -1 and 15.0 kJ mol -1 , respectively. Also reported are critically evaluated k p values for 25 °C over the entire MAA concentration range from dilute aqueous solution to bulk polymerization.
TL;DR: In this article, a series of amphiphilic conetworks of methacrylic acid (MAA) and methyl methacrylate (MMA) were synthesized using group transfer polymerization (GTP).
Abstract: A series of amphiphilic conetworks of methacrylic acid (MAA) and methyl methacrylate (MMA) were synthesized using group transfer polymerization (GTP). The MAA units were introduced via the polymerization of tetrahydropyranyl methacrylate (THPMA), followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. 1,4-Bis(methoxytrimethylsiloxymethylene)cyclohexane (MTSCH) was used as a bifunctional GTP initiator, while ethylene glycol dimethacrylate (EGDMA) served as the cross-linker. Nine of the conetworks were model conetworks, comprising copolymer chains between the cross-links of precise molecular weight and composition. Eight of the model conetworks were based on ABA triblock copolymers, while the ninth was based on a statistical copolymer. The tenth conetwork was not model but randomly cross-linked. The molecular weight and the composition of the linear conetwork precursors were analyzed by gel permeation chromatography and 1H NMR, respectively, and were fou...
TL;DR: Findings suggest that the PEG-b-poly(alkyl(meth)acrylate-co-methacrylic acid)s can self-assemble to form micelles which exhibit high loading capacities for CDN and release the drug in a pH-dependent fashion.
TL;DR: Seven amphiphilic conetworks of methacrylic acid and a new hydrophobic monomer, 2-butyl-1-octyl-methacrylate (BOMA), were synthesized using group transfer polymerization and the nanophase behavior of the conetwork was probed using small-angle neutron scattering and atomic force microscopy.
Abstract: Seven amphiphilic conetworks of methacrylic acid (MAA) and a new hydrophobic monomer, 2-butyl-1-octyl-methacrylate (BOMA), were synthesized using group transfer polymerization. The MAA units were introduced via the polymerization of tetrahydropyranyl methacrylate (THPMA) followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. Both THPMA and BOMA were in-house synthesized. Ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. Six of the conetworks were model conetworks, containing copolymer chains between cross-links of precise molecular weight and composition. The prepared conetwork series covered a wide range of compositions and architectures. In particular, the MAA content was varied from 67 to 94 mol %, and three different conetwork architectures were constructed: ABA triblock copolymer-based, statistical copolymer-based, and randomly cross-linked. The linear conetwork precursors were analyzed by gel permeation chromatography and 1H ...
TL;DR: Copolymers of methacrylic acid and ethylene dimethacrylate showed pH-dependent swelling behavior that was applied to the enteric release of fluorescein and ibuprofen.
Abstract: Initiated chemical vapor deposition (iCVD) is presented as an all-dry synthesis and coating method for applying methacrylic acid copolymers as pH-responsive controlled release layers. iCVD combines the strengths of liquid-phase chemical synthesis with a precision solvent-free chemical vapor deposition environment. Copolymers of methacrylic acid and ethyl acrylate were confirmed by a systematic shift in the carbonyl bond stretching mode with a shift in the comonomer ratio within the copolymer and by the ability to apply the Fineman-Ross copolymerization equation to describe copolymerization kinetics. Copolymers of methacrylic acid and ethylene dimethacrylate showed pH-dependent swelling behavior that was applied to the enteric release of fluorescein and ibuprofen.
TL;DR: In this paper, a controlled free-radical polymerization of methacrylic acid was performed at 73 and 83 °C using a methacric acid-based alkoxyamine and the nitroxide SG1 as a mediator in the presence of a small concentration of styrene, without protection of the carboxylic acid groups.
Abstract: The controlled free-radical polymerization of methacrylic acid was performed at 73 and 83 °C using a methacrylic acid-based alkoxyamine and the nitroxide SG1 as a mediator in the presence of a small concentration of styrene, without protection of the carboxylic acid groups. The solvent was 1,4-dioxane or ethanol, and no chain transfer to the solvent could be detected. Because of the presence of styrene, the polymerization exhibited the characteristics of a living one. In particular, the polymers could be chain-extended and were used as efficient macroinitiators in the polymerization of styrene, allowing well-defined, amphiphilic diblock copolymers to be synthesized.
TL;DR: NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.
