Synthesis and characterization of novel polyimides containing triazoles units in the main chain by click chemistry

In this study, some polyimides containing triazoles units in the main chain was prepared from the polymerization of dialkynes including imide linkages and diazides in the presence of Cu (I) catalyst in yield of 76.2–87.6%, with inherent viscosity of 0.37–0.53 dL g^?1. The obtained polymers are soluble in polar aprotic solvents such as N,N‐dimethyformamide (DMF), N,N‐dimethyacetamide (DMAc), dimethyl sulfoxide (DMSO), and N‐methyl‐2‐pyrrolidone (NMP). These polymers were characterized using FT‐IR, ¹H‐NMR, and elemental analysis techniques. Their thermal stability was evaluated with thermogravimetric (TGA) analysis and differential scanning calorimetry (DSC) techniques under a nitrogen atmosphere which is indicative of their good thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rapid and efficient DNA strand cross-linking by click chemistry

Click chemistry has been used to covalently cross-link complementary DNA strands between bases to form very stable duplexes. Several alkyne- and azide-modified uracil monomers were used to evaluate the effect of the linkers on the efficiency of the click reaction. All cross-linked duplexes had much higher thermal stabilities than non-cross-linked ones, with increases in melting temperature of up to 30 degrees C. In some cases, the conversion was near-quantitative, and the reaction was complete in 5 min.     

Copolymers of glycerol and propylene glycol diglycidyl ethers with aromatic dithiols

Monomers derived from renewable recourses have the potential to become the biobased alternatives for petroleum derived chemicals in the production of polymers. Glycerol, the byproduct of biodiesel refining, and propylene glycol derived from glycerol are promising candidates which can be used in the synthesis of polymers as they are or after chemical modification. The new copolymers of glycerol and propylene glycol diglycidyl ethers with aromatic dithiols were synthesized and investigated in this study. Their chemical structures were confirmed by IR, ¹H‐NMR spectroscopy, and gel permeation chromatography. The dependencies of the mechanical, thermal properties, swelling in the different solvents, biodegradability, and bioresistance of synthesized copolymers on their chemical structures were studied. The properties of some synthesized copolymer films were found to be comparable with those of commodity polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4367–4374, 2013     

New azo-chromophore-containing multiblock poly(butadiene)s synthesized by the combination of ring-opening metathesis polymerization and click chemistry

A combination of ring-opening metathesis polymerization (ROMP) and click chemistry approach was utilized for the first time in preparation of multiblock copolymers. The dibromo-functionalized telechelic poly(butadiene) (PBD) was synthesized firstly by ROMP of 1,5-cyclooctadiene in the presence of a symmetrical difunctional chain transfer agent and transformed into diazido-telechelic PBD, which was then reacted with a dialkynyl-containing azobenzene chromophore via click reaction, producing novel multiblock PBDs collected by azobenzene groups and newly formed triazole moieties. The monomer and polymer were characterized by IR, UV-vis, LC/MS, and NMR techniques. The produced multiblock copolymers have molecular weights within 13.3 and 57.8 kDa, and their polydispersity indices ranging from 1.98 to 2.38 by gel permeation chromatography measurement. The multiblock PBDs containing azo chromophores and triazole moieties with or without hydrogen-bonding interreaction with 4,4′-dihydroxybiphenyl molecule exhibited different photoisomerization efficiency from trans to cis as observation in UV-vis spectroscopy. The morphologies of multiblock PBDs were also investigated by atom force microscopy.     

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.     

