Biomimetic Synthesis of Water Soluble Conductive Polypyrrole and Poly(3,4‐Ethylenedioxythiophene)

Abstract

A novel biomimetic method for the synthesis of conducting molecular complexes of polypyrrole (PPYR) and poly(3,4‐ethylenedioxythiophene) (PEDOT) in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG‐Hematin) was used to catalyze the polymerization of pyrrole (PYR) and 3,4‐ethylenedioxythiophene (EDOT) in the presence of SPS to form PPYR/SPS and PEDOT/SPS complexes. UV‐VIS, FT‐IR, and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of SPS in this complex provides a unique combination of properties such as processability and water‐solubility.     

Peroxidase-catalyzed polymerization and depolymerization of coal in organic solvents

Peroxidases from horseradish roots (HRP) and soybean hulls (SBP) catalyze the efficient polymerization of a 4-kDa dimethylformamide (DMF)-soluble fraction of Mequininza (Spanish) lignite in 50% (v/v) DMF with an aqueous component consisting of acetate buffer, pH 5.0. Under these conditions, HRP and SBP catalyze the oxidation of free phenolic moieties in the coal matrix, thereby leading to oxidative polymerization of the low-molecular-weight coal polymers. The high fraction of nonphenolic aromatic moieties in coal inspired us to examine conditions whereby such coal components could also become oxidized. Oxidation of nonphenolic aromatic compounds was attempted using veratryl alcohol as a model substrate. SBP catalyzed the facile oxidation of veratryl alcohol at pH <3.HRP, however, was unable to elicit veratryl alcohol oxidation. The potential for SBP to catalyze interunit bond cleavage on complex polymeric substrates was examined using l-(3,4-dimethoxyphenyl)-2-(phenoxy)propan-1,3-diol (1) as a substrate. SBP catalyzed the Cα-Cβ and β-ether bond cleavage of this compound, suggesting that similar reactions on coal, itself, could lead to depolymerization. Depolymerization of a >50 Da coal fraction was achieved using SBP in 50% (v/v) DMF with an aqueous component adjusted to pH 2.2. Approximately 15% of the initial high-molecular-weight lignite fraction was depolymerized to polymers 4 Da in size. Hence, SBP is capable of catalyzing the depolymerization of coal in organic solvents, and this may have important ramifications in the generation of liquid fuels from coals.     

A New Approach to Catalyze Template Polymerization of Aniline Using Electrostatically Multilayered Hematin Assemblies

Abstract

In this work, we describe a new approach to catalyze the template polymerization of conducting polyaniline (Pani). Electrostatic layer‐by‐layer (ELBL) self‐assembly of a polyelectrolyte and a biomimetic catalyst, hematin has been utilized to construct a nanocomposite film catalyst. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV‐VIS‐NIR spectroscopy showed that a conductive form Pani was formed, not only as a coating on the surface of the ELBL composites, but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing pH and hematin concentration. It is believed that hematin sandwiched between positively charged polyelectrolytes in the composite films was slowly released into the solutions and then used to catalyze the template polymerization of aniline with SPS, resulting in a water soluble form of Pani. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize surfaces with conductive Pani and a potential method of reusability of the catalyst for improved cost effectiveness.     

The effect of pH on emulsion polymerization of styrene in the presence of an amphoteric emulsifier

An emulsion polymerization of styrene in the presence of an amphoteric emulsifier of the betaine type; N,N-dimethyl-n-laurylbetaine (LNB), has been studied at various pH values. The relationships between the physicochemical properties of LNB aqueous solutions, the emulsion polymerization process and the characteristics of the synthesized latex particles were studied under various pH conditions. The polymerization rate and the particle number concentration decreased with increasing pH of LNB aqueous solution and changed in shape at both ca. pH 4 and pH 8–10. The properties of LNB aqueous solution also changed with the pH and changed in shape at the same pH as that of the emulsion polymerization. These pH values were in good agreement with the pH at which the LNB molecule changed its ionic form. The number of synthesized latex particles was proportional to the number of LNB micelles in the solution, below pH 10. The particle size of the synthesized latex particles and the molecular weight of the latex polymers also changed with the properties of LNB aqueous solutions, accompanying the change of the ionic form of LNB molecules.     

