Molar Ratio Of Monomer Research Articles

Research on synthesis and salt thickening behavior of a binary copolymer amphiphilic polymer

Polymer flooding technology has become a common flooding technology in medium-high permeability reservoirs. With the gradual development of high salinity reservoirs, higher requirements for the salt resistance of polymers have been put forward. Herein, a novel binary copolymer amphiphilic polymer (PAMA) with salt thickening property was synthesized by free radical polymerization without soap. The synthetic parameters of polymer were optimized by using apparent viscosity as evaluation index which were as follows: the monomer molar ratio of AM:MALPS was 97:3, and the concentration of initiator and total monomer was 0.02% and 25% respectively, polymerization temperature of 45 °C, and the reaction time of 4.5 h. The PAMA was characterized by FT-IR and 1HNMR. Meanwhile, the salt thickening mechanism was analyzed combining with the apparent viscosity and microscopic structure. Finally, the injection performance of PAMA was explored with the core flooding experiment, and the feasibility of PAMA in high salinity reservoir was evaluated. The results showed that the increase of hydrodynamic radius and enhancement of hydrophobic association made PAMA had the property of salt thickening. The core flooding test also showed that PAMA had salt thickening behavior and anti-scouring capacity in porous medium in high salt reservoirs. The microscopic displacement experiments showed that PAMA could enhanced the oil recovery by displacing the “blind end” residual oil and the residual oil in pore intersection.

Synthesis and characterization of porous copolymers of 2‐hydroxyethyl methacrylate with ethylene glycol dimethacrylate

AbstractThe present study describes the synthesis and characterization of porous copolymers of 2‐hydroxyethyl methacrylate (HEMA) cross‐linked ethylene glycol dimethacrylate (EGDMA). They were synthesized in the regular microspheric shape via suspension–emulsion polymerization using toluene as a porogen. Different molar ratios of monomers (1:3, 1:2, 1:1, 2:1, 3:1) were applied in the syntheses. It was interesting to check if any of the above mentioned ratios can provide materials with an advantageous proportion of hydroxyl groups to the value of specific surface area. Additionally, we aimed into polymers with a good thermal stability. The obtained materials were characterized by elemental analysis, FTIR‐ATR spectroscopy, hydroxyl value (HV), low‐temperature nitrogen adsorption–desorption method, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). It was found that by tuning the molar ratio of functional monomer to the cross‐linker, it is possible to obtain copolymers with developed internal structure and a high HV. The optimal results were achieved for HEMA‐co‐EGDMA_1:2 (specific surface area: 111 m2/g, HV: 117 mg KOH/g). Furthermore, all the synthesized copolymers show a good thermal stability both in helium and air atmospheres. Their temperatures of 5% mass losses are over 230°C. The presented data indicate that the synthesized microspheres can be potentially use in various adsorption techniques including high temperature processes.

Polymerization of polyaniline under various concentrations of ammonium peroxydisulfate and hydrochloric acid by ultrasonic irradiation

AbstractEffects of various molar ratios of monomer (aniline), oxidant (ammonium peroxydisulfate), and dopant (hydrochloric acid) on the polymerization of polyaniline (PANI) were investigated using direct ultrasonic irradiation technique. The effects of varying molar ratio of dopant and oxidant on the structural stability, morphology, and electrical conductivity of the prepared PANI were studied. Firstly, a scheme derived from electrical conductivity point of view, by varying the molar ratio of ammonium peroxydisulfate (APS). As the molar ratio of APS to aniline (ANI) varied from 0.1 to 1.25, the conductivity of PANI reached a maximum of 0.24 S/cm at a ratio of 1. Thereafter, by fixing the optimized molar ratio of APS and aniline the molar ratio of hydrochloric acid (HCl) was varied. The conductivity of PANI increased with an increase of HCl concentration and reached a maximum of 0.5 S/cm at an HCl concentration of 2 M. Finally, the formation mechanism for polymerization of PANI were discussed using Fourier transform infrared spectra, ultraviolet–visible spectra, nuclear magnetic resonance spectroscopy, and X‐ray diffraction spectroscopy. The final product is in protonated form, possessing structural stability and electrically conductive.

