Synthesis of graft copolymers by ring-opening polymerization of 2-nonyl-and 2-phenyl-2-oxazoline initiated by macroinitiators containing benzylchloride functions

Graft copolymers with poly(2-nonyl-2-oxazoline) and poly(2-phenyl-2-oxazoline) graft arms have been synthesized using the "grafting from" method. Slightly branched statistical copolymers of isobutene and (m,p)-chloromethylstyrene, synthesized cationically, as well as linear homo-poly((m,p)-chloromethylstyrene) have been used as macroinitiators for the ring-opening polymerization of the substituted oxazolines. The graft copolymerizations were carried out in bulk and in benzonitrile solutions with and without addition of potassium iodide. The influence of the reaction conditions on the rate of polymerization and the different reactivities of 2-nonyl-2-oxazoline and 2-phenyl-2-oxazoline were discussed. Received: 26 February 1997/Revised: 26 March 1997/Accepted: 14 April 1997     

Development of a new azido-oxazoline monomer for the preparation of amphiphilic graft copolymers by combination of cationic ring-opening polymerization and click chemistry

A new monomer (2-(5-azidopentyl)-2-oxazoline) bearing an azido group was synthesized. The cationic ring-opening copolymerization of this monomer with 2-methyl-2-oxazoline resulted in a well-defined linear polymer backbone with pendant azido groups. Alkynyl-poly(d,l-lactide) was grafted onto the azido groups of poly(oxazoline) via a Huisgen 1,3-dipolar cycloaddition reaction to give a novel amphiphilic graft copolymer [poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline)-g-poly(d,l-lactide)] (P[(MeOx-co-PentOx)-g-LA]). Different graft copolymers were prepared with PLA of different lengths. Preliminary results of the self-association of this copolymer in water indicated the formation of nanoparticles, which suggests this copolymer may have applications as vehicles for drug delivery.     

Temperature responsive bio-compatible polymers based on poly(ethylene oxide) and poly(2-oxazoline)s

This review covers the LCST behavior of two important polymer classes in aqueous solution, namely poly(2-oxazoline)s and systems whose thermo-responsiveness is based on their structural similarity to poly(ethylene oxide) (PEO). In order to elucidate the progress that has been made in the design of new thermo-responsive copolymers, experimental data that were obtained by different research groups are compared in detail. Copolymerization with hydrophilic or hydrophobic comonomers represents a suitable method to tune the coil to globule transition temperature of several homopolymers, and incorporation of other monomers provided further interesting features, such as pH responsiveness or sensing properties. In addition, living and controlled polymerization techniques enabled access to defined end groups and more advanced polymer architectures, such as graft copolymers or double responsive block copolymers. The effect of such structural variations on the temperature responsive behavior of the (co)polymers is discussed in detail.     

Amphiphilic segmented polymer networks based on poly(2-alkyl-2-oxazoline) and poly(methyl methacrylate)

Amphiphilic segmented polymer networks (SPNs) have been prepared by free radical copolymerization of methyl methacrylate with α,ω-bisacrylate terminated poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline). DSC and DMTA analysis demonstrated the influence of the copolymer composition, the molecular weight and nature of the poly(2-alkyl-2-oxazoline)s and the polymerization conditions on the final phase morphology of the networks. A comparative phase morphology study of the polymer blends and SPNs revealed the more compatible phase morphology of the networks. The compatibility could be further increased by UV-induced network formation. The investigation of the solvent uptake in different solvents clearly demonstrated the amphiphilic nature of the SPNs.     

Synthesis and properties of poly(vinyl chloride-g-2-methyl-2-oxazoline)

Summary Poly(vinyl chloride-g-2-methyl-2-oxazoline) copolymers were prepared by grafting from the allyl chloride sites of PVC with KI or AgOSO₃CF₃ as coinitiators. Use of AgOSO₃CF₃ led to higher grafting efficiencies and higher contents of poly(2-methyl-2-oxazoline) in the graft copolymers. DTA analyses of the P(VC-g-Me-Oxz) identified the thermal transitions of this copolymer; TGA analyses showed that the graft copolymers were less thermally stable than the constituent homopolymers. Unlike blends of P(Me-Oxz) and PVC, the graft copolymers could be molded easily; the graft materials exhibited greater flexural moduli but lower HDT's than PVC.     

