Capillary electrochromatography with polymeric continuous beds synthesized via free radical polymerization in aqueous media using derivatized cyclodextrins as solubilizing agents

A novel synthetic route to amphiphilic acrylamide-based monolithic stationary phases for capillary electrochromatography (CEC) employing water-soluble cyclodextrins as solubilizing agents was explored. N,N'-Octamethylenebisacryamide and N,N'-dodecamethylenebisacryamide were synthesized and their solubilization in aqueous solution with derivatized and underivatized cyclodextrins of different cavity size was studied. Amphiphilic stationary phases were synthesized by free radical copolymerization of the bisacrylamide-cyclodextrin host-guest complexes with hydrophilic monomers and an additional hydrophilic cross-linker in aqueous solution. Complex formation in solution and removal of the complexed cyclodextrin from the polymer during synthesis was studied with 1H-NMR and solid state 13C-NMR spectroscopy and cyclodextrin-modified micellar electrokinetic chromatography. The impact of the incorporated alkylene groups in the acrylamide-based macroporous polymer on retention was studied with neutral solutes by CEC in the normal-phase elution mode and in the reversed-phase elution mode. Batch-to-batch reproducibility of the synthesis procedure and day-to-day repeatability of the separations achieved were investigated. With these capillaries, a sufficiently high electroosmotic flow velocity, a high reproducibility and repeatability of separation parameters and high plate numbers (up to 200,000 m(-1) were obtained.     

Copolymerization in N-vinylcaprolactam-N-vinylpyrrolidone and N,N-diethylacrylamide-N,N-dimethylacrylamide systems: The effect of composition and spatial structure of copolymers on their thermal sensitivity

Factors that affect the temperature-responsive properties of water-soluble polymers were revealed by studying the copolymerization of two pairs of monomers: N-vinylcaprolactam-N-vinylpyrrolidone and N,N-diethylacrylamide-N,N-dimethylacrylamide. In each pair, the first monomer forms a temperature-responsive polymer and the second gives a polymer soluble in water up to the boiling point. It was found that in all cases, the addition of the second (more hydrophilic) monomer resulted in a monotonous increase in the phase separation temperature in an aqueous copolymer solution, with the temperature rise being comparatively slow in the initial stage and sharply accelerating after the addition of more than 40–50 mol % second monomer. The phase-separation temperature versus copolymer composition curves for N,N-diethylacrylamide-N,N-dimethylacrylamide copolymers of iso-and heterotactic structure synthesized via anionic polymerization are rather similar. At the same time, the copolymers of both types prepared via radical polymerization are characterized by steeper curves, a pattern that may be due to a high content of the syndiotactic structure, however, changes in the copolymer spatial structure have a lesser effect on the phase separation temperature than the presence of units of a more hydrophilic monomer. The addition of a relatively low amount (20–25 mol %) of a less hydrophilic monomer imparts temperature sensitivity to polymers, such as polyvinylpyrrolidone or polydimethylacrylamide, which do not possess this property in the pure form.     

Association behavior of fluorine-containing and non-fluorine-containing methacrylate-based amphiphilic diblock copolymer in aqueous media

Fluorine-containing amphiphilic block copolymers, poly(sodium methacrylate)-block-poly(nonafluorohexyl methacrylate) (NaMAm-b-NFHMAn) (m:n = 61:12, 72:33, 64:57), and the corresponding non-fluorine-containing amphiphilic block copolymer, poly(sodium methacrylate)-block-poly(hexyl methacrylate) (NaMAm-b-HMAn) (m:n = 64:10, 69:37, 67:50), were synthesized. Both polyNaMA-b-polyNFHMA and polyNaMA-b-polyHMA formed micelles above critical micelle concentrations, (cmc's), around 3 x 10(-5) to 1 x 10(-4) mol/L, while neither polymer decreased surface tension of aqueous solutions. The size and shape of the micelles were examined by dynamic light scattering, small-angle neutron scattering, and small-angle X-ray scattering. PolyNaMA-b-polyHMA appeared to form only spherical micelles, while polyNaMA-b-polyNFHMA with a long NFHMA segment formed both spherical and rodlike micelles. The micelles of fluorine-containing block copolymers were obviously larger than those of non-fluorine-containing block copolymers with the same chain length and the same hydrophilic/hydrophobic chain ratio. The fluorine-containing block copolymer selectively solubilized fluorinated dye into the water phase when a mixture of decafluorobiphenyl and 2,6-dimethylnaphthalene was added to the micelle solution.     

