Preparation and properties of a new type of comb-shaped, amphiphilic cellulose derivative

Comb-shaped, amphiphilic O-(2- hydroxy-3-butoxypropyl) cellulose (HBPC) was prepared by a homogeneous reaction of cellulose with butyl glycidyl ether (BGE) in a 10% (w/w) LiCl--DMAc solution. It was found that: (a) the molar substitution (MS) of water-soluble HBPC ranges from 0.4 to 1.0, and is nearly equal to its degree of substitution (DS), indicating that the HBPC derivatives obtained are comb-shaped polymers; (b) the water-soluble HBPC shows a thermally reversible sol-gel transition in aqueous solution; and (c) the derivative having a DS of 0.6 shows surface activity with critical micelle concentration (cmc) in the order of 0.8 g/l and surface tension of 31.5 dyn/cm     

Preparation and self-assembly of pH-sensitive amphiphilic comb-shaped copolymer containing long fluorinated side chains

Novel pH-sensitive amphiphilic comb-shaped copolymers containing long fluorinated side chains, which combined the characteristics of pH-sensitivity from pendent tertiary amine groups, unique hydrophobic and fluorophobic characteristic from the fluorinated moieties and hydrophilicity from the poly (ethylene glycol) segments, were designed and synthesized via radical polymerizaion of 2-(Dimethylamino) ethyl methacrylate (DMAEMA), poly (ethylene glycol) methyl ether methacrylate (PEGMA) and homemade fluorinated macromonomer (PHFBMA-GMA). The physicochemical properties of polymeric micelles prepared therefrom were investigated. The chemical structures of the copolymers were characterized by GPC, FTIR and ¹H-NMR. The critical micelle concentrations (CMC) of the copolymers in different pH (5.0 and 7.4) were determined by fluorescence spectroscopy. Larger CMCs could be obtained in lower pH since the pronation of DMAEMA moieties enhanced the hydrophilicity. With increasing the amount, as well as the molecular weight, of PHFBMA-GMA, CMC decreased significantly. As pH decreased, particle size, as well as zeta potential of the polymeric micelles increased significantly, indicating significant pH-sensitivity of the polymeric micelles. Furthermore, larger polymeric micelles were obtained with larger amount, as well as higher molecular weight, of PHFBMA-GMA. Transmission electron microscopy (TEM) showed that the morphological shapes of the copolymers performed spherical micelles. The cytotoxicity test showed that the comb-shaped copolymers performed extremely low cytotoxicity. The pH-sensitive polymeric micelles prepared from the amphiphilic comb-shaped copolymers containing long fluorinated side chains could be potential candidates for nanotanks for hydrophobic or fluorophobic molecules and drug carriers and the facile preparation might fit for large scale industrialization.     

Liquid-crystalline properties of chiral malolactonate monomers and their comb-shaped polymers

A series of optically pure mesogenic ester precursors, and the malolactonate monomers containing mesogenic alcohols obtained from them were prepared and polymerized to homopolymers and copolymers. The liquid-crystalline properties of the precursors, monomers and polymers were investigated by differential scanning calorimetry, polarized light microscopy and wide angle X-ray diffraction. The liquid-crystalline properties of the chiral mesogenic precursors and monomers were only slightly influenced by the chemical structure, configuration and the alkyl spacer length of the mesogenic alcohol substituent of the ester. The precursor, 1-[6-(4'-hexyloxy-4-biphenylyl)oxyhexyl] hydrogen (S)-O-mesylmalate (V-(S)-6) formed smectic E and smectic A phases on melting, while the monomer, 6-(4'-hexyloxy-4-biphenylyl)oxyhexyl (R)-malolactonate (II-(R)-6) showed only a crystal-isotropic phase transition. In contrast, the homopolymer of the latter exhibited a chiral smectic C phase. Copolymers from 2-(4'-hexyloxy-4-biphenylyl)oxyethyl (R)-malolactonate (II-(R)-2) also formed chiral smectic C phases.     

Two-dimensional classification of amphiphilic monomers based on interfacial and partitioning properties. 1. Monomers of synthetic water-soluble polymers

A classification of amphiphilic monomers based on the interfacial and partitioning properties has been proposed. Monomers partitioned at equilibrium between two immiscible phases were ascribed with a pair of parameters: standard free energy of adsorption at the interface and standard free energy of partition between the two phases. These two parameters are represented in a form of two-dimensional diagram (both of them being normalized by kT factor). Comparison of the parameters in question gives information on energetic preferences of the molecules to be located at the interface or in the bulk phases. Four monomers of synthetic water-soluble polymers, namely, N-isopropylacrylamide, 1-vinylimidazole, N-vinylpyrrolidone and N-vinylcaprolactam have been classified according to the above method at various temperatures. The possibility to extend the classification to arbitrary chemicals is discussed.An erratum to this article can be found at     

