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Thermo- and pH-Responsive Poly(A-ProOMe)- graft -poly(AAc) Membrane for Selective Separation of Metal Ions

A protected tridehydropeptide containing (Z)-beta-(3-pyridyl)-alpha,beta-dehydroalanine (Delta(Z)3Pal) residue, Boc-Leu-Delta(Z)3Pal-Leu-OMe (1), was synthesized via Erlenmeyer azlactone method. X-ray crystallographic analysis revealed that the peptide 1 adopts an extended conformation, which is similar to that of a Delta(Z)Phe analog, Boc-Leu-Delta(Z)Phe-Leu-OMe (2).

Poly(ethylene-co-tetrafluoroethylene) (ETFE) films were irradiated by swift heavy ion-beams of 129Xe23+ with fluences of 0, 3 × 106, 3 × 107, 3 × 108 and 3 × 109 ions/cm2, followed by γ-ray pre-irradiation for radiation grafting of styrene onto the ETFE films and sulfonation of the grafted ETFE films to prepare highly anisotropic proton-conducting membranes. The fluence of Xe ions and the addition of water in the grafting solvent were examined to determine their effect on the proton conductivity of the resultant membranes. It was found that the polymer electrolyte membrane prepared by grafting the styrene monomer in a mixture of 67% isopropanol and 33% water to the ETFE film with an ion-beam irradiation fluence of 3.0 × 106 ions/cm2 was a highly anisotropic proton-conducting material, as the proton conductivity was three or more times higher in the thickness direction than in the surface direction of the membrane.

A novel helical peptide containing β-(3-pyirdyl)- l -alanine (Pal) and l -glutamic acid (Glu) residues has been designed and successfully prepared as a model ligand of metalloenzyme active sites. The helical peptide, Boc-Leu-Aib-Glu-Leu-Leu-Pal-Aib-Leu-OEt (1) (Boc = tert-butoxycarbonyl, Aib = 2-aminoisobutylic acid) yields fine crystals as an acetnitrile solvate. The metal ion binding affinities of 1 were tested for CoCl2 using UV/vis, CD, Raman, and 1H NMR spectroscopies. The non-linear fitting calculations have revealed the 1:1 complex for CoCl2 with the binding constant 3.6 (±0.7) × 102 M−1.

Hydrogels, which were synthesized by simultaneously occurring processes of radiation-induced polymerization and cross-linked reactions of acryloyl-l-proline methyl ester (APM) at 0 °C in aqueous alcohol solutions, exhibit an ultraslow volume change in response to variations in external temperature. The shrinking speed of the hydrogels prepared in aqueous alcohol is 1000 times slower than that of the hydrogel prepared in pure water; e.g., the hydrogel prepared in aqueous 1-propanol solution shrunk in 6 months. It is revealed that the ultraslow thermoresponse consists of quick- and slow-shrinking periods; the ratio between the two periods depends on the alcohol molecules in the solution. The generation of a hydroxyl group in the polymer network by the coupling reaction between α-hydroxyalkyl radical of alcohols and α-radical of proline moiety was confirmed by GC/MS analysis of the radiation products. The hydrogen bonding domain containing the hydroxyl groups is proposed to be responsible for the ultraslow r...

We prepared novel ion exchange membranes for possible use in polymer electrolyte fuel cells (PEFCs) by the radiation-induced graft copolymerization of styrene and new crosslinker bis(vinyl phenyl)ethane (BVPE) into crosslinked polytetrafluoroethylene (cPTFE) films and subsequent sulfonation and then investigated their water uptake, proton conductivity, and stability in an oxidizing environment. In contrast to the conventional crosslinker, divinylbenzene (DVB), the degree of grafting of styrene∕BVPE increased in spite of high crosslinker concentrations in the reacting solution (up to 70mol%). Quantitative sulfonation of the aromatic rings in the crosslinked graft chains resulted in the preparation of membranes with a high ion exchange capacity that reached 2.9meq∕g. The bulk properties of the membranes were found to exceed those of Nafion membranes except for chemical stability. The emphasis was on the fact that the BVPE-crosslinked membranes exhibited the higher stability in the H2O2 solution at 60°C compared to the noncrosslinked and DVB-crosslinked ones, as well as decreased water uptake and reasonable proton conductivity. These results are rationalized by considering the reactivity between styrene and the crosslinker, which is an important factor determining the distribution of the crosslinks in the graft component. In the case of BVPE, the crosslinks at a high density were homogeneously incorporated even into the interior of the membrane because of its compatibility with styrene while the far too reactive DVB led to a crosslink formation only near the surface. The combination of both the cPTFE main chain and BVPE-based grafts, i.e., a perfect “double” crosslinking structure, is likely to effectively improve the membrane performances for PEFC applications.

