Mixed micelles based on cationic and anionic amphiphilic diblock copolymers containing identical hydrophobic blocks

Through the use of the methods of turbidimetry, UV spectrophotometry, fluorescence spectroscopy, dynamic light scattering, and ultracentrifugation, micelle formation is studied for cationic (polysty-rene-poly-N-ethyl-4-vinylpyridium bromide) and anionic (polystyrene-sodium polyacrylate) diblock copolymers containing identical polystyrene blocks in dilute aqueous saline solutions. Mixing of aqueous dispersions of individual micelles is accompanied by the formation of only insoluble products, which likely are intermicellar interpolyelectrolyte complexes. At the same time, mixing of diblock copolymers in a nonselective solvent and its subsequent gradient replacement with water during suppressed interpolyelectrolyte interactions yields mixed diblock copolymer micelles, which are found to be dispersionally stable in an excess of charged units of any polymer component. The micelles are composed of an insoluble polystyrene core and a mixed interpolyelectrolyte corona, and their hydrodynamic characteristics are controlled by the ratio of charged units in the mixed diblock copolymers. The mixed micelles are found to be able to interact with the macromolecules of a homopolyelectrolyte, sodium poly(styrene sulfonate), in aqueous solutions and form ternary complexes. In this case, depending on the composition of the mixed micelles, ternary complexes can be dispersionally stable or can aggregate and precipitate.     

Temperature/Light Dual‐Responsive Inclusion Complexes of α‐Cyclodextrins and Azobenzene‐Containing Polymers

Three kinds of photoresponsive copolymers with azobenzene side chains were synthesized by radical polymerization of N‐4‐phenylazophenylacrylamide (PAPA) with N‐isopropylacrylamide (NIPAM), N,N‐diethylacrylamide (DEAM) or N,N‐dimethylacrylamide (DMAM) respectively. Their structures were characterized by FT‐IR, ¹H‐NMR and UV/Vis spectroscopy. Their reversible photoresponses were studied with or without α‐cyclodextrin (α‐CD), which showed that both the copolymers and their inclusion complexes with α‐CD underwent rapid photoisomerization. The lower critical solution temperature (LCST) of the copolymers and their inclusion complexes with α‐CD were investigated by cloud point measurement, which showed that the LCST of three kinds of copolymers increased largely after adding α‐CD. After UV irradiation on the solutions of copolymers and their inclusion complexes, the LCST of the copolymers increased slightly with the absence of α‐CD, while decreased largely with the presence of α‐CD. Furthermore, the LCST reverted to its originality after visible light irradiation. This change of LCST could be reversibly controlled by UV and visible light irradiation alternately. In particular, in the copolymer of PAPA and DMAM, the reversible water solubility of the inclusion complexes could be triggered by alternating UV and visible light irradiation.     

Contrast viscosity changes upon photoirradiation for mixtures of poly(acrylic acid)-based alpha-cyclodextrin and azobenzene polymers

Polymer-polymer interactions were investigated for mixtures of a poly(acrylic acid) (pAA) carrying azobenzene (pC12Azo) and two kinds of pAA carrying alpha-cyclodextrin (CD), in which CDs are attached to the main chain through the 3- and 6-positions in CD (p3alphaCD and p6alphaCD, respectively), using several techniques, such as viscosity and NMR measurements. Viscosity data exhibited contrast changes upon UV irradiation: thinning (p3alphaCD/pC12Azo) and thickening (p6alphaCD/pC12Azo). NOESY spectra confirmed that the contrast viscosity changes were ascribable to differences in how CD moieties interact with pC12Azo after photoisomerization of azobenzene moieties from trans to cis: dissociation of inclusion complexes (p3alphaCD/pC12Azo) and formation of interlocked complexes (p6alphaCD/pC12Azo).     