The influence of amphiphilic polymers on the photocatalytic activity of water-soluble porphyrin photosensitizers

The influence of amphiphilic polymers polyvinylpyrrolidone, poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 (propylene oxide-ethylene oxide triblock copolymer) on the catalytic activity of a number of water-soluble metal-free porphyrin photosensitizers was studied in the reaction of tryptophan photooxidation in aqueous solution. The introduction of the specified polymers was found to enhance the activity of carbon-substituted tetrafluorophenylporpyrin, photoditazine, and dimegin. It was ascertained that introduction of polyvinylpyrrolidone had the strongest effect on the increase in the photooxidation process rate; the change in the activity of porphyrins was 30–70%. The introduction of poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 was shown to enhance the rate of the process by 10–40%. It was concluded that this polymer effect was connected with the dissociation of aggregates, in which form porphyrin molecules were present in aqueous solutions, as indicated by an increase in fluorescence intensity of porphyrins. The introduction of polymers resulted in a bathochromic shift of the fluorescence bands for all porphyrins, which accounted for the formation of complexes of porphyrin sensitizers with the polymers.     

Photoregulation of the optical properties of comb-shaped polymers with mesogenic side groups

A new approach for photoregulation of supramolecular structure and optical properties of polyacrylic copolymers bearing azobenzene and cyanobiphenyl mesogenic groups is presented. The detailed study of photooptical behaviour, kinetics of photoinduced optical birefringence and mechanism of structural transformations taking place during a laser illumination are discussed.     

Adsorption of amphiphilic comb-shaped macromolecules on a patterned surface

The molecular-dynamics method is used to study the adsorption of A-graft-B macromolecules on patterned planar surfaces consisting of regions a and b that specifically interact with chain units. Surfaces with patterns in the form of circles of different radii and a spiral stripe are discussed. Effective recognition occurs during the adsorption of an A-graft-B macromolecule on these patterned surfaces. Recognition means that, for a proper combination of the architecture of a macromolecule and the energy parameters of its interaction with the plane regions, the macromolecule can be located along the boundary of a circle with a given radius or can stay in a given location of the spiral stripe.     

Analyzing the surface properties of acrylic-based water-soluble polymers

The surface properties of newly synthesized N-methoxy isopropyl acrylamide, N-methoxy isopropyl methacrylamide, cyclo propyl acrylamide, and cyclo propyl methacrylamide polymers were investigated using inverse gas chromatography. The highest dispersive component of the surface energy value was obtained for cyclo propyl methacrylamide at 30°C. The values obtained for all polymers were decreasing with the increasing temperature. The values obtained for the acidic and the basic parameters revealed strong basic characters for the surface of N-methoxy isopropyl methacrylamide and cyclo propyl methacrylamide polymers and weak basic characters for the surface of N-methoxy isopropyl acrylamide and cyclo propyl acrylamide polymers.     

Inhibitive properties of amphoteric, water-soluble cellulosic polymers on bentonite swelling

Amphoteric, water-soluble cellulose derivatives were prepared by the quaternization of anionic carboxymethylcellulose (CMC) with 3-chloro-2-hydroxypropyltrimethyl-ammonium chloride. These polymers suppress the swelling of bentonite more effectively than CMC and their inhibitive effect depends on the degree of quaternization, the molecular conformation and the type of counterions. Received: 13 October 1998 Accepted in revised form: 24 November 1998     

Epoxyallyl polymers: Preparation,structure, and properties

Ways to prepare epoxyallyl polymers with a structure of interpenetrating networks (IPNs) were considered. It was shown that the constructability and high adhesive and cohesive characteristics of obtained polymers evoke interest in the practicality of curing and structuring study for epoxyallyl IPNs and the properties of materials based on them.     

Adsorption and inhibition properties of associates based on water-soluble polymers

It was established on the basis of a set of physico-chemical data that polyelectrolyte complexes (PECs) are formed in a solution containing cation-active oligomers and low-molecular compounds. Here- with, the composition, structure, and stability of PECs depend on the ratio and nature of the initial ingredients. It was shown that the PECs formed in situ feature considerably higher adsorptivity on different interfaces as compared to the initial oligomers. This is due to an increase in the hydrophobicity of macroparticles under association and their enhanced displacement to the interface by the solvent and also an increase in the interaction of the PEC functional groups with the electrode surface due to conformation changes in the surface layer. An inhibiting effect of PECs in the case of Zn(II) ion discharge in polycrystalline electrode and that of Cd(II) on amalgam electrodes is considerably higher than in the case of the initial polyelectrolytes at similar concentrations, which is mainly due to the steric inhibition effect.     

Chromatic changes in the blends of electroactive polymers with comb-shaped flexible polymers

The effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb-shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3-dodecyl-thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p-dodecyl-benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT-IR spectra. Solvatochromism (red-shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)₄/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV-Vis-NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)₄/PODA ternary blends.     