仿细胞膜结构共聚物的合成及涂层性能

采用饥饿法将2-甲基丙烯酰氧乙基磷酰胆碱(MPC)分别与甲基丙烯酸十八烷基酯(SMA)、 甲基丙烯酸十二烷基酯(LMA)及甲基丙烯酸正丁酯(BMA)聚合, 通过改变投料比例和沉淀剂种类, 合成了一系列含磷酰胆碱基团的仿细胞膜结构的两亲性二元随机共聚物. ¹H NMR和元素分析结果表明, 合成的两亲性二元随机共聚物的组成与投料比相近. DSC结果表明, 聚合物具有较低的玻璃化转变温度. 表面张力及水的动态接触角(DCA)研究发现, 聚合物涂层表面具有明显的两亲性及表面结构易变性, 在空气中憎水基团在表面取向, 在水环境中亲水的磷酰胆碱基团则迁移取向到涂层表面形成仿细胞外层膜结构界面, 最终形成不溶于水的仿细胞膜结构涂层.     

Invertible architectures from amphiphilic polyesters

We synthesized and characterized novel amphiphilic polyesters with both hydrophilic and hydrophobic functionalities. The polyesters are soluble in organic and aqueous media and reveal the formation of inverse architectures whose behavior could be correlated to their chemical structure. We foresee that the amphiphilic properties of the polyesters reported here are obviously the basis of new architectures both in solution and on the solid surfaces, which could be used in a broad range of applications. The described synthesis of the copolymers is very simple and is based on commercially available products. That makes this approach attractive in various uses.     

Synthesis of New Amphiphilic Comb-Like Copolymers Based on Maleic Anhydride and α-Olefins

Summary: Novel amphiphilic comb-like poly(α-olefin-co-maleic anhydride) with a controlled ratio of hydrophilic (polyoxyethylene) and hydrophobic (polymethylene) side chains have been synthesized and characterized. The comb-like copolymers are soluble in organic and aqueous media and form micelles whose behaviour could be correlated to the chemical structure of polymers. We foresee that amphiphilic properties of the novel comb-like polymers are obviously the basis of new architectures in solution which could be used in a broad range of applications. Using micelles from these copolymers, silver nanoparticles with a narrow particle size distribution have been obtained as stable dispersion in both polar and non-polar media.     

Non-ionic amphiphilic homopolymers: synthesis, solution properties, and biochemical validation

A novel type of nonionic amphipols for handling membrane proteins in detergent-free aqueous solutions has been obtained through free-radical homo-telomerization of an acrylamide-based monomer comprising a C(11) alkyl chain and two glucose moieties, using a thiol as transfer reagent. By controlling the thiol/monomer ratio, the number-average molecular weight of the polymers was varied from 8 to 63 kDa. Homopolymeric nonionic amphipols were found to be highly soluble in water and to self-organize, within a large concentration range, into small, compact particles of ~6 nm diameter with a narrow size distribution, regardless of the molecular weight of the polymer. They proved able to trap and stabilize two test membrane proteins, bacteriorhodopsin from Halobium salinarum and the outer membrane protein X of Escherichia coli, under the form of small and well-defined complexes, whose size, composition, and shape were studied by aqueous size-exclusion chromatography, analytical ultracentrifugation, and small-angle neutron scattering. As shown in a companion paper, nonionic amphipols can be used for membrane protein folding, cell-free synthesis, and solution NMR studies (Bazzacco et al. 2012, Biochemistry, DOI: 10.1021/bi201862v).     

Synthesis and aggregation properties of amphiphilic mono and bisadducts of fullerene in aqueous solution

New amphiphilic[60]fullerene monoadduct TPF and bisadducts BTPF were synthesized and well-characterized. Their aggregation properties in aqueous solution was investigated by UV-vis and TEM methods. In aqueous solution, monoadduct TPF forms irregularly shaped and some rod-like aggregates, whereas bisadducts BTPF gives sphadcal aggregates with diameters of 50-150 rim. It indicated that the aggregation properties of amphiphilic fullerene derivatives depend on the number of hydrophilic     

Preparation of Cationic Mixed-Mode Acrylamide-Based Monolithic Stationary Phases for Capillary Electrochromatography