Thermo- and pH-responsive gel membranes were synthesized by γ -ray grafting of pH-responsive poly(acrylic acid) (AAc) onto thermo-responsive polymer gel of acryloyl- L -proline methyl ester (A-ProOMe). The gel membranes of poly(A-ProOMe) with 15 mol% graft chains of AAc exhibited both thermo- and pH-responses. Under the condition (pH 6.0, 30°C) in which the thermo-sensitive unit shrinks and the pH-sensitive unit swells, the selective permeation of Li ion over Co and Ni ions can be achieved.

Charcot-Marie-Tooth disease (CMT) is the most commonly inherited peripheral neuropathy. DNA duplication and point mutation of the gene encoding peripheral myelin protein 22 (PMP22) have been found in CMT type 1A dominants. To investigate the influence of the point mutation of PMP22 on the secondary structure, protected partial peptides in the putative first transmembrane domain, wild type Boc-IVLH(Bom)VAVLVLLFVSTIV-OMe (1) and its Pro16 mutant Boc-IVLH(Bom)VAVPVLLFVSTIV-OMe (2) were synthesized. Circular dichorism (CD)-spectral analysis suggested that peptide 1 adopts a stable alpha-helical conformation in membrane-mimetic solvent,1-BuOH/1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) system. On the contrary, the mutant 2 favors beta-sheet conformation in the same solvent system. Interestingly, alpha-helix to beta-sheet transition of 2 was observed at higher contents of 1-BuOH than 70%.

The impedance effect on the ion transport of lithium chloride through temperature- and pH-sensitive gel membranes was investigated. Both conductance and loss tangent show a relatively tigh value at temperatures near the lower critical solution temperature (14°C), followed by an abrupt drop with a further rise in temperature. The Figure show an example of changes in absolute complex conductance (Y), real conductance (G), and imaginary conductance (B) for a poly(acryloyl-L-proline methyl ester) gel membrane.

Acryloyl- l -proline methyl ester (A-ProOMe) gels were prepared by γ-ray irradiation of aqueous monomer solutions at temperatures ranging from 0 to 60°C. The gels with heterogeneously and homogeneously crosslinked structures were obtained by irradiation at temperatures higher and lower than the lower critical solution temperature (LCST) of approximately 14°C, respectively. The former gel had a faster shrinking rate than that of the latter gel. In contrast, the swelling rate of the gels changed drastically at irradiation temperatures between 20 and 30°C higher than the LCST. The irradiation temperature dependence of the responsive kinetics of the A-ProOMe gels was elucidated by observing the microscopic homogeneity of the gel network structure with a scanning electron microscope (SEM). These results clearly show that the responsive kinetics of the gels can be controlled by adjusting the irradiation temperature in relation to the homogeneity of the nanoscopically crosslinked structure and the microscopic gel network.

Poly(acryloyl-L-proline methyl ester)-based hydrogels containing 1 and 5% of a crosslinking agent were studied as drug delivery systems. The drug loading properties were investigated by matrix incubation into solutions containing biomolecules with molecular weight ranging between 300 and 65,000 Da. The loading yield was found to depend on both the crosslinking degree and the molecular weight of the drug. In vitro release studies were carried out with both swollen and dry matrices loaded with gentamicin, isoniazid and insulin. Gentamicin and isoniazid were released by a bimodal Fickian diffusion with a remarkable burst that was found to depend on both matrix crosslinking degree and physical state. In vivo, the subcutaneous implantation into mice of the isoniazid loaded matrices allowed for an efficient drug release for 800 h. In vitro insulin was released from the swollen matrices for 1500 h by diffusional Fickian mechanism while the dry ones displayed a lag time followed by Fickian diffusion release. The subcutaneous implantation of the insulin-loaded matrices into diabetic mice induced a remarkable decrease in the glucose concentrations in blood. In particular, the dry 1% matrices were found to maintain a low glucose level for 700 h.

A series of hydrogels containing each of the regioisomers, methacryloyl l -valine methyl ester (MA-ValOMe) and methacryloyl l -alanine isopropyl ester (MA-AlaOiPr), were prepared by radiation-induced polymerization. The regioisomers have both methyl and isopropyl groups but at different positions in the side chain of the hydrogels. We estimated the effect of the hydrophobic position in the side chain (spatial effect) on the volume phase transition temperatures (VPTT) of the hydrogels. When methacryloyl l -alanine methyl ester (MA-AlaOMe) hydrogel, showing a VPTT of 23°C, was used as a co-monomer, the VPTTs of copolymer hydrogels exhibited a prominent decrease when the MA-ValOMe and MA-AlaOiPr compositions were increased. In this case, the MA-ValOMe component, which has a hydrophobic group near the main chain of the hydrogels, decreased the VPTT more efficiently than Ma-AlaOiPr. The relationship between the VPTT and the co-monomer composition exhibited a linear correlation at temperatures above 0°C. Thus, the apparent VPTTs of homopolymer hydrogels, MA-ValOMe and MA-AlaOiPr, were estimated to be −78 and −25°C, respectively, by extrapolating 100% of the composition of the monomers from the linear VPTT versus the composition plot.

