Chiral separation of D,L‐tyrosine through nitrocellulose membrane

Enantioselective membrane was prepared using nitrocellulose as membrane material. The flux and permselective properties of membrane using water solution of D ,L ‐tyrosine as feed solution were studied. The top surface and cross‐section morphology of the resulting membrane were examined by scanning electron microscopy. The optical resolution of over 85% enantiomeric excess was achieved when the enantioselective membrane was prepared with 25 wt % nitrocellulose and 15 wt % N,N‐dimethylformamide in the casting solution of methanol, 10°C temperature of water bath for the gelation of the membrane, and the operating pressure and the feed concentration of the D ,L ‐tyrosine were 6 kgf/cm² and 0.25 mg/mL, respectively. Since the nitrocellulose contains a large amount of chirality active carbons on the backbone structure and is possible to form helical structure, it is considered to be the reason for the enantioselectivity of the membrane. This is the first report that nitrocellulose can be used as a membrane material. This work indicates that the large‐scale purification of chiral molecules from racemic mixtures will be realized by the enantioselective membrane technique in the near future and that the enantioselective nitrocellulose membrane could soon become very attractive for industrial uses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Optical resolution of racemic amino acid derivatives with chiral polyamides bearing glutamyl residue as a diacid component

Novel chiral polyamides with chiral environment in their main chains were obtained from aromatic diamine, 4,4′‐diaminodiphenylmethane (DADPM), and the D ‐isomer or the L ‐isomer of N‐α‐protected glutamic acid, such as N‐α‐benzyloxycarbonyl‐D ‐glutamic acid (Z‐D ‐Glu‐OH) or N‐α‐benzyloxycarbonyl‐L ‐glutamic acid (Z‐L ‐Glu‐OH), in the presence of triphenyl phosphite (TPP). Two types of newly prepared polyamide showed optical rotation, implying that there were asymmetric carbons in their main chains. Circular dichroism studies demonstrated that resulting chiral poly‐ amides took a helical structure. Optical resolution ability of those two types of polyamide was studied by adopting potential difference as a driving force for membrane transport. Membranes showed permselectivity toward racemic mixture of N‐α‐acetyltryptophan (Ac‐Trp). The permselectivity was dependent on the absolute configuration of diacid component. The permselectivity was expressed by diffusivity selectivity, which was determined by the presence of chiral helicity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chiral separation of D,L‐serine racemate using a molecularly imprinted polymer composite membrane

Molecularly imprinted (MIP) composite membranes were prepared using conventional interfacial polymerization technique that has been often used for the preparation of reverse osmosis (RO) membrane. Target molecules (D ‐serine) were used together with the piperazine (PIP) and Trimesoyl chloride (TMC) for the interfacial polymerization of the active layer with chiral spaces in it on the surface of the polysulfone ultrafiltration membranes. After formation of the polyamide composite membranes, the target molecules in the active layers were removed and MIP composite membranes were prepared. The MIP membranes prepared so were then characterized with analytical methods and proved to be effective for the selective permeation of D ‐serine. When serine racemate was used for optical resolution, the diffusion rate of the D ‐serine appeared to be faster than that of the L ‐serine and in permeates, the concentration of the D ‐serine increased with operation time. When the operating time reached 60 h, enantiomeric excess (% ee) of the serine mixture in permeates became about 80%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1866–1872, 2007     

Preparation and properties of porous L‐tryptophan imprinted latex membrane from core‐shell emulsion

Molecularly imprinted latex membrane (MILM) is prepared by core‐shell emulsion technique in the presence of a template molecule (L ‐Tryptophan). A hard inward and soft outward microstructure latex particle is designed to obtain MILM with both flexibility and impact strength. Molecularly imprinted layer with high crosslinking degree is grafted on the surface of core‐shell latex particles. NaCl, glucose, urea, polyethylene glycol, M_w 300, etc., are added during the film‐forming process to produce porous microstructure in MILM. Fourier transform infrared spectroscopy (FTIR) and Scatchard analysis are used to investigate the interaction between L ‐Tryptophan and MILM and the binding ability of the resultant MILM, respectively. The functional binding and separation performances in aqueous medium towards template are carried out. The results reveal that the content and type of porogen and the shell composition have significant effects on adsorption capacity and separation ability. MILM with glucose as porogen shows high recognition towards the template with adsorption separation factor reaching 9.06. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Molecular‐imprinted nylon membranes for the permselective binding of phenylalanine as optical‐resolution membrane adsorbents

