Photopolymerizaton of hyperbranched aliphatic acrylated poly(amide ester). II. Photopolymerization kinetics

A hyperbranched aliphatic poly(amide ester) ending with hydroxyl groups based on 4‐N,N‐di(2‐hydroxy ethyl)‐4‐ketobutyric acid (DKBA) and 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol (TMP) was modified with acryloyl chloride, resulting in a radiation‐curable, hyperbranched acrylated poly(amide ester). This hyperbranched polymer was characterized with respect to ultraviolet cure rate, unsaturation conversion, and mechanical properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1637–1641, 2001     

ICAR ATRP of methyl methacrylate catalyzed by FeCl3·6H2O/succinic acid

In this work, methyl methacrylate (MMA) was polymerized by initiator for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) method to obtain low molecular weight living polymers. The ATRP initiator was ethyl 2‐bromoisobutyrate, the catalyst ligand complex system was FeCl₃·6H₂O/succinic acid, and the conventional radical initiator 2,2′‐azobisisobutyronitrile was used as a thermal radical initiator. Polymers with controlled molecular weight were obtained with ppm level of Fe catalyst complex at 90°C in N,N‐dimethylformamide. The polymer was characterized by nuclear magnetic resonance (NMR). The molecular weight and molecular weight distribution of the obtained poly (methyl methacrylate) were measured by gel permeation chromatography method. The kinetics results indicated that ICAR ATRP of MMA was a “living”/controlled polymerization, corresponding to a linear increase of molecular weights with the increasing of monomer conversion and a relatively narrow polydispersities index. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study on esterification of acrylic phenolic resin by maleic anhydride and photocrosslinking properties of the alkali‐soluble product

An alkali‐soluble, photocrosslinkable polymer was synthesized by esterification of OH groups of acrylic phenolic resin with maleic anhydride. The OH groups were formed by the ring‐opening reaction of epoxy groups of epoxy phenolic resin with acrylic acid. The esterification conditions were studied. The results showed that it is better to use tetramethyl ammonium bromide as catalyst than N,N‐dimethylbenzylamine. The conversion of maleic anhydride in acetone can reach about 80% at 56°C for 4 h. The purified product was characterized by IR, DSC, and TGA. The product containing acrylate and maleic acid monoester groups, above a certain content, can be dissolved in 1% Na₂CO₃ solution. The photocrosslinkable properties of the product were investigated through selection of photoinitiator, accelarator, crosslinkable diluent monomer, etc. The acrylate and maleic acid monoester group‐containing phenolic resin exhibited very good photocrosslinking behavior, since it contains double bonds from both acrylate groups and maleic acid monoester groups. The activity of photoinitiator decreases in the order: isopropylthioanthraquinone > benzoin ethyl ether (BE) > anthraquinone (AQ) > benzophenone > Michel ketone (MK) > 2,2‐diethoxyacetophenone. The combination of some photoinitiators showed synergistic effects. The order of increasing activity for the accelerator is as follows: MK > ethyl p‐(dimethylamino)benzoate > N,N‐dimethylaniline > triethanolamine. The optimum diluent monomer is trimethylolpropane trimethacrylate. The gel content of the mixture of the resin and trimethylolpropane trimethacrylate could reach 85% using the combined photoinitiators of BE and AQ under UV exposure for 120 s. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1607–1614, 2005     

Synthesis and properties of PMR type poly(benzimidazopyrrolone‐imide)s

PMR type poly(benzimidazopyrrolone‐imide) or poly(pyrrolone‐imide) (PPI) matrix resin was synthesized using the diethyl ester of 4,4′‐(hexafluoroisopropylidene)diphthalic acid (6FDE), 3,3′‐diaminobenzidine, para‐phenylenediamine, and monoethyl ester of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid (NE) in anhydrous ethyl alcohol with N‐methylpyrrolidone. The homogeneous matrix resin solution (40–50% solid) was stable for a storage period of 2 weeks and showed good adhesion with carbon fibers, which ensured production of prepregs. The chemical and thermal processes in the polycondensation of the monomeric reactant mixture were monitored by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, etc. Thermosetting PPI as well as short carbon fiber‐reinforced polymer composites was accomplished at optimal thermal curing conditions. The polymer materials, after postcuring, showed excellent thermal stability, with an initial decomposition temperature > 540°C. Results of MDA experiments indicate that the materials showed > 70–80% retention of the storage modulus at 400°C and glass transition temperatures as high as 440–451°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1600–1608, 2001     