Thermal imidization and properties of polyimide with azobenzene side-chain for photo-alignment film

Azobenzene-containing polyimides (azo-PIs) have exceptional potential for photo-alignment of liquid-crystal (LC) molecules. In this study, the synthesis of PIs with azo-side chains (azo-PIs) via thermal imidization of azo-containing poly(amic acid) (PAA) precursors was investigated. The results indicated that the increasing azo-containing diamine promoted the imidization progress, leading to a relatively lower imidization temperature for the fabricating of azo-PI films. These azo-PIs films were investigated for application as photo-induced anisotropy films in liquid-crystal devices (LCDs). It was found that the pretilt angle of the photo-aligning azo-PI film was tunable by changing the mole ratio of azo-amine monomers. These azo-PI films exhibited good thermal stability, outstanding mechanical property and excellent performance in controlling the LC molecule alignment.

Research on combined-pour point depressant of methacrylate-acrylamide copolymers and ethylene-vinyl acetate copolymers for diesel fuel

The combined-pour point depressants (PPDs) have shown potential for the improvement of the cold flow properties of diesel. In this study, free radical polymerization was used to polymerize methacrylate (RMC) and acrylamide (AM) in different molar ratios (1:1, 3:1, 6:1, 9:1, 12:1, 15:1). Methacrylate-acrylamide copolymers (RMC-AM) were synthesized and analyzed through Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA) to characterize the copolymers. Through exploring the effect of different chain lengths and different monomer molar ratios on the solid point (SP) and cold filter-plugging point (CFPP) of diesel, C14MC-AM (9:1) showed relatively good performance (ΔSP = 25 °C, ΔCFPP = 10 °C). Then, ethylene–vinyl acetate copolymer (EVA) materials with different VA content were introduced in this study. Diesel treated with 1000 ppm of EVA-2 (VA = 28%) showed relatively good performance (ΔSP = 18 °C, ΔCFPP = 10 °C). C14MC-AM (9:1) was mixed with EVA −2 in different ratios (1:0, 4:1, 2:1, 1:1, 1:2, 1:4, and 0:1, namely, PPDC-1 ~ 7) to produce synergy and improve the cold flow properties of diesel. The ΔSP and ΔCFPP of diesel fuel treated with only 500 ppm PPDC-5 can reach 28 °C and 23 °C, respectively. In addition, the crystallization behavior and crystal morphology of the treated diesel fuel were discussed through differential scanning calorimeter, polarized optical microscope and rheological analysis. The results showed that the combined-PPD made the wax crystals dissolve in the diesel system. The wax crystals became more uniform and denser under the action of AM polar groups.

Optimal Experimental Conditions for Improving the Yield of Poly(limonene) from Photoinduced Polymerization

Limonene represents a possible candidate for the synthesis of polymers from renewable sources. However, because of some structural characteristics, the process yield tends to be considerably low (< 10%). In this sense, the evaluation of still unexplored alternative controlled strategies of synthesis, together with techniques of process optimization, can enable the increase in the polymer yield. Taking this into consideration, this study presents, for the first time, the optimal conditions for maximizing the poly(limonene) yield using a photoinduced polymerization route. The reactions were all conducted at a mild temperature (40 °C) and the polymer was characterized by nuclear magnetic resonance (1H-NMR and 13C-NMR). A face-centered design (FCD) was proposed for interpreting the effects of the reagent ratio (initiator, catalyst, and electron donor amine) on the polymerization. The monomer molar ratio was set to 100 with 6 h of polymerization time. All reagents exerted significant and positive effects on the yield, with the initiator having the most pronounced effect. The optimal conditions for maximizing the yield were as follows: molar ratios of the electron donor amine (PMDETA): 5‒8.5; catalyst (TX): 1‒1.7; and initiator (TBE): 1.7. Thus, ~ 18% yield could be achieved using a molar ratio of 100:8.5:1.7:1.7 (monomer:PMDETA:TX:TBE). It was observed that the polymer had good adhesion to steel when dried and moderate adhesion to glass. The polymer was insoluble in water and soluble in ethanol, tends to form suspension in solution of ethanol/water, in addition to being partially soluble in tetrahydrofuran and chloroform. These characteristics indicate that the material prepared herein is a promising renewable additive for coatings, films, or adhesives.

