Application of chitosan‐entrapped β‐galactosidase in a packed‐bed reactor system

The model enzyme β‐galactosidase was entrapped in chitosan gel beads and tested for hydrolytic activity and its potential for application in a packed‐bed reactor. The chitosan beads had an enzyme entrapment efficiency of 59% and retained 56% of the enzyme activity of the free enzyme. The Michaelis constant (K_m) was 0.0086 and 0.011 μmol/mL for the free and immobilized enzymes, respectively. The maximum velocity of the reaction (V_max) was 285.7 and 55.25 μmol mL^?1 min^?1 for the free and immobilized enzymes, respectively. In pH stability tests, the immobilized enzyme exhibited a greater range of pH stability and shifted to include a more acidic pH optimum, compared to that of the free enzyme. A 2.54 × 16.51‐cm tubular reactor was constructed to hold 300 mL of chitosan‐immobilized enzyme. A full‐factorial test design was implemented to test the effect of substrate flow (20 and 100 mL/min), concentration (0.0015 and 0.003M), and repeated use of the test bed on efficiency of the system. Parameters were analyzed using repeated‐measures analysis of variance. Flow (p < 0.05) and concentration (p < 0.05) significantly affected substrate conversion, as did the interaction progressing from Run 1 to Run 2 on a bed (p < 0.05). Reactor stability tests indicated that the packed‐bed reactor continued to convert substrate for more than 12 h with a minimal reduction in conversion efficiency. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1294–1299, 2004     

Copolymerization of ethylene/α‐olefins over (2‐MeInd)2ZrCl2/MAO and (2‐BzInd)2ZrCl2/MAO systems

Ethylene homopolymerization and ethylene/α‐olefin copolymerization were carried out using unbridged and 2‐alkyl substituted bis(indenyl)zirconium dichloride complexes such as (2‐MeInd)₂ZrCl₂ and (2‐BzInd)₂ZrCl₂. Various concentrations of 1‐hexene, 1‐dodecene, and 1‐octadecene were used in order to find the effect of chain length of α‐olefins on the copolymerization behavior. In ethylene homopolymerization, catalytic activity increased at higher polymerization temperature, and (2‐MeInd)₂ZrCl₂ showed higher activity than (2‐BzInd)₂ZrCl₂. The increase of catalytic activity with addition of comonomer (the synergistic effect) was not observed except in the case of ethylene/1‐hexene copolymerization at 40°C. The monomer reactivity ratios of ethylene increased with the decrease of polymerization temperature, while those of α‐olefin showed the reverse trend. The two catalysts showed similar copolymerization reactivity ratios. (2‐MeInd)₂ZrCl₂ produced the copolymer with higher M_w than (2‐BzInd)₂ZrCl₂. The melting temperature and the crystallinity decreased drastically with the increase of the α‐olefin content but T_m as a function of weight fraction of the α‐olefins showed similar decreasing behavior. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 928–937, 2000     

Immobilization of invertase onto dimer acid‐co‐alkyl polyamine

Invertase was immobilized onto the dimer acid‐co‐alkyl polyamine after activation with 1,2‐diamine ethane and 1,3‐diamine propane. The effects of pH, temperature, substrate concentration, and storage stability on free and immobilized invertase were investigated. Kinetic parameters were calculated as 18.2 mM for K_m and 6.43 × 10^?5 mol dm^?3 min^?1 for V_max of free enzyme and in the range of 23.8–35.3 mM for K_m and 7.97–11.71 × 10^?5 mol dm^?3 min^?1 for V_max of immobilized enzyme. After storage at 4°C for 1 month, the enzyme activities were 21.0 and 60.0–70.0% of the initial activity for free and immobilized enzyme, respectively. The optimum pH values for free and immobilized enzymes were determined as 4.5. The optimum temperatures for free and immobilized enzymes were 45 and 50°C, respectively. After using immobilized enzyme in 3 days for 43 times, it showed 76–80% of its original activity. As a result of immobilization, thermal and storage stabilities were increased. The aim of this study was to increase the storage stability and reuse number of the immobilized enzyme and also to compare this immobilization method with others with respect to storage stability and reuse number. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1526–1530, 2004     

Catalytic potential of a poly(AAc‐co‐HPMA‐cl MBAm)‐matrix‐immobilized lipase from a thermotolerant Pseudomonas aeruginosa MTCC‐4713