Characterization of acrylamide polymers for enhanced oil recovery

Four different copolymers, of acrylamide and acrylic acid, acrylamide and 2‐acrylamido‐2‐methyl propane sulfonic acid, N,N‐dimethylacrylamide and acrylic acid, and N,N‐dimethylacrylamide and 2‐acrylamido‐2‐methyl propane sulfonic acid (sodium salts), were prepared. The copolymers were characterized by their intrinsic viscosities and monomer ratios and with IR, ¹H‐NMR, and X‐ray diffraction (XRD) spectroscopy. No crystallinity was observed by differential thermal analysis, and this was well supported by XRD. All the polymers showed low decomposition temperatures. A number of decomposition temperatures were observed in differential thermogravimetry thermograms because of the elimination of gases such as CO₂, SO₂, CO, and NH₃. The replacement of the acrylate group with a sulfonate group produced polymers that were more compatible with brine, whereas the replacement of acrylamide with a more hydrophobic group such as N,N‐dimethylacrylamide produced a more shear‐resistant polymer. A N,N‐dimethylacrylamide‐co‐sodium‐2‐acrylamido‐2‐methyl propane sulfonate copolymer was better with respect to thermal stability when the polymer solution was aged at 120°C for a period of 1 month. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1869–1878, 2003     

Preparation and characterization of macroporous phenol‐furfural sulfonic acid resin catalyst

The macroporous phenol‐furfural sulfonic acid resin catalyst (PFuSR) was prepared. The resin was characterized by chemical analysis, thermal analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and reactions of esterification. There exist in PFuSR different kinds of acidic groups such as ? OH, ? COOH, and ? SO₃H. The catalytic relative activity of PFuSR in the reaction of acetic acid and n‐butanol is 104 times that of macroporous polystyrene sulfonic acid resin D72. Thermal analysis showed that PFuSR did not begin to desulfonate until temperatures of 220°C were reached. The resin is suitable for use continually up to 200°C, verified by successfully performing the reaction of maleic anhydride with 2‐ethyl‐1‐hexanol to form di‐2‐ethylhexyl maleate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1764–1769, 2001     

Synthesis and crosslinking behavior of a soluble,crosslinkable, and high young modulus poly(arylene ether nitriles) with pendant phthalonitriles

Poly(arylene ether nitriles) (PEN) with pendant phthalonitrile groups (PEN? CN) were obtained via the Yamazaki‐Higashi phosphorylation route of 4‐(4‐aminophenoxy)phthalonitrile (APN) with acid‐contained PEN (PEN? COOH) in the presence of CaCl₂. The chemical structure and molecular weight of PEN? CN were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, and Gel permeation chromatography. The synthesized PEN? CN had superior solubility in polar organic solvent and can be easily processed into thin films from the solutions of N‐methylpyrrolidone, dimethylsulfoxide, N,N′‐dimethylformamide, dimethylacetamide, and tetrahydrofuran. Compared with PEN? COOH, PEN? CN showed higher thermal stability with 5% weight loss temperatures (T_5%) up to 430°C. The glass transition temperature of PEN? CN was improved from 211 to 235°C measured by differential scanning calorimetry (DSC). In addition, it also exhibited excellent mechanical properties that Young's modulus reached to 3.5 GPa. Meanwhile, the effects of different aromatic amines and Lewis acid on the crosslinking behavior of PEN? CN were investigated by DSC. The results indicated that anhydrous Zinc chloride (ZnCl₂) was the best catalyst to lower the curing temperature among 2,6‐bis(4‐diaminobenzoxy) benzonitrile, 4,4‐diaminediphenyl sulfone, APN and ZnCl₂. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization and thermal degradation of dual temperature‐ and pH‐sensitive RAFT‐made copolymers of N,N‐(dimethylamino)ethyl methacrylate and methyl methacrylate

