Post-modification Method Research Articles

Amphiphilic Poly(3-hexylthiophene)-Based Semiconducting Copolymers for Printing of Polyelectrolyte-Gated Organic Field-Effect Transistors

Polyelectrolytes are promising electronically insulating layers for low-voltage organic field effect transistors. However, the polyelectrolyte–semiconductor interface is difficult to manufacture due to challenges in wettability. We introduce an amphiphilic semiconducting copolymer which, when spread as a thin film, can change its surface from hydrophobic to hydrophilic upon exposure to water. This peculiar wettability is exploited in the fabrication of polyelectrolyte-gated field-effect transistors operating below 0.5 V. The prepared amphiphilic semiconducting copolymer is based on a hydrophobic regioregular poly(3-hexylthiophene) (P3HT) covalently linked to a hydrophilic poly(sulfonated)-based random block. Such a copolymer is obtained in a three-step strategy combining Grignard metathesis (GRIM), atom transfer radical polymerization (ATRP) processes, and a postmodification method. The structure of the diblock copolymer was characterized using FT-IR, 1H NMR spectroscopy, and gel permeation chromatography...

Preparation of novel polyimide hybrid materials by multi-layered charge-transfer complex formation

A versatile method for the post-modification of sulfonated polyimides by charge-transfer (CT) complex formation between electron-deficient naphthalenediimide units in polyimide and electron-rich dihydroxynaphthalene was developed. CT complex hybrid films whose physicochemical properties, such as mechanical strength, differed from those of the original polyimide films were successfully fabricated. A versatile post-modification method for polyimides using CT complex formation between electron-deficient naphthalenediimide units in the polyimide and electron-rich dihydroxynaphthalene was developed. The film preparation by CT complex formation reported in this paper is an attractive method for functionalization of polyimides because many donor molecules and polyimides can be used. The supramolecular methodology shown here is quite simple, but is an innovative method for polyimide modification.

Comparative studies of irinotecan-loaded polyethylene glycol-modified liposomes prepared using different PEG-modification methods

Recently, a polyethylene glycol (PEG)-modification method for liposomes prepared using pH-gradient method has been proposed. The differences in the pharmacokinetics and the impact on the antitumor effect were examined; however the impact of PEG-lipid molar weight has not been investigated yet. The main purpose of this study is to evaluate the impact of PEG-lipid molar weight against the differences in the pharmacokinetics, the drug-release profile, and the antitumor effect between the proposed PEG-modification method, called the post-modification method, and the conventional PEG-modification method, called the pre-modification method. Various comparative studies were performed using irinotecan as a general model drug. The results showed that PEG-lipid degradation could be markedly inhibited in the post-modification method. Furthermore, prolonged circulation time was observed in the post-modification method. The sustained drug-release was observed in the post-modification method by the results of the drug-releasing test in plasma. Moreover, a higher antitumor effect was observed in the post-modification method. It was also confirmed that the same behaviors were observed in all comparative studies even though the PEG molecular weight was lower.In conclusion, the post-modification method has the potential to be a valuable PEG-modification method that can achieve higher preservation stability of PEG-lipid, prolonged circulation time, and higher antitumor effect with only half the amount of PEG-lipid as compared to the pre-modification method. Furthermore, it was demonstrated that PEG5000-lipid would be more desirable than PEG2000-lipid since it requires much smaller amount of PEG-lipid to demonstrate the same performances.

Comparative studies of polyethylene glycol-modified liposomes prepared using different PEG-modification methods

To address the issue of excess polyethylene glycol (PEG)-lipid degradation observed when PEG-modified liposomes are prepared using the pH-gradient method, a concept using a novel PEG-modification method, called the post-modification method, was proposed and evaluated. To assess the proof concept, a preservation–stability study and a pharmacokinetic study were performed that compared the conventional PEG-modification method, called the pre-modification method, with the post-modification method. The results show that PEG-lipid degradation could be markedly inhibited in the post-modification method. Furthermore, the post-modification method could be used without any manufacturing process difficulties, especially with high PEG-lipid content. In addition, a higher blood circulation capability was observed in the post-modification method. Through comparative studies, it was found that the post-modification method was advantageous compared to the pre-modification method. In conclusion, the post-modification method has the potential to be a novel PEG-modification method that can achieve a higher preservation stability of PEG-lipid, a greater ease of manufacturing, and a higher blood circulation capability, especially in the manufacturing of pH-gradient liposomal products.

