Living ring opening metathesis polymerization of mesogenic norbornene derivatives

A new class of SCLCPs was prepared by polymerizing mesogenic norbornene derivatives using Mo(CHCMe₂R)(N-2,6-C₆H₃-i-Pr₂)(O-t-Bu)₂ (R = CH₃ or Ph). Monomers based on norbornene ring systems were chosen because the rings are highly strained and therefore yield irreversible polymerizations. The Mo-alkylidene initiators were chosen because they initiate norbornene derivatives relatively fast and quantitatively, and provide stable chain ends which have low reactivity to both the internal double bonds of the polymer backbone and the functional groups present in the monomers. The apparent absence of termination and transfer reactions in ROMP results in polymerizations which appear to be living, and the fast initiation and irreversible chain growth leads to polymers with narrow molecular weight distributions in which the degree of polymerization is controlled by the ratio of monomer to initiator used. The resulting well-defined polymers were used to determine the most basic structure-property relationships of this new class of SCLCPs. The thermotropic behavior of both terminally attached and laterally attached SCLCPs based on polynorbornene backbones becomes independent of molecular weight at approximately 25 repeat units. In addition, polydispersity was found to have no effect on the breadth of nematic phase transitions in the terminally attached polymers, with the transition temperature determined simply by the number average degree of polymerization.     

VINYL POLYMERIZATION OF NORBORNENE CATALYZED BY [2-(2-BENZIMIDAZOLYL)-6-((1-ARYLIMINOETHYL)PYRIDYL)]NICKEL CHLORIDE/MAO SYSTEM

The catalytic system of[2-(2-benzimidazolyl)-6-((1-aryliminoethyl)pyridyl)]nickel chloride/MAO(methylalu- minoxane)was found to be good active for vinyl polymerization of norbornene and provided polymers with relative narrow molecular distributions.Various reaction parameters,such as the ratios of nickel precursor to MAO or monomer norbornene, and the nature of the ligands in complexes were carefully investigated to realize their effects on the catalytic activities, polymer molecular weight and molecular...     

Preparation of sterol-imprinted polymers with the use of 2-(methacryloyloxy)ethyl phosphate.

Steroid-selective polymers were prepared by the molecular imprinting technique, using 2-(methacryloyloxy)ethyl phosphate as functional monomer. The retentivity and selectivity of the obtained imprinted polymers were evaluated by liquid chromatography. The cholesterol-imprinted polymer showed higher affinity for cholesterol than that for cholesterol derivatives. The selectivity of the imprinted polymer was superior to the imprinted polymer prepared with the conventional functional monomer, 2-(trifluoromethyl)acrylic acid. Estradiol was also imprinted and gave similar results, demonstrating that 2-(methacryloyloxy)ethyl phosphate would be suitable for imprinted polymers of cholesterol and related compounds.     

Surprising Antibacterial Activity and Selectivity of Hydrophilic Polyphosphoniums Featuring Sugar and Hydroxy Substituents

There is currently an urgent need for the development of new antibacterial agents to combat the spread of antibiotic‐resistant bacteria. We explored the synthesis and antibacterial activities of novel, sugar‐functionalized phosphonium polymers. While these compounds exhibited antibacterial activity, we unexpectedly found that the control polymer poly(tris(hydroxypropyl)vinylbenzylphosphonium chloride) showed very high activity against both Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus and very low haemolytic activity against red blood cells. These results challenge the conventional wisdom in the field that lipophilic alkyl substituents are required for high antibacterial activity and opens prospects for new classes of antibacterial polymers.     