Poly{[(N,N‐(dimethylamino)ethyl methacrylate]‐co‐(methyl methacrylate)} copolymers of various compositions were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization at 70 °C in N,N‐dimethylformamide. The polymer molecular weights and molecular weight distributions were obtained from size exclusion chromatography, and they indicated the controlled nature of the RAFT polymerizations; the polydispersity indices are in the range 1.1–1.3. The reactivity ratios of N,N‐(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) (r_DMAEMA = 0.925 and r_MMA = 0.854) were computed by the extended Kelen–Tüdös method at high conversions, using compositions obtained from ¹H NMR. The pH‐ and temperature‐sensitive behaviour were studied in aqueous solution to confirm dual responsiveness of these copolymers. The thermal properties of the copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The kinetics of thermal degradation were determined by Friedmann and Chang techniques to evaluate various parameters such as the activation energy, the order and the frequency factor. © 2012 Society of Chemical Industry     

Water‐soluble dual responsive polythiophene‐g‐poly(methoxyethoxy ethyl methacrylate)‐co‐poly(N,N‐diethylamino ethyl methacrylate) for different applications

Polythiophene (PT) based dual responsive water‐soluble graft copolymer (PT‐g‐[poly(methoxyethoxy ethyl methacrylate)‐co‐poly(N,N‐diethylamino ethyl methacrylate)]) (PT‐g‐P(MeO₂MA‐co‐DEAEMA)) (PTDE) has been synthesized by random copolymerization of methoxyethoxy ethyl methacrylate (MeO₂MA) and N,N‐diethylamino ethyl methacrylate (DEAEMA) at 30 °C on the 2,5‐poly(3‐[1‐ethyl‐2‐(2‐ bromoisobutyrate)] thiophene) (PTI) macroinitiator using the Cu based atom transfer radical polymerization technique. The PTDE graft copolymer was characterized by gel permeation chromatography and ¹H NMR techniques and it exhibits thermo‐reversible solubility in water showing a lower critical solution temperature of ca 42 °C in neutral aqueous solution. The PTDE graft copolymer contains a fluorescent PT backbone, and interestingly the system exhibits doubling of fluorescence intensity with rising temperature over the temperature range 41–45 °C at pH 7. The PTDE system therefore acts following the principle of the polymeric AND logic gate and it is also found to be effective in sensing of nitroaromatics, particularly picric acid. The influence of chain hydrophobicity on the logic operation and on the sensing of nitroaromatics is discussed. © 2014 Society of Chemical Industry     

Copolymerization of N‐(4‐carboxyphenyl) itaconimide or N‐(4‐carboxyphenyl) itaconamic acid with methyl methacrylate

This paper describes the synthesis and characterization of N‐(4‐carboxyphenyl) itaconamic acid (CPA) and N‐(4‐carboxyphenyl) itaconimide (CPI) obtained by reacting itaconic anhydride with p‐aminobenzoic acid. Structural and thermal characterization of CPA and CPI was done using ¹H‐NMR, FTIR, and differential scanning calorimetry (DSC). Copolymerization of CPA or CPI with methyl methacrylate (MMA) in solution was carried out at 60 °C using azobisisobutyronitrile as an initiator and dimethyl acetamide or THF as solvent. Feed compositions having varying mole fractions of CPA or CPI ranging from 0.05–0.20 or 0.1–0.5 were taken to prepare copolymers. Copolymerizations were terminated at low percentage conversion. Structural characterization of copolymers was done by ¹H‐NMR and elemental analysis. Copolymer composition was determined using percentage nitrogen content. The reactivity ratios were r₁ (MMA) = 0.68 ± 0.06 and r₂ (CPI) = 0.46 ± 0.06. The intrinsic viscosity [η] was determined using an Ubbelohde suspension level viscometer. [η] decreased with increasing mole fraction of N‐(p‐carboxyphenyl) itaconimide or N‐(p‐carboxyphenyl) itaconamic acid in copolymers. Glass transition temperature and thermal stability of the copolymers were determined using DSC and thermogravimetric analysis, respectively. The glass transition temperature (T_g) as determined from DSC scans increased with increasing amounts of CPA or CPI in copolymers. A significant improvement in the char yield was observed upon copolymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1909–1915, 2005     

