Transfer Free Radical Research Articles

Improving Microcystis aeruginosa removal efficiency through enhanced sonosensitivity of nitrogen-doped nanodiamonds

Traditional methods for algae removal in drinking water treatment, such as coagulation and sedimentation, face challenges due to the negative charge on algae cells’ surfaces, resulting in ineffective removal. Ultrasonic cavitation has shown promise in enhancing coagulation performance by disrupting extracellular polymer structures and improving cyanobacteria removal through various mechanisms like shear force and free radical reactions. However, the short lifespan and limited mass transfer distance of free radicals in conventional ultrasonic treatment lead to high energy consumption, limiting widespread application. To overcome these limitations and enhance energy efficiency, advanced carbon-based materials were developed and tested. Nitrogen-doped functional groups on nanodiamond surfaces were found to boost sonosensitivity by increasing the production of reactive oxygen species at the sonosensitizer-water interface. Utilizing low-power ultrasound (0.12 W/mL) in combination with N-ND treatment for 5 min, removal rates of Microcystis aeruginosa cells in water exceeded 90 %, with enhanced removal of algal organic matters and microcystins in water. Visualization through confocal microscopy highlighted the role of positively charged nitrogen-doped nanodiamonds in aggregating algae cells. The synergy between cell capturing and catalysis of N-ND indicates that efficient mass transfer of free radicals from the sonosensitizer’s surface to the microalgae’s surface is critical for promoting cyanobacteria floc formation. This study underscores the potential of employing a low-intensity ultrasound and N-ND system in effectively improving algae removal in water treatment processes.

Marine‐Derived Nanozyme‐Crosslinked Self‐Adaptive Hydrogels for Programmed Regulating the Regeneration Process

AbstractSelf‐adaptive hydrogels that can specifically respond to pathological cues and match the highly ordered tissue regeneration process are significantly on‐demand for effective wound management. Herein, multifunctional marine‐derived gold clusterzyme (AuNCs)‐based self‐adaptive hydrogels with microenvironment triggered release behavior are elaborately fabricated for on‐demand antioxidant, anti‐inflammatory and immunoregulation. The marine mussel‐derived catechol ligands (L‐3,4‐dihydroxyphenylalanine) endow AuNCs with enhanced superoxide dismutase‐mimic activity due to their high affinity to superoxide anion free radical (O2−•) and unique electron transfer mechanism, leading to 100% inhibition of O2−•. Upon uniformly crosslinking with phenylboronic acid‐modified marine‐derived sodium alginate (PBA‐Sa), the obtained AuNCs@PBA‐Sa hydrogels exhibit outstanding self‐healing property, tunable degradation and good removability. Meanwhile, AuNCs can greatly enhance the mechanical property and confer the hydrogel with favorable tissue adhesion for rapid hemostasis. Furthermore, injectable AuNCs@PBA‐Sa hydrogels can not only adapt their shape to the irregular wound, but also smartly adapt their microstructure to the physiological microenvironment of diabetic wound, leading to the responsive release of AuNCs upon the break of boronate ester bonds. The released gold clusterzymes can actively induce the generation of M2‐macrophage, demonstrating an outstanding anti‐inflammatory and pro‐regeneration effect. Therefore, the present multifunctional clusterzyme‐based self‐adaptive hydrogels hold great potential for remolding the dynamic tissue regeneration microenvironment and smart wound management.

Unveiling distinct influencing mechanisms of Br- on NDMA formation during ozonation of actual water Matrixes: Identification of precursors and brominated substance