Forming water-soluble CdSe/ZnS QDs using amphiphilic polymers, stearyl methacrylate/methylacrylate copolymers with different hydrophobic moiety ratios and their optical properties and stability

The amphiphilic stearyl methacrylate/methylacrylic acid copolymers (PSMs) were used as phase transfer reagents to convert CdSe/ZnS core-shell quantum dots (QDs) in chloroform to water-soluble PSMs-coated quantum dots (PSM-QDs). The optical properties and stability of PSM-QDs were influenced by the hydrophobic moiety ratios of PSMs, the PSM/QDs mass/volume ratio and the reaction time. The resulting PSM-QDs on optimum reaction conditions retained 60% of the photoluminescence value of the original CdSe/ZnS QDs in chloroform. The carboxylate-based PSM-QDs survived UV irradiation in air for at least 15 days. Upon UV irradiation, the PSM-QDs became about 2 times brighter than the original CdSe/ZnS QDs in chloroform, and the UV-brightened PL can retain the brightness for at least several months. Experimental results further confirmed the stability of PSM-QDs against strong acid, photochemical and thermal treatments. In addition to good performance of PSM-QDs, the synthesis of PSM and the corresponding water-soluble QDs is relatively simple.     

梳形抗盐聚合物在聚合物驱油中的应用

三次采油技术已成为我国提高原油采收率的主要措施之一。研制新型高效驱油用聚合物是降低成本,提高采油量的关键。目前国内外研制的新型高效驱油用聚合物主要为两性聚合物、耐温耐盐单体共聚物、疏水缔合聚合物、复合(或多元组合)型聚合物、共混聚合物和梳形聚合物等。     

Synthesis of chiral, amphiphilic, and water-soluble macrocycles via urea formation

A simple, efficient, and flexible procedure for the synthesis of chiral, amphiphilic, and water-soluble macrocycles is reported. Acylation of p-xylylenediamine with N^α-Fmoc-protected glycine, l-aspartic acid, l-glutamic acid, and l-arginine, followed by removal of Fmoc-groups, gave amino acid:p-xylylene conjugate diamines, which were converted to ten macrocycles via stepwise urea formation using p-nitrophenyl chloroformate. l-Aspartic acid-containing macrocyles proved to be soluble in aqueous buffers and a macrocycle containing four aspartate residues was found to recognize arginine and arginine esters with moderate affinity.     

Optical properties of thermally responsive amphiphilic gold nanoparticles protected with polymers

Amphiphilic thermally responsive gold nanoparticles have been prepared by protecting the particles with both polystyrene, PS, and poly(N-isopropylacrylamide), PNIPAM, chains. Particles form a monolayer on a water surface in a Langmuir trough, and according to in situ spectroscopic measurements, the surface plasmon resonance, SPR, band undergoes a blue-shift during the monolayer compression. The compression-induced blue-shift is related to a change in the conformation of tethered PNIPAM chains; the phenomenon is discussed on the basis of Mie-Drude theory. In contrast, a red-shift in the SPR of the multilayers of the same nanoparticles transferred at different temperatures has been observed with increasing the deposition cycle, attributed to the presence of a weak interparticle coupling in the multilayer.     

Preparation and properties of some water-soluble cobalt (III)–poly-4-vinylpyridine complexes

Water-soluble cobalt(III) chelates having a polymeric ligand such as cis-[Co(en)_2-PVPCl]Cl₂ and cis-[Co-(trien)PVPCl]Cl₂ (PVP = poly-4-vinylpyridine) were prepared by substitution reactions between cobalt(III) chelate and PVP in water–alcohol solution. PVP of different degrees of polymerization was used as the ligand in preparation of these complexes. The PVP complexes were identified and their properties ascertained by microanalysis and by a study of the infrared, ultraviolet, visible, and PMR spectra. Most of the characteristic properties of these complexes may be ascribed to the polymeric structure of the PVP ligand.     

Preparation and properties of vesicles from condensable amphiphilic amino acids

Three double‐chain amphiphiles with amino acid groups as hydrophilic moiety were synthesized. These amphiphiles can be easily dispersed in buffer solution to form transparent dispersion. Examination of the dispersion by transmission electron microscopy (TEM) showed the formation of stable vesicular aggregates, which was also confirmed by the ability to encapsulate water‐soluble dyes. Since amino acid groups are located on the surface of the vesicles, water‐soluble carbodiimide can induce the condensation of these groups to form peptide. The phase transition temperatures of these vesicles were estimated by differential scanning calorimetry (DSC), and a decrease of phase transition temperature was observed after polycondensation due to the disturbance of the ordered arrangement of the hydrophobic chains. The leakage rate of the vesicles before and after condensation was studied by monitoring the increase of fluorescence intensity of water‐soluble dye. These vesicles belong to the least permeable ones and the leakage rate can be controlled by varying the degree of condensation or the temperature.