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

Well‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chemical sensing materials II: Electrically conductive peroxide crosslinked SEBS copolymers systems

Chemical sensing materials based on electrically conductive styrene–ethylene butylene–styrene (SEBS) triblock‐copolymers systems were investigated. Systems based on crosslinked rather than thermoplastic SEBS systems can be exposed to a wide range of chemical environments. Composites of SEBS containing various amounts of CB and Varox DBPH (peroxide crosslinking agent) were prepared by blending at relative low temperatures, limiting the peroxide activation, and then compression molding at elevated temperatures. Samples containing CB at a level near the corresponding percolation threshold were used for the sensing experiments. Structure characterization included crosslink level and density, dynamic mechanical analysis (DMA), and calorimetry (DSC). The crosslinked SEBS composites exhibit large reversible changes in conductivity on exposure to various solvents and air drying cycles The observed electrical conductivity changes on solvent sorption/desorption is based on the polymer reversible swelling, resulting in breakdown and reconstruction of conductive CB networks, respectively. Sensing performance depends mainly on the solvents solubility parameter and volatility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Generation of a mono-ubiquitinated PCNA mimic by click chemistry

Genotoxic stress results in more than 50 000 damaged DNA sites per cell per day. During DNA replication, processive high‐fidelity DNA polymerases generally stall at DNA lesions and have to be displaced by translesion synthesis DNA polymerases, which are able to bypass the lesion. This switch is mediated by mono‐ubiquitination of the processivity factor proliferating cell nuclear antigen (PCNA). To further investigate the regulation of the DNA polymerase exchange, we developed an easy and efficient method to synthesize site‐specifically mono‐ubiquitinated PCNA by click chemistry. By incorporating artificial amino acids that carry an azide (Aha) or an alkyne (Plk) in their side chains, into ubiquitin (Ub) and PCNA, respectively, we were able to link the two proteins site‐specifically by the Cu^I‐catalyzed azide–alkyne cycloaddition. Finally, we show that the synthetic PCNA–Ub is able to stimulate DNA synthesis by DNA polymerase δ, and that DNA polymerase η has a higher affinity for PCNA–Ub than to PCNA.     

基于巯基-炔的“点击”化学研究进展

＂点击＂化学由于具有原料易得、反应条件温和、高的产率和选择性等特点,已受到人们的广泛关注。巯基-炔反应是近年来被证实的一种新型＂点击＂反应,具有简单、高效以及通用等特性。本文综述了＂点击＂化学的定义、特点、发展历程及应用,系统介绍了巯基-炔＂点击＂反应的机理及其在制备功能分子和表面修饰方面的研究进展,主要包括树枝状聚合物、超支化聚合物、网状聚合物、功能材料等的制备和材料的表面改性。最后对巯基-炔＂点击＂反应的发展前景进行了展望。     

Synthesis of pH-sensitive,water-soluble paclitaxel prodrugs based on norbornene-functional polylactide by copper-free click chemistry

In this study, a novel polymeric prodrug based on norbornene-functional polylactide with functionalized paclitaxels (LEV-PTXL) covalently conjugated to water-soluble polymer carrier via a pH-sensitive hydrazone bond was developed. A series of water-soluble PTXL prodrugs with decent drug contents of 17.3 and 24.7 wt% (denoted as PTXL prodrugs 1 and 2) were prepared. The molecular structures and characteristics were confirmed by ¹H NMR, Fourier transform infrared, and gel permeation chromatography. In vitro release studies showed that PTXL release rate from polymeric prodrug were significantly accelerated under acidic medium, due to the acid-cleavable hydrazone linkage. As illustrated by cytotoxicity study, while the corresponding polymer carrier was nontoxic, the polymeric prodrug exhibited higher therapeutic efficacy toward MCF-7 and A549 (IC50 = 0.19 and 4.94 µg PTXL equiv/mL, respectively) cancer cells. The norbornene-functional polylactide-based polymeric prodrug has appeared as a novel anticancer nanomedicine for cancer therapy.     

pH and organic solvent‐sensitive properties of crosslinked polymeric spheres formed by a soap‐free emulsion polymerization

Narrowly distributed poly (styrene‐co‐(4‐vinylpyridine)) microspheres are facilely prepared by a soap‐free emulsion polymerization, and their structures and properties are investigated by TEM, FTIR spectra, DSC, and DLS, respectively. The sizes and glass transition temperatures of the polymeric spheres increase with an increase of 4‐vinylpyridine in the reactive system. In addition, these polymeric spheres show good stability in water and a series of organic solvents due to their crosslinked structures. When poly(styrene‐co‐(4‐vinylpyridine)) microspheres are obtained in the reactive system where the weight ratio of 4‐vinyl pyridine to styrene is less than 4/6, they can be well dispersed in water as well as in organic solvents such as ethanol, toluene and DMF, and show obvious pH sensitive and organic solvent‐sensitive characteristics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Methyl methacrylate and acrylamide crosslinked macroporous copolymers