Bromide ion (Br-) in water sources has been found to affect the formation of carcinogenic non-brominated N-nitrosodimethylamine (NDMA) during ozonation of typical amines. The increasing bromide levels bring more concern due to climate change and industrial discharge, but its effects on actual water matrixes were still unclear. In this study, NDMA formation from three actual water matrixes during ozonation as the Br- concentration increased from 0 to 100 µM were investigated (promotion (100.4 ∼ 231.6 ng/L), promotion then inhibition (399.5 ∼ 461.2 ∼ 428.2 ng/L), and subtle influence (51.9 ± 6.9 ng/L)); from which the NDMA precursors were screened and 8 precursors were selected for exploring the influencing mechanisms. The results indicated that the roles of Br- on NDMA formation significantly depended on the water characteristics of actual matrixes. A total of 16 typical NDMA precursors, which were mainly derived from industrial, agricultural and pharmaceutical sources, were identified. Moreover, 6 brominated substance (Br-DMA, Br-UDMH, Br-DMSC, Br-DMS, Br-TMDS, Br2-TMDS), which were thought to play a crucial role in promoting NDMA formation, were also identified in actual water by precursor ion scan (PIS) method. Hypobromous acid (HOBr), which has been proved to be the culprit to the generation of brominated substances, tend to attack the electron-donating groups of amines, such as acylamino (–NHCO-R) or amidogen (–NH2) groups. However, the reactive bromine species (∙Br and ∙Br2-) was inclined to attack the aromatic and anti-oxidant moieties then result in Br- release, as no bromine substitution but free radical transfer reaction occurs. Therefore, decreasing HOBr formation is the crucial step to reduce NDMA generation. This work would provide technical guide for NDMA risks control during ozonation of Br--amines co-containing water matrixes.

Integrating Hybrid Perovskite Nanocrystals into Metal-Organic Framework as Efficient S-Scheme Heterojunction Photocatalyst for Synergistically Boosting Controlled Radical Photopolymerization under 980 nm NIR Light.

S-scheme heterojunction photocatalyst MAPbI3@PCN-222 with light absorption extending to the NIR region is constructed by embedding organic-inorganic hybrid perovskite (MAPbI3) into porphyrinic Zr-MOF (PCN-222). Both in situ X-ray photoelectron spectroscopy, ultraviolet photoelectron spectral characterization, and photocatalytic polymerization experiment prove the formation of S-scheme heterojunction. MAPbI3@PCN-222 with a low dosage (90 ppm) displays an impressive photocatalytic ability for 980 nm light-mediated photoinduced electron/energy-transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization in air. The well-defined controllable-molecular weight polymers including block copolymers and ultrahigh-molecular weight polymers can be achieved with narrow distributions (Mw/Mn < 1.20) via rapid photopolymerization. The industrial application potential of the photocatalyst also has been proved by scale-up synthesis of polymers with low polydispersity under NIR light-induced photopolymerization in a large-volume reaction system (200 mL) with high monomer conversion up to 99%. The penetration photopolymerization through the 5 mm polytetrafluoroethylene plate and excellent photocontrollable behavior illustrate the existence of long-term photogenerated electron transfer of heterojunction and abundant free radicals in photopolymerization. The photocatalyst still retains high catalytic activity after 10 cycles of photopolymerization in air. It is revealed for the first time that the special PET-RAFT polymerization pathway is initiated by the aldehyde-bearing α-aminoalkyl radical derived from the oxidization of triethanolamine (TEOA) by the heterojunction photocatalyst. This research offers a new insight into understanding the NIR-light-activated PET-RAFT polymerization mechanism in the presence of TEOA.

Preparation of CuO loaded cation exchange resin composites and its degradation of polyacrylamide aqueous solution

Macroporous cation exchange resins (CER) were used as carriers, and CuO loaded cation exchange resin composites was successfully prepared under thermostatic oscillation and hydrothermal conditions. The results showed that the as-prepared composites exhibited obvious shell-core structure. The different amounts of NaOH affected the micro morphology of CuO on the surface and in the internal pores of the resin, and also affected the percentage content of Cu element. XRD characterization clearly revealed that the products were monoclinic crystal system CuO species with a grain size of about 16 nm. The highest degradation rate of polyacrylamide (PAM) by CuO@IER-1g reached 81.94%, after 6 cycles CuO@CER-1g has still good photocatalytic activity, and the decrease in degradation rate was the combined effect from the adsorption of ion exchange resins and the electron-hole pairs formed by CuO and a series of free radical transfer reactions under ultraviolet light. This study has important theoretical basis and practical significance for enriching ion exchange theory, developing the photocatalytic industry, and purifying the environment.