Thermoresponsive Molecular Brushes with a Rigid-Chain Aromatic Polyester Backbone and Poly-2-alkyl-2-oxazoline Side Chains

A new polycondensation aromatic rigid-chain polyester macroinitiator was synthesized and used to graft linear poly-2-ethyl-2-oxazoline as well as poly-2-isopropyl-2-oxazoline by cationic polymerization. The prepared copolymers and the macroinitiator were characterized by NMR, GPC, AFM, turbidimetry, static, and dynamic light scattering. The molar masses of the polyester main chain and the grafted copolymers with poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline side chains were 26,500, 208,000, and 67,900, respectively. The molar masses of the side chains of poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline and their grafting densities were 7400 and 3400 and 0.53 and 0.27, respectively. In chloroform, the copolymers conformation can be considered as a cylinder wormlike chain, the diameter of which depends on the side chain length. In water at low temperatures, the macromolecules of the poly-2-ethyl-2-oxazoline copolymer assume a wormlike conformation because their backbones are well shielded by side chains, whereas the copolymer with short side chains and low grafting density strongly aggregates, which was visualized by AFM. The phase separation temperatures of the copolymers were lower than those of linear analogs of the side chains and decreased with the concentration for both samples. The LCST were estimated to be around 45 °C for the poly-2-ethyl-2-oxazoline graft copolymer, and below 20 °C for the poly-2-isopropyl-2-oxazoline graft copolymer.     

NMF effect on photosensitized charge separation using partially quaternized poly(1-vinylimidazole)-bound ruthenium(II) complexes

The solvent effects on the photosensitized charge separation using partially quaternized poly(1-vinylimidazole)-bound ruthenium(II) complexes (RuQPIm), in which bis(2,2′-bipyridine)ruthenium(II) complexes are coordinated to the imidazolyl residues on the poly(1-vinylimidazole) partially quaternized by 1-bromohexadecane and the degree of quaternization is 19 (RuQPIm-19) and 44 (RuQPIm-44) molar percentage, have been investigated in methanol and methanol–NMF (NMF: N-methylformamide). These systems consist of RuQPIm-19 and RuQPIm-44 as photosensitizers, 1,1′-dimethyl-4,4′-bipyridinium dication (MV²⁺) and 1,1′-didodecyl-4,4′-bipyridinium dication (C₁₂V²⁺) as electron acceptors, and triethanolamine (TEOA) as a sacrificial donor. The addition of NMF mainly affect the forward and back reactions in the charge separation reactions. In RuQPIm-19 systems, the reaction proceeds through an interactive process, which is through the viologen having π–π interaction for MV²⁺ and van der Waals interaction for C₁₂V²⁺. In contrast, the reaction proceeds through a direct process by MV²⁺ having no interaction and through an interactive process by C₁₂V²⁺ undergoing van der Waals interaction with the polymer for RuQPIm-44 systems. For MV²⁺, the rates of MV^·+ formation increased, although the quenching efficiency decreased with increasing NMF content for RuQPIm-19 and RuQPIm-44. These results are attributed to stabilization of MV^·+ species by π–π interaction for RuQPIm-19 and steric repulsion between MV^·+ species and RuQPIm-44; namely, the restriction of the back reactions by these effects. In contrast, for C₁₂V²⁺, the rates of C₁₂V^·+ formation decreased and the quenching efficiency increased with the addition of NMF. These are attributed to that the addition of NMF increases the van der Waals interaction of the C₁₂V²⁺ with these polymers and the diffusion of the C₁₂V^·+ species into the bulk solution; namely, the back reaction is accelerated. Furthermore, it is suggested that the conformational changes in these polymers contribute to the charge separation reaction.     

