Xylanase recovery effect of extraction conditions on the aqueous two-phase system using experimental design

The partitioning of xylanase produced byPenicillium janthinellum in aqueous two-phase systems (ATPS) using poly(ethylene glycol) (PEG) and phosphate (K₂HPO₄/KH₂PO₄) was studied employing a statistical experimental design. The aim was to identify the key factors governing xylanase partitioning. The interactions of five factors (PEG concentration molecular weight, concentration of buffer K₂HPO₄/KH₂PO₄, pH, and NaCl concentration) and their main effects on the partition coefficient (K) were evaluated by means of a 2⁵ full-factorial experimental design with four center points. The %PEG, %NaCl, and pH were the most important factors affecting the response variable (K). Response surface methodology (RSM) was adopted and an empirical second-order polynomial model was constructed on the basis of the results. The optimum partition conditions were pH 7.0, PEG = 8.83% and NaCl = 6.02%. Adequacy of the model for predicting optimum response value was tested under these conditions. The experimental xylanase partition coefficient (K) was 2.21, whereas its value predicted by the model was 2.33. These results indicate that the predicted model was adequate for the process. PEG molecular weight and phosphate concentration did not affect the xylanase partition coefficient.     

Polymeric networks by the cationic crosslinking reaction of poly(allenyl ether)s having oligo(oxyethylene) moieties in the side chain

Cationic crosslinking reactions of poly(allenyl ether)s having oligo(oxyethylene) moieties prepared by the radical polymerization of the corresponding allenyl ethers were carried out under some varied reaction conditions. For instance, a crosslinked polymer was obtained in 82% yield by the treatment of poly(ethylene glycol methyl allenyl ether) ( 1a ) with 1.2 mol% of BF₃·OEt₂ ( 2 ) under high concentration in dichloromethane (46 wt %). The gels obtained showed good swelling properties in water, alcohols, and polar organic solvents such as dichloromethane. In particular, the degrees of swelling of these gels in aqueous sodium chloride (1M) were quite similar to those in ion-free water, indicating that these gels served as nonionic hydrogels. © 1994 John Wiley & Sons, Inc.     

Quaternary (liquid + liquid) equilibria of aqueous two-phase poly (ethylene glycol), poly (DMAM–TBAM), and KH2PO4: Experimental and generalized Flory–Huggins theory

Quaternary (liquid + liquid) equilibrium (LLE) data of the aqueous two-phase poly (ethylene glycol), poly (N,N-dimethylacrylamide-t-butylacrylamide) with abbreviation name poly (DMAM–TBAM) as a hydrophobic association water-soluble copolymer and KH₂PO₄ has been determined experimentally at T = 338.15 K. Furthermore, the generalized Flory–Huggins theory with two electrostatic terms (the Debye–Hückel and Pitzer–Debye–Hückel) was used for correlation of the phase behavior of the quaternary system and the interaction parameters between all species were calculated.It was found that addition of poly (DMAM–TBAM) copolymer as well as changing the temperature can shift the binodal curves of aqueous two-phase systems containing polyethylene glycol (PEG) and salt. Also, the phase behavior of the DMAM–TBAM copolymer with some salts containing sodium chloride, ammonium hydrogen phosphate, potassium hydrogen phosphate, and sodium carbonate were studied experimentally at T = 338.15 K and the effect of the salt type on the their binodal curves was determined.     

Extraction and determination of morphine in compound liquorice using an aqueous two-phase system of poly(ethylene glycol)/K2HPO4 coupled with HPLC

An aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)/K₂HPO₄ coupled with high performance liquid chromatography (HPLC) method was developed for the separation and determination of morphine in compound liquorice. Morphine and its analogs were used as model compounds to investigate influence of various factors on extraction behaviors of ATPS, such as the types and concentrations of salts, PEG molecular mass, temperature and pH. It was observed that the types of salt had much influence on extraction efficiencies of morphine and its analogs. The results indicated that hydrophobic force cooperating with hydrogen bond interaction between analytes and phases played important role in extraction process. In the optimal system of containing 0.5 g PEG2000 and 1.5 g K₂HPO₄, the recoveries of the spiked standards for the analytes were all 91.7-100.3% with relative standard deviation of 1.0-3.0%. Morphine in compound liquorice was determined by the proposed method and the results were consistent with those of LC-MS method. Compared with conventional liquid-liquid extraction or solid-phase extraction, this extraction method can be completed in one operation and is low-cost. Since the entire extraction process is organic solvent-free, this new technique is environmental friendly.     