Polyurea microcapsules: Surface modification and capsule size control

AbstractA postmodification method for polyurea microcapsule (PUMC) surfaces using functional polyelectrolytes is reported in this article. Fluorescein isothiocyanate (FITC) was used to probe the chemistry on PUMC surface and label nucleophilic groups on the surface, in particular amines. As well, a fluorescently labeled polyanion containing electrophilic acetoacetate groups was used to covalently react with these nucleophilic groups on the PUMC surfaces. This modification causes charge reversion of the originally cationic PUMC and enables subsequent layer‐by‐layer (LbL) coating using other polyelectrolytes, allowing for covalent or noncovalent modification of the capsule surface. All modification steps were monitored using either laser scanning confocal microscopy or fluorescence microscopy. Optical and fluorescence microscopy of PUMC wall cross‐sections embedded in resin confirmed that the modifications were restricted to the outer surface of PUMCs, offering minimum interference of this modification method with other capsule wall properties. In addition, a simple T‐junction type microfluidic device based on a commercially available MicroTEE was designed to produce narrowdisperse PUMCs. This device was easy to set up and operate and was proved to be an useful tool for making monodisperse emulsions and narrowdisperse MCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Preparation of Perphenylcarbamoylated β-Cyclodextrin-silica Hybrid Monolithic Column with “One-Pot” Approach for Enantioseparation by Capillary Liquid Chromatography

Perphenylcarbamoylated β-cyclodextrin-silica (Ph-β-CD-silica) hybrid monolithic columns for enantioseparation in capillary liquid chromatography (cLC) have been prepared by a "one-pot" approach via the polycondensation of alkoxysilanes and in situ copolymerization of mono (6(A)-N-allylamino-6(A)-deoxy)-Ph-β-CD and vinyl group on the precondensed siloxanes. The morphologies of the Ph-β-CD-silica hybrid monolithic columns were characterized by optical microscopy and scanning electron microscopy (SEM), showing the uniform monolithic matrixes tightly bonded onto the capillary wall. The content of Ph-β-CD incorporated in monolithic matrix by the "one-pot" approach was ca. 2.9 times higher than that by postmodification method. The permeability of the Ph-β-CD-silica chiral hybrid monolithic column was 3.63 × 10(-14) m(2), and the minimum plate height was 12 μm corresponding to 83,300 theoretical plates/meter. Enantioseparations of 13 racemates were achieved by the Ph-β-CD-silica hybrid monolithic column. In this work, since the prepolymerization system mainly consisted of organic solvent (methanol (MeOH), N,N-dimethylformamide (DMF)), the limitation and difficulty of the use of water insoluble organic monomers in the previously reported "one-pot" method was circumvented. Therefore, various β-CD derivatives as well as other hydrophobic monomers could thus be used to prepare organic-silica hybrid monolithic columns with the "one-pot" process.

Synthesis and characterization of aluminium containing CIT-1 and their structure–property relationship to hydrocarbon trap performance

The present work focuses on the synthesis of Al-CIT-1 by various post-modification procedures of B-CIT-1 and their structure–property relation to hydrocarbon trap performance. Al substitution in B-CIT-1 was carried out by three different post-modification procedures, viz., direct exchange (Al-CIT-1_DEX), insertion (Al-CIT-1_INS), and impregnation (Al-CIT-1_IMP), and characterized in detail by various physico-chemical techniques such as XRD, N 2 adsorption, SEM, NH 3-TPD, XPS, and solid state 27Al and 29Si MAS NMR. The Al-CIT-1 samples were tested for their adsorption–desorption characteristics of toluene, and 2,2,4-trimethylpentane (2,2,4-TMP) to understand the Al distribution in CIT-1 as well as the efficacy of these materials as hydrocarbon traps. The Al distribution in Al-CIT-1 plays a critical role in the adsorption–desorption characteristics of toluene and 2,2,4-TMP. Al-CIT-1 with high relative proportion of framework Al and less extraframework Al (Al-CIT-1_DEX) showed maximum toluene and 2,2,4-TMP adsorption capacity. The presence of finely distributed extraframework Al 2O 3 species in Al-CIT-1_INS modify the pores and causes a slow release of toluene during desorption. Al-CIT-1_IMP with less Al content and acidity showed the lowest toluene desorption temperature. Large amount of surface Al species hinder a relatively bulky molecule 2,2,4-TMP to access the available active sites of tetrahedral Al and the associated Brϕnsted sites in the zeolite, and as a result, Al-CIT-1_INS showed hardly any adsorption towards 2,2,4-TMP. Thus, by varying the post-modification method and treatment condition, it is possible to tune the performance of Al incorporated CIT-1 as a useful material for hydrocarbon trap.