Antimicrobial Peptide Modifications against Clinically Isolated Antibiotic-Resistant Salmonella

Antimicrobial peptides are promising molecules to address the global antibiotic resistance problem, however, optimization to achieve favorable potency and safety is required. Here, a peptide-template modification approach was employed to design physicochemical variants based on net charge, hydrophobicity, enantiomer, and terminal group. All variants of the scorpion venom peptide BmKn-2 with amphipathic α-helical cationic structure exhibited an increased antibacterial potency when evaluated against multidrug-resistant Salmonella isolates at a MIC range of 4–8 µM. They revealed antibiofilm activity in a dose-dependent manner. Sheep red blood cells were used to evaluate hemolytic and cell selectivity properties. Peptide Kn2-5R-NH₂, dKn2-5R-NH₂, and 2F-Kn2-5R-NH₂ (variants with +6 charges carrying amidated C-terminus) showed stronger antibacterial activity than Kn2-5R (a variant with +5 charges bearing free-carboxyl group at C-terminus). Peptide dKn2-5R-NH₂ (d-enantiomer) exhibited slightly weaker antibacterial activity with much less hemolytic activity (higher hemolytic concentration 50) than Kn2-5R-NH₂ (l-enantiomer). Furthermore, peptide Kn2-5R with the least hydrophobicity had the lowest hemolytic activity and showed the highest specificity to Salmonella (the highest selectivity index). This study also explained the relationship of peptide physicochemical properties and bioactivities that would fulfill and accelerate progress in peptide antibiotic research and development.     

Antimicrobial polymers prepared by ROMP with unprecedented selectivity: a molecular construction kit approach

Synthetic Mimics of Antimicrobial Peptides (SMAMPs) imitate natural host-defense peptides, a vital component of the body's immune system. This work presents a molecular construction kit that allows the easy and versatile synthesis of a broad variety of facially amphiphilic oxanorbornene-derived monomers. Their ring-opening metathesis polymerization (ROMP) and deprotection provide several series of SMAMPs. Using amphiphilicity, monomer feed ratio, and molecular weight as parameters, polymers with 533 times higher selectivitiy (selecitviy = hemolytic concentration/minimum inhibitory concentration) for bacteria over mammalian cells were discovered. Some of these polymers were 50 times more selective for Gram-positive over Gram-negative bacteria while other polymers surprisingly showed the opposite preference. This kind of "double selectivity" (bacteria over mammalian and one bacterial type over another) is unprecedented in other polymer systems and is attributed to the monomer's facial amphiphilicity.     

Stepwise polymerization of 1,1-diphenylethylene derivatives by acid catalysts

The polymers containing units of 1,1,3,3-tetraphenylbut-1-ene [unit (I)] and/or units of 3-methyl-1,1,3-triphenylindan [unit (II)] in the main chain were prepared by acid-catalyzed dimerization of 1,1-diphenylethylene applied to its bifunctional derivatives, for example bis[p-(1-phenylvinyl)phenyl]methane. The structure of yielded polymers depended on catalyst, solvent, temperature, and the molar ratio between the catalyst and the monomer. The molecular weight of polymer having unit (I) was determined by the equilibrium existing between 1,1-diphenylethylene moiety and unit (I). It was shown clearly by gel permeation chromatography that the molecular weight of polymer having unit (II) grew further after the equilibrium mentioned above had been accomplished. The mechanism of the polymerization is discussed.     

两亲性ABA三嵌段共聚物的合成及其自组装行为研究

用Grubbs第二代催化剂引发降冰片烯类单体(NBEDE)和链转移剂在离子液体[bmim][BF4]中的开环易位聚合(ROMP)反应,反应体系保持均相,无聚合物析出,得到两端为叔溴的遥爪型官能化聚合物(Br-PNBEDE-Br).以Br-PNBEDE-Br作为大分子引发剂,在离子液体介质中引发甲基丙烯酸2-(二甲氨基)乙酯(DMAEMA)的原子转移自由基聚合(ATRP),制得分子量分布较窄的两亲性三嵌段共聚物(PDMAEMA-PNBEDE-PDMAEMA).利用动态激光光散射(DLS),原子力显微镜(AFM),透射电镜(TEM)等技术,考察嵌段共聚物在选择性溶剂/共溶剂(H2O/THF)中的胶束行为,以及溶液pH值对胶束的影响.结果表明,TEM观察到胶束为球形,由于TEM和AFM是在干态下测得胶束的粒径,而DLS是在溶液中测定胶束的流体力学直径,所以TEM和AFM得到的胶束粒径小于DLS的结果.不同pH值对胶束尺寸大小有明显的影响,胶束微粒随着pH值的增大而增大.     