Association of polyacrylic acids with metronidazole

Intermolecular interactions in mixtures of dilute solutions of poly acids with 1-(β-hydroxyethyl)-2-methyl-5-nitroimidazole were studied by viscometry, potentiometry, and IR spectroscopy. The rheological behavior of dilute aqueous solutions of polyacrylic and polymethacrylic acids and of metronidazole at a total concentration of the components of 0.1 wt % was examined. The composition dependences of the specific viscosity show positive deviations from the additivity with a maximum at approximately 50% relative content of the poly acid. In these mixtures, polyelectrolytic complexes stabilized by hydrogen bonds are formed. The strength of the associates increases with an increase in the temperature to 40°C. Hydrophobic groups in macromolecules of the poly acid play a significant role in stabilization of the complexes. In aqueous solutions metronidazole interacts with acrylic, methacrylic, and hydrochloric acids, and in the solid state it forms linear hydrogen-bonded associates.     

兼具有强阴离子性与疏水缔合性的丙烯酰胺三元共聚物

在微乳液介质中实施了丙烯酰胺 (AM)、苯乙烯 (St)、2 丙烯酰胺基 2 甲基丙磺酸钠 (NaAMPS)的共聚合 ,制备了既含有强阴离子性基团 (—SO3Na)又含有疏水基团 (St)的丙烯酰胺三元共聚物AM NaAMPS St;通过红外光谱法、紫外分光光度法及元素分析法对共聚物的结构及组成进行了表征 ;稀释外推粘度法测定了共聚物的特性粘数 ;测定了共聚物纯水溶液及盐水溶液的表观粘度 ;荧光探针法考察了三元共聚物的疏水缔合性以及离子基团对疏水缔合性的影响规律 .实验结果表明 ,在聚丙烯酰胺 (PAM )分子主链上同时引入强阴离子性基团与疏水基团后 ,阴离子的电粘效应与疏水基团的疏水缔合作用相互协同 ,会使共聚物水溶液的黏度显著提高 ;盐溶液对疏水缔合作用的增强效应与强阴离子基团对盐的较大容忍度相互结合 ,会使共聚物水溶液的抗盐性能明显得以提高 ;大分子链上的强阴离子基团磺酸根的存在 ,在一定程度上会削弱疏水基团之间的疏水缔合作用 ,即对疏水基团的疏水缔合行为会产生一定的负性影响 .     

Graft copolymers composed of high molecular weight poly(ethylene oxide) backbone and poly(N-isopropylacrlylamide) side chains and their thermoassociating properties

Novel, water-soluble thermoassociative graft copolymers based on high molecular weight (HMW) poly(ethylene oxide-co-glycidol) backbone and relatively short grafts of poly-N-isopropyl acrylamide (NIPAAm) were prepared. The copolymer precursors with two architectures (block and graft) were synthesized using Ca-amide-alkoxide initiators. The OH groups in the copolymer precursors have been utilized for grafting NIPAAm using ceric ion (Ce⁴⁺) redox initiation. The idea was to imprint the “smart” properties of PNIPAAm grafts into common HMW poly(ethylene oxide). The sensitive moieties undergo reversible association transitions by changing the temperature of dilute and semidilute aqueous solutions of the copolymers. Associative properties were studied by viscosity and rheology measurements. Two types of interactions, induced by heating, depending on the copolymer concentration namely intra- and intermolecular association were observed.     

A Polymer/Peptide Complex‐Based Sensor Array That Discriminates Bacteria in Urine

A negatively charged poly(para ‐phenyleneethynylene) (PPE) forms electrostatic complexes with four positively charged antimicrobial peptides (AMP). The AMPs partially quench the fluorescence of the PPE and discriminate fourteen different bacteria in water and in human urine by pattern‐based fluorescence recognition; the AMP‐PPE complexes bind differentially to the components of bacterial surfaces. The bacterial species and strains form clusters according to staining properties (Gram‐positive and Gram‐negative) or genetic similarity (genus, species, and strain). The identification and data treatment is performed by pattern evaluation with linear discriminant analysis (LDA) of the collected fluorescence intensity data.     