Novel crosslinked thermoresponsive hydrogels with controlled poly(ethylene glycol)—poly(propylene glycol) multiblock copolymer structure

New thermoresponsive crosslinked hydrogels with controlled multiblock copolymer structure were prepared from equimolar amounts of α,ω-diamino poly(propylene glycol)s with molecular weights (MW) 230, 400, and 2,000 g mol^?1 and diepoxy-terminated poly(ethylene glycol)s of approximate MW 1,000; 2,000; and 4,000 g mol^?1. Their thermoresponsive character was investigated on the 10–70 °C interval, while the swelling behavior was tested at 21, 37, and 50 °C. All hydrogels displayed temperature sensitivity, but a volume phase transition was noticed only in the case of poly(propylene glycol) (PPG)₂₀₀₀-containing hydrogels. The volume phase transition temperature (T _VPT ) depended on the MW of the hydrophilic poly(ethylene glycol) (PEG) chains attached to the PPG₂₀₀₀ block, as well as on the added salts. Longer PEG blocks determined a shift of T _VPT towards higher values, while the influence of the salt added was in agreement with the Hofmeister series, except for NaH₂PO₄ which determined the destruction of the hydrogel network. The equilibrium swelling degree depended on the MW of both PEG and PPG blocks, as well as on temperature. The analysis of the swelling process indicated a modification of the gel characteristics with temperature and second-order kinetics for the water penetration into the hydrogel.     

Thermal gelation or gel melting: (ethylene glycol)113‐(l‐alanine)12 and (ethylene glycol)113‐(l‐lactic acid)12

When PEG (M.W.～5000 Daltons) is conjugated to poly(l ‐alanine), the polymer aqueous solutions (<10.0 wt.%) undergo sol‐to‐gel (thermal gelation), whereas it is conjugated to poly(l ‐lactic acid), the polymer aqueous solutions (>30.0 wt.%) undergo gel‐to‐sol (gel melting) as the temperature increases. In the search for molecular origins of such a quite different phase behavior, poly(ethylene glycol)‐poly(l ‐alanine) (PEG‐PA; EG₁₁₃‐A₁₂) and poly(ethylene glycol)‐poly(l ‐lactic acid) (PEG‐PLA; EG₁₁₃‐LA₁₂) are synthesized and their aqueous solution behavior is investigated. PEG‐PAs with an α‐helical core assemble into micelles with a broad size distribution, and the dehydration of PEG drives the aggregation of the micelles, leading to thermal gelation, whereas increased molecular motion of the PLA core overwhelms the partial dehydration of PEG, thus gel melting of the PEG‐PLA aqueous solutions occurs. The core‐rigidity of micelles must be one of the key factors in determining whether a polymer aqueous solution undergoes sol‐to‐gel or gel‐to‐sol transition, as the temperature increases. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, , 52, 2434–2441     

Diffusion of poly(ethylene glycol) and ectoine in NIPAAm hydrogels with confocal Raman spectroscopy

The diffusion behavior of poly(ethylene glycol) (PEG) in N-isopropylacrylamide (NIPAAm) hydrogels was investigated using confocal Raman spectroscopy with regard to temperature (25°C, 30°C and 35°C), PEG concentration (10 and 40?wt.%), PEG molecular weight (2,000 and 12,000?g/mol) and addition of the compatible solute ectoine (0.1 and 2?wt.%). Swelling and shrinking of the gels was observed by means of confocal Raman spectroscopy. The swelling behavior of NIPAAm gels in aqueous solutions of PEG and ectoine was found to resemble the swelling behavior in pure water with regard to temperature, i.e., the gel shrinks with increasing temperature. However, the presence and concentration of PEG and ectoine influence the swelling behavior by lowering the volume phase-transition temperature of the gel and facilitating shrinking. In some cases, a re-swelling of the gel was observed after the initial shrinking at the onset of PEG diffusion, which can be explained by PEG changing the chemical potential in the gel phase as it diffuses into the sample allowing the water to re-enter. The expulsion of water from the gel during shrinking and the so-caused increase of PNIPAAm and PEG concentrations in some cases led to the PEG diffusion seemingly being faster in more shrunken gels despite of their higher diffusion resistance.     