A series of amphiphilic macroporous mixed-mode acrylamide-based continuous beds bearing positively charged quaternary ammonium groups is synthesized for capillary electrochromatography (CEC) under variation of the concentration of the cationic monomer in the polymerization mixture. Positively charged mixed-mode monolithic stationary phases are synthesized in pre-treated fused silica capillaries of 100 µm I.D via single step free radical copolymerization of cyclodextrin-solubilized N-tert-butylacrylamide, a hydrophilic crosslinker (piperazine diacrylamide), a hydrophilic neutral monomer (methacrylamide), and a positively charged monomer ([2-(methacryloyloxy)ethyl]trimethyl ammonium methyl sulfate) in aqueous solution containing the lyotropic salt ammonium sulfate as a pore-forming agent. The synthesized monolithic stationary phases contain hydrophobic, hydrophilic, and charged functionalities. They can be employed for the CEC separations of different classes of neutral and charged solutes (with varied polarity) in the reversed-phase mode, in the normal-phase mode, in the ion-exchange mode, in a mixed-mode, or in the hydrophilic interaction liquid chromatography (HILIC) mode. The influence of the concentration of the cationic monomer in the polymerization mixture on retention factor, electroosmotic mobility, and methylene selectivity (α_meth) is studied under isocratic conditions for alkylphenones in the reversed-phase mode by capillary electrochromatography (CEC). Scanning electron microscopy (SEM) micrographs demonstrate that the morphology of the synthesized monoliths (i.e., the domain size) is strongly influenced by the variation of the concentration of the cationic monomer in the polymerization mixture.     

Substrate effect on the formation of hydrogels with heterogeneous network structure

It was found that when an aqueous solution of vinyl monomers is polymerized on a hydrophobic substrate, obvious heterogeneity occurs in the region of the interface. This substrate effect was observed on polytetrafluroethylene (Teflon), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinylchloride (PVC), but not on hydrophilic substrates. Compared with synthesis on hydrophilic surfaces, the surfaces of hydrogels synthesized on a hydrophobic substrate exhibit a larger degree of swelling, a lower surface coefficient of friction and elastic modulus, weaker interfacial adhesion, and reduced interaction with biological cells. This substrate effect has been observed for many types of aqueous monomer solutions. It was found that the above properties are related to the loosely cross-linked architecture, containing some graft-like polymer chains, that is formed on the gel surface when the gel is prepared on a hydrophobic substrate. To understand the mechanism of the substrate effect, two novel optical methods, electric speckle pattern interferometry (ESPI) and real-time laser sheet refraction (RT-LSR), were developed. It was found that oxygen trapped in the composite interface between the monomer solution and rough hydrophobic substrates played an important role in the substrate effect.     

SYNTHESIS AND CHARACTERIZATION OF WATER-SOLUBLE BLOCK COPOLYMERS WITH AN END-TAGGED NAPHTHALENE PROBE

Water-soluble A-B block copolymers of 2-perfluoroethyl-2-oxazoline or 2-pentyl-2-oxazoline as hydrophobic monomers and 2-methyl-2-oxazoline as hydrophilic monomer were prepared by means of the living cationic ring-opening polymerization. The polymerization was initiated with N-methyl-2-(1-naphthyl)-2-oxazolinium trifluoromethanesulfonate as fluorescence label followed by sequential addition of the hydrophobic and the hydrophilic monomer. The polymerization was monitored by ¹H NMR spectroscopy and gel permeation chromatography (GPC) measurements. The results revealed that fluorophilic block copolymers can be prepared by this method while lipohilic block copolymers are not accessible by this monomer sequence. Micelle formation of the fluorophilic block copolymers in aqueous solution was studied by means of steady-state fluorescence spectroscopy which confirmed strong intermolecular excimer formation of the terminal bounded naphthalene moiety. In chloroform as a good solvent for both blocks, only monomer fluorescence could be observed.     