Oxidation and exothermic properties of long flame coal spontaneous combustion under solid-liquid-gas coexistence and its microscopic mechanism analysis

Coal spontaneous combustion (CSC) wastes valuable resources and does great damage to the environment. To study the oxidation and exothermic properties of CSC under solid-liquid-gas coexistence conditions, a C600 microcalorimeter was used to analyze the heat released by the oxidation of raw coal (RC) and water immersion coal (WIC) under different air leakage (AL) conditions. The experimental results showed that the AL was negatively correlated with the heat release intensity (HRI) in the initial stages of coal oxidation, but as the oxidation proceeded, the AL and the HRI gradually showed positive correlations. The HRI of the WIC was lower than that of the RC under the same AL conditions. However, since water participated in the generation and transfer of free radicals in the coal oxidation reaction and promoted the development of coal pores, the HRI growth rate of the WIC was higher than that of the RC during the rapid oxidation period, and the self-heating risk was higher. The heat flow curves for the RC and WIC in the rapid oxidation exothermic stage could be fitted with quadratic functions. The experimental results provide an important theoretical basis for the prevention of CSC.

Insights into glycine pyrolysis mechanisms: Integrated experimental and molecular dynamics/DFT simulation studies

Understanding pyrolysis pathways of nitrogen-rich biomass is a key to the pyrolytic production of value-added N-rich biochar and bio-oil or the removal of fuel-N to avoid NOX emission. Laboratory pyrolytic experiments referring to horizontal tube furnace pyrolyzer and several real-time analytic instruments, and numerical simulations involving reactive force field molecular dynamics (ReaxFF MD) and density functional theory (DFT) were integrated to explore the pyrolysis of glycine (Gly), which is the simplest amino acid or organic N-carrier in biomass. The major products, reaction pathways, and some theoretical data were obtained and compared with the previous studies to understand the Gly pyrolysis mechanisms. Dehydration of Gly to afford H2O as well as glycylglycine and diketopiperazine (DKP), and decarboxylation of Gly to produce CO2 as well as amines were the dominant reactions at the initial pyrolysis stage, and H free radical transfer was the dominant way to induce these reactions. The pyrolysis of Gly and its derivatives such as glycylglycine and DKP yielded common products such as CO2, NH3, HCN, HNCO, CO, acetic acid, and acetamide; other chemicals including cyclobutanol, propane, alanine, dimethylamine, acetonitrile, and methylamine were also observed, which was different from previous studies. These findings provided a new insight into the pyrolysis mechanisms of Gly, and also showed a great potential of the integrated experiment and simulation on such investigations.

Catalytic ethanolysis of Dahuangshan lignite and directional upgrading of two derived soluble mixtures

An in-situ and ex-situ cascade upgrade strategy was designed and used for upgrading Dahuangshan lignite-derived soluble mixtures (LDSMs) to obtain value-added chemicals and clean liquid fuels (CLFs), respectively. In the H2-free catalytic ethanolysis, Ni/mordenite can effectively activate ethanol and promote the transfer of various free radicals including H·, CH3CH2·, and CH3CH2O·, which synchronously facilitates the cleavage of bridged bonds in Dahuangshan lignite and the in-situ removal of heteroatoms (HAs) from LDSMs. As a result, the total yield of LDSMs increased from 40.6 to 66.5 wt%, wherein that of ethanol-soluble portion (ESP) increased from 21.4 to 32.4 wt%. Interestingly, alkanes and arenes with higher relative content (RC, 38.1%) were detected in ESPC (for catalytic ethanolysis), while arenols (24.7%) dominate ESPN (for ethanolysis). The analysis with a quadrupole exactive orbitrap mass spectrometer further confirmed the significant decrease in the relative abundance of HAs, especially Ox class species, in ESPC. In addition, ESPN and ESPC with different properties were further used for enriching derived chemicals and for obtaining CLFs by catalytic hydroconversion (CHC), respectively. After the CHC, the total RCs of alkanes and cyclanes in the soluble portion (SP) are as high as 71.3%, and the content of HA-containing organic compounds was further decreased. Therefore, such SP containing less HAs is an attractive CLF precursor. A ternary mixed solvent was also designed for rapidly separating the SP from ESPN. The total RC of alkanes and arenes in PE5 as well as arenols in M5 are as high as 79.4 and 70.9%, respectively. Molecular dynamics simulations were further used to reveal the rapid enrichment mechanisms with ternary mixed solvents.