The volume phase transitions of poly(acryloyl- l -proline methyl ester (A-ProOMe)) gels in mixtures of water and various alcohols (methyl, ethyl, propyl, and t-buthyl alcohols) were investigated. The poly(A-ProOMe) gels showed two swelling phases (first swell, 0–10 vol%; second swell, 50–80 vol%) and two shrinking phases (first shrink, 10–50 vol%; second shrink, 80–100 vol%) in the presence of each aqueous alcohol under alcohol concentrations ranging from 0 to 100 vol%. The swelling profiles at second swell and second shrink varied in terms of the solvent alcohols; this difference was quantitatively elucidated by taking into account the hydrophobicity of the solvents using dynamic hydration numbers as a parameter of the alcohol's hydrophobicity. The gels showed a shrinking phase in the region of high alcohol concentration (second shrink), which had not been observed in other hydrogels such as NIPAAm. Infrared spectra of the poly(A-ProOMe) revealed that the hydrogen bonding of the amide moiety of poly(A-ProOMe) plays a key role in the gel's sensitivity to the solvent composition, resulting in the sudden shrinking.

A sequential polydepsipeptide, Boc-(Leu-Leu-Lac)3-Leu-Leu-OEt (1) (Lac = L-lactic acid residue) has been synthesized by the segment condensation method. The sequential unit of 1, -Leu-Leu-Lac-, is consisted of two amino acid residues and one hydroxy acid residue. X-ray diffraction measurement with an imaging plate detector and a direct-methods procedure of Shake-and-Bake successfully revealed the crystal structure of 1. In the solid state, the 11-mer depsipeptide, 1, have clear alpha-helical conformation even with the three ester linkages.

N-isopropylacrylamide (NIPAAm)- and methacryloyl-L-alanine methyl ester (MA-ALa-OMe)-grafted cellulose samples were prepared by photografting on dissolving pulp from softwoods, which was oxidized with periodic acid. The grafted samples exhibited a temperature-responsive character, where they swelled and shrank in water at 0°C and 50°C, respectively. The magnitude of the character increased with an increase in the percentage of grafting, and it was nearly equal between the NIPAAm- and MA-ALa-OMe-grafted samples. The temperature-responsive character of the grafted samples was improved by treating them with crosslinkers such as N,N′-methylenebis-acrylamide and di-ethylene glycol dimethacrylate. The extent of the improvement largely depended on the concentration of crosslinker, temperature of crosslinking treatment, and nature of grafted chains.

Poly(acryloyl-L-proline-methyl ester) (1) has optically active side chain, and constitutes thermoresponsive hydrogels upon crosslinking. In this study, we have prepared uncrosslinked polymer of 1 with a 10-kGy irradiation dose of γ-ray. For this polymer, 1, variable temperature circular dichroism (CD) and 1 H NMR spectra have been studied in the range of 0-30 °C. The intense CD spectrum at 0 °C suggests that the side chains in 1 have an ordered orientation. The CD intensity decreases gradually with increasing temperature. The decreased intensity of CD spectra indicates that the disordering occurs for the side-chain orientation. The CD band shape changes discontinuously at 20 °C. In the 1 H NMR spectra, signals disappear above 20 °C. These spectral change at 20 °C indicate that the phase transition occurs at around 20 °C from swollen to shrunken phase. Even after the phase transition, the CD spectra are still changing with isochromic point at 212 nm. It appears that the side-chain conformation is still changing from one state to the other state in the shrunken phase polymers.

Poly(methacryloyl-L-alanine-methyl ester) (1) has an optically active side chain and consists of thermoshrinking hydrogels upon crosslinking. We synthesized an uncrosslinked polymer of 1 by the γ-ray polymerization method. For the prepared polymer, variable-temperature circular dichroism (CD) and 1H NMR spectra were studied, and we found conformational changes in the optically active side chains during the thermally induced phase transition. Intense CD spectra reveal ordered conformation in the side chain of 1 below the phase transition temperature (∼28 °C). A well-resolved 1H NMR spectrum of 1 at 0 °C shows that the conformational angles in the polymer side chain are fixed at low-energy minima. With increasing temperature, the frozen side chain starts rotating vigorously and takes an unordered orientation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2671–2677, 2000