Determination of the enantiomeric composition of guest molecules by chemometric analysis of the UV-visible spectra of cyclodextrin guest-host complexes

Multivariate statistical techniques were applied to the UV spectra of a series of solutions at pH 12 containing a fixed concentration (30 mM) of beta-cyclodextrin (beta-CD) and a fixed concentration (15 mM) of 2-phenylglycine (phi-Gly) with various known enantiomeric compositions. Multivariate correlation of the spectral data for the solutions containing the phi-Gly/beta-CD guest-host complexes with the known enantiomeric composition of the phi-Gly samples was accomplished by partial-least-squares regression. When the multivariate model was used to predict the enantiomeric purity of a test set of samples over the mol fraction range of 0.5-0.9 R-phi-Gly, the average magnitude of the relative errors in the mol fraction determination of enantiomeric composition was 3%. A plot of the enantiomeric composition predicted by the model versus the known enantiomeric composition of the calibration set gave a straight line with a correlation coefficient of 0.955, a slope of 1.05, and an offset of 5.61 x 10-4.     

Celluloses in an ionic liquid: the rheological properties of the solutions spanning the dilute and semidilute regimes

The ionic liquid of 1-allyl-3-methylimidazolium chloride ([amim]Cl) was used as the good solvent to dissolve celluloses. Cellulose concentration covers the range of 0.1-3.0 wt %, spanning both the dilute and semidilute regimes. The rheological properties of the cellulose ionic liquid solutions have been investigated by steady shear and oscillatory shear measurements in this study. In the steady shear measurements, all the cellulose solutions show a shear thinning behavior at high shear rates; however, the dilute cellulose solutions show another shear thinning region at low shear rates, which may reflect the characteristics of the [amim]Cl solvent. In the oscillatory shear measurements, for the dilute regime, the reduced dimensionless moduli are obtained by extrapolation of the viscoelastic measurements for the dilute solutions to infinite dilution. The frequency dependences of the reduced dimensionless moduli are intermediate between the predictions from the Zimm model and elongated rodlike model theories, while the fitting by using a hybrid model combining these two model theories agrees well with the experimental results. For the semidilute regime, the frequency dependences of moduli change from the Zimm-like behavior to the Rouse-like behavior with increasing cellulose concentration. In the studied concentration range, the effects of molecular weight and temperature on solution viscoelasticities and the relationship between steady shear viscosity and dynamic shear viscosity are presented. Results show that the solution viscoelasticity greatly depends on the molecular weight of cellulose; the empirical time-temperature superposition principle holds true at the experimental temperatures, while the Cox-Merz rule fails for the solutions investigated in this study.     

Micellization and gelation of aqueous solutions of star-shaped PEG-PCL block copolymers consisting of branched 4-arm poly(ethylene glycol) and polycaprolactone blocks

Star-shaped block copolymers consisting of non-toxic poly(ethylene glycol) and biodegradable polycaprolactone ((PEG5K-PCL)₄) were synthesized by ring-opening polymerization of the ε-caprolactone monomer with hydroxyl-terminated 4-armed PEG as initiator. These biodegradable, amphiphilic star block copolymers showed micellization and sol-gel transition behaviors in aqueous solution with varying concentration and temperature. In the dilute aqueous solutions of star block copolymers, micellization behavior occurred over specific concentration. The 1,6-diphenyl-1,3,5-hexatriene (DPH) solubilization method was used to determine the critical micellization concentration (CMC) of star block copolymers. The obtained micelle size increased with increasing hydrophobic PCL block length. In high-concentration solutions, the star block copolymers showed temperature-sensitive sol-gel transition behavior. The morphology of the micelle and gel was investigated by atomic force microscopy (AFM). As a result, the micelles showed a core-corona spherical structure at concentration near CMC, while the gel showed a mountain-chain-like morphology picture. It was proposed that with increasing the micelle concentration the worm-like micelle clusters formed firstly and the gel was constructed by the packing of micelle clusters.     

Water-Soluble Random and Graft Copolymers for Utilization in Enhanced Oil Recovery

Copolymer structure has a marked effect on solution properties and thus behavioral characteristics of water-soluble copolymers utilized in enhanced oil recovery. The ability of random and graft copolymers to maintain large hydrodynamic volumes in dilute solutions in the presence of mono- and divalent electrolytes is critical for mobility control. The differences in viscosity behavior are described for a series of random and graft copolymers of acryl-amide with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS), diacetone acrylamide (DAAM), and sodium acrylate (NaA) as a function of polymer microstructure, temperature, concentration, and added electrolytes. Copolymers of AM-NaAMPS show enhanced salt tolerance and phase stability over their AM-NaA counterparts with similar compositions and molecular weights. The AM-DAAM copolymers show unusual solution behavior with increases in viscosity in the presence of added salt.     