Eco-Friendly Synthesis and Antimicrobial Performance of New Heteropolymer Composites

Heteropolymeric materials of resorcinol, aniline, urea, and formaldehyde are synthesized by 1:1:1:3 molar ratios of the respective monomers with different percentages of hydrophilic bentonite via a mixed condensation polymerization in an aqueous acidic media. The heteropolymeric material and heteropolymeric/hydrophilic bentonite were characterized by Fourier transform FT-IR spectroscopy and UV–Vis absorption spectra. The surface morphology of heteropolymer composites was recorded at various magnification powers by SEM which revealed well-defined granular spherical morphology of variable size in the range of 0.220 μm to 1.370 μm. Moreover, small pieces of bentonite were inserted and distributed through the field with different particle sizes. They cumulated and condensed in certain zones forming some plaques of different sizes. The heteropolymeric material is soluble in most of the organic solvents including, THF, DMF, and DMSO. It is also dissolved in concentrated HNO3. The new synthesized heteropolymeric material was examined as an antimicrobial agent. The current procedure introduces an inexpensive and eco-friendly approach for developing new heteropolymer composites acquiring the requested new functionality.

Anionic/nonionic surfactants for controlled synthesis of highly concentrated sub-50 nm polystyrene spheres.

Polystyrene nanospheres are of great importance in 3D hard templating along with many other fields like pharmaceuticals and coatings. Therefore, it is important to be able to prepare polystyrene beads with different sphere sizes that suit each application. In this work, the emulsion polymerization method was used to prepare monodispersed polystyrene (PS) spheres with an average size of 50 nm, using styrene monomer, sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) as surfactants, and potassium persulfate (KPS) as the initiator. The average size and size distribution of the PS spheres were controlled by optimizing the synthesis parameters such as the concentration of the monomer, initiator, and surfactant, the type of surfactant, and the time and temperature of polymerization. The shape, size, and size distribution of the prepared PS spheres were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The preparation of perfectly spherical PS spheres as small as 50 nm with a narrow size distribution is obtained using 8% styrene with (5% SDS and 2% KPS of the styrene amount) at 90 °C, with the monomer and surfactant molar ratio and concentration and the polymerization temperature being the dominating factors that affect the PS bead size.

Synthesis and Characterization of Sodium Carboxymethyl Starch‐Graft Acrylamide/1‐Vinyl‐2‐Pyrrolidone Copolymers via Central Composite Design and Using as Filtration Loss Agent in Drilling Muds

AbstractA graft copolymer is synthesized with graft copolymerization of acrylamide (AM) and 1‐vinyl‐2‐pyrrolidone (NVP) grafting onto sodium carboxymethyl starch (CMS) via central composite design (CCD). The initiation system consists of potassium persulfate (KPS) and sodium hydrogen sulfite (SBS). The copolymer is confirmed by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, scanning electron microscopy, thermogravimetric experiment, and elemental analysis. The rheological performance, filtration loss, cake thickness, and cake fictional coefficient of the drilling mud containing copolymer are evaluated. The results show that copolymers have ability to thicken and reduce filtration volume and have no obvious influence on the thickness and fictional coefficient of the mud cake. Response surface methodology (RSM) is exerted for variable evaluation and optimization. The results indicate that initiator concentration is the main contributing factor to decrease filtration volume and the optimum results are 1.5 wt% (initiator concentration), 1.82 (mole ratio of monomer to starch [AGU]), 66.02 °C (reaction temperature), 3.87 h (reaction time). The predicted value and the actual experimental value are 8.64 and 9 mL respectively with an error of 4.01%. The small error indicates that there is a small deviation between the actual and the predicted values, which also shows that the model is reasonable.

New superhydrophobic nanocomposites as anti-corrosion coating films. Part I: Synthesis and characterization of poly (styrene/vinyl acetate)-SiO2 nanocomposites as a water-repelling surface via nanoemulsion polymerization technique

This paper aims to synthesize new robust superhydrophobic coated films to protect the carbon steel petroleum pipelines from corrosion. Three (styrene/vinyl acetate) copolymers with monomer molar ratio of (0.17:0.43), (0.17:0.22), and (0.34:0.22) denoted as C1-, C2-, and C3-copolymers, respectively, were synthesized as hydrophobic coating materials. SiO2 nanoparticles (SiO2-NPs) with an average size ranging from 91 to 98 nm were prepared via the sol-gel technique. Two functionalized SiO2-NPs using dodecyl triethoxysilane and hexadecyl trimethoxysilane as precursors were synthesized. Two composites denoted as N- and M-composites were physically fabricated by incorporating the functionalized SiO2-NPs into a C3-copolymer matrix. The chemical structures of the prepared copolymers and the purified SiO2 nanoparticles were elucidated by FT-IR and 1H NMR spectroscopies. The molecular weights of the prepared copolymers were measured using gel permeation chromatography. Thermo-gravimetric analysis (TGA) was used to investigate the thermal properties of the prepared copolymers and the composites. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques displayed the surface topography of the carbon steel surfaces coated by C3-copolymer and (N- and M-) composites. The results showed that a highly superhydrophobic (water-repellent) coating film was achieved by M-composite with a static contact angle of 162.87 ± 0.81o.