PEROXIDASE,HEMATIN, AND PEGYLATED-HEMATIN CATALYZED VINYL POLYMERIZATIONS IN WATER

Horseradish peroxidase-, hematin- and pegylated-hematin mediated polymerization of sodium styrene sulfonate and sodium acrylate in water is reported. Molecular weight and yields were influenced by the concentrations of hydrogen peroxide and initiator, 2,4-pentanedione. Hematin and pegylated-hematin were studied in lieu of peroxidase at pH 11.0 and 7.0 in aqueous solution, respectively. Polymer with a high molecular weight (Mn = 223,520) was formed when the pegylated-hematin was used as the catalyst. The results demonstrate vinyl polymerizations in an all aqueous process in high yield and molecular weight catalyzed by peroxidase as well as biomimetic catalysts.     

Performance of a Flow-Through Enzyme Reactor Prepared from a Silica Monolith and an α-Poly(D-Lysine)-Enzyme Conjugate

Horseradish peroxidase (HRP) is covalently bound in aqueous solution to polycationic α-poly(D-lysine) chains of ≈1000 repeating units length, PDL, via a bis-aryl hydrazone bond (BAH). Under the experimental conditions used, about 15 HRP molecules are bound along the PDL chain. The purified PDL-BAH-HRP conjugate is very stable when stored at micromolar HRP concentration in a pH 7.2 phosphate buffer solution at 4 °C. When a defined volume of such a conjugate solution of desired HRP concentration (i.e., HRP activity) is added to a macro- and mesoporous silica monolith with pore sizes of 20–30 µm as well as below 30 nm, quantitative and stable noncovalent conjugate immobilization is achieved. The HRP-containing monolith can be used as flow-through enzyme reactor for bioanalytical applications at neutral or slightly alkaline pH, as demonstrated for the determination of hydrogen peroxide in diluted honey. The conjugate can be detached from the monolith by simple enzyme reactor washing with an aqueous solution of pH 5.0, enabling reloading with fresh conjugate solution at pH 7.2. Compared to previously investigated polycationic dendronized polymer-enzyme conjugates with approximately the same average polymer chain length, the PDL-BAH-HRP conjugate appears to be equally suitable for HRP immobilization on silica surfaces.     

Radiation synthesis of a water-soluble temperature sensitive polymer, activated copolymer and applications in immobilization of proteins

In this work the radiation polymerization of N-isopropylacrylamide (NIPAAM) in aqueous solutions has been carried out and a water-soluble, temperature sensitive polymer and copolymer were obtained by using γ-rays from Co-60 source at room temperature. We have gained the optimum dose and dose—rate of radiation synthesis of linear polyNIPAAM through determining conversion yield and viscosity. In order to immobilize protein (BSA) and enzyme (HRP) into this water-soluble polymer, we prepared an activated copolymer, poly ( N-isopropylacrylamide-co-N-acryloxysuccinimide). The BSA and HRP has been immobilized onto the activated copolymer. The BSA (HRP) / copolymer conjugates still kept the original thermally sensitive properties of the linear polyNIPAAM. The conjugation yield of BSA to the activated copolymer decreased with increasing of dose. The thermal stability of the immobilized HRP was stable at 0 °C for a long time and has, at least, 4 days stability at room temperature. Immobilized HRP activity was lowered when the temperature was raised above its LCST. This phenomenon was reversible and the immobilized HRP regained activity below its LCST. The optimum pH of the immobilized HRP shifted from ca.5 upward to ca.7.     