Preparation and characterization of the copolymer containing N‐pyridyl bi(methacryl)imide unit

The copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was prepared based on the reaction of polymethacrylic acid with 2‐pyridylamine. The molecular structure was characterized by ¹H‐NMR, FTIR, UV–Vis, and circular dichroism techniques. The physical properties of polymethacrylic acid change significantly after an introduction of 6 mol % N‐2‐pyridyl bi(methacryl)imide unit. In particular, the thermal degradation of the polymer was systematically studied in flowing nitrogen and air from room temperature to 800°C by thermogravimetry at a constant heating rate of 10°C/min. In both atmospheres, a four‐stage degradation process of the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was revealed. The initial thermal degradation temperature T_d, and the first, second, and third temperatures at the maximum weight‐loss rate T_dm1, T_dm2, and T_dm3 all decrease with decreasing sample size or changing testing atmosphere from nitrogen to air, but the fourth temperature at the maximum weight‐loss rate T_dm4 increases. The maximum weight‐loss rate, char yield at elevated temperature, four‐stage decomposition process, and three kinetic parameters of the thermal degradation were discussed in detail. It is suggested that the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide exhibits low thermal stability and multistage degradation characteristics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1673–1678, 2002     

Specific interactions in 4‐hydroxybenzoic acid/poly(2‐vinylpyridine)/poly(N‐vinyl‐2‐pyrrolidone) blends

The specific interactions in ternary 4‐hydroxybenzoic acid (HBA)/poly(2‐vinylpyridine) (P2VPy)/poly(N‐vinyl‐2‐pyrrolidone) (PVP) blends were studied by differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, and electron microscopy. FTIR study shows the existence of hydrogen‐bonding interactions between HBA and P2VPy as well as PVP. The addition of a sufficiently large amount of HBA produces a blend showing one glass‐transition temperature (T_g). Microscopic study shows a drastic reduction in domain size in single‐T_g blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 901–907, 2001     

Synthesis,characterization, and thermal behavior study of methyl methacrylate polymers containing 4‐carbazole substitutes

A new polymerizable monomer, [4‐(9‐ethyl)carbazolyl]methyl methacrylate ( 2 ), was synthesized by reacting of methacrylic acid and 4‐hydroxymethyl‐9‐ethyl carbazole ( 1 ) by esterification procedure in the presence of N,N′‐dicyclohexylcarbodiimide. The resulting monomer was then polymerized free‐radically to form the poly(methyl methacrylate) containing 4‐(9‐ethyl)carbazolyl pend ent groups. Also, copolymerization of monomer 2 with various acrylic monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and n‐butyl acrylate by azobisisobutyronitrile as a free radical polymerization initiator gave the related copolymers in high yields. The structure of all the resulted compounds was characterized and confirmed by FTIR and ¹H NMR spectroscopic techniques. The average molecular weight of the obtained polymers was determined by gel permeation chromatography using tetrahydrofurane as the solvent. The thermal gravimetric analysis and differential scanning calorimeter instruments were used for studying of thermal properties of polymers. It was found that, with the incorporation of bulky 4‐(9‐ethyl)carbazolyl substitutes in side chains of methyl methacrylate polymers, thermal stability and glass transition temperature of polymers are increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4989–4995, 2006     

Preparation of poly(vinyl butyral) with high acetalization rate

Poly(vinyl alcohol) (PVA) can be dissolved in a nonaqueous medium in the presence of catalytic concentration of ethyl nitrate dimethyl sulfoxide, C₂H₅ONO₂ · DMSO (EN · DMSO). From the PVA solution, poly(vinyl butyral) (PVBu) was prepared by acid‐catalyzed homogeneous acetalization of PVA with butyraldehyde. The formation of PVBu was confirmed by IR and ¹H‐NMR spectra. The degree of acetalization of PVBu was found to be 95 mol %, which was verified by ¹H‐NMR data and acetylation method. The molecular mass of the polymer was determined by GPC method. The glass transition temperature, T_g, was measured from differential scanning calorimetric (DSC) thermograms. Thermal stabilities were checked by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). The acetal decomposed in three stages. The corresponding initial decomposition temperatures were found to be 285, 390, and above 500°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1182–1186, 2001     