Room temperature sphere-to-rod growth and gelation of PEO-PPO-PEO triblock copolymers in aqueous salt solutions

The effects of NaCl and KF on the sphere-to-rod micellar growth behavior of triblock copolymers having two different compositions, (EO)20(PO)70(EO)20 (P123) and (EO)26(PO)40(EO)26 (P85), have been studied by dynamic light scattering (DLS), small angle neutron scattering (SANS) and dilute solution viscometry. NaCl can effectively tune the sphere-to-rod growth temperature of the micelles of both these copolymers and induce micellar growth down to the room temperature and below. The growth behavior is found to be dependent on the composition of the copolymer as P123 being more hydrophobic shows the room temperature growth in the presence of ethanol at significantly lesser NaCl concentration than the less hydrophobic copolymer P85. DLS studies depict for the first time the growth driven transition of the copolymer solutions from dilute to semi-dilute regime as a function of copolymer and salt concentrations. KF can also induce room temperature growth of the P123 micelles at lesser salt concentration than NaCl but it fails to induce any such growth of the P85 micelles. A pseudo-binary temperature-concentration phase diagram on 15% copolymer solutions shows the variation of the sphere-to-rod transition temperature and the cloud point of the copolymer solutions as a function of salt concentration.     

高分子表面活性剂P(AM-co-OPMA)的合成与表征

辛基酚聚氧乙烯醚(10)(OP-10)与马来酸酐在95℃下反应,合成了辛基酚聚氧乙烯醚马来酸单酯(OPMA);并在水溶液中与丙烯酰胺(AM)单体进行共聚合,获得了高分子表面活性剂P(AM-co-OPMA);考察了引发剂用量、单体组成、单体总浓度及反应温度对共聚物特性粘数与阴离子度的影响.通过红外光谱、紫外光谱、荧光发射光谱和电导滴定对共聚物结构和组成进行了表征;利用视频光学接触角测量仪分别测定了共聚物表面和界面张力.结果表明,在聚丙烯酰胺分子主链上引入OPMA链节后,不仅保持了PAM优良的增稠能力(特性粘数达764.31 mL/g),且赋予了共聚物较高的表面活性(浓度为1.5 g/L共聚物水溶液的表面和界面张力分别可达53.94 mN/m和5.41 mN/m).     

Solution behavior of sulfonate ionomer interpolymer complexes

The interaction of metal sulfonate ionomers with polymers containing low levels of amines has been investigated in solution. For example, zinc sulfo EPDM and a styrene/vinyl pyridine copolymer form such complexes over broad concentration ranges. The resultant solutions offer enhanced viscosities at dilute polymer concentrations. At high polymer levels solutions based on these complexes are lower in viscosity than the ionomer alone. These interpolymer complexes have been shown to exhibit an improved property/rheology balance in bulk systems. In solution, polymer complexes provide control of hydrocarbon solution viscosity not available with conventional polymers. Reduced viscosity-concentration studies suggest that these polymer complexes are a result of the amine-containing polymer interacting with intramolecular-associated ionomer coils, which at higher concentrations form a pseudonetwork.     

Rheology of aqueous solutions of polyglycidol-based analogues to pluronic block copolymers

The aqueous solution properties of a series of polyglycidol-poly(propylene oxide)-polyglycidol (PG-PPO-PG) block copolymers were investigated by means of rheology. The copolymers are considered as analogues to the commercially available Pluronic, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO), block copolymers in which the flanking PEO blocks are substituted by blocks of structurally similar PG bearing a hydroxyl group in each repeating monomer unit. In the dilute regime, the samples normally behave as Newtonian fluids. Shear thinning was observed only for the solutions of LGP65 (the copolymer of 50 wt % PG content) as well as at concentrations well above the critical micellization concentration for the rest of the copolymers. The zero shear viscosities exhibited pronounced maxima at PG content of 50 wt % and were found to decrease with increasing temperature. The concentrated solutions were investigated using oscillatory measurements. Large hystereses were observed during the temperature sweeps 15-70-15 degrees C. The evolutions of the loss and storage moduli with frequency, PG content, and temperature displayed transitions from a non-elastic to elastic behavior of the solutions. A phase diagram showing areas of predominant elasticity or fluidity was constructed.     