Polymer gels based on methacryloyl-DL-amino acid methyl esters with different alkyl groups on the α-carbon (MA-DL-AA-OMe) were synthesized to evaluate the apparent lower critical solution temperature (LCST) from the composition-induced volume phase transition behavior of their copolymer gels as a function of the temperature. Methacryloyl-DL-alanine methyl ester (MA-DL-AlaOMe) gel showed a thermo-responsive volume phase transition around 22°C, which is close to its LCST of 25°C. In contrast with this, methacryloyl-DL-amino acid methyl ester (MA-DL-AAOMe) gels with alkyl groups on the α-carbon larger than ethyl (Et) collapsed without a volume phase transition. Based on an extrapolated linear plot between the volume phase transition temperatures (VPTTs) estimated using data from the composition-induced volume phase transition at a given temperature and composition for the copolymer gels MA-DL-AlaOMe/MA-DL-AbuOMe and MA-DL-AlaOMe/methacryloyl-norvaline methyl ester (MA-DL-nValOMe), the apparent LCST was estim...

The volume phase transition of nonionic hydrogels was controlled with a very small amount of variation (pinpoint variation) of the side chains far from the main chain. The copolymer hydrogels poly(methacryloyl-alanine methyl ester-co-methacryloyl-alanine ethyl ester) [poly(MA-Ala-OMe-co-MA-Ala-OEt)] and poly(methacryloyl-alanine alkylamide-co-methacryloyl-alanine ethyl ester) [poly(MA-Ala-NR2-co-MA-Ala-OEt)] were studied to investigate how pinpoint variation controls the volume phase transition. All copolymer hydrogels showed a volume phase transition from a swollen phase to a collapsed phase at a definite MA-Ala-OEt content at a specific temperature. The MA-Ala-OEt content at the midpoint of the transition linearly decreased with elevation of the temperature, and the decrease was larger for poly(MA-Ala-OMe-co-MA-Ala-OEt) than for poly(MA-Ala-NR2-co-MA-Ala-OEt). These results suggest that the association of the side chains controlling the swelling character of the hydrogels depends on the interacting ester–ester or ester–amide groups, and the former is larger than the latter. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 56–62, 2001

Ultrasonic irradiation largely accelerated ceric salt initiated grafting of glycidyl methacrylate (GMA) on regenerated cellulose film (cellophane thickness = 20 μm) at 60°C in air. The grafting under ultrasonic irradiation was characterized by a higher percent of grafting and graft efficiency and a lower density of GMA-grafted chains in the surface layer of the grafted films compared to the unirradiated system, which was obtained by attenuated total reflectance IR measurements. The grafted films were subjected to amination with ethylenediamine (En) at 70°C for 3 h in N,N-dimethylformamide. The amount of epoxy groups in the grafted films, which participated in the reaction with En, reached about 50–60 mol % and was slightly lower for the grafted film prepared in the irradiated system than that prepared in the unirradiated one. Adsorption of cupric ions with the aminated samples was performed at pH 5.0 using Clark–Lubs buffer solution and cupric chloride. The adsorption was extremely retarded for the aminated sample prepared using the unirradiated sample compared to that prepared using the irradiated one. The retarded adsorption phenomenon is discussed in terms of a larger formation of crosslinked structures on the surface layer of the former sample during the amination. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2462–2469, 1999

Swelling-controlled drug delivery copolymer gels were synthesized by introducing thermo- and pH-responsive methacryloyl-glycine (MA-Gly) of pH-responsive methacrylic acid (MA-Ac) into thermo-responsive acryloyl- l -proline ethyl ester (A-ProOEt). The threshold of swelling for copolymer gels consisting of A-ProOEt/MA-Gly and A-ProOEt/MA-Ac with a composition of 40/60 mol% was found to be pH 3.0 and pH 5.5, respectively, in buffer solutions at 37°C. The diffusion characteristics of 2-(3-benzoylphenyl)propionic acid (ketoprofen) from such copolymer gels were evaluated in buffer solutions at pHs more than 5.5, and it was found that A-ProOEt/MA-Gly gel possessed a Case II transport, while the A-ProOEt/MA-Ac gel exhibited a non-Fickian (or anomalous) diffusion behavior under the same conditions.

Gramicidin S (GS) analogs in which the Ndelta atoms of the two Orn side chains are linked by an oligomethylene bridge [-(CH2)n-; n=3-5] were prepared via the bis(p-nitrobenzenesulfonyl) derivative [Orn(NBS)2,2']GS. For comparison the nonbridged secondary amino group-containing analog [Orn(Me)2,2']GS was also prepared. 1H NMR and CD spectral analysis indicated that these analogs adopt the same beta-sheet conformation as GS. The antimicrobial activities of these analogs were very similar, but were slightly dependent on the bridge chain length, the trimethylene-bridged analog being the most potent.