Synthesis, characterization and optical properties of a series of copolymers bearing 1-ethynylpyrene and ethynylbenzene units

AbstractA novel series of copolymers were obtained from the copolymerization of 1-ethynylpyrene (EP) (known as pyrenylacetylene) and ethynylbenzene (EB) (named also phenylacetylene) with WCl6 as catalyst and toluene as solvent, using different monomer molar ratios EP/EB (80:20, 60:40, 50:50; 40:60, 20:80). The optical properties of the obtained copolymers Poly(EP-co-EB) were determined by absorption and fluorescence spectroscopy. Absorption spectra of the copolymers Poly(EP-co-EB) showed that copolymers containing phenylacetylene units possess a lower degree of conjugation than the homopolymer trans-poly(1-ethynylpyrene) (trans-PEP), since they showed a twisted conformation. These results were confirmed by emission spectroscopy showing the formation of excimers for those copolymers containing high pyrene content.

Synthesis of amphiphilic block copolymers via ring opening polymerization and reversible addition‐fragmentation chain transfer polymerization

AbstractAmphiphilic block copolymers were synthesized via a dual initiator chain transfer agent (inifer) that successfully initiated the ring opening polymerization (ROP) of l‐lactide (LLA) and subsequently mediated the reversible addition‐fragmentation chain transfer (RAFT) polymerization of poly(ethylene glycol) ethyl ether methacrylate (PEGEEMA). The formation of each polymer block was confirmed using 1H nuclear magnetic resonance spectroscopy, as well as gel permeation chromatography, and comprehensive kinetics studies provide valuable insights into the factors influencing the synthesis of well‐defined block copolymers. The effect of monomer concentration, reaction time, and molar ratios of inifer to catalyst on the ROP of LLA are discussed, as well as the ability to produce poly(lactide) blocks of different molecular weights. The synthesis of hydrophilic PPEGEEMA blocks was also monitored via kinetics to provide a better understanding of the role the chain transfer agent plays in facilitating the complex and sterically demanding RAFT polymerization of PEGEEMA.

Reactor Blend and Nanocomposite of Polyethylene Using a Binary Catalyst of Metallocene/Nickel

The present study aimed to conduct the ethylene polymerization using two binary catalytic systems to evaluate the resulting reactor blend of polyethylene. Subsequently, the study continued to explore the effects of catalyst to monomer molar ratio, reaction temperature, ethylene pressure and nanofillers on the catalysts activity, molar mass, thermal behavior, structural and morphological properties of the obtained polyethylene. The catalytic system containing α-diimine catalyst based on nickel showed higher activity, higher melting point (75.6 × 104 g polyethylene/(mol catalyst h), 125°C, respectively) and the extent of crystallinity (up to 48.5%) in comparison with the analogous system bearing pyridine-imine catalyst. The augmentation of nanoparticles increased the branching content in the system with α-diimine catalyst based on nickel, while these trends were reverse in pyridine-imine catalyst system, so that the branches were reduced as the nanoparticle concentration was increased. SEM images revealed distinct fibrous phases and the presence of obvious and well dispersed nanoparticles in the prepared nanocomposites. The synthesized polyethylene blend exhibited high thermal stability.

Polymer/BiOBr-Modified Gauze as a Dual-Functional Membrane for Heavy Metal Removal and Photocatalytic Dye Decolorization.

It is crucial to remove heavy metals and dyes before discharging industrial effluents. Gauze substrate was surface-modified by coating with a polymeric adsorbent and a spray coating of BiOBr photocatalyst to develop a novel dual-functional membrane, polymer/BiOBr-modified gauze, for water remediation. The polymeric adsorbent was crosslinked to prevent the dissolving of the adsorbent during operation in contaminated water. The morphology and surface chemistry of the modified gauze were characterized before and after the adsorption of Ni2+. The surface wettability, isotherms, and kinetics of Ni2+ adsorption were studied. We also studied the effect of pH, initial Ni2+ concentration, monomer molar ratio, and monomer chemical structure on the Ni2+ adsorption capacity. To achieve a high Ni2+ adsorption capacity and good photocatalytic decolorization activity, the amount of decorated BiOBr was tuned by changing the spray-coating time to optimize the exposed BiOBr and polymer on the surface. The optimized dual-functional membrane PB20 possesses excellent adsorption capacity (650 mg g−1) for Ni2+ ions and photocatalytic decolorization activity (100% degradation of RhB within 7 min). Decorating the optimized amount of BiOBr on the surface can introduce photocatalytic decolorization activity without sacrificing the adsorption capacity for Ni2+.