Catalytic Isomerization of Dimethyltetralin over Silicon- and Boron-Modified H-BEA Zeolites

Silicon- and Boron-modified H-BEA(Si/Al ratio of 12.5) were prepared by chemical liquid deposition (CLD) of tetraethyl orthosilicate (TEOS) and post-modification method using boric acid, respectively. The catalytic performance of the modified H-BEA catalysts was evaluated for the isomerization of 2,7-dimethyltetralin (DMT) to 2,6-DMT. It was found that the silylation with TEOS passivated preferentially the external acid sites of H-BEA zeolite while the Boron passivated both of the external and internal acid sites. The strong Bronsted acid sites were responsible for the side reactions such as dealkylation, cracking and transalkylation and can be prevented effectively by the silylation and boronation of BEA zeolite.

Mesoporous SBA-15-supported chiral catalysts: preparation, characterization and asymmetric catalysis

Two mesoporous silica-supported chiral Rh and Ru catalysts 5 and 6 with ordered two-dimensional hexagonal mesostructures were prepared by directly postgrafting organometallic complexes RhCl[( R)-MonoPhos(CH 2) 3Si(OMe) 3][( R, R)-DPEN] and RuCl 2[( R)-MonoPhos(CH 2) 3Si(OMe) 3][( R, R)-DPEN] (DPEN = 1,2-diphenylethylenediamine) on SBA-15. During the asymmetric hydrogenation of various aromatic ketones under 40 atm H 2, both catalysts exhibited high catalytic activities (more than 97% conversions) and moderate enantioselectivities (33–54% ee). Furthermore, the chiral Rh catalyst 5 could be easily recovered and used repetitively five times without significantly affecting its catalytic activity and enantioselectivity. A catalytic comparison of the mesoporous silica-supported chiral Rh catalyst 4 prepared by a postmodification method is also discussed.

Preparation of polyacrylamide hydrogels at various charge densities by postmodification

AbstractIn this study, first polyacrylamide hydrogels were synthesized by free‐radical crosslinking polymerization of acrylamide monomer with N,N′‐methylenebis(acrylamide) as a crosslinker in an aqueous solution at 22°C. Then, a series of hydrogels at various charge densities were prepared by partial hydrolysis of polyacrylamide precursors in a 0.1M sodium hydroxide solution at 60°C. The hydrolysis time was varied between 20 and 180 min. The chemical structures and internal morphologies of the hydrogels before and after alkaline hydrolysis were characterized with attenuated total reflectance/Fourier transform infrared and scanning electron microscopy measurements. The swelling ratio of the hydrolyzed hydrogels was measured in buffer solutions at various pHs. From differential curves of dQv/dpH versus pH (where Qv is the equilibrium swelling ratio of the hydrogels), the volume phase transition pH of the hydrogels was found to be 4.33 ± 0.05, regardless of the charge density of the hydrogels. In water at 22°C, the hydrogels with greater charge density showed a more rapid swelling rate because of their higher porosity and hydrophilicity. Moreover, in buffer solutions with the pH changing from 9.0 to 2.0 at 22°C, the hydrogels with greater charge density also exhibited a more rapid deswelling rate than the hydrogels with less charge density. In conclusion, the postmodification method is a good way of preparing pH‐sensitive hydrogels with fast responsiveness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis of SBA-15/carbon composite with an ink-bottle-like pore structure by a novel pulse CVD technique

A novel and easy post modification method, pulse chemical vapor deposition (pulse CVD), was developed to tailor the pore-opening of SBA-15 while largely keeping its surface area and pore volume. By using acetylene as carbon precursor and nitrogen as carrier gas, the pore-mouth of SBA-15 was effectively reduced from 8.1 nm to 5.1 nm within 5 min while maintaining the pore body at 8.1 nm. This ink-bottle-structured SBA-15/carbon composite only losses 12% BET specific surface area and 16% total pore volume, respectively. The SBA-15/carbon composite is highly hexagonally ordered and has similar particle morphology as the original SBA-15. The effect of three pore modification factors—the number of cycles of pulse CVD, the ratio of acetylene/nitrogen and the feeding time of carbon precursor, on the final pore structure of the SBA-15/carbon composite is also studied.