Thermally reversible hydrogels were synthesized by radiation-induced copolymerization of acryloyl- l -proline methyl ester with hydrophilic or hydrophobic monomers. The swelling behaviour was found to be affected by a proper balance of the latter. In particular, the transition temperature of the different hydrogels shifted to higher or lower values depending on the presence of hydrophilic or hydrophobic moieties in the polymer chain, respectively. Acetaminophen, an analgesic and antipyretic drug, was entrapped into some hydrogels and a wide range of release rates was obtained according to the nature of the comonomers. A novel thermoresponsive hydrogel was also prepared by radiation polymerization of acryloyl- l -proline methyl ester in the presence of 4-acryloyloxy acetanilide, an acrylic derivative of acetaminophen. Again, the swelling curves showed an inverse function of temperature. It was shown that with this hydrogel bearing the drug covalently attached to the polymer backbone, the hydrolysis process was the rate-determining process of the drug release.

The effect of saturated fatty acid sodium salts (C n ), sodium laurate (C 12 ), sodium myristate (C 14 ), sodium palmitate (C 16 ), and sodium stearate (C 18 ), on the swelling of poly(acryloyl- l -proline methyl ester) (A-ProOMe) gel was investigated in different pH solutions. The C n -loaded gels collapsed in a buffer solution with pH 3.0, while they expanded in a buffer solution with pH 6.5. This effect was strongly influenced by the number of methylene units in C n , as the threshold for causing this sensitivity existed between C 12 and C 14 . On the other hand, a pulsatile release of ketoprofen occurred when the gel was cycled in buffer solutions between pH 3.0 and pH 6.5. This behavior may be attributable to the surface-regulated mechanism.

Hydrogels that reversibly swell or shrink in water with decreasing or increasing temperature, respectively, were obtained by γ ray-induced polymerization of acryloyl-l-proline methyl ester in the presence of different amounts of a crosslinking agent. The role of water in the hydrated polymers was investigated by DSC and 1H-NMR relaxometry. From the curves of fusion of water determined by the former it was possible to ascertain that the amount of both freezing and non freezing water decreased with increasing the crosslinker percentage and/or swelling temperature. Moreover, at the temperatures higher than 37°C, the water absorbed by the different hydrogels is mostly present as non freezing water. The 1H-NMR relaxometry study enabled the spin–spin and spin–lattice relaxation curves to be analyzed. It was possible to distinguish three “populations” of protons and identify two of them with protons of freezing and non freezing water determined by DCS.

Effect of ultrasonic irradiation on ceric salt (Ce4+)-initiated grafting of methyl methacrylate (MMA) on regenerated cellulose film (thickness = 20 μm) was investigated under an air atmosphere in water solvent at 60°C. The grafting system with the ultrasonic irradiation was characterized by higher percentage of grafting and graft efficiency than the system without the irradiation. Reaction of cellulose with Ce4+ was also accelerated by the ultrasonic irradiation. No accelerating effect of grafting due to the ultrasonic irradiation was observed for the system under reduced pressure of 5 torr. The effect of the ultrasonic irradiation on the average molecular weight of MMA-grafted chains was also studied. Moreover, the surface layer of the resulting grafted films was examined by attenuated total reflection–infrared (ATR–IR) measurement and scanning electron microscopy (SEM) observation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 251–258, 1999

Three isomers of cyclomaltoheptaose derivatives, 1a–c, which possess five mesitylenesulfonyloxy groups on their C-6 atoms, were prepared. Assignment of the regiosiomers was performed by their conversion into compounds containing five 3,6-anhydroglucose units followed by 1H NMR analyses. The structures of the pentakis(3,6-anhydro) derivatives were also confirmed by their derivation from the known bis(TBDMS) derivatives.

Novel cyclodextrin dimers (1, 2, 3 and 4) whose cyclodextrins were linked with sulfur-containing linkers, namely a thiodipropanamide, a dithiodipropanamide, a thiodiethanamide, or a dithiodiethanamide linker, were synthesized by a reaction of 6-amino-6-deoxycycIoheptaose 7 with the corresponding dicarboxylic acids. For their preparation, dicyclohexylcarbodiimide, l-(3-dimethylaminopropyl)-3-ethylcarbodiimideand(benzotriazol-l-yloxy) tripyrroIidinophosphonium hexafluorophosphate were examined as coupling reagents. 'H NMR studies of the dimers suggested an intramolecular inclusion of the linker moiety to the cyclodextrin cavity, which affected the complexation of guest molecules. Dimer 4 was converted to another type of dimer 5 by reductive cleavage of the disulfide bond to generate thiol group-containing mononieric species followed by a substitution reaction with 6-O-tosyl derivative 6.