Synthesis of pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] copolymer and gold nanoparticle stabilization by its micelles

Novel pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (chitosan‐g‐PDMAEMA) copolymers were successfully synthesized by homogeneous atom transfer radical polymerization (ATRP) under mild conditions. Chitosan macroinitiator was prepared by phthaloylation of amino groups of chitosan and subsequent acylation of hydroxyl groups of chitosan with 2‐bromoisobutyryl bromide. The copolymers were obtained by ATRP of 2‐(N,N‐dimethylamino)ethyl methacrylate and they can self‐assemble into stable micelles in water. Hybrid micelles with a PDMAEMA corona incorporating gold nanoparticles (Au NPs) were prepared in situ via the reduction of HAuCl₄ with NaBH₄. The pH and temperature responses of the copolymer micelles and hybrid micelles were characterized using UV‐visible spectroscopy and dynamic laser light scattering. The morphology of the micelles was observed using transmission electron microscopy and atomic force microscopy. The PDMAEMA corona of the micelles acts as the ‘nanoreactor’ and the ‘anchor’ for the in situ formation and stabilization of Au NPs. Therefore, the spatial distribution of Au NPs within the micelles can be tuned by varying the temperature and pH value. Copyright © 2010 Society of Chemical Industry     

The studies on the stimuli‐response of poly (N,N‐dimethylamino ethyl methacrylate/acrylic acid‐co‐acrylamide) complex hydrogel under DC electric field

A polyelectrolyte complex hydrogel, poly (N,N‐dimethylaminoethyl methacrylate/acrylic acid‐co‐acrylamide) hydrogel designed as PDMEAA, was prepared by the free radical copolymerization in aqueous solutions. Without chemical crosslinker, PDMEAA hydrogel network was formed by electrostatic attraction of the proton‐transfer between acrylic acid and N,N‐dimethylamino ethyl methacrylate. Since the electrostatic attraction could be weakened by the application of electric field, PDMEAA hydrogel was decomposed under contacted electric field. Various factors such as gel composition, the species and concentration of electrolytes, voltage, and the experimental set‐ups, could effect the decomposing process of PDMEAA hydrogel. In CaCl₂ and MgCl₂ solutions, PDMEAA hydrogel had no change under electric field. And in high concentration of NaCl and Na₂SO₄ solutions, PDMEAA hydrogel has been eroded linearly with the increasing time applied electric field. In low concentration of NaCl and Na₂SO₄ solutions, however, a swelling process was found before the erosion. The stimuli‐responsive mechanism was investigated through scanning electron microscope (SEM) and gel permeation chromatography (GPC). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rapid removal of Cr(VI) ions from aqueous solutions by the macroporous poly(N,N′‐dimethylamino ethyl methacrylate) hydrogels

To improve the adsorption ability of hexavalent chromium [Cr(VI)], the macroporous poly(N, N′‐dimethylamino ethyl methacrylate) [poly(DMAEMA)] hydrogels were successfully fabricated by free‐radical copolymerization in ethanol/water mixture using N, N′‐dimethylamino ethyl methacrylate (DMAEMA) as the monomer, N, N′‐methylenebisacrylamide (MBAA) as the cross‐linker, and Na₂SO₄ solution as the porogen. The effects of various parameters, such as the concentration of Na₂SO₄ solutions, the dosage of MBAA, pH values, adsorption kinetic, and isotherm curves, were all investigated through systematic experiments. Scanning electron microscope (SEM) was employed to characterize the various pore structures. The experimental results showed that the influence of Na₂SO₄ solution to the pore morphology in the matrix was significant. The poly(DMAEMA) hydrogels can effectively adsorb Cr(VI) ions in aqueous media, and the macroporous structures could obvious improve the response rate and adsorption capacity. These results prove that the macroporous poly(DMAEMA) gels can be treated as a potential material for environmental pollution control. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and properties of organosoluble polyimides based on novel flourene‐ring containing diacetamido‐diamine