Poly(ethylene glycol)–poly(L‐lactide) star block copolymer hydrogels crosslinked by metal–ligand coordination

The aqueous solution behavior and thermoreversible gelation properties of pyridine‐end‐functionalized poly(ethylene glycol)–poly(L ‐lactide) (PEG–(PLLA)₈–py) star block copolymers in the presence of coordinating transition metal ions were studied. In aqueous solutions, the macromonomers self‐assembled into micelles and micellar aggregates at low concentrations and formed physically crosslinked, thermoreversible hydrogels above a critical gel concentration (CGC) of 8% w/v. In the presence of transition metal ions like Cu(II), Co(II), or Mn(II), the aggregate dimensions increased. Above the CGC, the gel–sol transition shifted to higher temperatures due to the formation of additional crosslinks from intermolecular coordination complexes between metal ions and pyridine ligands. Furthermore, as an example, PEG–(PLLA)₈–py hydrogels stabilized by Mn(II)–pyridine coordination complexes were more resistant against degradation/dissolution when placed in phosphate buffered saline at 37 °C when compared with hydrogels prepared in water. Importantly, the stabilizing effect of metal–ligand coordination was noticeable at very low Cu(II) concentrations, which have been reported to be noncytotoxic for fibroblasts in vitro. These novel PEG–(PLLA)₈–py metallo‐hydrogels, which are the first systems to combine metal–ligand coordination with the advantageous properties of PEG–PLLA copolymer hydrogels, are appealing materials that may find use in biomedical as well as environmental applications like the removal of heavy metal ions from waste streams. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

The influence of PEG macromonomers on the size and properties of thermosensitive aqueous microgels

We describe the preparation and thermal response of aqueous microgels based on poly(N-vinyl caprolactam) containing grafted poly(ethylene glycol) (PEG) chains. These microgels were synthesized by free radical copolymerization of vinyl caprolactam and acetoacetoxyethyl methacrylate in the presence of methoxy-capped poly(ethylene glycol)methacrylate macromonomers. We show that variation of the amount of PEG macromonomer or the length of the PEG chain provides effective control of the microgel diameter in the range 60–220 nm. The presence of the grafted PEG chains improves the colloidal stability of the microgels. The incorporation of the PEG macromonomers into microgel structure decreases the swelling degree and induces a shift of the volume phase transition to higher temperatures. This paper is dedicated to Professor Haruma Kawaguchi in honor of his many contributions to the field of polymer particle synthesis and applications.     

Study of cloud point extraction and high-performance liquid chromatographic determination of isoniazid based on the formation of isonicotinylhydrazone

Isoniazid (INH) reacted with p-dimethylaminobenzaldehyde (DABD) in the presence of trichloroacetic acid to give isonicotinylhydrazone (INZ) having λ_max 365 nm. Cloud point extraction (CPE) is carried out to extract INH and IHZ in aqueous solutions using surfactant poly(ethylene glycol) 4000 (PEG4000), respectively. Langmuir model is used to study the adsorption behaviors of the two solutes on micelles of PEG4000. A linear correlation is found between variation of PEG4000 concentration required for feed concentration of the two solutes and used to predict PEG4000 concentration required for extracting INH and IHZ in CPE procedure. The results calculated show that, for a desired recovery level of 90%, only can IHZ be sufficiently extracted by PEG4000. In this experiment, the feed concentration of PEG4000 is defined by above-mentioned correlation, and the effects of other operating parameters, e.g., concentration of salt, pH and centrifugation time on extraction of PEG4000-IHZ system have also been studied in detail. The proposed CPE method coupled with HPLC-UV system is successfully used for the determination of INH in urine sample.     