Mechanism and kinetics of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin in a membrane microchannel reactor

The highly efficient selective aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin was achieved in a membrane microchannel reactor. The efficiency of benzyl alcohol oxidation was remarkably improved in the micro-structured chemical system, achieving a conversion and benzaldehyde selectivity of 82% and 98%, respectively, in 6.5 min. The classification and transfer of free radicals, as well as the oxygen-transfer mechanism, were determined by in situ EPR (electron paramagnetic resonance) and in situ UV–visible spectroscopy. Further kinetic studies revealed that the oxidation of benzyl alcohol follows the Michaelis–Menten kinetics, with Km = 0.133 mol/L.A mathematic kinetic model was proposed, and the kinetic model fitted the experimental data well. The mathematical model can predict the reaction process at a wide range of benzyl alcohol concentrations, which is beneficial for the process optimization and reactor design.

The distribution of 4‐hydroxy‐hexenal and 4‐hydroxy‐nonenal in different vegetable oils and their formation from fatty acid methyl esters

SummaryThe formation of 4‐hydroxy‐hexenal (HHE) and 4‐hydroxy‐nonenal (HNE) in eight vegetable oils was investigated at 180 °C. HHE was only detectable in soybean (SBO), rapeseed (RO) and linseed oils (LO). HNE was measured in all tested oils, but was found mainly in corn (CO), sunflower (SO) and soybean oil (SBO). Oil‐dependent formation of HHE/HNE was remarkably observed. Furthermore, different fatty acid methyl esters in tricaprylin, as model oil systems, were constructed to demonstrate their characteristic contribution to HHE/HNE formation. As expected, HHE and HNE originated from the oxidative degradation of methyl linolenate (MLN) and methyl linoleate (ML) respectively. Whereas low concentrations of MLN (&lt;5.0%) and ML (&lt;1.0%) produced no detectable HHE/HNE. The results suggested MLN/ML could induce both HHE/HNE formation and pro‐oxidation at higher concentrations. Unexpectedly, methyl stearate and methyl oleate slightly promoted HHE/HNE formation, which might be attributed to free radical transfer mechanisms during thermal oxidation.

Cracked Naphtha Reactivity: Effect of Free Radical Reactions

The problems faced when dealing with thermally cracked naphtha are vast, from gum formation in storage units to fouling and deactivation of catalysts. Our interest was to gain a better understanding of the initiation of cracked naphtha fouling. The thermal reactivity of cracked naphtha from an industrial bitumen upgrading facility was investigated. The naphtha was exposed to temperatures of 200, 250, and 300 °C for a period of 1 h. No free radicals were detected in the naphtha feed using electron spin resonance spectrometry, yet, after heating, evidence of free radical reactions was found. The influence of heating was investigated for both the naphtha on its own and the naphtha in combination with α-methylstyrene (AMS). AMS was employed as a probe molecule that facilitated detection of free radical transfer reactions. The potential contribution of oxygen as free radical initiator was also investigated by heating naphtha at different oxygen partial pressures. Heating of naphtha and AMS mixtures resulted in...

Chemical Functionalization of Graphene Oxide by Poly(styrene sulfonate) Using Atom Transfer Radical and Free Radical Polymerization: A Comparative Study

ABSTRACTPoly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH2) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31 wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1 nm (free radical polymerization method) and 6 nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.

Synergistic Interactions between Ti–OOH and (PO4[WO2(O2)]4)3- of HPW/Zn-Ti Hydrotalcites: Efficient Heterogeneous Catalysts for the Epoxidation of Fatty Acid Methyl Ester