In this work the synthesis of a crosslinked macroporous copolymer was effected from methyl methacrylate and acrylamide. The synthesis process began with emulsion prepolymerization, followed by sol–gel copolymerization until a hard block was obtained. Determination of the properties of the obtained material was carried out by FTIR, mercury porosimetry, and SEM microscopy. The material was characterized by a porous structure with open pores. The macroporous copolymer obtained can be used for polymer–analog reactions and the transformation of amide and ester groups into acyl azide groups. It can be used as a hard inert support for the immobilization of enzymes, or other proteins, by condensation of acyl azide group on polymer with the free amino group from the base amino acid of enzyme/protein. For the immobilization of microorganisms it can be used by vacuum diffusion of microorganism suspension into the porous structure, without active group transformation reactions. With microorganisms in the polymer pores, microorganism colonies form within the copolymer by microbial fermentation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 387–395, 2004     

Preparation of acrylic copolymers and crosslinking agents and properties as a film

Copolymers of butyl acrylate (BA)‐methyl methacrylate (MMA)‐acrylic acid (AA) and intraparticle crosslinking agents containing N‐methylol acrylamide (NMA) and ethylene glycol dimethacrylate (EGDMA) were prepared by emulsion copolymerization. After that, films were prepared from the mixture of copolymers and the interparticle crosslinking agents. The interparticle crosslinking agents were prepared from hexamethylene diisocyanate and aziridine ethanol. Mixtures of the copolymer and the interparticle crosslinking agent were cast to films and crosslinked in a convection oven. The effects of the contents of the intra/interparticle crosslinking agents were also evaluated. By increasing the contents of EGDMA, roughness of the films was increased because of the effects of EGDMA acting as an intraparticle crosslinking agent. By increasing the contents of the interparticle crosslinking agent, roughness was also increased by the reaction between the copolymers and interparticle crosslinking agent. Tensile strength and water and chemical resistance of the film were increased, whereas elongation of film was decreased by increasing the contents of interparticle crosslinking agents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

点击化学法制备SBS-TMA型阴离子交换膜及其性能

以聚苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）为基质、炔丙基三甲胺盐（PTMA）为碱性功能基团,通过点击化学（click chemistry）法合成聚合物SBS-TMA,采用浇铸成膜法制得扩散渗析（DD）性能优异的均质型阴离子交换膜。借助核磁共振仪（¹H NMR）、扫描电镜（SEM）对聚合物的结构、形貌表征;借助热重分析仪（TG）、精密天平对膜的热、酸性稳定性能表征。研究了功能基团含量和温度双重因素对其DD性能的影响,结果表明：在室温下,当功能基团的含量为0.20（即SBS-TMA-0.20）时,膜的扩散系数（U_H⁺）为2.86×10^-2m/h,分离系数（S）为28.1,该膜的DD性能是商业膜DF-120（U_H⁺=9×10^-3m/h,S=18）的2～3倍;当系统温度由25℃升至70℃时,膜SBS-TMA-0.20的U_H⁺值由2.86×10^-2m/h增加至4.48×10^-2m/h,它的S值由28.1增加至30.1,随后由30.1快速下降至16.2。     