聚(丙烯酸-共聚-苯并-18-冠醚-6-丙烯酰胺)的铯离子响应特性及其铯离子检测性能

制备了一种聚(丙烯酸-共聚-苯并-18-冠醚-6-丙烯酰胺)（PAB）线形共聚物,并系统研究了不同丙烯酸含量的PAB线形共聚物对铯离子的响应特性及其用于铯离子浓度检测的性能。结果表明,在不同浓度的铯离子溶液中,PAB线形共聚物的低临界溶解温度（LCST）会随着铯离子浓度增加向低温迁移;在实验范围内,当PAB线形共聚物中的丙烯酸质量分数为30%时,其铯离子响应特性最有利于水溶液中铯离子浓度的检测。通过系统实验研究,确立了PAB共聚物的LCST与水溶液中铯离子浓度的关系函数;利用该关系函数,可简单地通过测定未知铯离子浓度的PAB溶液LCST,即可推断出该溶液中的铯离子浓度。该研究为铯离子的便捷检测提供了新手段。     

Modification of polysilanes: Preparation of comb-like graft copolymers

Poly(methylphenylsilylene) has been functionalized by protodearylation with trifluoromethanesulfonic acid. Comb-like graft copolymers have been prepared by polymerizing tetrahydrofuran. 2-methyl-2-oxazoline, and isobutylvinyl ether from a partially triflated poly(methylphenylsilylene) backbone. Model studies using trimethylsilyl trifluoromethanesulfonate to initiate the cationic polymerization of these organic monomers indicated that a promoter was required to achieve more efficient initiation.     

Catalytic wet oxidation of p-coumaric acid: Partial oxidation intermediates, reaction pathways and catalyst leaching

The catalytic oxidation of p-coumaric acid, a compound representative of the polyphenolic fraction typically found in olive processing and wine-distillery wastewaters, has been investigated using various homogeneous and heterogeneous catalysts. Experiments have been performed with homogeneous Fe²⁺, Cu²⁺, Zn²⁺ and Co²⁺ ions at pH = 1, and with metal oxide catalysts in suspension at pH 3.5, 7 and 12. Additional uncatalyzed experiments have been performed and the results are compared to those of the catalyzed runs. The temperature was 403 K and the oxygen partial pressure was 2.8 MPa in all runs. The distribution of the reaction intermediates was determined, using HPLC and GCMS as the main analytical techniques, and reaction pathways are speculated. It was found that the use of catalysts could increase the rate of destruction of p-coumaric acid compared to the uncatalyzed reaction, while the distribution of the intermediate compounds was strongly dependent on the pH of the solution. A CuO·ZnOAl₂O₃ heterogeneous catalyst was found to be effective for the oxidation of p-coumaric acid although leaching of dissolved metals to the solution was found to occur. The stability of the heterogeneous catalysts was investigated by measuring the extent of metal leaching into the solution. The results are discussed with respect to the impact of various conditions (catalyst, pH) on the oxidation of p-coumaric acid and compared to those of the uncatalyzed reaction, studied in previous work.     

Peptide-Mimicking Poly(2-oxazoline)s Displaying Potent Antimicrobial Properties

Poly(2-oxazoline)s have excellent biocompatibility and have been used as FDA-approved indirect food additives. The inert property of the hydrophilic poly(2-oxazoline)s suggests them as promising substitutes for poly(ethylene glycol) (PEG) in various applications such as anti-biofouling agents. It was recently reported that poly(2-oxazoline)s themselves have antimicrobial properties as synthetic mimics of host defense peptides. These studies revealed the bioactive properties of poly(2-oxazoline)s as a new class of functional peptide mimics, by mimicking host defense peptides to display potent and selective antimicrobial activities against methicillin-resistant Staphylococcus aureus both in vitro and in vivo, without concerns about antimicrobial resistance. The high structural diversity, facile synthesis, and potent and tunable antimicrobial properties underscore the great potential of poly(2-oxazoline)s as a class of novel antimicrobial agents in dealing with drug-resistant microbial infections and antimicrobial resistance.     