Photografting ( λ >300 nm, 60°C) of acrylic acid (AA) on low-density polyethylene (PE) film (thickness=30 μm), on which xanthone photoinitiator was coated earlier, was largely accelerated when small amounts of N , N ′-methylenebisacrylamide (MBAAm) (0.67 and 3.3 mol% of AA monomer used) were added to the system. The addition of MBAAm did not affect distribution of the grafted chains in the cross section of the resultant AA-grafted PE film, which was measured by electron probe microanalysis. The AA-grafted samples were subjected to peroxidation with hydrogen peroxide in the presence of methanesulfonic acid at 25°C for 3 h to yield polymeric peracids. The amount of peracids formed was smaller for the grafted samples prepared in the system with MBAAm than those prepared in the system without MBAAm. Moreover, thermal decomposition of the polymeric peracids at 40°C was largely retarded for the former samples compared to the latter samples. These results suggest the formation of a cross-linked structure in the AA-grafted chains, which are introduced into PE substrate by photografting in the presence of MBAAm.

Three isomers of cyclomaltoheptaose derivatives, la-c, which possess five mesitylenesulfonyloxy groups on their C-6 atoms, were prepared. Assignment of the regiosiomers was performed by their conversion into compounds containing five 3,6-anhydroglucose units followed by 'H NMR analyses. The structures of the pentakis(3,6-anhydro) derivatives were also confirmed by their derivation from the known bis(TBDMS) derivatives.

Thermo-responsive poly(N-isopropylacrylamide, NIPAAm) was grafted onto etchedtrack copolymer films with cylindrical pores of diameter 2.5 μm by means of post-polymerization at 60°C for 30 min after pre-irradiation of 30 kGy, using γ-rays from a60Co source to obtain a layer with a surface graft yield of 0.18 mg/cm2. The permeation of p-nitrophenol (PNP) through NIPAAm-grafted etched-track films, when measured at 30°C, was markedly depressed, to 7.12 × 10−5 cm/min, compared with those measured below and above this temperature, e.g. 3.84 × 10−3 cm/min at 29°C and 2.46 × 10−3 cm/min at 31°C. This phenomenon can be explained by the existence of a theta-point (⊝) temperature, at which the hydrophilic interaction between the linear polymer of NIPAAm and water apparently disappears, resulting in permeation retardation of the water soluble PNP.

Photografting of methacrylic acid (MAA) on low-density polyethylene (PE) film (thickness=30 μm), on which xanthone photoinitiator was coated earlier, was investigated at 60°C in the presence of ethylene glycol dimethacrylate derivatives (EGDMA) with different numbers of ethylene glycol unit between two double bonds in the molecule, such as di-, tetra- and nona-ethylene glycol dimethacrylates (2EG, 4EG and 9EG, respectively). Addition of the EGDMA (0.3–3 mol% of MAA used) to the grafting system largely accelerated the photografting and the magnitude of the enhancement decreased in the order of 9EG>4EG>2EG. EGDMA component was incorporated into MAA-grafted PE films and the content decreased in the order of 2EG>4EG>9EG. MAA-grafted chains of the grafted PE films (sample with EGDMA) prepared by photografting in the presence of EGDMA tended to appear at the film surface compared to those of the grafted films (sample without EGDMA) prepared in the system without EGDMA, which was measured by electron probe microanalysis and attenuated total reflection infrared spectroscopy. The MAA-grafted PE films exhibited a pH-responsive character, which was evaluated by measuring a dimensional change of the grafted films. The grafted films shrank in acidic media, but swelled in alkaline media. The sample with EGDMA showed a larger pH-responsive character than the sample without EGDMA though there was no large difference in the character among EGDMA. The phenomenon was discussed in terms of the MAA-grafted chains with a branched structure, which was suggested by differential scanning calorimetry of the grafted films.

Thermoresponsive porous gel membranes were synthesized by a simultaneously occurring process consisting of radiation-induced polymerization and crosslinking in aqueous solutions at various concentrations of acryloyl-L-proline methyl ester(A-ProOMe) without a crosslinker. Permeation of p-nitrophenol (PNP) through a thermoresponsive porous gel membrane obtained at a monomer concentration of 80% (w/w) drastically reduced around 14°C, the lower critical solution temperature (LCST) of linear poly(A-ProOMe) in water, from 0.60 × 10−3 cm/min at 10°C to no permeation at 18°C, accompanied by changes in both size and shape of pores associated with gel shrinkage. Moreover, it was found that porous gel membranes with a porosity of approximately 60% had a greater PNP permeability constant through porous gel membranes with mutually connected pores obtained at a monomer concentration of 50% (w/w) than individually supported pores obtained at a monomer concentration of 70% (w/w). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1495–1500, 1998

Radiation-induced polymerization of acryloyl-L-proline methyl ester, an α-aminoacid-containing monomer, in the presence of a crosslinking agent and a hydrophilic monomer gave rise to polymer hydrogels whose water content at equilibrium was found to decrease as the swelling temperature increased. Some hydrogel samples were obtained with entrapped acetaminophen, an analgesic and antipyretic drug. It was ascertained that the release of the drug was controlled by both the hydrophilicity of the polymer matrices and the environmental temperature.