Hemolytic and Antimicrobial Activities Differ Among Saponin-rich Extracts From Guar, Quillaja, Yucca, and Soybean

Hemolytic and antibacterial activities of eight serial concentrations ranged from 5-666 µg/mL of saponin-rich extracts from guar meal (GM), quillaja, yucca, and soybean were tested in 96-well plates and read by enzyme-linked immunosorbent assay plate-well as 650 nm. Hemolytic assay used a 1% suspension of chicken red blood cells with water and phosphate buffered saline as positive and negative controls, respectively. Antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli were evaluated using ampicillin and bacteria without saponin-rich extract as positive and negative controls, respectively. The 100% MeOH GM and commercial quillaja saponin-rich extracts were significantly the highest in both hemolytic and antibacterial activities against all bacteria at the same concentration tested. Soybean saponin-rich extract had no antibacterial activity against any of the bacteria at the concentrations tested while yucca saponin-rich extract had no antibacterial activity against the gram-negative bacteria at the concentrations tested. GM and quillaja saponin-rich extracts were hemolytic, while yucca and soybean saponin-rich extracts were not hemolytic at the concentrations tested. No saponin-rich extract source had antibacterial activity against S. typhimurium or E. coli at the concentrations tested. Both GM and quillaja saponin-rich extracts exhibited antibacterial activity against S. aureus. Saponin-rich extracts from different plant sources have different hemolytic and antibacterial activities.     

Synthesis and antibacterial activities of water‐soluble methacrylate polymers containing quaternary ammonium compounds

New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and ¹H and ¹³C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by ¹H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006     

Synthesis,characterization, and biological activity of [2‐oxo‐2‐(4‐acetyl) phenyl amino] ethylene methacrylate and its derivatives

A new type of methacrylate monomer, [2‐oxo‐2‐(4‐acetyl) phenyl amino] ethylene methacrylate (APEMA), was synthesized. The oxime, 2,4‐dinitrophenylhydrazone, and thiosemicarbazone derivatives of poly{[2‐oxo‐2‐(4‐acetyl) phenyl amino] ethylene methacrylate} [poly(APEMA)] were prepared with hydroxylamine hydrochloride, 2,4‐dinitrophenylhydrazine, and thiosemicarbazone hydrochloride, respectively. The radical homopolymerization of APEMA was performed at 65 °C in a 1,4‐dioxane solution with benzoyl peroxide as an initiator. The monomer and its homopolymer were characterized with Fourier transform infrared and NMR techniques. The thermal stabilities of poly(APEMA) and its derivatives were investigated with thermogravimetric analysis and differential scanning calorimetry. The ultraviolet stability of the polymers were compared. The solubility and inherent viscosity of the polymers were also determined. The number‐average and weight‐average molecular weights and polydispersity index of the polymers were determined with gel permeation chromatography. The antibacterial and antifungal effects of the monomer and the polymer and its derivatives were also investigated on various bacteria and fungi. The activation energies of the thermal degradation of the polymers were calculated with the Ozawa method. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3157–3169, 2004     

Amphiphilic water soluble cationic ring opening metathesis copolymer as an antibacterial agent

Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC ₅₀ = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer.     

7-氧杂降冰片烯的官能化及其开环易位聚合

设计合成了含氧化乙烯重复单元和咪唑盐侧基的降冰片烯类单体,用Grubbs催化剂(PCy3)2Ru(CHPh)Cl2(1)和(SIMes)(PCy3)Ru(CHPh)Cl2(2)对单体进行了开环易位聚合(ROMP).考察了单体在不同条件下(溶剂、温度等)的聚合反应,尤其是在离子液体中ROMP的聚合特征.结果表明,2的催化活性比1的高;2催化单体在有机溶剂中聚合所得聚合物的分子量不可控,而在离子液体[BMIm]PF6中能够顺利进行均相聚合反应,且对聚合物的分子量可控性较好.用核磁共振谱(NMR)对合成的单体及聚合物的结构进行了表征.用差示扫描量热法(DSC)测定聚合物的玻璃化转变温度为-17.34℃,采用循环伏安法测得聚合物的电化学稳定窗口为3.0V.     