A series of HPW/Zn-Ti layered double hydroxides (LDHs) were prepared by immobilizing phosphotungstic acid (HPW) on the Zn-Ti LDHs. Systematically characterizations were performed to elucidate their structure. These HPW/Zn-Ti LDHs hybrids were used as heterogeneous catalysts in the epoxidation of fatty acid methyl ester (FAMEs) with H2O2. The HPW/Zn-Ti LDHs showed higher activity than bulk HPW and Zn-Ti LDHs. The conversion of FAMEs and the selectivity to epoxy fatty acid methyl ester (EFAME) were up to 90.6 and 86.0%, respectively. (PO4[WO2(O2)]4)3- was presumed to be the active site for the epoxidation in this work. The formed oxygen-donating intermediate Ti-OOH transferred oxygen free radicals to (PO4[WO2(O2)]4)3- in the catalytic process, accelerating the transfer of oxygen free radicals. Therefore, high catalytic activity of HPW/Zn-Ti LDHs is related to the potential synergistic interactions of Ti-OOH and PW anions.

Photomediated Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride.

This review summarizes recent research on novel photochemical methods for the initiation and control of the polymerization of main chain fluorinated monomers as exemplified by vinylidene fluoride (VDF) and for the synthesis of their block copolymers. Such reactions can be carried out at ambient temperature in glass tubes using visible light. Novel, original protocols include the use of hypervalent iodide carboxylates alone or in conjunction with molecular iodine, as well as the use of photoactive transition metal carbonyls in the presence of alkyl, fluoroalkyl, and perfluoroalkyl halides. An in-depth study of the reaction parameters highlights the use of dimethyl carbonate as a preferred polymerization solvent and outlines the structure-property relationship for hypervalent iodide carboxylates and halide initiators in both the free radical and iodine degenerative transfer controlled radical polymerization (IDT-CRP) of VDF. Finally, the rational selection of metal carbonyls that are successful not only as IDT mediators but, more importantly, in the quantitative activation of both PVDF-CH2-CF2-I and PVDF-CF2-CH2-I chain ends toward the synthesis of well-defined PVDF block copolymers is presented.

Ethanol organosolv lignin as a reactive filler for acrylamide‐based hydrogels

ABSTRACTHydrogels based on acrylamide (AM) and ethanol organosolv lignin (EOL) with high swelling and good mechanically elastic properties were synthesized in an alkaline solution. EOL was used as a reactive filler for the preparation of AM‐based hydrogels. The impact of EOL addition on the physicochemical properties of AM‐based hydrogels was investigated using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy, and their mechanical properties were examined. The water swelling ratio of the prepared hydrogels increased with the increase of EOL content, and their maximum swelling ratio could reach up to 180. Mechanical measurements indicated that their tensile strength was highly dependent on the amount of EOL, and their elongation at break reached up to 1400%. The formation mechanism of EOL composite hydrogels was probably that most of AM was synthesized into the crosslinked poly(acrylic amide) network, and small quantities of AM was hydrolyzed to acrylic acid ions under alkaline condition. The chain transfer of free radicals from AM and/or AA to EOL molecules occurred in the polymerization process. With increasing EOL content in the hydrogels, an interpenetrating polymer network might be mainly formed by the hydrogen bonding between EOL and AA and/or AM molecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42638.

Stackable, Covalently Fused Gels: Repair and Composite Formation

Combining modeling and experiment, we created multilayered gels where each layer was “stacked” on top of the other and covalently interconnected to form mechanically robust materials, which could integrate the properties of the individual layers. In this process, a solution of new initiator, monomer, and cross-linkers was introduced on top of the first gel, and these new components then underwent living (co)polymerization to form the subsequent layer. We simulated this process using dissipative particle dynamics (DPD) to isolate factors that affect the formation and binding of chemically identical gel as well as incompatible layers. Analysis indicates that the covalent bond formation between the different layers is primarily due to reactive chain-ends, rather than residual cross-linkers. In the complementary experiments, we synthesized multilayered gels using either free radical (FRP) or atom transfer radical polymerizations (ATRP) methods. Polymerization results demonstrated that chemically identical mat...

Electron transfer-initiated epoxidation and isomerization chain reactions of β-caryophyllene.