Styrene polymerization with some new macro or macromonomeric azoinitiators having peg units

Several new macroinitiators and macromerinitiators (macroinimers) were synthesized and evaluated for the bulk polymerization of sytrene at 60°C. Macroinitiators were prepared from the reaction of 4,4′-dicyano-4,4′ azovaleryl chloride ( 1 ) with poly(ethylene glycol) (PEG) with a M_ω of 400 and with either benzoyl chloride, acetyl chloride, phenyl isocyanate, or poly(ethylene glycol) oleyl ether. Macromer initiators were also prepared from the reaction of 1 with PEG having M_ω values of 200, 400, 600, 1000, or 1500 and with 4-vinylbenzyl chloride. The bulk polymerization of styrene by macroinimers gave crosslinked styrene-PEG block copolymers, while the polymerization by macroinitiators gave soluble copolymers. The molecular weights of the styrene-PEG block copolymers obtained with macroinitiators having either oleyl, benzoyl, or phenyl urethane end groups were 22000–29000 g/mol. DSC measurements showed that the crosslinked block copolymers had crystalline PEG units with melting transitions ranging from 11–37°C. © 1994 John Wiley & Sons, Inc.     

The preparation and characterisation of novel polyether gels

Poly(ethylene oxide)s end-capped with n-alkane chains (C₁₆-C₂₁) have been found to form stable gels in aqueous media. The crosslinks are believed to occur through association of the n-alkane chains. The dependence of the degree of swelling of the gels on the lengths of the alkane and poly(ethylene oxide)(M_n= 10000, 20000 and 30000) chains were studied. Degrees of swelling have been compared with results predicted by simple network theory.     

Ionizable hydrogels of new type based on poly(ethylene glycol) phosphates

Partly charged poly(ethylene oxide) networks have been prepared by the cure reaction of multifunctional poly(ethylene glycol) phosphate precursors with the diglycidyl ether of triethylene glycol as a crosslinking agent. These new hydrogels display all the features of swelling behaviour characteristics of polyelectrolyte networks. The degree of volume swelling of the hydrogels varies from 16–95 (in distilled water) to 11–45 (in 0.1 M sodium chloride solution) and 7–20 ml/ml (in 0.52 M potassium sulfate as a Θ-solvent). Average chain length, ionic group content, and structure of gels are evaluated from the swelling data.The gelation point occurs at much higher crosslinking ratios and overall P-OH groups conversion than those predicted from the precursor functionality. The role of possible side reactions and some kinetic reasons for the ‘delayed’ gelation are discussed.     

Amphiphilic poly(ethylene glycol) gels and their swelling features

This article describes the preparation of poly(ethylene glycol) (PEG) ‐based gels for removal of both organic solvents and water through a clean synthesis process without using any initiator, catalyst, activator, or liquid medium. The synthesis of the gels is based on the condensation of different molecular weights of PEG macromolecules with the nine‐functional crosslinker tris[3‐(trimethoxysilyl) propyl] isocyanurate (ICS). Solid‐state ¹³C and ²⁹Si cross‐polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and elemental analysis were used to characterize the prepared sorbents. Thermal properties of the synthesized sorbents were examined using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The swelling capacities of the sorbents were determined by swelling tests in dichloromethane (DCM), tetrahydrofuran (THF), benzene, acetone, and toluene. The water absorbency of the PEG‐based sorbents is also investigated. The effect of the reaction time and reaction temperature on swelling features of the sorbents was studied systematically. The prepared PEG gels have high swelling ratios both in polar and nonpolar solvents. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of interpolymer complexation in swollen polyelectolyte networks using solid‐state NMR spectroscopy

Copolymer networks of poly(methacrylic acid) (PMAA) and poly(ethylene glycol) (PEG) exhibit large changes in their swelling behavior over a narrow pH range due to the reversible formation/dissociation of interpolymer complexes between the polymer chains. Intepolymer complexation occurs in copolymer gels of PMAA and PEG due to hydrogen bonding between protonated acid groups and the ether groups of the PEG. Because of their nature, these gels have been identified for use as delivery vehicles for macromolecular drugs. In this work, solid‐state, nuclear magnetic resonance nuclear Overhauser enhancement (NOE) experiments were performed to detect the molecular level complexation between PMAA and deuterated PEG in copolymer blends and crosslinked networks. For gels swollen in acidic media at room temperature or at 37 °C, strong enhancements were detected in the ¹³C resonance of the PEG carbons. The NOE was generated due to energy transfer between the rapidly rotating methyl group protons and the deuterated PEG carbons. The presence of the NOE was indicative of close packing of the polymer chains and was evidence of the presence of the intermacromolecular complexes. In basic solutions, no NOE was detected in the PEG, as the complexes were dissociated and the chains were separated in space. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2823–2831, 2000     