Nylon 6, nylon 6,6, and terephthalic phenylene polyamide (TPPP) were functionalized by phase‐inversion molecular imprinting to add L ‐phenylalanine recognition ability. Formic acid containing 20 wt % nylon and 8 wt % L ‐phenylalanine was used as the solvent for the cast solution of the imprinting process. The resultant porous membranes behaved as membrane adsorbents that separated the L /D mixture of the substrate. The imprinted nylon 6 and nylon 6,6 presented high selectivity to the L ‐form substrate with respect to the TPPP membranes, but the imprinted TPPP membranes showed higher binding capacity with 0.57 μmol/g for L ‐phenylalanine. The apparent partition coefficients of L ‐ and D ‐forms by the imprinted membranes were 6.8, 4.2, and 1.7 for nylon 6, nylon 6,6, and TPPP, respectively. The separation manner of the L ‐ and D ‐forms from the mixture was also confirmed by membrane filtration under 1.5 kgf/cm² of applied pressure. The imprinted nylon 6, nylon 6,6, and TPPP membranes had separation factors of L ‐ and D ‐phenylalanines of 1.1, 1.1, and 1.2, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 620–626, 2005     

Preparation of molecularly imprinted polymer coatings with the multiple bulk copolymerization method for solid‐phase microextraction

The multiple bulk copolymerization method, which was developed in our previous works, was further investigated with prometryn, tetracycline, and propranolol as templates for the preparation of molecularly imprinted polymer (MIP) coatings on silicon fibers for solid‐phase microextraction. The preparation conditions (e.g., the solvent, monomer, crosslinker, component proportions, polymerization time, and number of coating procedures) were investigated systemically in an effort to enhance the coating thickness, surface morphology, and reproducibility. The methodology was examined, and some common specialties were explored in the preparation of three MIP‐coated fibers. Even after the coating procedure was repeated 10 times, the prometryn, tetracycline, and propranolol MIP‐coated fibers were prepared reproducibly with coating‐thickness relative standard deviations of 2.6, 3.0, and 5.1%, respectively; they were highly homogeneous, and a compact morphological structure was obtained. The extraction capacities of prometryn, tetracycline, and propranolol with corresponding MIP‐coated fibers were approximately 10.4, 3.9, and 3.3 times as much as those with the nonimprinted polymer (NIP)‐coated fibers, respectively, and the selectivity factors of prometryn, tetracycline, and propranolol MIP coatings for the template molecules and structural analogues were 2.2–10.4, 2.2–3.9, and 1.3–3.3, respectively, in comparison with the corresponding NIP coatings. In comparison with commercial polydimethylsiloxane/divinylbenzene coatings that were approximately 3 times thicker, the extracted amounts of prometryn, tetracycline, and propranolol were 4.2, 12.3, and 7.7 times higher with prometryn, tetracycline, and propranolol MIP coatings, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of water‐compatible molecularly imprinted polymers for caffeine with a novel ionic liquid as a functional monomer

Water‐compatible molecularly imprinted polymers (MIPs) for caffeine were synthesized in aqueous medium with a new functional monomer, 1‐(α‐methyl acrylate)‐3‐methylimidazolium bromide (1‐MA‐3MI‐Br), which had π–π and hydrogen‐bonding interactions. Caffeine‐imprinted polymers were prepared in suspension polymerization with 1‐MA‐3MI‐Br and methacrylic acid (MAA), which only had hydrogen bonding, as a functional monomer. For the specific binding characteristics of the new functional monomer 1‐MA‐3MI‐Br, the adsorption capacity and relative separation factor (β) of MIPs for caffeine were significantly enhanced. The maximum adsorption capacities of 1‐MA‐3MI‐Br–MIP and MAA–MIP imprinted microspheres for caffeine were 53.80 and 28.90 μmol/g, respectively. Moreover, the relative separation factors were measured by comparison of the separation characteristics under competitive adsorption conditions. The results showed that the β of MAA–MIP for caffeine relative to theophylline was only 1.65; this showed a very poor recognition selectivity for caffeine, but β of 1‐MA‐3MI‐Br–MIP for caffeine with respect to theophylline was remarkably enhanced to 3.19; this showed an excellent recognition selectivity and binding affinity toward caffeine molecules in an aqueous environment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enantioseparation via EIC‐OSN: Process design and improvement of enantiomers resolvability and separation performance

