Investigations of the dissociation behavior and interfacial adsorption characteristics of polyelectrolytes from poly(acrylamido‐2‐methyl‐1‐propane sulfonic acid) with an octadecyl side chain

Water‐soluble polymeric amphiphiles derived from acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and octadecyl monomers in which the linker groups vary among acryloyl [octadecyl methacrylate (ODMAc)], maleate [octadecyl maleate ester (ODME)], and maleamic acid [octadecyl maleamic acid (ODMA)] have been synthesized. The dissociation behavior in water from potentiometric titration suggests that these polymers show resistance to neutralization. This might arise from coil structures, which effect the destabilization of sulfonate ions because of a proximity effect. The effect of the ? COOH group in modifying the dissociation behavior in the copolymers AMPS–ODME and AMPS–ODMA is indicated. The ratio of the intensities of the third vibronic peak (I₃) to the first vibronic peak (I₁) of the fluoroprobe pyrene in the presence of polymer solutions shows negligible changes as a function of pH, and this suggests the retention of micropolarity. The high I₃/I₁ value observed in the presence of the ODMAc polymer suggests intermolecular association. The reduction in the reduced viscosity with the concentration of the polymers suggests the polyelectrolyte behavior of all the copolymers. The progressive decrease in the reduced viscosity from 120 to 95 mL/g when the degree of ionization increases from 0.5 to 1 for the ODME polymer suggests changes in the solution structure. AMPS–ODMA and AMPS–ODME polymers exhibit significant adsorption at the interface and exhibit equilibrium surface tensions of 58.8 and 56.3 mN/m, respectively. The lower surface activity and higher reduced viscosity of ODMAc polymer solutions further support the formation of intermolecular associated or network structures. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 314–324, 2006     

Fluorescence study of chromophore labeled strong polyelectrolyte bound with oppositely charged surfactant

Four strong polyelectrolyte samples of 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) and N,N-dimethylacrylamide (DMAA) were radically copolymerized with a single label of naphthalene or pyrene, with both labels and without label, containing about 40 mol % AMPS. Fluorescence nonradiative energy transfer (NRET) I_Py/I_Np, anisotropy r, I₁/I₃ and excimer emission I_E/I_M of pyrene labels were observed in dilute aqueous solutions with and without cationic surfactant of cetyltrimethylammonium bromide (CTAB). The overlap concentration was determined as 3 g/L from the appearance of intermolecular excimer. The variation of intra- and intermolecular NRET with total polyelectrolyte concentration showed that the charged chains preferentially interpenetrated each other rather than reduce their coil volume as their concentration beyond the overlap threshold. By binding with CTAB, the polyelectrolyte chain became more coiled as known from the reduced viscosity. The intramolecular NRET was dominant when [CTAB]Д᎒^-5 M and then the intermolecular NRET occurred at higher CTAB concentrations with hydrophobic aggregation between CTAB tails bound on different polyelectrolyte chains. The CTAB concentration corresponding to the maxima of I_Py/I_Np just is equal to the AMPS monomer concentration, indicating the formation of 1:1 binding between surfactant and polyelectrolyte in very dilute solutions. Added salt of NaCl up to 0.1 M hardly affected the intramolecular NRET but affected the I_Py/I_Np value for the intermolecular NRET.     

SYNTHESIS AND PROPERTIES OF POLYACETYLENES CONTAINING CARBAZOLE AND AMINO ACID MOIETIES

 Novel 9-proparylcarbazole monomers containing amino acid moieties, 2-N-(tert-butoxycarbonyl)-L-alanine-9-proparylcarbazole ester (1), 2-N-(tert-butoxycarbonyl)-L-O-cyclohexyl-L-glutamic acid-9-proparylcarbazole ester (2) and 2-N-(tert-butoxycarbonyl)-L-phenylalanine-9-proparylcarbazole ester (3) were synthesized and polymerized with (nbd)Rh+[η⁶-C₆H₅B–(C₆H₅)₃] to give the corresponding polymers with number-average molecular weights ranging from 7050 to 10500 in 70%-86% yields. The polymers were completely soluble in toluene, CHCl₃, CH₂Cl₂, THF and DMSO, but insoluble in hexane, diethyl ether and MeOH. The specific rotation studies revealed that poly(1)-(3) do not took predominantly one-handed helical structures in the solvents although they possess chiral groups. The polymers emitted fluorescence in 0.40%–2.35% quantum yields. The cyclic voltammograms of the polymers indicated that the polymers exhibited electrochemical properties.     

Inter- and intramolecular N-terminal methyl–side chain interactions in N-acetyl-L-glutamic acid oligomeric benzyl ester solutions. 1H NMR study

Oligomeric N-acetyl-L-glutamic acid benzyl esters with exact residue number (2, 3 or 4) have been synthesized by a stepwise procedure. The aggregational behavior of these oligomeric molecules in dioxane and benzene has been investigated by use of ¹H NMR. In particular, the concentration dependence of the ¹H signals for the N-terminal CH₃ protons has provided evidence that an intermolecular CH₃···? interaction plays a critical role in the formation of aggregates and that an intramolecular CH₃···? interaction occurs in the monomolecular state.     