铜镍双金属催化剂上糠醛水相选择性偶联加氢-重排制环戊酮

生物质资源高效催化转化制备高附加值化学品具有重要的科学意义与工业应用潜力.生物质基糠醛催化加氢-重排制备环戊酮是一条具有吸引力的"非石油"制备路线,但该过程面临副产物多、环戊酮选择性难以提高等难题,除糠醛外,中间物种也很容易发生多种聚合副反应.因此,探索中间物种聚合副反应的条件和作用机制,是提高目标产物环戊酮的选择性和收率的关键.本文制备了CuNi/Al-MCM-41双金属纳米过渡金属催化剂,通过精确调控介质水的pH值和原料浓度,实现了糠醛加氢-重排耦合制备环戊酮的高选择性和高收率.在2.0 MPa H2,160oC和近中性条件下反应5 h,糠醛的转化率为99.0％,环戊酮的选择性达到97.7％;其催化性能远远高于单组份铜或镍催化剂以及其它分子筛载体(MCM-41,SBA-15,HY,ZSM-5)负载的CuNi双金属催化剂.研究结果表明,高度分散在MCM-41上的少量Al组分,有利于Cu,Ni金属组分相互均匀分散.XPS结果表明,双金属催化剂CuNi/Al-MCM-41中Cu和Ni具有明显的电子结合能偏移,表明Ni向Cu转移电子;耦合催化反应性能的提高可能与CuNi双金属协同作用及电荷转移效应有关.傅立叶变换红外光谱和质谱结果表明,聚合副反应对反应体系的pH值敏感.在酸性条件下,中间产物糠醇在反应体系中容易发生聚合,导致糠醇重排生成3-羟基环戊烯酮的选择性降低;在碱性条件下,3-羟基环戊烯酮转化为4-羟基-环戊-2-烯酮后,容易进一步发生聚合副反应.在近中性条件下可有效避免中间体的聚合,提高加氢重排生成环戊酮的选择性.此外,降低原料糠醛的初始浓度,有利于降低聚合等副反应,能够进一步提高目标产物环戊酮的收率.本文为研制双金属纳米过渡金属催化剂以及利用双金属协同作用等方面提供新的启示,为解决生物质原料转化过程中普遍存在的聚合副反应和碳平衡降低等问题提供了新思路.     

Enzymatically Synthesized Conducting Polyaniline Nanocomposites: A Solid‐State NMR Study

Abstract

The chiral conducting polyaniline (PANI) nanocomposites [polyacrylic acid/polyaniline/(?) camphorsulphonic acid (CSA)] were synthesized using enzyme, horseradish peroxidase (HRP) in the aqueous buffer solution at pH 4.3. It appears that the enzyme HRP apart being a biocatalyst, plays an important role during the polymerization, which allows PANI to prefer a specific helical conformation whether the induced chirality in the monomer‐CSA complex is either by (+)CSA or (?)CSA. In this paper, we report, the structural characterization of these nanocomposites by solid‐state ¹³C cross‐polarization with magic angle spinning (CP/MAS) NMR techniques. The structural features of PANI in the conducting form of nanocomposite (as‐synthesized) are similar to that of enzymatically and chemically synthesized PANI. Preliminary data also suggest that some portion of nanocomposite samples are not completely doped. Dedoping of as‐synthesized PANI nanocomposite with aqueous NH₄OH shows the spectral features that of the emeraldine base form. Solid‐state ¹³C NMR data suggest that it is possible to detach PAA and CSA from PANI in the nanocomposite material.     

Design of a poly(L‐histidine)‐carbohydrate conjugate for a new pH‐sensitive drug carrier

A poly(L ‐histidine) (PLH)‐carbohydrate conjugate has been synthesized as a new macromolecule extracting pH‐dependent properties of PLH with imidazole groups. Because of poor water solubility at physiological pH, the application of PLH with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the PLH modified with aliphatic primary amino groups suddenly precipitated out of the aqueous medium above pH 6.0 as a result of the deprotonation of the imidazole groups, the water solubility of PLH was improved at physiological pH by the conjugation of the aminated PLH with hydrophilic maltopentaose. The resulting PLH‐maltopentaose conjugates and metalloporphyrins formed the complexes which varied their assembling structure below pH 6.0. The PLH‐maltopentaose would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal pH. Copyright © 2004 John Wiley & Sons, Ltd.     