Surface stabilization of gold by sol–gel post-modification of alumina support with silica for cyclohexane oxidation

Abstract Gold nanoparticles were stabilized on alumina support by silica via a surface sol–gel post-modification method and applied for the catalytic cyclohexane oxidation to cyclohexanone and cyclohexanol using oxygen in the absence of any solvent and initiator. The results show that the surface doping of alumina support with silica is highly effective in stabilizing gold nanoparticles subjected to calcination at 500 °C for 3 h. Moreover, the catalytic activity in terms of specific reaction rate and the selectivity to cyclohexanone are appreciably enhanced probably due to a decreased acidity and hydrophilicity by surface substitution of alumina with silica.

Large-Pore Mesoporous Organosilicas Functionalized with trans-(1R,2R)-Diaminocyclohexane: Synthesis, Postmodification, and Catalysis

Large-pore mesoporous ethane-silicas functionalized with trans-(1R,2R)-diaminocyclohexane were synthesized in an acidic medium by one-step co-condensation of 1,2-bis(trimethoxysilyl)ethane and N-[(trimethoxysilyl)benzyl]-(−)-(1R,2R)-diaminocyclohexane using triblock copolymer P123 as template. The postmodification of trans-(1R,2R)-diaminocyclohexane in the pore of the mesoporous ethane-silicas was further demonstrated by reaction with p-toluenesulfonyl chloride. The modified material (complexed with [RhCp*Cl2]2) exhibits much higher conversion and ee [53% conversion with 68% ee (R)] than the original material [18% conversion with 38% ee (S)] for the asymmetric transfer hydrogenation of acetophenone under air atmosphere in HCOONa−H2O. Various aromatic ketones can be converted to the corresponding chiral alcohol with moderate to good enantioselectivities [18−81% ee (R)]. The co-condensation method associated with the postmodification method is one of the alternatives for the synthesis of mesoporous materials containing new functionalities.

Acidic properties of sulfonic acid-functionalized FSM-16 mesoporous silica and its catalytic efficiency for acetalization of carbonyl compounds

Propyl-sulfonic acid-functionalized FSM-16 mesoporous silica (SO 3H-FSM) is prepared by a conventional post-modification method. For the acetalization of carbonyl compounds with ethylene glycol, SO 3H-FSM shows a higher rate and 1,3-dioxolane yield than conventional heterogeneous solid acids such as zeolites, montmorillonite K10 clay, silica-alumina, and the sulfonic resin. SO 3H-FSM is stable during the reaction, with no leaching and deactivation of sulfonic acid groups, and is reusable without loss of its activity. The acidity and hydrophilicity of SO 3H-FSM are well characterized by the microcalorimetry of NH 3 adsorption, NH 3-TPD, and H 2O-TPD, and the result is compared with those for various aluminosilicate zeolites (HZSM5, HBEA, HY) and K10 clay. It is found that NH 3-TPD is not suitable for characterizing the acidity of SO 3H-FSM, because the decomposition of SO 3H groups on SO 3H-FSM begins above 200 °C. An NH 3 adsorption microcalorimetric experiment at 150 °C shows that, compared with HZSM5, SO 3H-FSM has a smaller number of acid sites but has a similar number of strong acid sites with ammonia adsorption heat above 140 kJ mol −1. Comparison of the structural properties and catalytic results shows that a large pore diameter and low hydrophilicity are required to obtain high activity. Brønsted acid sites with a relatively strong acid strength are more suitable for this reaction, but the high acid concentration is not indispensable. The high activity of SO 3H-FSM should be caused by the presence of the strong Brønsted acid sites in the mesopore with a relatively low hydrophilicity, where both reactants can smoothly access the acid sites.

Synthesis and solvent-sensitive fluorescence properties of a novel surface-functionalized chitosan film: potential materials for reversible information storage

Pyrenesulfonylchloride (PSC) was prepared and convalently bound to glutaraldehyde (Glu) crosslinked chitosan (CS) films by a post modification method. The monomer emission of pyrene (Py) immobilized on the CS films was weak both at dry and wet state if super-pure water was used to wet the films. However, upon addition of salts or replacing the super-pure water with tap water the monomer emission increased dramatically whereas the change in the excimer emission was hardly observed. Furthermore, the increasing process could last as long as 7 h. In contrast, the emission returned to the original intensity at once when the films were washed with super-pure water three to four times. The process could be repeated for at least five times.