A purified alkaline thermo‐tolerant lipase from Pseudomonas aeruginosa MTCC‐4713 was immobilized on a series of five noble weakly hydrophilic poly(AAc‐co‐HPMA‐cl MBAm) hydrogels. The hydrogel synthesized by copolymerizing acrylic acid and 2‐hydroxy propyl methacrylate in a ratio of 5 : 1 (HG_5:1 matrix) showed maximum binding efficiency for lipase (95.3%, specific activity 1.96 IU mg^?1 of protein). The HG_5:1 immobilized lipase was evaluated for its hydrolytic potential towards p‐NPP by studying the effect of various physical parameters and salt‐ions. The immobilized lipase was highly stable and retained ～92% of its original hydrolytic activity after fifth cycle of reuse for hydrolysis of p‐nitrophenyl palmitate at pH 7.5 and temperature 55°C. However, when the effect of pH and temperature was studied on free and bound lipase, the HG_5:1 immobilized lipase exhibited a shift in optima for pH and temperature from pH 7.5 and 55°C to 8.5 and 65°C in free and immobilized lipase, respectively. At 1 mM concentration, Fe³⁺, Hg²⁺, NH₄⁺, and Al³⁺ ions promoted and Co²⁺ ions inhibited the hydrolytic activities of free as well as immobilized lipase. However, exposure of either free or immobilized lipase to any of these ions at 5 mM concentration strongly increased the hydrolysis of p‐NPP (by ～3–4 times) in comparison to the biocatalysts not exposed to any of the salt ions. The study concluded that HG_5:1 matrix efficiently immobilized lipase of P. aeruginosa MTCC‐4713, improved the stability of the immobilized biocatalyst towards a higher pH and temperature than the free enzyme and interacted with Fe³⁺, Hg²⁺, NH₄⁺, and Al³⁺ ions to promote rapid hydrolysis of the substrate (p‐NPP). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4252–4259, 2006     

Enhanced Heat Stability of α‐Chymotrypsin through Single‐Enzyme Confinement in Attoliter Liposomes

The entrapment of α‐chymotrypsin (α‐CT) within 70–140 nm liposomes formed from POPC (1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine) leads to an unexpected and remarkable increase in the thermal stability of the enzyme. This finding is based on the observation that heating aqueous suspensions of α‐CT‐containing POPC liposomes to 80 °C for 30 minutes resulted in partial enzyme inactivation, whereas the same treatment of aqueous solutions of free α‐CT inactivated the enzyme completely. The stabilizing effect of enzyme confinement in the attoliter volumes of the liposomes was found to increase with decreasing numbers of α‐CT molecules per liposome. Single‐enzyme confinement was particularly effective, as intermolecular interactions between heat‐denatured α‐CT molecules (causing irreversible inactivation) are not possible.     

Covalent immobilization of trypsin onto thermo‐sensitive poly(N‐isopropylacrylamide‐co‐acrylic acid) microspheres with high activity and stability

Poly(N‐isopropylacrylamide‐co‐acrylic acid) (P(NIPAM‐co‐AA)) microspheres with a high copolymerized AA content were fabricated using rapid membrane emulsification technique. The uniform size, good hydrophilicity, and thermo sensitivity of the microspheres were favorable for trypsin immobilization. Trypsin molecules were immobilized onto the microspheres surfaces by covalent attachment. The effects of various parameters such as immobilization pH value, enzyme concentration, concentration of buffer solution, and immobilization time on protein loading amount and enzyme activity were systematically investigated. Under the optimum conditions, the protein loading was 493 ± 20 mg g^?1 and the activity yield of immobilized trypsin was 155% ± 3%. The maximum activity (V_max) and Michaelis constant (K_m) of immobilized enzyme were found to be 0.74 μM s^?1 and 0.54 mM, respectively. The immobilized trypsin showed better thermal and storage stability than the free trypsin. The enzyme‐immobilized microspheres with high protein loading amount still can show a thermo reversible phase transition behavior. The research could provide a strategy to immobilize enzyme for application in proteomics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43343.     