Ionic-liquid supported oxidation reactions in a silicon-based microreactor

The combination of microfabrication and reaction engineering techniques has the potential to produce powerful microreactors. In a microreactor, aqueous buffers provide high electroosmatic mobility and no external pumping is required. While numerous reactions have been demonstrated to be highly efficient in microreactors, so far there has been no report on the epoxidation of cyclohexene in a microreactor. This is mainly due to the reduced solubility of cyclohexene in aqueous media. The greater volatility of cyclohexene leading to long reaction times is another reason. To improve the solubility of cyclohexene in the reaction buffer, a water soluble ionic-liquid 1-butyl-3-methylimidazolium tetrafluoroborate was used, also for the first time in microreactor work. In this letter, four different catalysts (i.e., manganese(II) and copper(II) complexes of Schiff and reduced Schiff bases) were synthesized and used for the oxidation reactions considered. The reactions were monitored by gas chromatography/mass spectrometry. The microreactor performance was evaluated by comparing with a conventional (batch scale) reaction. Catalytic activities and yields were found to be relatively high for the copper(II) complexes as compared with the conventional route.     

Synthesis and Properties of Self‐doped Polyaniline with Polycationic Templates via Biocatalysis

The enzyme horseradish peroxidase (HRP) was used to polymerize acid‐functionalized anilines to make self‐doped polymer in the presence of a polycationic template. Anionic templates such as sulfonated polystyrene (SPS) could not function as a suitable template for the polymerization of acid‐functionalized aniline derivatives. Several types of polyelectrolytes were used as templates to observe the structural effects and doping behavior of polyaniline/template complexes. The synthesis is straightforward and the conditions are mild in that the polymerization of conducting polyanilines may be carried out in buffered solutions as high as pH 6, with a stoichiometric amount of hydrogen peroxide and catalytic amount of enzyme. The conductivity of these enzymatically synthesized self‐doped polymers was relatively high without additional doping due to the self‐doping of the acid moieties. The conductivity did not decrease dramatically at pH 3 as is the usual case of unsubstituted HCl‐doped polyaniline and maintained good conductivity even at pH 6. The measured conductivity at pH 4～pH 6 is around 10^?4 S/cm to 10^?6 S/cm.     

Enzymatic polymerization of phenol catalyzed by horseradish peroxidase in aqueous micelle system

Enzymatic polymerization of phenol catalyzed by horseradish peroxidase (HRP) has been carried out in aqueous micelle system using sodium dodecyl benzene sulfonate (SDBS) as a surfactant. The addition of SDBS to buffer greatly enhances the polymer yield. With a usage of SDBS over 0.4 g for 5 mmol of phenol monomer, the polymer could be obtained almost quantitatively. The number-molecular weight of the THF-soluble part determined by GPC is increased from 1100 to 2000 with increasing the dosage of SDBS. The phenol polymerization maintains high yields in aqueous micelle system over a wide pH range from 4 to 10. The activity of enzyme in buffer is so high that the phenol polymerization in aqueous micelle system could be completed only in 2 h with high yield. The resulting polymer is a kind of powdery material, which is partly soluble in DMF, DMSO and THF. IR analysis showed that the polymer structure contained a mixture of phenylene and oxyphenylene units. From TG analysis, the polymer was found to possess high thermal stability.     

Enzyme‐Initiated Free‐Radical Polymerization of Molecularly Imprinted Polymer Nanogels on a Solid Phase with an Immobilized Radical Source

An enzyme‐mediated synthetic approach is described for the preparation of molecularly imprinted polymer nanoparticles (MIP‐NPs) in aqueous media. Horseradish peroxidase (HRP) was used to initiate the polymerization of methacrylate or vinyl monomers and cross‐linkers by catalyzing the generation of free radicals. To prevent entrapment of the enzyme in the cross‐linked polymer, and to enable it to be reused, HRP was immobilized on a solid support. MIPs based on 4‐vinylpyridine and 1,4‐bis(acryloyl)piperazine for the recognition of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and salicylic acid were synthesized in an aqueous medium. MIPs for the protein trypsin were also synthesized. MIP nanoparticles with sizes between 50 and 300 nm were obtained with good binding properties, a good imprinting effect, and high selectivity for the target molecule. The reusability of immobilized HRP for MIP synthesis was shown for several batches.     

聚(甲基丙烯酸N,N-二甲氨基乙酯)的温度和pH敏感性及其对乳液稳定性的影响

甲基丙烯酸N,N-二甲氨基乙酯的均聚物(PDMAEMA)在水中的溶解性具有温敏性,即低温溶解、高温不溶,而且其低临界溶液温度(LCST)与pH密切相关.本文重点考察了PDMAEMA水溶液在不同温度、pH值、溶液离子强度时的相转变特性,并研究了水溶液中乳化剂对PDMAEMA的疏水相互作用和增溶稳定作用.将PDMAEMA的温敏相转变行为同有关乳液的稳定性相关联,揭示了改善乳液稳定性的内在机制.     