Gene expression abundance dictated exopolysaccharide modification in Rhizobium radiobacter SZ4S7S14 as the cell's response to salt stress

A molecular and metabolic behaviour of EPS-producing and salt-tolerant bacterium Rhizobium radiobacter SZ4S7S14 along with its practical application in salt-stress was investigated. The research target was identification and expression profiles of a large EPS biosynthesis gene cluster, possible structural modification of EPS under salt-stress effect and analysis of the gene(s) relative expression and structural modification correlation. As expected, transposons insertions were identified within or near the coding regions of exoK and exoM, previously known large gene cluster that is required for EPS I synthesis. Different expression levels of exoK and exoM in different salt-stress models resulted in structural modification of EPS, which was seen basically in monomers molar ratio. As a result of downregulation of the genes the strain produced EPS samples with monomers ratio: (1) Glu:Man:Gal:Xyl:Ara:Rha:Rib = 31.21:3.02:2.77:1:0.91:0.64:0.41 (in 0.25% NaCl); (2) Glu:Man:Gal:Xyl:Ara:Rha:Rib = 7.65:1:0.69:0.22:0.2:0.16:0.1 (in 0.5% NaCl); (3) Glu:Man:Gal:Ara:Xyl:Rha:Rib = 9.39:1.89:1:0.58:0.52:0.46:0.26 (in 1% NaCl); and (4) Glu:Man:Ara:Xyl:Rib:Gal = 7.9:2:2:1.58:1.1:1 (in 2.0% NaCl), whereas in control (without NaCl): Glc:Man:Gal:Xyl:Ara:Rha:Rib = 11.66:1:0.90:0.37:0.37:0.15:0.14. It was found that, salt-stress not only leads to downregulation of a large EPS biosynthesis gene cluster, including exoK and exoM genes, but also impacting on their relative expression degree, re-groups of the monomers within the EPS matrix and dictates molar ratio of the monosaccharides in the final metabolite.

In-situ polymerization of pyrrole in PVA-PVP matrix: Optimization of oxidant/monomer ratio and its effect on dielectric properties of polymer blend films

Free standing and flexible polymer blend films of PPy (poly pyrrole) doped in PVA (poly vinyl alcohol) – PVP (poly vinyl pyrrolidone) matrix with varying concentrations of PPy have been prepared by solution cast technique at room temperature. In-situ polymerization of pyrrole monomer (Py) in PVA-PVP matrix has been carried out using FeCl3 as oxidant. The effect of monomer amount and monomer to oxidant ratio on the dielectric parameters (such as dielectric constant, dielectric loss, loss tangent, ac conductivity, complex electric modulus, complex impedance) of PPy doped PVA-PVP polymer blend films have been studied in the frequency range of 20 Hz to 2 MHz. Two different molar concentrations (0.15 M and 0.30 M) of oxidants have been taken and for each oxidant concentration, four varying concentrations of monomer have been used to optimize the results. The blend films having oxidant to monomer molar concentration ratio of 0.5 in both the cases (i.e. 0.15 M and 0.30 M) have been found to be smooth, flexible, mechanically strong and easy to process. These films have shown very systematic change and improved values of dielectric parameters within the experimental frequency range. Enhanced dielectric parameters (complex permittivity, ac conductivity and electric modulus) values for films having oxidant to monomer molar ratio of 0.5 suggest the organized growth of PPy chain in the matrix of PVA-PVP.

Efficient Processing of Reactions Involving Diazonium Salts: Meerwein Arylation in an Impinging-Jet Reactor

This work reports a novel approach for performing high-throughput synthesis of Meerwein arylation in an impinging-jet reactor. The multistep reaction was performed in a single reactor via in situ diazonium salt generation followed by Meerwein arylation. The work involves many iterations between experiments and simulations (where we integrate simulating the flow, heat transfer, and reaction simultaneously) for optimization of conditions in an inverted impinging-jet reactor. The effect of design variables viz. catalyst concentration, inlet temperature, and monomer mole ratio on the yield of the desired product was studied in detail, and the simulation results were used to plan the continuous experiments. An infrared camera was used to monitor the transient reactor temperature for steady-state analysis. The lab-scale inverted impinging-jet reactor with over 93% isolated yield can offer a space-time yield of 277.78 tons/m3/day. The numbering-up of an inverted impinging-jet reactor can be an effective way for cleaner production of products through typical Meerwein arylation.