Epoxy‐derived pHEMA membrane for use bioactive macromolecules immobilization: Covalently bound urease in a continuous model system

Poly(2‐hydroxyethylmethacrylate) (pHEMA) membranes were prepared by UV‐initiated photopolymerization of HEMA in the presence of an initiator (α‐α′‐azobisisobutyronitrile, AIBN). The epoxy group, i.e., epichlorohydrin, was incorporated covalently, and the urease was immobilized onto pHEMA membranes by covalent bonding through the epoxy group. The retained activity of the immobilized enzyme was found to be 27%. The K_m values were 18 and 34 mM for the free and the immobilized enzymes, respectively, and the V_max values were found to be 59.7 and 16.2 U mg⁻¹ for the free and the immobilized enzyme. The optimum pHs was 7.2 for both forms, and the optimum temperature for the free and the immobilized enzymes were determined to be 45 and 50°C, respectively. The immobilized urease was characterized in a continuous system and during urea degradation the operational stability rate constant for the immobilized enzyme was found to be 5.83 × 10⁻⁵ min⁻¹. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2000–2008, 2000     

β‐Galactosidase immobilization into poly(hydroxyethyl methacrylate) membrane and performance in a continuous system

The activity of β‐galactosidase immobilized into a poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane increased from 1.5 to 10.8 U/g pHEMA upon increase in enzyme loading. The K_m values for the free and the entrapped enzyme were found to be 0.26 and 0.81 mM, respectively. The optimum reaction temperatures for the free and the entrapped β‐galactosidase were both found to be 50°C. Similarly, the optimum reaction pH was 7.5 for both the free and the entrapped enzyme. The immobilized β‐galactosidase was characterized in a continuous system during lactose hydrolysis and the operational inactivation rate constant (k_iop) of the entrapped enzyme was found to be 3.1 × 10⁻⁵ min⁻¹. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1367–1373, 1999     

Immobilization of pepsin on an acrylamide/2‐hydroxyethyl methacrylate copolymer and its use in casein hydrolysis

Pepsin was immobilized through covalent bonding on a copolymer of acrylamide and 2‐hydroxyethyl methacrylate via the individual and simultaneous activation of both groups. The extent of enzyme coupling upon the activation of both the amino and hydroxyl groups of the copolymer resulted in a synergistic effect. However, the order of activation of the support was critical. The covalently bound enzyme retained more than 50% of its activity even after six cycles. The storage stability of the covalently bound enzyme was 60% after storage for 1 month, whereas the free enzyme lost all of its activity within 10 days of storage at 35°C. The Michaelis constant (K_m) and maximum reaction velocity (V_max) were 1.1 × 10^?6 and 0.87 for the free enzyme and 1.2 × 10^?6 and 0.98 for the covalently bound enzyme when the enzyme concentration was kept constant and the substrate concentration was varied. Similarly, K_m and V_max were 6.73 × 10^?11 and 0.47 for the free enzyme and 7.59 × 10^?11 and 0.545 for the covalently bound enzyme when the substrate concentration was kept constant and the enzyme concentration was varied; this indicated no conformational change during coupling, but the reaction was concentration‐dependent. The hydrolysis of casein was carried out with a fixed‐bed reactor (17 cm × 1 cm). Maximum hydrolysis (90%) was obtained at a 2 cm³/min flow rate at 35°C with a 1 mM casein solution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1544–1549, 2005     

Chemoselective hydrolysis of methyl 2‐acetoxybenzoate using free and entrapped esterase in K‐carrageenan beads

Porcine liver esterase was entrapped in natural polysaccharides K‐carrageenan and retention of its activity was determined using p‐nitrophenyl acetate as the substrate. The optimum pH for esterase activity of entrapped enzyme showed a little shift towards acidic side. Immobilized enzyme showed improved thermal and storage stability. The entrapped esterase retained 50% of its activity after eight repetitive cycles. Michaelis constant K_m for the free and entrapped enzymes was almost same indicting no conformational change during immobilization. Maximum velocity V_max was observed to decrease on immobilization. The free and entrapped esterase was used for selective hydrolysis of methyl 2‐acetoxybenzoate to methyl 2‐hydroxybenzoate in batch process as well as in a fixed bed reactor. The hydrolysis was observed to be 99% within 2 h for free as well as immobilized enzyme in batch process. The rate of hydrolysis was found to depend on pH. The turn over number of selective hydrolysis in batch and fixed bed reactor was 3.08 × 10⁶ and 1.19 × 10⁷, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Immobilization of a nonspecific chitosan hydrolytic enzyme for application in preparation of water‐soluble low‐molecular‐weight chitosan