This article presents a mathematical model to assess and optimize the separation performance of an enantioselective inclusion complexation‐organic solvent nanofiltration process. Enantiomer solubilities, feed concentrations, solvent compositions, permeate solvent volumes, and numbers of nanofiltrations were identified as key factors for process efficiency. The model was first tested by comparing calculated and experimental results for a nonoptimized process, and then, calculations were carried out to select the best operating conditions. An important finding was that the optimal configuration varied with the objective function selected, e.g., resolvability versus yield, with a boundary on product optical purity. The model also suggested that the process efficiency could benefit from diafiltration of the distomer and from the use of higher feed concentrations. However, the latter strategy would result in higher losses of eutomer. To address this drawback, a multistage process was evaluated using the verified process model. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Online prediction of subcutaneous glucose concentration for type 1 diabetes using empirical models and frequency‐band separation

Online glucose prediction which can be used to provide important information of future glucose status is a key step to facilitate proactive management before glucose reaches undesirable concentrations. Based on frequency‐band separation (FS) and empirical modeling approaches, this article considers several important aspects of on‐line glucose prediction for subjects with type 1 diabetes mellitus. Three issues are of particular interest: (1) Can a global (or universal) model be developed from glucose data for a single subject and then used to make suitably accurate on‐line glucose predictions for other subjects? (2) Does a new FS approach based on data filtering provide more accurate models than standard modeling methods? (3) Does a new latent variable modeling method result in more accurate models than standard modeling methods? These and related issues are investigated by developing autoregressive models and autoregressive models with exogenous inputs based on clinical data for two groups of subjects. The alternative modeling approaches are evaluated with respect to on‐line short‐term prediction accuracy for prediction horizons of 30 and 60 min, using independent test data. © 2013 American Institute of Chemical Engineers AIChE J 60: 574–584, 2014     

Preparation and characterization of a pseudo‐template imprinted polymer with a chirality‐matching monomer for the separation of cinchona alkaloids by high‐performance liquid chromatography

A hydroquinidine‐imprinted stationary selector with chiral recognition for cinchona alkaloids was prepared by bulk polymerization with (+)‐(2R,3R)‐N,N′‐diallyl‐L ‐tartardiamide as a functional monomer, and the recognition properties of the polymers for quinidine (QD) were analyzed with high‐performance liquid chromatography. By optimizing the preparation conditions and chromatographic conditions, such as the ratio of the mobile phase and flow rate, QD and quinine could be completely separated to the best resolution of 2.25. The chiral molecularly imprinted polymers (CMIPs) combined the virtues of traditional brush‐type chiral selectors with existing CMIPs. The results show a substantial synergistic effect between the chiral monomer and the chiral cavity of the resulting CMIPs in chiral recognition. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of process parameters on extraction equilibria for the chiral separation of amines and amino‐alcohols with a chiral crown ether

Reactive extraction is studied as a promising chiral separation technique for commercial production scale. For chiral separation of amines and amino alcohols, a chiral crown ether was identified as a versatile enantioselective extractant. In this paper, the influence of various process conditions on the extraction performance is studied experimentally, and a predictive model is constructed based on the chemical and physical equilibria. It was found that the operational selectivity in one extraction step is mainly determined by the complexation constants between crown ether and enantiomers (which are dependent on solvent and temperature) and by the extractant concentration, whereas the distribution ratio is also strongly influenced by the pH. The model gives an excellent prediction of the operational selectivity and a good explanation for the system's responses to changes in process conditions. The model can be used as a basis for a multistage equilibrium extractor model and for conceptual process design. Under optimal process conditions, an operational selectivity >1.5 was obtained for five out of seven model compounds, with satisfying distribution ratios (D ～ 1–10). Copyright © 2006 Society of Chemical Industry     

Preparation of composite‐imprinted alumina membrane for effective separation of p‐hydroxybenzonic acid from its isomer using Box–Behnken design–based statistical modeling