Thermal degradation of copolymers based on 2-substituted oxazolines and β-methylhydrogenitaconate

Summary The thermal stabilities of poly(-methylhydrogenitaconate-co-2-methyl-2-oxazoline) and poly(-methylhydrogenitaconate-co-2-ethyl-2-oxazoline) obtained by spontaneous copolymerization have been studied by programmed thermogravimetric analysis over the temperature range from 293 K to 773 K under a flow of nitrogen. Most of the copolymers do not show weight loss until 473 K and they degrade in one step. The kinetic parameters Ea, n and A were obtained following one method of thermogravimetric analysis. The reaction order for all copolymers was 1.0. The poly(-methylhydrogenitaconate-co-2-methyl-2-oxazoline)s were the most thermostable copolymers.     

One-step synthesis of poly(2-oxazoline)-based amphiphilic block copolymers using a dual initiator for RAFT polymerization and CROP

A range of poly(2-oxazoline) (POx)-based amphiphilic block copolymers were synthesized using 4-cyano-4-(dodecylthiocarbonothioylthio)pentyl-4-methylbenzenesulfonate (CDPS) as a dual initiator for reversible addition-fragmentation chain transfer (RAFT) polymerization and cationic ring-opening polymerization (CROP) in a one-step procedure. Methyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, and N-isopropylacrylamide were polymerized for the hydrophobic block, and 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline were used as the hydrophilic block. RAFT polymerization and CROP proceeded independently in a controlled manner and resulted in amphiphilic block copolymers with a narrow molecular weight distribution. CDPS was found to be a useful dual initiator for the one-step synthesis of POx-based amphiphilic block copolymers via a combination of RAFT polymerization and CROP.     

Organization of poly(2-ethyl-2-oxazoline)-block-poly(2-phenyl-2-oxazoline) copolymers in water solution

Diblock copolymers were prepared from 2-ethyl-2-oxazoline and 2-phenyl-2-oxazoline via living cationic polymerization using sequential addition of the monomers. Copolymer assemblies in aqueous solutions and on surface were studied with respect to changes in the hydrophilic-hydrophobic balance induced by increasing the length of the hydrophobic poly(2-phenyl-2-oxazoline) segment while the hydrophilic poly(2-ethyl-2-oxazoline) chain was kept constant with an average of 60 monomer units. The copolymer with a short segment of four 2-phenyl-2-oxazoline units assembled into highly hydrated aggregates that decreased twice in size after drying. Their structure was destroyed and network morphologies were formed upon spin-coating. The increase of the length of the hydrophobic segment resulted in aggregates that dissociated to micelle-sized particles when subjected to mechanical shear by spin-coating or filtering. These observations imply that the aggregates are multi-core structures originating from the assembly of primarily formed micelles. The copolymer self-assembly was evidenced by a combination of techniques: DLS, SLS, AFM and SEM.     

Alternative to Poly(2-isopropyl-2-oxazoline) with a Reduced Ability to Crystallize and Physiological LCST

In this work, we sought to examine whether the presence of alkyl substituents randomly distributed within the main chain of a 2-isopropyl-2-oxazoline-based copolymer will decrease its ability to crystallize when compared to its homopolymer. At the same time, we aimed to ensure an appropriate hydrophilic/lipophilic balance in the copolymer and maintain the phase transition in the vicinity of the human body temperature. For this reason, copolymers of 2-ethyl-4-methyl-2-oxazoline and 2-isopropyl-2-oxazoline were synthesized. The thermoresponsive behavior of the copolymers in water, the influence of salt on the cloud point, the presence of hysteresis of the phase transition and the crystallization ability in a water solution under long-term heating conditions were studied by turbidimetry. The ability of the copolymers to crystallize in the solid state, and their thermal properties, were analyzed by differential scanning calorimetry and X-ray diffractometry. A cytotoxicity assay was used to estimate the viability of human fibroblasts in the presence of the obtained polymers. The results allowed us to demonstrate a nontoxic alternative to poly(2-isopropyl-2-oxazoline) (PiPrOx) with a physiological phase transition temperature (LCST) and a greatly reduced tendency to crystallize. The synthesis of 2-oxazoline polymers with such well-defined properties is important for future biomedical applications.     