Synthesis and Antibacterial Action of Poly(DMAEMA-BC)with Various Molecular Weights

Antibacterial polymers of dimethylaminoethyl methacrylate benzyl ammonium chloride(DMAEMA-BC) with various molecular weights(Mws) were prepared under controlling radical polymerization conditions. The Mws of these polymers were determined by means of static multiangle laser light scattering and viscosity method. A Mark-Houwink equation was established to be [η]=0.154M0.764 for the Mw evaluation of poly(DMAEMA-BC)s. The effects of the Mws of these poly(DMAEMA-BC)s on their antibacterial activities against E. coli and S. aureus were investigated by various methods including viable cell counting, electrical conductivity titration, intracellular constituent leakage tests and electron microscopy. Our results indicate that the antibacterial efficiency of DMAEMA-BC was significantly enhanced after the monomers were polymerized into a polymer and increased obviously with the Mws,as a result of the increase of charge density. Further investigation of the molecular basis underlying the anti-bacterial role of these polymers revealed that poly(DMAEMA-BC) promoted the release of potassium ion from the membrane of bacterial cells and the release increased significantly with the Mws of the polymers used.     

新型功能单体分子印迹聚合物的研究进展

分子印迹聚合物是近年发展起来的新型重要分子识别材料,功能单体是其识别性能最重要的影响因素之一,因此,对新型功能单体分子印迹聚合物的研究越来越受重视.基于分子印迹聚合物在固相萃取、色谱柱分离、传感器等方面的应用,对新型功能单体分子印迹聚合物的研究进展进行了综述.     

Growth and structure of surface-initiated poly(n-alkylnorbornene) films

We report the surface-initiated growth of poly(alkylnorbornene) films via ring-opening metathesis polymerization (ROMP). The films are grown by exposure of a vinyl-terminated self-assembled monolayer (SAM) on gold to Grubbs first-generation catalyst and the subsequent exposure to an alkylnorbornene monomer. We investigate the influence of alkyl side chains on the structure, barrier, surface properties, and the growth kinetics of surface-initiated ROMP-type poly(norbornene) films. Rate constants for film growth are estimated for the comparison of monomer reactivity. The rate constant for film growth decreases by 3 orders of magnitude from norbornene to decylnorbornene, indicating a strong effect of chain length on initiation and/or propagation rates. Reflectance-absorption infrared spectroscopy is used to show the molecular level packing within the poly(alkylnorbornene) films is disrupted by the alkyl side chains. Tapping-mode atomic force microscopy is used to show that norbornene, butylnorbornene, and hexylnorbornene polymerize from the surface to form dense coatings, whereas decylnorbornene polymerizes to form isolated polymer clusters. The methyl terminus of the alkyl side chains increases the hydrophobicity of the poly(alkylnorbornene) films (thetaA(H2O) = 109-114 degrees) beyond that of a typical poly(norbornene) film (thetaA(H2O) approximately 106 degrees). The additional hydrophobicity throughout the film correlates with superior resistances against redox probes (Rf approximately 105 Omega.cm2) for poly(hexylnorbornene) when compared to polynorbornene (Rf approximately 104 Omega.cm2). The resistance of the poly(decylnorbornene) film (Rf approximately 102 Omega.cm2) is consistent with its nonuniform, cluster-like morphology.     