Highly selective composite imprinted membrane for p‐hydroxybenzonic acid (p‐HB) was prepared by using semicovalent imprinting technique. A thermally reversible covalent bond was used to link p‐HB molecule to a functional alkoxysilane monomer to generate covalently bound imprint precursor. This precursor was incorporated into a cross‐linked functional silica sol with the tetraethoxysilane as cross‐linker via a typical acid‐catalyzed, sol‐gel synthesis. Then, the SCIM was prepared through dipping and grafting on the upper side and inner pores of the Al₂O₃ microporous membrane and then removing of the template molecule after thermal treatment. Compared with composite imprinted membrane via noncovalent imprinting approach as well as the black Al₂O₃ microporous membrane, the SCIM exhibited higher membrane flux and selective rebinding of p‐HB as well as showing excellent permeability for p‐HB. Response surface methodology was used to investigate the best combination of separation conditions in the dynamic separation process. The optimal conditions for the separation of p‐HB from salicylic acid were as follows: the p‐HB concentration of 5 mg L^?1, the temperature of 10°C, and the flow rate of 1 mL min^?1. Under these conditions, the experimental selective separation factor was 32.75 ± 0.91%, which was close to the predicted selectivity coefficient value. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40621.     

Fabrication of a novel cellulose acetate imprinted membrane assisted with chitosan‐wrapped multi‐walled carbon nanotubes for selective separation of salicylic acid from industrial wastewater

Highly selective cellulose acetate (CA) blend imprinted membranes for salicylic acid (SA) removal were synthesized by phase inversion technique with chitosan as a functional polymer and chitosan‐wrapped multi‐walled carbon nanotubes (CHI‐wrapped MWCNTs) as the additives. The surface and cross‐sectional morphology of membranes were strongly affected by the amount of CHI‐wrapped MWCNTs. As compared to M₁‐MIM, M₂‐MIM, and M₄‐MIM, the M₃‐MIM with 2.0 wt % CHI‐wrapped MWCNTs showed higher membrane flux, faster kinetic, binding capacity and better selectivity for SA. The experimental data of adsorption kinetic were well fitted to the pseudo‐second‐order kinetic model by multiple regression analysis. The M₃‐MIM had the maximum adsorption capacity for SA. The selectivity coefficients of SA to p‐hydroxybenzoic acid (p‐HB) and acetylsalicylic acid (ASA) over M₃‐MIM were 6.3090 and 6.0019, respectively, showing that M₃‐MIM had excellent binding affinity and selectivity for separation of SA from SA‐contained aqueous solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42654.     

Preparation of porous poly(oxymethylene) membrane with high durability against solvents by a thermally induced phase‐separation method

Porous poly(oxymethylene) membranes were prepared as new solvent‐resistant membranes by a thermally induced phase‐separation method. Porous structures were formed by solid–liquid phase separation (polymer crystallization) rather than liquid–liquid phase separation. The pores existed in the intraspherulitic and interspherulitic regions. The effects of the polymer weight percentage and cooling rate on toluene permeance and solute rejection were investigated. The solvent resistance of the membranes was tested by the immersion of the membranes in organic solvents for 1 month, and high durability against the solvents was confirmed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1993–1999, 2002     

Poly[poly(oxypropylene) phosphate] macroionophores for transport and separation of cations in a hybrid: Cation‐exchange polymer and liquid membrane system

Poly[poly(oxypropylene) phosphate]s (PPOPP, M_n = 5800, 8100, 10,400), with different POP units (400, 1200, 2000), were synthesized and applied as cation‐selective macroionophores in a multimembrane hybrid system (MHS). The solution of PPOPP in dichloroethane formed the flowing liquid membrane (FLM) circulating between two polymer cation‐exchange membranes, and subsequently, between two polymer‐made pervaporation (PV) membranes. It was found that the PPOPP macroionophores activate the preferential transport of Zn²⁺ cations from aqueous solutions containing competing Cu²⁺, Ca²⁺, Mg²⁺, K⁺, and Na⁺ cations. The following separation orders were observed for PPOPPs with POP‐400 and POP‐1200: Zn²⁺ > Cu²⁺ ? Ca²⁺, Mg²⁺, K⁺, Na⁺, and for PPOPP with POP‐2000: Zn²⁺ > Cu²⁺,Ca²⁺ ? Mg²⁺, K⁺, Na⁺. Always, the particular cations are separated as: Zn²⁺ > Cu²⁺, Ca²⁺ > Mg²⁺, and K⁺ > Na⁺. The properties of PPOPPs were compared to respective transport and separation characteristics corresponding to those of respective poly(propylene glycol)s and poly(oxypropylene) bisphosphates. The results of investigation indicate that the bifunctional character of PPOPPs is caused by the presence of ionizable groups and probably pseudocyclic POP structures. By comparing the separation of cations in the simple MHS[FLM] system and the system supported by pervaporation unit [MHS[FLM‐PV] it was found that continuous dehydration of an organic FLM improves the system overall performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1436–1445, 2004     