pH- and temperature-responsive hydrogels of acrylic acid,N-isopropylacrylamide and a non-ionic surfmer: phase behaviour,swelling properties and drug release

Copolymer hydrogels composed of N-isopropylacrylamide (NIPAM), acrylic acid (AA) and the non-ionic surfactant monomer (surfmer) ω-methoxy poly(ethylene oxide)₄₀undecyl-α-methacrylate (PEO-R-MA-40) were prepared and studied with regard to swelling behaviour and drug release behaviour. The gels were prepared upon γ-irradiation of the corresponding aqueous comonomer solution in a one-step reaction. Transparent, stable hydrogels were obtained. Studies of light transmission indicate a dual pH- and T-responsive behaviour, which originates from the AA and NIPAM content of the gels, respectively. Presence of large amounts of surfmer increases the phase transition temperature, but also increases the network density, which lowers the permeability of the gels. Swelling properties and release of ibuprofen (Ibu) were studied in simulated gastric fluid (SGF, pH 1) and phosphate buffer solution (PBS, pH 6.8). It was found that swelling and release are controlled by the nature and quantity of comonomers, pH, temperature and ionic strength of the aqueous phase. Swollen gels shrink in SGF and PBS, whereas dry gels exhibit a strong swelling both in SGF and PBS. Copolymer gels of AA and surfmer exhibit a strong, linear release of Ibu in SGF and PBS. If NIPAM is copolymerized in the gel, the drug release is decelerated in SGF probably due to formation of hydrogen bonds between NIPAM and Ibu at low pH. For example, a gel composed of 10 % (w/w) NIPAM, 1 % (w/w) AA and 1.5 % (w/w) surfmer exhibits a release of 10 % within 2 h in SGF and 58 % within 20 h in PBS.     

New neutral and ionic poly(ethylene oxide) networks by radical polymerization

New opportunities resulting from a turn to radical polymerization in the synthesis of poly(ethylene oxide) (PEO) networks are discussed and exemplified. Several series of such networks have been prepared by radical homo‐ and copolymerization in aqueous media of “macromonomers”, i.e. partly methacrylated poly(ethylene glycol) (PEG) of varied molecular weight (MW ≅ 2000‐12000) and functionality (f_n ≅ 1.25‐1.8). This family of gels as a whole has the volume swelling degree Q in the range of 10 to 200 ml/ml. The hydrogels are characterized by means of Q, elastic modulus, swelling pressure, and with the use of some probes. The swelling behaviour of neutral hydrogels of this kind is briefly resumed. The multifunctional junctions formed in the propagation reaction of methacrylate end groups determine their main peculiarity. Anomalous elastic behaviour of the swollen networks prepared at high concentration of polymer has been observed and attributed to the network chains stretching of the same nature as in polymer stars or brushes. The junctions' functionality (F ≈ 20‐300) is evaluated from these data as well as from MW of the soluble models of network junctions. The PEO networks with charged units in junctions have been obtained by copolymerization of macromonomers with some ionic (meth)acrylic monomers. These gels display all the polyelectrolyte features, e.g. enhanced Q values in water (up to 50‐70) and, contrary to neutral PEO gels, the strong dependence on salt content. However, the osmotic contribution of mobile ions into swelling is shown to be low due to localization of charges in the junctions. The hydrogels that combine PEO and polymethacrylic acid chains capable of interpolymer complexation have been prepared and studied. They show much higher swelling in pure water (Q up to 200), strong deswelling by NaCl, and very sharp drop in swelling (ca. two order in Q) at pH ≈ 4.5‐5.5 due to complexation.     