Abstract: Molecular crowding, an important feature of the molecular environments in biological cells, was applied to the synthesis of antibody-mimic polymers selective for a group of biologically active compounds, the triazine herbicides. Synthesis of these polymers was conducted using molecular imprinting under molecular crowding conditions, whereby atrazine (a template molecule) was complexed with methacrylic acid (a functional monomer) in the presence of a macromolecular crowding agent (either poly(methyl methacrylate) (PMMA) or polystyrene (PS)) followed by cross-linking with ethylene glycol dimethacrylate. After removal of atrazine from the polymer matrix, the retention properties and selectivity of the resultant polymers were assessed by chromatographic tests. The addition of a crowding-inducing agent resulted in polymers with superior retention properties and excellent selectivity for triazine herbicides, as compared to polymers prepared without addition of a crowding-inducing agent. An imprinted polymer prepared in the presence of PS as a crowding agent exhibited a retention factor for atrazine an order of magnitude larger than that of an imprinted polymer prepared in the absence of a crowding agent. NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.
TL;DR: In this article, double layer surfactant coated magnetic particles were first synthesized and then a rich poly-(N-isopropylacrylamide) (PNIPAM) shell layer was attached using double layer magnetic particles as the seeds.
TL;DR: Data showed that some monomers have a natural selectivity for some herbicides, which can be further enhanced by imprinting, and a good correlation was found between the binding score of the monomers and the affinities of the corresponding polymers.
TL;DR: P pH-sensitive systems could be useful for preparation of a muccoadhesive system and controlled release of N-(4-hydroxyphenyl)-2-( 4-methoxyphenol) acetamide in SGF and SIF and drug release studies showed that the increasing content of MAA in the copolymer enhances hydrolysis in SIF.
Abstract: The purpose of this study is to develop novel intestinal- -specific drug delivery systems with pH sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs were synthesized by free radical copolymeriza- tion of methacrylic acid, poly(ethyleneglycol monomethyl ether methacrylate) and a methacrylic derivative of N-(4- -hydroxyphenyl)-2-(4-methoxyphenyl) acetamide in the presence of ethylene glycol dimethacrylate as crosslink- ing agent. The effect of copolymer composition on the swelling behavior and hydrolytic degradation were stu- died in simulated gastric (SGF, pH 1.2) and intestinal flu- ids (SIF, pH 7.0). The dynamic swelling behavior of these hydrogels was investigated to determine the mechanism of water transport through these hydrogels. The mecha- nism of water transport through the gels was significant- ly affected by the pH of the swelling medium and beca- me more relaxation-controlled in a swelling medium of pH 7.0. The swelling and hydrolytic behaviors of hydro- gels were dependent on the content of methacrylic acid (MAA) groups and caused a decrease and increase in gel swelling in SGF and SIF, respectively. Drug release studi- es showed that the increasing content of MAA in the co- polymer enhances hydrolysis in SIF. These results suggest that pH-sensitive systems could be useful for preparati- on of a muccoadhesive system and controlled release of N-(4-hydroxyphenyl)-2-(4-methoxyphenyl) acetamide.
TL;DR: The critical micellization concentration, estimated by means of fluorescence spectroscopy with the use of pyrene as a polarity probe, is decisively determined by the length of the PIB block and is insensitive to changes in the lengthof the PMAA block.
Abstract: Ionic amphiphilic diblock copolymer polyisobutylene-block-poly(methacrylic acid) (PIBx-b-PMAAy), with various lengths of nonpolar (x = 25−75) and polyelectrolyte (y = 170−2600) blocks, spontaneously dissolve in aqueous media at pH >4, generating macromolecular assemblies, the aggregation number of which depends on external stimuli (pH and ionic strength). Spherical micellar morphology with a compact core formed by the PIB blocks and a swollen corona built up from the PMAA blocks was deduced by cryogenic transmission electron microscopy. The micelles were further characterized by means of dynamic and static light scattering as well as small-angle neutron scattering. The critical micellization concentration, estimated by means of fluorescence spectroscopy with the use of pyrene as a polarity probe, is decisively determined by the length of the PIB block and is insensitive to changes in the length of the PMAA block.
TL;DR: In this paper, the binding properties of malachite green (MG) molecularly imprinted polymers were evaluated in acetonitrile by equilibrium rebinding experiments, and the binding sites were found to have a good selectivity and specificity for MG.