Langmuir films of naphthenic acids at different pH and electrolyte concentrations

Langmuir films of naphthenic acids at different pH and electrolyte concentrations are reported. The polydisperse naphthenic acids were commercially available, while two single-component naphthenic acids [5#(H)-cholanoic acid and 1-naphthalenepentanoic acid, decahydro- (9CI)] were synthesized. 1-naphthalenepentanoic acid, decahydro- is too water-soluble to form stable monolayers. 5#(H)-Cholanoic acid and Fluka naphthenic acid form stable films when cations are present in the aqueous subphase. At lower pH the cations are less influential since the naphthenic acids are not protolysed and metal naphthenates cannot be formed. pK_a^s for 5#(H)-cholanoic acid is determined to 5.65. The micellisation of the naphthenates at high pH is described.     

Fourier transform IR spectroscopic study on phase transitions of copolymers of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide and alkyl acrylates in water

Copolymers of N-isopropylacrylamide (IPA) and alkyl acrylates [methyl acrylate (MA), ethyl acrylate, and butyl acrylate] or vinyl acetate have been prepared and their phase transitions in water have been observed by means of IR spectroscopy. The incorporation of these alkyl acrylates into a poly(IPA) (PIPA) chain induces a decrease in the phase-transition temperatures, T_p, and the magnitude increases with increasing size of the alkyl chains. The profiles of the C=O stretching absorption bands of the ester groups [9(C=O)_ester] and the IR bands due to IPA units exhibit critical changes at the T_p of these copolymers. The 9(C=O)_ester bands shift slightly toward higher wavenumbers (blueshift) upon phase transition, while the amide I and amide II bands of the IPA units undergo a blueshift and a redshift, respectively. Analysis of the 9(C=O)_ester band of PIPA-MA by using a curve-fitting method shows that it consists of three components, at 1,703, 1,720, and 1,738 cm^-1. The relative peak area of the largest component (1,720 cm^-1) is almost constant, and those of the 1,703-cm^-1 and 1,738-cm^-1 components increase and decrease with increasing temperature during the phase transition, respectively. However, the changes are rather small, suggesting that changes in hydrogen bonding of the C=O groups of MA units upon phase transition are not significant. The 9(C=O)_ester bands of other comonomers examined here also exhibit similar changes. The situation is consistent with the change in the hydration states of the amide groups of IPA units, most of which associate with water molecules through hydrogen bonds even after the phase separation.     

Synthesis and characterization of copolymers based on benzothiadizole-thiophene-phenylenevinylene

<正>Two novel copolymers based on benzothiadizole-thiophene-phenylenevinylene have been synthesized through palladium catalyzed triple-bond polycondensation method.The copolymers exhibit good solubility in common organic solvents such as CHCl_3,CH_2Cl_2 and THF.The structures and properties of the two copolymers are characterized by FT-IR, ~1H-NMR,UV-Vis absorbance(Abs),gel permeation chromatography(GPC),thermal gravimetric analysis and cyclic voltammetry(CV).The copolymers of P_1 and P_2 show absorption spectra with maximum peak at 532 nm and 573 nm in solution,respectively.Compare to their monomers M_1 and M_2,the absorption peaks of P_1 and P_2 were red-shifted by 34 nm and 54 nm respectively.Thermal gravimetric analysis demonstrated that the polymers were stable and little weight loss was observed below 300℃.Cyclic voltammetry experiments showed that the band gaps of the copolymers were 1.81 eV and 1.62 eV,respectively,suggesting their potential for applications as organic solar cell materials.     

Effect of electrolytes on the physicochemical behaviour of sodium dodecyl sulphate micelles

The values of the critical micelle concentration (cmc) and the degree of electrolytic micelle dissociation, a, for sodium dodecyl sulphate (SDS) as a function of the concentrations of the electrolytes added, NaCl, KCl, NaF, NaClO₄, NH₄ClO₄, and Mg(ClO₄)₂, have been determined. The values of the SDS cmc have been shown to depend on the kind and concentration of the electrolyte cations. The electrolyte cations cause a decrease of the cmc in the following order: Na⁺4⁺+2+. Moreover, a depends on the kind and concentration of the electrolyte added. The electrolyte anions have a much smaller effect on the values of a than the cations. The anions enhance a in the following order: F^->ClO₄^->Cl^-. The effect of different electrolyte cations on a is observed; moreover the values of a either increase or decrease with the electrolyte concentration. Other micellization parameters of SDS versus the concentration of the electrolytes added have been calculated.     