Simplified preparation of low polydispersity,low molecular weight poly(D,L‐lactic acid) by liquid/liquid phase separation for drug delivery systems with discussion of molecular weight characterization

Poly(D ,L ‐lactic acid) (PLA) has been widely used in pharmaceutics and medicine. Low molecular weight (LMW) PLA is especially useful for rapidly degrading biomaterials such as those used for short‐duration drug delivery systems. There is scant information available in the literature regarding the purification and analysis of LMW PLA. In this paper we report (1) a convenient and effective polymer purification/fractionation technique to produce LMW PLA with narrow molecular weight distribution (MWD) and (2) analyses that were used to characterize the molecular weight and MWD of these polymers. A novel, convenient and effective temperature‐induced solution‐phase separation method was developed to produce narrow MWD, LMW (600–2000 g mol^?1) PLA. Molecular weights determined using gel permeation chromatography (GPC) with universal calibration, unlike those determined with the commonly used conventional calibration, showed good agreement with those obtained using several independent direct techniques. The phase separation induced by temperature reduction of a polymer in a single solvent system provided a simple and effective technique to produce narrow MWD, LMW PLA polymers. Additional advantages of this technique are: (1) only one solvent is required; (2) the risk of local complete solid polymer precipitation is eliminated; (3) it is reversible and not dependent on the rate of cooling; and (4) use of chlorinated solvents is avoided. This technology may open up a new opportunity for manufacturing LMW polymers with narrow MWD. We also found that GPC with universal calibration is a more accurate method than GPC with the commonly used conventional calibration for characterizing these polymers, and is straightforward to use especially now that on‐line viscosity detectors are widely available. Copyright © 2010 Society of Chemical Industry     

Proposal for selecting two‐color combinations with various affections. Part I: Introduction of the method

A method is proposed for selecting two‐color combinations with various feelings. Feelings used are pleasantness, contrast, floridness, warmth, and their combinations. The proposed method is given by its flow chart for selecting the candidates of two‐color combinations adapting to target feeling(s). The effectiveness of the proposed method is shown by the correlation coefficients between observed and predicted values for four kinds of feelings. Munsell H V/Cs of each component color are necessary for prediction; the prediction formulas are given for estimating the degree of each feeling for any two‐color combinations. The proposed method can be expanded to three‐color combinations. This proposal is expected to assist color designers, who can choose their usable color combinations from the candidates selected by the proposed method. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 128–134, 2009     

Sulphonation of polystyrene‐butadiene rubber with chlorosulphonic acid for proton exchange membrane: Kinetic study

Proton exchange membrane for fuel cell application was synthesized from a hydrophobic polystyrene‐butadiene rubber (PSBR) via sulphonation at different temperatures (22, 35, 55, 65, and 75°C) and varying time with chlorosulphonic acid. Infra‐red spectroscopy (IR) and proton nuclear magnetic resonance (¹H‐NMR) were used to confirm the occurrence of sulphonation. Sulphonation occurred only on the phenyl ring with a maximum degree of sulphonation of 70.96 mole percent. Consequently, 10^?3–10^?2 S/cm proton conductivity was achieved. Two models for the reaction kinetics were investigated: first‐order reversible and first‐order irreversible, respectively. However, the reaction kinetic was found to obey the first‐order reversible model. The activation energy (E_a) of the reaction was calculated to be 41.56 kJ/mol of PSBR repeat unit, which is an indication that the reaction is nonspontaneous. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010