Radical‐medicated end‐group transformation of amphiphilic methacrylate random copolymers for modulation of antimicrobial and hemolytic activities

This work describes synthesis of antimicrobial methacrylate copolymers by reversible addition‐fragmentation chain transfer (RAFT) polymerization and examines the versatility of this approach for improving chemical optimization to create potent, non‐toxic antimicrobial polymers. Specifically, this study focuses on the radical‐mediated transformation of end group of antimicrobial peptide‐mimetic polymer. RAFT polymerization using 2‐cyano‐2‐yl‐dithiobenzoate provided a statistical methacrylate copolymer consisting of aminobutyl and ethyl groups in the side chains. The following radical‐mediated modification using free radical initiators successfully transformed the ω‐end group of parent copolymer from dithiobenzoate to a cyanoisobutyl or aminoethyl cyanopentanoate group without any significant changes to the polymer molecular weight. In general, the parent polymer and variants showed a broad spectrum of activity against a panel of bacteria, but low hemolytic activity against human red blood cells. The parent copolymer with the dithiobenzoate end‐group showed highest antimicrobial and hemolytic activities as compared with other copolymers. The copolymers caused membrane depolarization in Staphylococcus aureus, while the ability of copolymers for membrane disruption is not dependent on the end‐group structures. The synthetic route reported in this study will be useful for further study of the role of polymer end‐groups in the antimicrobial activity of copolymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 304–312     

Enantiomeric separation using temperature-responsive chiral polymers composed of L-valine diamide derivatives in aqueous liquid chromatography

This paper describes enantiomer separation by aqueous liquid chromatography using chiral stationary phases (CSPs) in which temperature-responsive polymers derived from acryloyl-L-valine N-methylamide (1) and its N,N-dimethylamide analogue (2) were bound on silica gel supports. The linear polymers composed of monomer 1 and monomer 2 are temperature-responsive in solution and their aggregation and extension states related to water solubility are reversible at particular critical temperatures. During chromatography, enantioselectivity and retentivity for solute enantiomers were controlled by column temperature, which changes the aggregation and extension states of the chiral polymers depending upon their interior hydrophobic nature. Two different types of CSPs were made: a temperature-responsive linear polymer derived from 3-mercaptopropyl silica gel, and another polymer cross-linked with ethylene dimethacrylate from 3-methacryloyloxypropyl silica gel. The former CSP could separate racemic N-(3,5-dinitrobenzoyl(DNB))amino acid isopropyl esters. Retention of the amino acid derivatives was prolonged with an increase in column temperature. Enantioselectivity was also enhanced with temperature increase until the particular critical temperature. The latter, cross-linked CSP could not provide enantioselectivity for the amino acid derivatives in aqueous media, although the chiral valine diamide moieties were effective for enantiomer separation in non-aqueous media. The degree of hydrophobicity and volume of the bonded phase formed by the polymers on the support surface was determined by measuring the fluorescence of pyrene.     

蜂毒肽类似物的合成和生物活性研究

Melittin(GIGAVLKVLTTGLPALISWIKRKRQQ-NH₂)是蜂毒中含26个氨基酸残基的多肽,具有抗菌和溶血等生物活性,是典型的阳离子抗菌肽.本文设计合成了蜂毒肽C端15残基肽片段(GLPALISWIKRKRQQ-NH₂)及其类似物(15残基).研究了Melittin及这些合成肽的抗菌活性、溶血活性、疏水性及二级结构.结果表明,合成的类似物的溶血活性明显降低,抗菌活性基本保留,且与其疏水性相关.类似物中与碱性氨基酸簇(KRKR)距离较远的残基的疏水性对其抗菌活性有较大的贡献.多肽溶血与抗菌机理不同.类似物的抗菌活性和溶血活性与其二级结构(α-螺旋结构)没有明显的相关性.     

Gas permeation and sorption studies on stereoregular polynorbornene

Advances in the field of membrane gas separation over the past decade have encouraged the search for even better polymers and membranes for gas separation. They also have motivated studies on the relationship between the structure and the gas transport properties of different classes of polymers. Interest has recently been demonstrated in the literature in norbornene polymers with different side groups. These polymers can easily be prepared via ring-opening metathesis polymerization (ROMP) of norbornene (bicyclo[2.2.1]hept-2-ene) derivatives. So far, information on the microstructure of the polymers is scarce, so little is known about the influence of stereochemistry and tacticity of the polymer on gas separation properties. In this work, we present gas permeability and selectivity data for stereoregular unsubstituted polynorbornene. It will be shown that a high order of tacticity has a positive effect on both permeation and separation results. © 1997 John Wiley & Sons, Inc.