Free-radical polymerization of guanidine acrylate and methacrylate and the conformational behavior of growing chains in aqueous solutions

Monomer salts based on acrylic acids and guanidine—guanidine acrylate and methacrylate—have been synthesized, and the kinetic features of their free-radical polymerization in aqueous solutions have been studied. When polymerization is carried out in organic solvents (methanol, ethanol, or dioxane), the system is heterogeneous over the entire range of monomer concentrations. In aqueous solutions, the reaction systems are homogeneous only at small initial monomer concentrations (less than 1.30 and 0.40 mol/l for guanidine acrylate and methacrylate, respectively; the ammonium persulfate concentration is 5 × 10^?3 mol/l; pH ～ 6.5; 60°C). At higher concentrations, microheterogeneity appears from small conversions (～1%). This phenomenon is associated with the coiling of growing polymer chains owing to associative interactions between guanidine groups occurring in the monomer solution and carboxyl groups of (meth)acrylate polymer units. In aqueous solutions over the entire range of monomer concentrations (0.2–2.5 mol/l), the kinetic orders are the same as in the case of corresponding acrylic acids. The effects of composition of reaction solutions on changes in the initial rate of polymerization and the conformational behavior of the systems under study have been ascertained.     

Synthesis of novel poly(ethylene glycol) based amphiphilic polymers

The synthesis of new amphiphilic polyesters based on poly(ethylene glycol) (PEGs) and studies on their solution properties are reported. Two novel monomers, dimethyl 5-n-butoxy isophthalate (2) and dimethyl 5-n-octoxy isophthalate (3) were synthesized. Three series of novel amphiphilic polyesters, i.e. poly(ethyleneoxy isophthalate)s (10-15), poly(ethyleneoxy n-butoxy isophthalate)s (16-21) and poly(ethyleneoxy n-octoxy isophthalate)s (22-27) have been synthesized from PEGs of different sizes and dimethyl isophthalates 1-3 via the transesterification-polycondensation using dibutyltin diacetate as a catalyst. The structures of the polyesters were established from a detailed analysis of their spectra, i.e. FTIR, ¹H-NMR (one- and two-dimensional) and ¹³C-NMR. By adjusting the ratio of hydrophobic (diesters) and hydrophilic (PEGs) segments in polymers, their main chain structures and solution properties could be changed. The viscosity molecular weights (M_v) of polymers, obtained from Mark-Houwink-Sakurada relationship having poly(ethylene terephthalate) as a model, were in the range of 4500-32,000 g/mol. Intrinsic viscosities were studied based on polymer backbone length (PEGs effect) and pendant group (diesters effect) and these were found to be dependent on molecular weights of the PEGs used.     

Synthesis and surface characterization of an amphiphilic fluorinated copolymer via emulsifier-free emulsion polymerization of RAFT

The hydrophobic monomer dodecafluoroheptyl methacrylate has been copolymerized with hydrophilic monomer methacrylic acid in aqueous solution without any additional emulsifier used via a two-step polymerization process of RAFT. The FTIR and GPC results indicated that amphiphilic copolymers with a narrow molecular weight distribution and well-defined blocks have been synthesized successfully. And the copolymers are likely to form steady micelles in the emulsion. Indicated by TEM, it is clear that micelles with a diameter of 70-120 nm have been formed. Despite a content of 22 wt% of hydrophilic carboxyl, films formed by casting the emulsion onto the baseplate can be hydrophobic after heating treatment.     

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 use of derivatized cyclodextrins as solubilizing agents in the preparation of macroporous polymers employed as amphiphilic continuous beds in capillary electrochromatography

Employing solubilization by complexation with CDs, new mixed-mode monolithic stationary phases for CEC and micro-LC were synthesized. Free radical copolymerization was performed in aqueous solution with a CD-solubilized hydrophobic monomer, a water-soluble crosslinker (piperazinediacrylamide), and a charged monomer (vinylsulfonic acid). Different hydrophobic methacrylate monomers (isobornyl, adamantyl, cyclohexyl, and phenyl methacrylate) were investigated. Chromatographic properties of the synthesized monoliths were studied with aqueous and nonaqueous mobile phases with hydrophobic and polar analytes. Due to the amphiphilic nature of the polymers synthesized, the elution orders obtained correspond to the RP mode and to the normal-phase mode dependent on the polarity of the mobile phase. However, observations made with polar solutes and polar mobile phase can only be explained by a mixed-mode retention mechanism. The influence of the total monomer concentration (%T) on the chromatographic properties and on the specific permeability was elucidated. Run-to-run, day-to-day, and capillary-to-capillary reproducibility of electroosmotic mobility and retention factors were determined. Comparison of retention data with those of a commercial octadecyl silica gel HPLC column reveals that the methylene selectivity of the monolithic capillaries prepared in this study is very similar to that of routinely used octadecyl silica gels.     