Viscosity behavior of poly(glyceryl methacrylate) in the presence of borate and phenylboronate ions

The viscosity behavior of polyelectrolyte solutions induced by borate or phenylboronate complexation with poly(glyceryl methacrylate) (PGM) has been investigated. In dilute solutions borate ions can form monodiol (1/1) complexes and didiol (2/1) intramolecular complexes. Both types of complex are anionic. Thus, the polymer is characterized by the existence of charged sites on the chain and loops formed by intramolecular complexation. On the contrary, phenylboronate can only give monodiol 1/1 complexes. In the presence of passive salt, the charges are screened. By addition of borate ion to a PGM solution, a decrease of the initial polymer viscosity due to loop formation is first observed, then the anionic charges fixed on the chain by complex formation induce an expansion of the polyelectrolyte and the viscosity of the solution increases. The situation is different for the PGM-phenyl boronate system, where no intramolecular crosslink is present. In this case the viscosity of the solution increases with phenyl boronate concentration. But for a fixed complexing ion concentration it will tend to that of the neutral polymer when NaCl is added. ©1995 John Wiley & Sons, Inc.     

Construction of supramolecular polymers with alternating alpha-, beta-cyclodextrin units using conformational change induced by competitive guests

Supramolecular polymers having alternating alpha- and beta-cyclodextrin (CD) units have been prepared by using conformational change induced by competitive guests. Although each CD unit does not form intermolecular complexes, a mixture of an alpha-CD derivative and a beta-CD derivative formed intermolecular complexes to give supramolecular polymers having alternating CD units. This is the first example of construction of supramolecular polymers with alternating alpha-, beta-cyclodextrin units.     

Viscosity of dilute solutions of styrene copolymers in the course of polymer-analogous transformations

The properties of dilute solutions of styrene copolymers and their porphyrin derivatives prepared via the functional group transformations have been studied in DMF at 20–35°C. The effect of the copolymer composition, on the intrinsic viscosity, the Huggins constant, the macromolecule dimensions, and thus on the interaction with solvent has been elucidated. The nature and content of functional groups in the polymer influence the behavior of macromolecule coil in the solution. Introduction of the porphyrin fragment loosens the macromolecular coil, but does not qualitatively change the solution behavior.     

Application of the theory of dilute polymer solutions to the assessment of the structure and properties of styrene-acrylic acid copolymers

Properties of dilute solutions of polystyrene and styrene-acrylic acid copolymers in DMF and ethyl acetate were studied in the temperature range 20–35°C. It was shown that the dependences of the intrinsic viscosity and Huggins constants on temperature for the copolymers differ from that for polystyrene. Comparison of the “quality” of the solvents was carried out.     

Light-responsive hydrophobic association of azobenzene-modified poly(acrylic acid) with neutral surfactants

Photoresponsive association between azobenzene-modified poly(acrylic acid)s (AMPs) and the nonionic surfactants tetraethylene glycol monododecyl ether and octadecyl ether (C12E4 and C18E4) has been achieved in dilute aqueous solution. The binding was investigated by (i) spectrophotometry that probes the polarity close to the azobenzene chromophore, (ii) capillary electrophoresis to obtain the amount of C12E4 bound per polymer chain, and (iii) pressure-area curves of Langmuir films to obtain information on the adsorption of AMP at the water-C18E4 interface. Increasing hydrophobicity of AMP (with increasing degree of modification with azobenzene side-groups) tightened the association with C12E4 in the dark. Exposure to UV light rapidly converted the azobenzene to their more polar cis isomer, which in turn weakened the association with surfactant. Almost complete photorelease of bound C12E4 was obtained with the optimal structure of AMP. Adsorption on large interfaces is much less sensitive to light. The possible origin of the photoresponse is analyzed in terms of AMP affinity for surfactant assemblies and azobenzene penetration in the hydrophobic core of micelles. We propose that the photoswing of polarity is amplified by the binding to small micelles because of the small number of anchors involved. A few azobenzene anchors afford tight binding in the dark, but also detach more easily than the whole AMP chain upon photoisomerization.