Hyperbranched Poly(ester-enamine) from Spontaneous Amino-yne Click Reaction for Stabilization of Gold Nanoparticle Catalysts.

Hyperbranched polymers have garnered much attention due to attractive properties and wide applications, such as drug-controlled release, stimuli-responsive nano-objects, photosensitive materials and catalysts. Herein, two types of novel hyperbranched poly(ester-enamine) (hb-PEEa) were designed and synthesized via the spontaneous amino-yne click reaction of A2 monomer (1, 3-bis(4-piperidyl)-propane (A2a ) or piperazine (A2b )) and B3 monomer (trimethylolpropanetripropiolate). According to Flory's hypothesis, gelation is an intrinsic problem in an ideal A2 +B3 polymerization system. By controlling the polymerization conditions, such as monomer concentration, molar ratio and rate of addition, a non-ideal A2 +B3 polymerization system can be established to avoid gelation and to synthesize soluble hb-PEEa. Due to abundant unreacted alkynyl groups in periphery, the hb-PEEa can be further functionalized by different amino compounds or their derivates. The as-prepared amphiphilic PEG-hb-PEEa copolymer can readily self-assemble into micelles in water, which can be used as surfactant to stabilize Au nanoparticles (AuNPs) during reduction of NaBH4 in aqueous solution. As a demonstration, the as-prepared PEG-hb-PEEa-supported AuNPs demonstrate good dispersion in water, solvent stability and remarkable catalytic activity for reduction of nitrobenzene compounds.

Comparative study of catalase immobilization via adsorption on P(MMA-co-PEG500MA) structures as an effective polymer support

In this study, poly[methyl methacrylate-co-poly(ethylene glycol) methacrylate] (P(MMA-co-PEG500MA)) copolymers were used for catalase (CAT) immobilization. Firstly, P(MMA-co-PEG500MA) copolymers were synthesized by using different amount of methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (PEG500MA) monomers. The synthesized copolymers were characterized by different analysis techniques. Afterward, CAT enzyme was immobilized via physical adsorption method onto the P(MMA-co-PEG500MA) copolymers. P3 sample containing 1:1 (PEG500MA:MMA) monomer molar ratio was selected as model support because of exhibiting optimum surface porosity and thermal stability. A high immobilization yield (76%) was achieved under optimized conditions. The immobilized enzyme displayed improved tolerance towards pH and temperature changes. After immobilization, the optimum pH shifted from 7.5 to 7.0, whereas the optimum temperature remained unchanged at 35 °C. Immobilized enzyme showed good reuse potential and excellent storage stability. After 10 consecutive uses, immobilized enzyme maintained about 51.0% of its initial activity. Furthermore, free enzyme completely lost its initial activity after 4 weeks, while immobilized enzyme maintained approximately 65% of the initial activity at 25 °C. Approximately twofold decrease in Km was obtained which means that the affinity of enzyme to the substrate improved after immobilization. Finally, it can be concluded that the prepared P(MMA-co-PEG500MA) copolymer structure can be an ideal matrix for CAT immobilization.

Rapid synthesis of polyimide precursors by solution polymerization using Continuous-flow microreactors

Preparation method is of importance for development and application of polymers. Herein, we proposed a continuous-flow strategy for the preparation of polyimide precursors through solution polymerization in microreactors for the first time. The polymerization time was significantly reduced from several hours in a batch reactor to twenty minutes in a microreactor. Lower temperature, more appropriate molar ratio of monomers and longer residence time in the polymerization process resulted in poly(amic acid)s with higher molecular weights. Moreover, the relationship between the molecular weight and the residence time was used to discuss the polymerization kinetics. Meanwhile, the rapid preparation of poly(amic acid)s from pyromellitic dianhydride (PMDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), benzophenone-3,3′,4,4′- tetracarboxylic dianhydride (BTDA), 4,4′ - oxydiphthalic dianhydride (ODPA), or cyclobutane tetracarboxylic dianhydride (CBDA) was achieved in the microreactor. In particular, the number-average molecular weight of the PAA prepared by BTDA and 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether (6FODA) reached 36.3 kg / mol at the polymerization time of 19.6 min. This work demonstrated that microreactors would provide a promising and efficient pathway to prepare polyimide precursors with high molecular weights.