NOVEL AMPHIPHILIC FLUORESCENT GRAFT COPOLYMER： SYNTHESIS, CHARACTERIZATION AND ENCAPSULATION OF A HYDROPHOBIC AGENT

Novel amphiphilic fluorescent graft copolymer （PVP-PyAHy） was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-（1-pyrenebutyryl）-N＇-acryloyl hydrazide （PyAHy） with hydrophilic precursor polymers of vinyl-functionalized poly（N-vinylpyrrolidone） （PVP） in DMF. The copolymer is amphiphilic and has intrinsic fluorescence. FT-IR, ^1H-NMR, TEM, gel permeation chromatography-multi-angle laser light scattering, UV-Vis spectroscopy and fluorescence spectroscopy were used to characterize this copolymer. The TEM observation shows that the copolymer PVP-PyAHy forms micelles in aqueous solution. Results of fluorometric measurements illustrate that the critical micelle concentration （CMC） value of PVP-PyAHy in aqueous solution is about 0.90 mg/mL. To examine the encapsulation ability of the copolymer in aqueous media, methyl yellow was employed as a model hydrophobic agent. The loading level of the polymer to methyl yellow is 8.8 mg/g. The cytotoxicity assays for Madin Darby Canine Kidney （MDCK） cells shows good biocompatibility of PVP-PyAHy in vitro. These results suggest the potential of this copolymer PVP-PyAHy as drugs delivery carrier and fluorescent tracer.     

SYNTHESIS OF AMPHIPHILIC COPOLYMERS BASED ON ACRYLATES BY FREE-RADICAL POLYMERIZATION AND THEIR APPLICATION IN ALKYD EMULSIONS

Novel amphiphilic copolymers which contained poly(ethylene glycol) side-chain, long-chain alkyl pendant groups, and carboxyl groups have been synthesized by the conventional free-radical copolymerization of special monomers. The products were characterized by analysis of Fourier transform infrared spectroscopy (FT-IR), Gel Permeation Chromatography (GPC), and ¹H NMR. Based on the measurement of surface tension of aqueous copolymer solutions with various concentrations at an air/water interface, the critical micelle concentrations (CMC) was found to be lower along with the increase of copolymer concentration. Experimental results showed that CMC of this kind of amphiphilic polymer appeared in the range of 0.01～0.1 g/L. The amphiphilic polymer was mixed with an anionic surfactant (SDBS) in different proportions at aqueous solution and then successfully used in the preparation of alkyd emulsions. The results were compared with those of alkyd emulsions without polymeric surfactant. Steric stabilization of amphiphilic polymer was investigated by the observation of the stability of alkyd emulsions. The emulsions were stable after resting at ambient temperature for four months.     

两亲性树形-线团大单体的合成及其丙烯酸共聚乳液的流变行为

将3,4,5-三(十六烷基氧基)苯甲酰氯先后与分子量为1000的聚乙二醇、甲基丙烯酰氯反应合成了一种新的可聚合两亲性树形-线团大单体——3,4,5-三(十六烷氧基)苯甲酰氧基聚氧乙烯甲基丙烯酸酯(6).通过核磁、红外、元素分析等对产物进行了表征.然后将其与甲基丙烯酸、丙烯酸乙酯进行乳液共聚合,制备了一种疏水树形侧链改性...     

Polymerization of oligo(ethylene glycol) (meth)acrylates: Toward new generations of smart biocompatible materials

Monomers composed of a (meth)acrylate moiety connected to a short poly(ethylene)glycol (PEG) chain are versatile building‐blocks for the preparation of “smart” biorelevant materials. Many of these monomers are commercial and can be easily polymerized by either anionic, free‐radical, or controlled radical polymerization. The latter approach allows synthesis of well‐defined PEG‐based macromolecular architectures such as amphiphilic block copolymers, dense polymer brushes, or biohybrids. Furthermore, the resulting polymers exhibit fascinating solution properties in aqueous medium. Depending on the molecular structure of their monomer units, non linear PEG analogues can be either insoluble in water, readily soluble up to 100 °C, or thermoresponsive. Thus, these polymers can be used for building a wide variety of modern materials such as biosensors, artificial tissues, smart gels for chromatography, and drug carriers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3459–3470, 2008