Effect of Polymer and Surfactant‐Polymer Couples on the Acid-Catalyzed Hydrolysis of Phenyl Urea

The mechanism of the hydrolysis decomposition of phenyl urea in acid, polymer, and surfactant‐polymer media was investigated, the addition‐elimination mechanism with rate determining attack of water at N‐protonated substrate having already been studied. This study has introduced the polymer PEG (MW‐400) and (surfactant‐polymer) (ceteyl trimethyl ammonium bromide‐poly ethylene glycol) (CTAB‐PEG), (cetyl pyridinium bromide‐polyethylene glycol) (CPC‐PEG) (sodium dodecyl sulphate‐poly ethylene glycol) (SDS‐PEG), (Triton X‐100‐poly ethylene glycol) (TX‐100‐PEG), and (Brij35‐poly ethylene glycol) (Brij35‐PEG) in acid media. The results indicate that the presence of polymer and surfactant‐polymer enhances the rate of reaction at 80°C in the presence of 0.9 M H₂SO₄. Kinetic studies show that the reaction obeyed first‐order kinetics. The reaction kinetics can be well explained by micellar catalysis models like the PPIE.     

ENHANCED WATER SORPTION OF A SEMI-INTERPENETRATING POLYMER NETWORK (IPN) OF POLY(2-HYDROXYETHYL METHACRYLATE) (PHEMA) AND POLY(ETHYLENE GLYCOL) (PEG)

ABSTRACT

An attempt was made to enhance the water-sorption capacity of polymers of 2-hydroxyethyl methacrylate (HEMA) by preparing its semi-interpenetrating polymer network (IPN) with a hydrophilic polymer such as poly(ethylene glycol) (PEG). The effects of various factors, such as history of the polymer sample, chemical architecture of the IPN, presence of salt ions in the swelling medium, and temperature of the swelling medium, were investigated on the water sorption kinetics of the IPNs. The IPN was characterized by IR spectral analysis and various structural parameters, such as molecular weight between crosslinks (M_c), crosslink density (q) and number of elastically effective chains (V_e), were evaluated. The IPNs were also assessed for their antithrombogenic potential.     

Synthesis of poly(ethylene glycol)/polypeptide/poly(D,L‐lactide) copolymers and their nanoparticles

Core‐shell structured nanoparticles of poly(ethylene glycol) (PEG)/polypeptide/poly(D ,L ‐lactide) (PLA) copolymers were prepared and their properties were investigated. The copolymers had a poly(L ‐serine) or poly(L ‐phenylalanine) block as a linker between a hydrophilic PEG and a hydrophobic PLA unit. They formed core‐shell structured nanoparticles, where the polypeptide block resided at the interface between a hydrophilic PEG shell and a hydrophobic PLA core. In the synthesis, poly(ethylene glycol)‐b‐poly(L ‐serine) (PEG‐PSER) was prepared by ring opening polymerization of N‐carboxyanhydride of O‐(tert‐butyl)‐L ‐serine and subsequent removal of tert‐butyl groups. Poly(ethylene glycol)‐b‐poly(L ‐phenylalanine) (PEG‐PPA) was obtained by ring opening polymerization of N‐carboxyanhydride of L ‐phenylalanine. Methoxy‐poly(ethylene glycol)‐amine with a MW of 5000 was used as an initiator for both polymerizations. The polymerization of D ,L ‐lactide by initiation with PEG‐PSER and PEG‐PPA produced a comb‐like copolymer, poly(ethylene glycol)‐b‐[poly(L ‐serine)‐g‐poly(D ,L ‐lactide)] (PEG‐PSER‐PLA) and a linear copolymer, poly(ethylene glycol)‐b‐poly(L ‐phenylalanine)‐b‐poly(D ,L ‐lactide) (PEG‐PPA‐PLA), respectively. The nanoparticles obtained from PEG‐PPA‐PLA showed a negative zeta potential value of ?16.6 mV, while those of PEG‐PSER‐PLA exhibited a positive value of about 19.3 mV. In pH 7.0 phosphate buffer solution at 36 °C, the nanoparticles of PEG/polypeptide/PLA copolymers showed much better stability than those of a linear PEG‐PLA copolymer having a comparable molecular weight. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011