Method for introducing grafted chains consisting of two types of monomer components, acrylic acid (AA) and N-isopropylacrylamide (NIPAAm), into low-density polyethylene (PE) film (thickness = 25 μm) was investigated by two photografting technique using xanthone photoinitiator at 60°C. In the first method (one-step method), AA and NIPAAm binary monomers were graftcopolymerized onto PE film. In the second method (two-step method), AA was first photografted onto PE film and then NIPAAm was further introduced into the AA-grafted PE film by a second-step photografting. Water absorbencies of the grafted films (one- and two-step samples) prepared by the one- and two-step methods, respectively, decreased in the order of AA-grafted film > one-step sample > two-step sample > NIPAAm-grafted film. The water absorbency steeply decreased at 20 to 40°C with increasing temperature when immersed in water at the temperatures (5–60°C) for 24 h. Thermosensitivity, which was defined as the ratio of water absorbencies of the grafted samples at 5 and 60°C, was higher for the one-step sample than the two-step one. The different extent of the water absorbency and the thermosensitivity between both samples is discussed in terms of location of grafted chains in the film substrate, which was determined by electron probe microanalysis and attenuated total reflection–infrared measurements, and monomer sequence distribution of the grafted chains. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2057–2064, 1998

The synthesis of cellulose peroxides of the peracid type having a temperature-responsive function was studied by using carboxymethyl cellulose (CMC) and acrylic acid (AA)-grafted cellulose, into which the temperature-responsive component, poly(N-isopropylacrylamide) [poly(NIPAAm)], was introduced by a photografting method (λ > 300 nm). Dissolving pulp from softwoods was used as cellulose sample. NIPAAm-grafted CMC samples prepared by photografting with CMC peroxide exhibited a slightly larger temperature-responsive character than the samples prepared by photografting with xanthone photoinitiator, where the grafted CMC samples swelled and shrank in water at 5 °C and 60 °C, respectively. Ungrafted and NIPAAm-grafted CMC samples were subjected to peroxidation with hydrogen peroxide in the presence of methanesulfonic acid. About 90% of the initial amount of peroxide on the ungrafted CMC sample disappeared after thermal decomposition at 50 °C for 60 min. On the other hand, about 50% of the peroxide on the NIPAAm-grafted CMC sample remained stable under the same conditions. Peroxides on AA/NIPAAm-grafted samples, which were prepared by photografting of AA/NIPAAm binary monomers followed by peroxidation with hydrogen peroxide, were more stable towards thermal decomposition than those on NIPAAm-grafted samples.

Derivatives of gramicidin S (GS) and its mono- and di-d-cyclohexylalanined-Cha) analogs possessing various protecting groups on Orn side chains were prepared.1H NMR spectra of the unsymmetrically protected analogs [Orn(X)2, Orn(X′)2′,d-Cha4]GS were similar to the composites of the spectra of the symmetrical derivatives [Orn(X)2,2′,d-Cha4,4′]GS and [Orn(X′)2,2′]Gs, revealing the proximity of the protecting groups of NδH of Orn residues at the 2 and 2′ positions to the side chains ofd-Phe (ord-Cha) residues at the 4 and 4′ positions, respectively. The results indicated the presence of H-bonds between the N°H of Orn and the carbonyl ofd-Phe residues in the i→i+2 sense and not in i→i-3, which was also supported by the ROESY analysis. The substantially strong H-bonds can explain the observed resistance of the urethane NH of the Orn side chains in the GS derivatives to the N-methylation with CH3I−Ag2O in DMF.

Crystals of the title compound, C10H18N2O2S, which is an enanti­opure N-protected l-prolinethio­amide, were successfully grown from a tetra­hydro­furan solution. Inter­molecular N—H⋯O hydrogen bonds are observed between thio­amide —NH2 and Boc-carbonyl C=O groups, but the thio­amide C=S group is not involved in hydrogen bonding.

Ion beams with an energy of 10 MeV/n were used for producing porous membranes of poly(ethylene terephthalate) and poly(diethyleneglycol-bis-allylcarbonate) films. The condition to obtain cylindrical pores was explained by the relation between the relative etching rate and restricted energy transfer from ion beams to polymer films. The porous membranes were chemically modified either by copolymerizing or by grafting such hydrogel monomers as N-isopropylacrylamide and acryloyl-l-proline methyl ester. The obtained membranes changed pore size in response to the change in environmental conditions such as temperature. The change was followed by electron microscopy. A cyclic change in conductivity of potassium ion through the membrane of a single pore was observed when the temperature of the dialysis cell containing a 0.1 M KCl solution was cycled between two temperatures. The selectivity of organic ion passing through the membrane drastically changed at the phase transition temperature of the attached hydrogel layer.