Density functional complexation study of metal ions with poly(carboxylic acid) ligands. Part 1. Poly(acrylic acid) and poly(α-hydroxy acrylic acid)

We have studied metal ion complexation with poly(carboxylic acid) ligands using density functional methods and a continuum-solvation model (COSMO). Geometry optimisations have been carried out for metal complexes of poly(acrylic acid-co-maleic acid), poly(methyl vinyl ether-co-maleic acid), and poly(epoxy succinic acid) oligomers. The complexation energies for Mg²⁺, Ca²⁺, Mn²⁺, and Fe³⁺ have been calculated and they have been corrected with previously determined metal specific correction parameters. The most effective ligand for all the metal ions was found to be poly(epoxy succinic acid). With Ca²⁺, poly(epoxy succinic acid) was found to form 6-coordinated complex with three metal-coordinating carboxylate oxygen, two ether oxygens, and one hydroxyl oxygen atom. All the other metals favoured 5-coordinated complexation geometry with four metal-coordinating carboxyl oxygens and one ether oxygen atom.     

新型嗜热耐碱脂肪酶的纯化表征及应用

将来源于解脂嗜热互营杆菌（Thermosyntropha lipolytica）的脂肪酶（TlLipA）基因tll1导入大肠杆菌BL21（DE3）中表达,通过热处理和镍柱亲和层析获得纯酶,并对其酶学性质进行研究。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）显示TlLipA分子量为53×10³,其最适反应温度为65℃,最适反应pH为8.0。在55~65℃范围内酶活较高且比较稳定;在pH^{7.0~11.0于室温保存1 h后,残留相对酶活仍达80%以上。1 mmol/L 金属离子Zn2+、Fe3+和试剂SDS,0.05%（质量分数）Tween 80,对酶活力具有强烈的抑制作用,残留相对酶活皆低于15%;1 mmol/L Mg2+、Mn2+对酶活力表现出轻微的激活作用。由底物专一性实验可得,该酶对辛酸对硝基苯酯（C8）和癸酸对硝基苯酯（C10）偏好明显。以棕榈酸对硝基苯酯（p-NPP）为底物,该酶动力学参数K_m值为0.23 mmol/L,V_max为33.50 mmol/(L·min),k_cat为22.83 _S-1。以重组脂肪酶为催化剂在无溶剂体系中制备生物柴油,含水率20%,酶加量200 U/g油,醇油比为4∶1的条件下,在55℃催化大豆油反应48 h,收率可达91.75%。}     

Purification and characterization of novel thermo-alkaline lipase and its application