A nonspecific chitosan hydrolytic enzyme, cellulase, was immobilized onto magnetic chitosan microspheres, which was prepared in a well spherical shape by the suspension crosslinking technique. The morphology characterization of the microspheres was carried out with scanning electron microscope and the homogeneity of the magnetic materials (Fe₃O₄) in the microspheres was determined from optical micrograph. Factors affecting the immobilization, and the properties and stabilities of the immobilized enzyme were studied. The optimum concentration of the crosslinker and cellulase solution for the immobilization was 4% (v/v) and 6 mg/mL, respectively. The immobilized enzyme had a broader pH range of high activity and the loss of the activity of immobilized cellulase was lower than that of the free cellulase at high temperatures. This immobilized cellulase has higher apparent Michaelis–Menten constant K_m (1.28 mg/mL) than that of free cellulase (0.78 mg/mL), and the maximum apparent initial catalytic rate V_max of immobilized cellulase (0.39 mg mL^?1 h^?1) was lower than free enzyme (0.48 mg mL^?1 h^?1). Storage stability was enhanced after immobilization. The residual activity of the immobilized enzyme was 78% of original after 10 batch hydrolytic cycles, and the morphology of carrier was not changed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1334–1339, 2006     

Synthesis of poly[(2‐oxo‐1,3‐dioxolan‐4‐yl)methyl vinyl ether‐co‐N‐phenylmaleimide] and its miscibility in blends with styrene‐acrylonitrile or poly(vinyl chloride)

The aim of the study was to investigate the synthesis of a copolymer bearing cyclic carbonate and its miscibility with styrene/acrylonitrile copolymer (SAN) or poly(vinyl chloride) (PVC). (2‐Oxo‐1,3‐dioxolan‐4‐yl)methyl vinyl ether (OVE) as a monomer was synthesized from glycidyl vinyl ether and CO₂ using quaternary ammonium chloride salts as catalysts. The highest reaction rate was observed when tetraoctylammonium chloride (TOAC) was used as a catalyst. Even at the atmospheric pressure of CO₂, the yield of OVE using TOAC was above 80% after 6 h of reaction at 80°C. The copolymer of OVE and N‐phenylmaleimide (NPM) was prepared by radical copolymerization and was characterized by FTIR and ¹H‐NMR spectroscopies and differential scanning calorimetry (DSC). The monomer reactivity ratios were given as r₁ (OVE) = 0.53–0.57 and r₂ (NPM) = 2.23–2.24 in the copolymerization of OVE and NPM. The films of poly(OVE‐co‐NPM)/SAN and poly(OVE‐co‐NPM)/PVC blends were cast from N‐dimethylformamide. An optical clarity test and DSC analysis showed that poly(OVE‐co‐NPM)/SAN and poly(OVE‐co‐NPM)/PVC blends were both miscible over the whole composition range. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1809–1815, 2000     

Characteristics of poly(AAc5‐co‐HPMA3‐cl‐EGDMA15) hydrogel‐immobilized lipase of Pseudomonas aeruginosa MTCC‐4713

Four series of noble networks were synthesized with acrylic acid (AAc) copolymerized with varying amount of 2‐hydroxy propyl methacrylate or dodecyl methacrylate (AAc/HPMA or AAc/DMA; 5:1 to 5:5, w/w) in the presence of ethylene glycol dimethacrylate (EGDMA; 1, 5, 10, 15, and 20%, w/w) as a crosslinker and ammonium per sulfate (APS) as an initiator. Each of the networks was used to immobilize a purified lipase from Pseudomonas aeruginosa MTCC‐4713. The lipase was purified by successive salting out with (NH₄)₂SO₄, dialysis, and DEAE anion exchange chromatography. Two of the matrices, E_15a, i.e. [poly (AAc₅‐co‐DMA₁‐cl‐EGDMA₁₅)] and I_15c, i.e. [poly (AAc₅‐co‐HPMA₃‐cl‐EGDMA₁₅)], that showed relatively higher binding efficiency for lipase were selected for further studies. I_15c‐hydrogel retained 58.3% of its initial activity after 10th cycle of repetitive hydrolysis of p‐NPP, and I_15c was thus catalytically more stable and efficient than the other matrix. The I_15c‐hydrogel‐immobilized enzyme showed maximum activity at 65°C and pH 9.5. The hydrolytic activity of free and I_15c‐hydrogel‐immobilized enzyme increased profoundly in the presence of 5 mM chloride salts of Hg²⁺, NH₄⁺, Al³⁺, K⁺, and Fe³⁺. The immobilized lipase was preferentially active on medium chain length p‐nitrophenyl acyl ester (C:8, p‐nitrophenyl caprylate). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4636–4644, 2006     