TL;DR: The influence of the solvent on the molecular recognition capability of molecularly imprinted polymers (MIPs) was studied in this paper, where the energy difference (ΔE) of a molecule in vacuum and in a given solvent was calculated using density functional theory (DFT) at B3LYP/6-31+G** level, and used as a measure of the affinity of the solvents to the molecule.
TL;DR: In this paper, a variety of catalysts consisting of MgO, SiO 2, Al 2 O 3 and ZrO 2 were evaluated in the aldol condensation of propionic acid with formaldehyde to produce methacrylic acid.
TL;DR: In this article, the effect of pH and ionic strength of buffer solutions on swelling behavior of polyelectrolyte hydrogels was examined, and the results indicated that the hydrogel were strikingly sensitive to pH value and ICI strength.
Abstract: Novel polyelectrolyte hydrogels based on methacrylic acid (MAA) and acrylonitrile (AN) monomers were prepared in the presence of a cross‐linker, N,N‐methylenebisacrylamide. The effect of pH and ionic strength of buffer solutions on swelling behavior of the hydrogels was examined. In particular, a reversible swelling behavior at pH 1.4 and 7.4 solutions was investigated. The structure and morphologies of the sensitive hydrogels were characterized by a Fourier transformation infrared spectroscopy (FTIR) and a scanning electron microscope (SEM). A differential scanning calorimeter (DSC) was used to analyze the state of water and to quantitively determine the amount of free water, non‐freezing bound water, and so on. The results indicated that the hydrogels were strikingly sensitive to pH value and ionic strength of buffer solutions. The swelling ratios of gels increased with the increase in pH values, but decreased with ionic strength increased. The gels presented reversible phase transition characteristics ...
TL;DR: In this paper, the authors measured the propagation rate of free-radical methacrylic acid (MAA) polymerization in aqueous solution using the pulsed laser polymerization -size-exclusion chromatography (PLP-SEC) technique.
Abstract: Propagation rate coefficients, k p , of free-radical methacrylic acid (MAA) polymerization in aqueous solution are presented and discussed. The data has been obtained via the pulsed laser polymerization - size-exclusion chromatography (PLP-SEC) technique within extended ranges of both monomer concentration, from dilute solution up to bulk MAA polymerization, and of degree of ionic dissociation, from non-ionized to fully ionized MAA. A significant decrease of k p , by about one order of magnitude, has been observed upon increasing monomer concentration in the polymerization of non-ionized MAA. Approximately the same decrease of k p occurs upon varying the degree of MAA ionization, α, at low MAA concentration from α = o to α = 1. With partially ionized MAA, the decrease of k p upon increasing MAA concentration is distinctly weaker. For fully ionized MAA, the propagation rate coefficient even increases toward higher MAA concentration. The changes of k p measured as a function of monomer concentration and degree of ionization may be consistently interpreted via transition state theory. The effects on k p are essentially changes of the Arrhenius pre-exponential factor, which reflects internal rotational mobility of the transition state (TS) structure for propagation. Friction of internal rotation of the TS structure is induced by ionic and/or hydrogen-bonded intermolecular interaction of the activated state with the molecular environment.
TL;DR: The apparently promising TPPS/DEAEMA:HEMA system is a poor candidate for clinical application as a postoperative antibacterial treatment for intraocular lenses while the apparently equivalent cationic system TMPyP/MAA: HEMA displays all the required properties.
Abstract: Novel surface-modified hydrogel materials have been prepared by binding charged porphyrins TMPyP (tetrakis(4-N-methylpyridyl)porphyrin) and TPPS (tetrakis(4-sulfonatophenyl)porphyrin) to copolymers of HEMA (2-hydroxyethyl methacrylate) with either MAA (methacrylic acid) or DEAEMA (2-(diethylamino)ethyl methacrylate). The charged hydrogels display strong electrostatic interactions with the appropriate cationic or anionic porphyrins to give materials which are intended to be used to generate cytotoxic singlet oxygen (1O2) on photoexcitation and can therefore be used to reduce postoperative infection of the intraocular hydrogel-based replacement lenses that are used in cataract surgery. The UV/vis spectra of TMPyP in MAA:HEMA copolymers showed a small shift in the Soret band and a change from single exponential (161 μs) triplet decay lifetime in solution to a decay that could be fitted to a biexponential fit with two approximately equal components with τ = 350 and 1300 μs. O2 bubbling reduced the decay to a ...