一种基于点击化学的高性能亲水抗菌聚氨酯合成与表征

以聚己内酯1000（PCL1000）、异佛尔酮二异氰酸酯（IPDI）、2,2-双（溴甲基）-1,3-丙二醇、叠氮化钠（NaN₃）等为原料合成了侧链带有叠氮基团的可点击聚氨酯预聚体,以1,1,3,3-四甲基胍（TMG）、3-溴丙炔合成了抗菌单体2-炔丙基-1,1,3,3-四甲基胍（TMG-Al）,随后以点击反应为连接策略制备了环保水性接触型抗菌聚氨酯。采用红外光谱（FTIR）、核磁共振波谱（NMR）表征了小分子单体的化学结构;通过抑菌圈实验验证了涂膜的接触型抗菌效果及非渗透特性,为接触型抗菌领域的研究提供了一种新的合成方法。抗菌结果显示,当水性聚氨酯中引入质量分数为5%的TMG-Al时,抗菌聚氨酯即可对革兰氏阴性菌（大肠杆菌）及革兰氏阳性菌（金黄色葡萄球菌）产生显著的杀灭效果,抗菌率达99.9%。     

Synthesis of poly(cyclohexene oxide)‐block‐polystyrene by combination of radical‐promoted cationic polymerization,atom transfer radical polymerization and click chemistry

The combination of radical‐promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)‐block‐polystyrene (PCHO‐b‐PSt). Alkyne end‐functionalized poly(cyclohexene oxide) (PCHO‐alkyne) was prepared by radical‐promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2‐diphenyl‐2‐(2‐propynyloxy)‐1‐ethanone (B‐alkyne) and an onium salt, namely 1‐ethoxy‐2‐methylpyridinium hexafluorophosphate, as the initiating system. The B‐alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well‐defined bromine‐terminated polystyrene (PSt‐Br) was prepared by ATRP using 2‐oxo‐1,2‐diphenylethyl‐2‐bromopropanoate as initiator. Subsequently, the bromine chain end of PSt‐Br was converted to an azide group to obtain PSt‐N₃ by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt‐N₃ and PCHO‐alkyne was performed with Cu(I) catalysis in order to obtain the PCHO‐b‐PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry     

Application of microwave‐assisted click chemistry in the preparation of functionalized copolymers for drug conjugation

The aim of this study is to develop azido‐carrying biodegradable polymers and their postfunctionalization with alkynyl compounds via click chemistry and to investigate their potential use in drug delivery. Azido polymers were prepared by ring‐opening polymerization of cyclic carbonate monomer, 2,2‐bis(azidomethyl)trimethylene carbonate (ATC) with lactide using stannous octoate as catalyst. Several alkynyl compounds were selected to investigate the feasibility and reaction condition of click chemistry. With microwave‐assisting, the reaction time of click chemistry was shortened to 5 min. By using poly(ethylene glycol) (PEG) as macroinitiator, amphiphilic block copolymer mPEG‐b‐P(LA‐co‐ATC) was obtained and it could self‐assemble into micelles by solvent replacement method. The pendant groups were used for conjugating anticancer drugs gemcitabine and paclitaxel and fluorescent dye Rhodamine B. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide was used to assay the cytotoxicity of the conjugate micelles against SKOV‐3 and HeLa cell lines. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Amphiphilic chitosan graft copolymer via combination of ROP, ATRP and click chemistry: Synthesis, self-assembly, thermosensitivity, fluorescence, and controlled drug release

Novel amphiphilic chitosan-g-poly(ε-caprolactone)-(g-poly(2-(2-methoxyethoxy)ethyl methacrylate)-co-oligo(ethylene glycol) methacrylate) (CS-g-PCL(-g-P(MEO₂MA-co-OEGMA))) copolymers with double side chains of PCL and P(MEO₂MA-co-OEGMA) were synthesized via combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP) and click chemistry. The molar ratio of PCL and P(MEO₂MA-co-OEGMA) was varied through variation of the feed ratio and the coupling efficiency of click chemistry is comparatively high. The graft copolymers can assemble into spherical micelles. The micelles show thermosensitive properties and the lower critical solution temperatures (LCSTs) were influenced by CS chains and the ratio of PCL and P(MEO₂MA-co-OEGMA) side chains. Moreover, the micelles can reversibly swell and shrink in response to the change of temperatures. Furthermore, the micelles present obvious fluorescence and the fluorescent intensity can be adjusted by altering the temperatures. The investigation of doxorubicin release from the micelles indicated that the release rate of the drug could be effectively controlled by altering the temperatures.