A copolymer of poly[2,2′‐(m‐phenylene)‐5,5′‐ bibenzimidazole] and poly(2,5‐benzimidazole) for high‐temperature proton‐conducting membranes

A novel copolymer of polybenzimidazoles was prepared by copolymerization of 3,3′‐diaminobenzidine tetrahydrochloride, 3,4‐diaminobenzoic acid and isophthalic acid in polyphosphoric acid at 200 °C. The polymerization could be performed within 90–110 min with the assistance of microwave irradiation. The solubility of the copolymer obtained in N,N‐dimethylacetamide (DMAc) was improved compared with those of poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] and poly(2,5‐benzimidazole). Thus copolymer membranes could be readily prepared by dissolving the copolymer powders in DMAc with refluxing under ambient pressure. The decomposition temperature of the copolymer was about 520 °C in air according to thermogravimetric analysis data. The proton conductivity and mechanical strength of the phosphoric acid‐doped copolymer membranes were investigated at elevated temperatures. A conductivity of 0.09 S cm^?1 at 180 °C and a tensile stress at break of 5.9 MPa at 120 °C were achieved for the acid‐doped copolymer membranes by doping acids in a 75 wt% H₃PO₄ solution. Copyright © 2010 Society of Chemical Industry     

α‐Amylase immobilized by Fe3O4/poly(styrene‐co‐maleic anhydride) magnetic composite microspheres: Preparation and characterization

Fe₃O₄/poly(styrene‐co‐maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface‐anhydride groups/g microsphere, were obtained. Free α‐amylase was immobilized on the microspheres containing reactive surface‐anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α‐amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α‐amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005     

Immobilization of glucoamylase on the plain and on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres

Immobilization glucoamylase onto plain and a six‐carbon spacer arm (i.e., hexamethylene diamine, HMDA) attached poly(2‐hydroxyethylmethacrylate‐ethyleneglycol dimethacrylate) [poly(HEMA‐EGDMA] microspheres was studied. The microspheres were prepared by suspension polymerization and the spacer arm was attached covalently by the reaction of carbonyl groups of poly(HEMA‐EGDMA). Glucoamylase was then covalently immobilized either on the plain of microspheres via CNBr activation or on the spacer arm‐attached microspheres via CNBr activation and/or using carbodiimide (CDI) as a coupling agent. Incorporation of the spacer arm resulted an increase in the apparent activity of the immobilized enzyme with respect to enzyme immobilized on the plain of the microspheres. The activity yield of the immobilized glucoamylase on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres was 63% for CDI coupling and 82% for CNBr coupling. This was 44% for the enzyme, which was immobilized on the plain of the unmodified poly(HEMA‐EGDMA) microspheres via CNBr coupling. The K_m values for the immobilized glucoamylase preparations (on the spacer arm‐attached microspheres) via CDI coupling 0.9% dextrin (w/v) and CNBr coupling 0.6% dextrin (w/v) were higher than that of the free enzyme 0.2% dextrin (w/v).The temperature profiles were broader for both immobilized preparations than that of the free enzyme. The operational inactivation rate constants (k_iop) of immobilized enzymes were found to be 1.42 × 10^?5 min^?1 for CNBr coupled and 3.23 × 10^?5 min^?1 for CDI coupled glucoamylase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2702–2710, 2001     

A low,particle‐sized,nonporous support for enzyme immobilization: Uniform poly(glycidyl methacrylate) latex particles