Heavy ion beams with energy in the order of 10 MeV/n were irradiated onto polyethylene terephthalate (PET) and polydiethyleneglycol-bis-allylcarbonate commercially known as CR-39 for producing organic porous membranes. The condition to obtain cylindrical pores was accounted for the relation of restricted energy loss, REL, from ion beams to the polymer films with relative etching rate, Q, in the region along ion's trajectory versus non-irradiated region. Then the porous membranes were chemically modified by grafting such monomers as N-isopropylacrylamide and acryloyl-L-proline methyl ester onto the surface of pores to impart the characteristic of the hydrogel obtained from these polymers to the membrane. The pore size of the membrane changed from an open state to a completely closed state when environmental conditions such as temperature were changed. The permeation of water, choline, insulin and albumin through the membrane was controlled by temperature. An abrupt change of permeability was observed at the phase transition temperature of the hydrogel.

We studied the track response for the copolymer of CR-39 monomer with N-isopropylacrylamide (NIPAAm) as well as etching properties. It was found that copoly (CR-39/NIPAAm/Naugard 445) composed in wieght ratio of 99/1/0.01 is highly sensitive to low LET particles in the region below 10 keV/μm of LET 200 eV and able to record normally incident particles of LET 200 ev down to ∼1.5 keV/μm, recording protons up to the energy of 27 MeV. These results were compared with the responses for two types of CR-39 detectors containing a small quantity of antioxidant. The threshold energy proton registration is discussed.

Intelligent chemical valves responding to a slight change of temperature were created by the combination of ion beam-chemical etching technique and a novel material consisting of an ion track detector material diethyleneglycol-bis-allylcarbonate (CR-39) and a thermo-responsive gel acryloyl-L-proline methyl ester (A-ProOMe). The changes in size of ion-track pores in etched films were measured microscopically by repetition between 0 and 30°C at 24-h intervals for a 50 μm thick copoly(CR-39/A-ProOMe, 60 40 mol % ) film which was obtained by etching in aqueous 6M NaOH solution at 60°C after an 11.6 MeV/n 208Pb ion irradiation and, as a result, it was found that the pore size in the film obtained by etching for 10 min is reversibly changed from a perfectly closed pore at 0°C to a fully opened pore with a diameter of 0.30 μm at 30°C.

A novel thin membrane synthesized by copolymerizing diethyleneglycol-bis-allylcarbonate (CR-39) with a minor amount of acryloyl-L-proline methyl ester (A-ProOMe) was etched by an aqueous NaOH solution after a 6.19 MeV/n 84Kr ion irradiation to produce ion-track membranes. The ion-track membranes were chemically modified by radiation-induced grafting of A-ProOMe. We found that a polymer gel of A-ProOMe shows a characteristic volume phase transition around a lower critical solution temperature (LCST) of 14°C, namely thermo-responsive function. The changes in size of pores in the grafted membrane under different temperatures in water were measured by both the scanning electron microscopy (SEM) and the atomic force microscopy (AFM). The pore was controlled from an open state above LCST to a completely closed state below LCST. The permeability of p-nitrophenol through the grafted membrane was also measured by changing the temperature of the cell.

The title peptide compound, C23H31Cl3N2O6, is a synthetic inter­mediate as a plasmodium falciparum blood-stage antigen. There is an intra­molecular N—H⋯O hydrogen bond between the urethane and benzyl ether groups. The relatively low melting point is attributed to the lack of an inter­molecular hydrogen-bond network.

The title compound, C18H31Cl3N2O5, an enanti­opure dipeptide trichloro­ethyl ester, is one of two starting fragments in the synthesis of cyclo­sporin O analogs. In the crystal structure, mol­ecules are linked by N—H⋯O=C hydrogen bonds, forming a β-spiral assembly along the c axis.

Bisfunctional biphenylene monomers were designed, synthesized, and inspected as building blocks for aromatic polyketone synthesis. Starting from 2,2′-dimethoxybiphenylene (1), a highly activated acyl-acceptant biphenylene monomer affording high molecular weight polyketones, two types of biphenylene monomers were developed: 5,5′-bis(3[4]-chlorobenzoyl)-2,2′-dimethoxybiphenylenes (6) which readily gave the corresponding polyketones by nickel-catalyzed aromatic coupling polymerization and 2,2′-bis(trifluoromethyl)-4,4′-biphenylenedicarboxylic acid (27) which reacted with biphenylene 1 in P2O5CH3SO3H to give the corresponding fluorinated aromatic polyketone, selectively. The related model reactions for both monomer synthesis and polymerization were also investigated.

The practical synthetic method for a series of substantially novel fluorine-containing polyfunctional aromatic compounds, 3-trifluoromethyl-4-halobenzonitriles [halo = Cl, Br, and F], was established by using copper-cyano complexes as effective Sandmeyer cyanating reagents.