The abundant sesquiterpene β-caryophyllene can be epoxidized by molecular oxygen in the absence of any catalyst. In polar aprotic solvents, the reaction proceeds smoothly with epoxide selectivities exceeding 70 %. A mechanistic study has been performed and the possible involvement of free radical, spin inversion, and electron transfer mechanisms is evaluated using experimental and computational methods. The experimental data-including a detailed reaction product analysis, studies on reaction parameters, solvent effects, additives and an electrochemical investigation-all support that the spontaneous epoxidation of β-caryophyllene constitutes a rare case of unsensitized electron transfer from an olefin to triplet oxygen under mild conditions (80 °C, 1 bar O2 ). As initiation of the oxygenation reaction, the formation of a caryophyllene-derived radical cation via electron transfer is proposed. This radical cation reacts with triplet oxygen to a dioxetane via a chain mechanism with chain lengths exceeding 100 under optimized conditions. The dioxetane then acts as an in situ-formed epoxidizing agent. Under nitrogen atmosphere, the presence of a one-electron acceptor leads to the selective isomerization of β-caryophyllene to isocaryophyllene. Observations indicate that this isomerization reaction is a novel and elegant synthetic pathway to isocaryophyllene.

Effect of Functionalized Graphene Oxide with Hyper-Branched Flame Retardant on Flammability and Thermal Stability of Cross-Linked Polyethylene

In this work, GO was functionalized by a hyper-branched flame retardant, which was synthesized by the reaction of N-aminoethyl piperazine and di(acryloyloxyethyl)methylphosphonate. Subsequently, the resultant functionalized GO (FGO) was incorporated into the cross-linked polyethylene (XLPE) to enhance the flame retardancy of the matrix. Transmission electron spectroscopy images indicated that FGO exhibited uniform dispersion in XLPE matrix and strong adhesion with the matrix by cross-linking, which improved barrier effect due to reduced heat release and the free radical transfer between the matrix and graphene nanosheets. The incorporation of FGO into XLPE matrix endowed polymer composites with flame retardancy and thermal stability. In addition, the homogeneous dispersion of functionalized GO with a hyper-branched flame retardant in the polymer matrix improved the antioxidation and mechanical properties of XLPE–FGO nanocomposites compared to the XLPE–GO samples, as demonstrated through the oxidative induction temperature and time test, oven aging test and mechanical test.

Modification of cellulose by graft polymerization for use in drug delivery systems

Cellulose-based biodegradable polymers—as microspheres or hydrogels—are suitable for drug delivery systems. In this work, cellulose microfibers were converted to cellulose esters for subsequent graft copolymerization either by free radical or atom transfer radical polymerization (ATRP). For the former, carboxymethyl cellulose (CMC) was prepared and then modified through grafting of poly(hydroxyethyl acrylate) or polyacrylamide. ATRP was achieved by chloroacetylation of cellulose followed by graft copolymerization of hydroxyethyl acrylate or acrylamide monomers. The degree of substitution for CMC and chloroacetylated cellulose (CAC) was determined by the method described in US Pharmacopeia NF24 and by titration method, respectively. CMC, CAC, and the grafted copolymers were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, and atomic force microscopy; the latter technique clearly shows the chain growth of the synthetic polymers on the backbone surface. Furthermore, cephalexin antibiotic was loaded on the copolymers, and the resultant in vitro drug release studied in three different media (buffer solutions with pH equal to 3, 6.1, and 8).

Synthesis, post-modification and characterization of linear polystyrene-based supports for interaction with immobilized biocatalysts

A series of linear polystyrene-based supports has been synthesized using conventional or controlled (reversible addition fragmentation chain transfer or nitroxide-mediated) free radical polymerizations, in order to modulate their molecular weight characteristics. Polymer post-modification via esterification of the primary hydroxyl alcohol functionalities, pendant from the polymer backbone, with a mandelic acid derivative introduces efficiently (>85% yield) racemic, enzyme-cleavable moieties. A study of the interactions of these polymeric substrates with immobilized penicillin G acylase, in mixed organic/aqueous buffer solvent systems, results in a modest enantioselectivity (comparable with that of racemic mandelic acid methyl ester), but reveals that the biocatalytically active moieties on the linear polymers can be cleaved with first-order rate kinetics, as observed with small molecules in solution; the reaction rates (which can differ by more than one order of magnitude) are influenced both by the synthetic polymer length and by the polymer structure resulting from the method of polymerization used. Copyright © 2012 Society of Chemical Industry