A new diacetamido‐diamine monomer, N′‐[7‐(acetyl‐4‐aminoanilino)‐9,9‐dioctylflouren‐2‐yl]‐N′‐4‐aminophenyl) acetamide (ADOAc), with flourene‐based structure was prepared from the reaction of 4‐aminoacetanillide with 2,7‐dibromo‐9,9‐dioctylfluorene in the presence of 10 mol % CuI, 20 mol % N,N′‐dimethylethylene diamine as catalyst and K₂CO₃ as base. Two new flourene‐ring containing polyimides were prepared from the reaction of ADOAc with aromatic dianhydrides such as pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) via chemical imidization of poly(amic acid). The new diamine and the related polyimides were characterized by using conventional methods such as FT‐IR, NMR, and elemental analysis. The polyimides obtained from the reaction of ADOAc with PMDA (PIa) and of ADOAc with BTDA (PIb) had inherent viscosity of 0.49 and 0.58 dL/g respectively, and showed excellent solubility in a variety of organic solvents. The polyimides of PIa and PIb showed excellent thermal stability with 10% weight loss in nitrogen atmosphere at temperatures of 418°C and 407°C and T_g of 172°C and 167°C, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of chiral smectic side‐chain liquid crystalline polysiloxanes and ionomers containing sulfonic acid groups

The synthesis of new chiral smectic A (S_A) side‐chain liquid crystalline polysiloxanes (LCPs) and ionomers (LCIs) containing 4‐allyloxy‐benzoyl‐4‐(S‐2‐ethylhexanoyl) p‐benzenediol bisate (ABB) as mesogenic units and 4‐[[4‐(2‐propenyloxy)phenyl]azo]benzenesulfonic acid (AABS) as nonmesogenic units is presented. The chemical structures of the monomers and polymers are confirmed by FTIR spectroscopy or ¹H–NMR. Differential scanning calorimetry (DSC), optical polarizing microscopy, and X‐ray diffraction measurements reveal that all the polymers P_I–P_IV and ionomers P_V–P_VI exhibit S_A texture. The results seem to demonstrate that the tendency toward the S_A‐phase region increases with increasing sulfonic acid concentration, and the thermal stability of the S_A phase is determined by the flexibility of the polymer backbones and the interactions of sulfonic acid groups. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2335–2340, 2001     

A Double Prodrug with Improved Membrane Permeability over the Parent Chelator HBED Provides Superior Cytoprotection against Hydrogen Peroxide

The clinical use of N,N′‐bis(2‐hydroxybenzyl)ethylenediamine‐N,N′‐diacetic acid (HBED) has been hindered by its lack of bioavailability. N,N′‐bis(2‐boronic pinacol ester benzyl)ethylenediamine‐N,N′‐diacetic acid methyl, ethyl, and isopropyl esters 7 a – c , respectively, and their dimesylate salts 8 a – c , are double prodrugs that mask the two phenolate and two carboxylate donors of HBED as boronic esters and carboxylate esters, respectively. Their activation by chemical hydrolysis and oxidation, their passive diffusivity, and their cytoprotective capabilities have been investigated here. 8 a – c hydrolyzed in minimum essential medium at 37 °C with half‐lives of 0.69, 0.81, and 2.28 h, respectively. The intermediate formed, 9 [N,N′‐bis(2‐boronic acid benzyl)ethylenediamine‐N,N′‐diacetic acid], then underwent oxidative deboronation by H₂O₂ to give HBED (k=1.82 m ^?1 min^?1). Solubility measurements in mineral oil and in phosphate buffer indicated that 7 a had a better balance between lipid and aqueous solubilities than did HBED. 7 a was also able to passively diffuse across a lipid‐like silicone membrane (log flux=?0.36), whereas HBED‐HCl was not. 8 c provided better protection to retinal cells than did HBED against a lethal dose of H₂O₂ (84 % vs. 28 % protection, respectively, at 44 μm ). These results suggest that the double prodrugs have better membrane permeability than does HBED, and therefore could be therapeutically useful for improving the delivery of HBED.