Well-Defined Poly(butyl cyanoacrylate) Nanoparticles via Miniemulsion Polymerization

Summary: Despite the high reactivity of the monomer, nanoparticles with a hydrophobic core based on poly(butyl cyanoacrylate) and a hydrophilic shell based on poly(ethylene oxide) PEO were synthesized in one step by miniemulsion polymerization. Colloidal properties of the nanoparticles were controlled by the structure and the amount of amphiphilic polymer in the aqueous phase, while the molecular weight of core depended on pH of the continuous phase and the polymerization mechanism (anionic or radical). The evolution of the molecular weight of the synthesized poly(butyl cyanoacrylate) was followed as a function of time at pH 7.4 by size exclusion chromatography. As expected, the degradation kinetics depended on the polymerization mechanism. Finally, a model compound, pyrene, was encapsulated in the synthesized nanoparticles. Its release was found to depend on the conditions of nanoparticles synthesis, especially on the polymerization mechanism.     

The Effect of pH on Emulsion Polymerization of Styrene in the Presence of an Amphoteric Emulsifier

The emulsion polymerization of styrene in the presence of an amphoteric emulsifier of the amino acid type, N-lauroyl-1-N, N-dimethyllysine (DMLL), has been studied at various pH values. The polymerization rate and the particle number concentration increased with increasing pH of the aqueous DMLL solution and these curves changed in slope at approximately pH 4 and pH 9. The physicochemical properties of the aqueous DMLL solution, such as CMC and the aggregation number, changed with the pH and similarly changed in slope at almost the same pH as the emulsion polymerization. These pH values were in good agreement with the pH at which the ionic form of the DMLL molecule changes. The number of latex particles formed changed in proportion to the number of DMLL micelles in the solution. The particle size and the molecular weight of the synthesized latex particles were also dependent on the physicochemical solution properties accompanying the change in the ionic forms of DMLL.     

The cupric sulfate–hydrazine system as an initiator of vinyl polymerization. I. The polymerization of methyl methacrylate in aqueous solution in the presence of oxygen

The cupric sulfate–hydrazine system has been used to initiate the aqueous solution polymerization of methyl methacrylate at pH 9.25 in the presence of oxygen. At cupric sulfate concentrations greater than the saturation solubility of cupric hydroxide, hydrazine is adsorbed on, and decomposes on, the surface of the hydroxide. The kinetics of the decomposition are zero-order both in the absence and the presence of monomer. The initiation of the polymerization occurs both at the surface of the cupric hydroxide on to which some monomer is adsorbed and also in solution. Below the saturation solubility of cupric hydroxide, the initiation reaction between cupric ions and hydrazine occurs in solution.     

Carboxymethyl poly(L‐histidine) as a new pH‐sensitive polypeptide at endosomal/lysosomal pH

A carboxymethyl poly(L ‐histidine) has been synthesized as a new pH‐sensitive polypeptide at endosomal/lysosomal pH. Because of its poor water solubility at physiological pH, an application of poly(L ‐histidine) with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the unmodified poly(L ‐histidine) suddenly precipitates out of the aqueous medium above pH 6.0 as the result of the deprotonation of the imidazole groups, the water solubility of the resulting carboxymethyl poly(L ‐histidine) has been improved at physiological pH. A solution turbidity measurement proved that no significant effect on a rapid aggregate formation or phase separation of serum proteins is induced by carboxymethyl poly(L ‐histidine). Hemolysis assay showed that the carboxymethyl poly(L ‐histidine) enhances membrane disruptive ability at endosomal/lysosomal pH. The cellular uptake of luciferase in the presence of the carboxymethyl poly(L ‐histidine) increases intracellular luciferase activity, which suggests that the carboxymethyl poly(L ‐histidine) makes the luciferase escape from lysosomal degradation. The carboxymethyl poly(L ‐histidine) would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal/lysosomal pH. Copyright © 2007 John Wiley & Sons, Ltd.