The uniform and nonporous poly(glycidyl methacrylate) (poly(GMA)) latex particles, 1.7 μm in size, were first tried as a support in enzyme immobilization. For this purpose, α‐chymotrypsin (CT) was selected as the model enzyme. The low particle size and nonporous character of the selected support allowed to carry out the enzyme–subtrate interaction on a sufficiently large surface area (3.36 m²/g) and in the absence of intraparticular diffusion limitations. This property is particularly important when the immobilized CT is used for the substrates with high molecular weights (i.e., proteins). The latex particles were synthesized by dispersion polymerization of GMA. The reactive character of poly(GMA) allowed the direct attachment of primary amine groups onto the particles. Confocal laser scanning microscopy (CLSM) showed that primary amine groups were preferentially located on the particle's surface. Hence, the selected enzyme, CT was immobilized on the surface of nonporous particles via glutaraldehyde activation. For CT‐immobilized poly(GMA) particles, the maximum activity (r_m) and Michealis constant (K_m) were found to be 17.2 μmol/mg CT min and 121.6 μm, respectively. No significant loss was observed in the activity of immobilized CT, during the course of experiments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 818–824, 2006     

Surface‐active amphiphilic poly[(2‐acrylamido‐2‐methylpropanesulfonic acid)‐co‐(N‐isopropylacrylamide)] nanoparticles as stabilizer in aqueous emulsion polymerization

This work reports the effect of nanogel solid particles on the surface and interfacial tension of water/air and water/styrene interfaces. Moreover, the work aimed to use nanogels as a stabilizer for miniemulsion aqueous polymerization. A series of amphiphilic crosslinked N‐isopropylacrylamide (NIPAm) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) copolymer nanogels were synthesized based on an aqueous copolymerization batch method. Divinylbenzene and N,N‐methylene bisacrylamide were used as crosslinkers. The morphologies of the prepared nanogels were investigated using transmission and scanning electron microscopies. The lower critical transition temperatures were determined using differential scanning calorimetry. The surface tension of colloidal NIPAm/AMPS dispersions was measured as functions of surface age, temperature and the morphology of the NIPAm/AMPS nanogels. The NIPAm/AMPS nanogels reduced the surface tension of water to about 30.1 mN m^?1 at 298 K with a small increase at 313 K. Surface activities of these nanogels in water were determined by surface tension measurements. The NIPAm/AMPS dispersions had high surface activity and were used as a stabilizer to prepare a crosslinked poly(styrene‐co‐AMPS) microgel based on emulsion crosslinking polymerization. © 2013 Society of Chemical Industry     

Soybean oil based resin: A new tool for improved immobilization of α‐amylase

Acrylated epoxidized soybean resin has been utilized to immobilize the α‐amylase via UV‐curing technique. Among the numerous methods that exist for enzyme immobilization, entrapment and covalent binding are the focus of this study. The properties of immobilized enzyme were investigated and compared with those of the free enzyme. Upon immobilization by the two methods, the catalytic properties of the enzyme were not considerably changed as compared with that of nonimmobilized form; only the pH profile was broadened for the immobilized enzyme. The free enzyme lost its activity completely in 20 days, where as storage and repeated usage capability experiments demonstrated higher stability for the immobilized form. Immobilized enzyme prepared by attachment method possesses relatively higher activity compared with the activity of those obtained by entrapment method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4757–4761, 2006     

Synthesis and clay stabilization of a water‐soluble copolymer based on acrylamide,modular β‐cyclodextrin,and AMPS

A modular β‐cyclodextrin copolymer for clay stabilization was prepared from 2‐O‐(allyloxy‐2‐hydroxyl‐propyl)‐β‐cyclodextrin (XBH), acrylamide (AM), 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS), and sodium acrylate (NaAA) via redox free‐radical copolymerization. The effects of reactive conditions (such as initiator concentration, monomer ratio, reaction temperature, and pH) on the apparent viscosity of the copolymer were investigated and the optimal conditions for the copolymerization were established. The copolymer obtained was characterized by infrared spectroscopy, scanning electron microscope, viscosity measurements, rheological measurement, core stress test, and X‐ray diffractometry. The crystalline interspace of MMT could be reduced from 18.95323 Å to 15.21484 Å by copolymer AM/NaAA/AMPS/XBH. And this water‐soluble copolymer also showed remarkable anti‐shear ability, temperature resistance, and salt tolerance (1000 s^?1, viscosity retention rate: 35%; 120°C, viscosity retention rate: 75%; 10,000 mg/L NaCl, viscosity retention rate: 50.2%; 2000 mg/L CaCl₂, viscosity retention rate: 48.5%; 2000 mg/L MgCl₂, viscosity retention rate: 42.9%). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013