In order to excavate thermo-alkaline lipases from bacterial living in extreme conditions, we try to express new gene from Thermosyntropha lipolytica DSM 11003, an anaerobic, thermophilic, alkali-tolerant bacterium which grows in alkaline hot springs Lake Bogoria in Kenya and explore its application in biodiesel production. The lipase gene (tll1) of 1434 bp were ligated at the Nco I / EcoR I sites of the expression vectors pET28a to yield the construct of pET28a-TLL1. The strain harboring pET28a-TLL1 was cultivated for expression at 25℃, the specific activity of 1.99 U/mg protein were detected in disrupted cells. The recombinant lipase TlLipA was purified by a simple two-step procedure involving heat treatment and Ni-chelating affinity chromatography. The subunit of purified TlLipA showed a molecular mass of 53×10³ on 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The purified TlLipA exhibited optimal activity at 65℃ and pH 8.0 and it was stable from 55℃ to 65℃. The enzyme remained above 80% of its original activity at pH ranging from 7.0 to 11.0 and at room temperature for 1 h. The activity of TlLipA was little unaffected by Co²⁺, K⁺, Na⁺, and Ni²⁺, and a little activated by Mg²⁺ and Mn²⁺, ^{but were significantly inhibited by Zn2+, Fe3+, and SDS, and Tween 80 under the assay conditions. The purified recombinant TlLipA had a specific activity of 22.11 U/mg protein using p-nitrophenyl palmitate (p-NPP) as substrate. Determined by Sigma-Plot of reaction rate on p-NPP, the K_m was 0.23 mmol/L, the V_max was 33.50 mmol/(L·min), and the k_cat was 22.83 s-1. The enzyme was also active towards p-NPP, p-nitrophenyl laurate (p-NPL), p-nitrophenyl myristate (p-NPM) and p-nitrophenyl caproate (p-NPC), moreover TlLipA exhibited a strong preference for p-nitrophenol decanoate (p-NPD) and p-nitrophenyl octoate (p-NPO). Using recombinant lipase as a catalyst to prepare biodiesel in a solvent-free system, with a water content of 20%, an enzyme dosage of 200 U/g oil, and an alcohol-to-oil ratio of 4∶1, catalyzed soybean oil reaction at 55℃ for 48 h, the yield can reach 91.75%.}     

Selective extraction of In(III), Ga(III) and Zn(II) using a novel extractant with phenylphosphinic acid

A new extractant, [N,N-di(2-ethylhexyl)amino]methylphenylphosphinic acid (DEAPP), was synthesized to de-velop the mutual separation techniques of In(III), Ga(III) and Zn(II). The extraction selectivity for In(III), Ga(I I) and Zn(II) with DEAPP was higher than that of the commercial phosphorus acid extractants such as D2EHPA and PC-88A. The extraction selectivity for metal ions in 1 mol·L?1 aqueous ammonium nitrate solution with DEAPP was in the following order:In(III) N Ga(III) N Zn(II). These selective extraction behaviors indicate that the amino moiety of DEAPP plays an important role in the mutual separation of In(III), Ga(III) and Zn(II). The extraction equilibria of In(I I), Ga(II ) and Zn(II) with DEAPP (=HR) were expressed by the following reactions:In3++2eHRT2?InR3eHRT+3H+, Ga3++1.5eHRT2+NO3??GaR2eHRTeNO3T+2H+, and Zn2++2eHRT2?ZnR2eHRT 2 + 2H+. The extraction equilibrium constants of In(III), Ga(III) and Zn(II) with DEAPP were determined to be Kex,M=1.7 × 104 [dm3·mol?1], 4.17 [(dm3·mol?1)0.5], and 1.55 x 10?2 [–], respectively.     

Chiral-nematic self-ordering of rodlike cellulose nanocrystals grafted with poly(styrene) in both thermotropic and lyotropic states

Graft copolymers of rodlike cellulose nanocrystals (CNC) with poly(styrene) (PSt) were synthesized through atom transfer radical polymerization (ATRP). The hydroxyl groups on CNC were esterified with 2-bromoisobutyrylbromide to yield 2-bromoisobutyryloxy groups, which were used to initiate the polymerization of poly(styrene). The graft copolymers were characterized by thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The size of the original CNC is 10-40 nm in width and 100-400 nm in length, which was characterized by atomic force microscopy (AFM). The thermal and liquid crystalline properties of the graft copolymers were investigated by differential scanning calorimeter (DSC) and polarizing optical microscope (POM). The graft copolymers exhibit fingerprint texture in both thermotropic and lyotropic states. In thermotropic state, the PSt-grafted CNC orient spontaneously in isotropic melt (PSt side chains acting as a solvent). The thermotropic liquid crystal phase behavior is similar to the lyotropic phase behavior.