Influence of flocculant charge on the dewaterability of flocculated clay suspensions

The influence of charged components of cationic polyelectrolytes on the dewatering of clay-containing suspensions was investigated with a view to better predicting the efficiency of flocculating agents. In flocculation and dewatering experiments on suspensions of harbour sediment and gravel washings, flocculating agents of the polyacrylamide-co-(trimethylammoniumpropyl chloride) (PTCA) type exhibited different dewatering efficiencies depending on the degree of cationicity, F. For harbour sediment, a dewatering index, I_D, of 80 was achieved with the highly charged PTCA 3 (F=40%) at 30% lower flocculant dose than with the weakly cationic PTCA 1 (F=3%). However, for gravel washings PTCA 1 proved to be more effective: for comparable degrees of dewatering (I_D=80) approximately 40% less flocculant was required than for PTCA 3. In shear experiments on gravel washings and model suspensions with particles of differing size (d₅₀=0.5 und 5.7 µm) weakly cationic PTCA 1 exhibited an increased floc stability at lower concentrations than is necessary to achieve maximum I_D values. For harbour sediments and model suspensions with unimodal particle size distributions this stability did not occur until the doses used were higher than the concentrations needed to achieve maximum I_D values.     

Strong electric-field effects on the doubly-excited intrashell states of He below the He+(N = 2) threshold

The method of complex-coordinate rotation is used to investigate electric-field effects on the doubly-excited 2s2p ¹P⁰, 2p^{2 1}D^e, 2p^{2 3}P^e and 2s2p ³P⁰ states of He. Strong electric-field strengths up to F=0.02 Ry are used in our present study. Products of Slater orbitals are used to represent the two-electron wave functions, with l_max=8 being employed for the individual electron. Block matrices with up to L_max=5 (H-states) are used to investigate the convergence behavior for the resonance parameters (resonance energy and width). When the external electric field is turned on, "classic" Stark effect is observed for the M=0 and M=ǃ components of the two singlet-spin states and for the M=ǃ components of the triplet-spin states. Comparisons are made with other calculations when available.     

Correlation of architecture with excimer emission in 100% pyrene‐labeled self‐assembled polymers

Pyrene was incorporated as pendant unit to side‐chain urethane methacrylate polymers having a short ethyleneoxy or a long polyethyleneoxy spacer segment. The short‐spacer pyrene urethane methacrylate was also incorporated either as block or random copolymer (1:9) along with polystyrene. The excimer emission was observed to be different for different polymers with the random copolymer exhibiting the lowest efficiency. But, the total quantum yield was highest (? = 0.58) for random copolymer due to the high emission coefficient of monomer compared to that of excimer. The polymer dynamics were compared by steady state emission and fluorescence decay in THF or THF/water (9:1) solvent mixture and films. The solid state decay profile showed decay without a rise time indicating presence of ground state aggregates. In THF/water (9:1), the decay profile at the excimer emission (500 nm) showed a rise time indicating dynamic excimers. The evolution of excimeric emission centred ～430 or ～480 nm as a function of temperature was also studied in THF/water (9:1). The I_E/I_M ratio for the λ_{343 nm} excitation exhibited steady increase with temperature with the block copolymer PS‐b‐PIHP exhibiting the highest ratio and highest rate of increase; whereas, the random copolymer PS‐r‐PIHP had the lowest I_E/I_M ratios. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Dynamics of adsorbed poly(methyl acrylate) and poly(methyl methacrylate) on silica

Deuterium NMR and modulated differential scanning calorimetry (MDSC) were used to probe the behavior of ultrathin adsorbed poly(methyl acrylate) (PMA). The spectra for the bulk methyl-labeled PMA-d₃ were consistent with the motions of the polymer segments being spatially homogeneous. For the polymers adsorbed on silica, multicomponent line shapes were observed. The segmental mobility of the surface polymers increased with increased adsorbed amounts. In contrast to the behavior of the polymers in bulk, the adsorbed lower-molecular-mass PMA-d₃ was less mobile than the adsorbed high-molecular-mass polymer. The presence of a polymer overlayer was sufficient to suppress the enhanced mobility of the more-mobile segments of the adsorbed (inner) polymer. MDSC studies on adsorbed poly(methyl methacrylate) showed that the glass-transition temperature of the thin polymer films increased and broadened compared to the behavior of the polymer in bulk. The presence of a motional gradient with the less-mobile segments near the solid-polymer interface and the more-mobile segments near the polymer-air interface was consistent with the experimental observations.     

Critical composition of ionic–nonionic mixed micelles for counterion condensation

In the mixed micelles of an ionic surfactant (sodium dodecyl sulfate) with a nonionic surfactant (N-decanoyl-N-methylglucamide, hexaoxyethylene glycol-mono-n-decylether, and hexaoxyethylene glycol-mono-n-dodecylether), the critical mole fraction, X_ic, of the ionic surfactant has been determined, below which the counterion is completely released from the micelles. The values of X_ic are 0.074, 0.11, and 0.11, for the respective nonionic surfactants. The valences, i.e., the aggregation numbers of the ionic surfactant, of the mixed micelles at X_ic are almost close to each other, around 6. At X_ic, the critical surface charge density (about 0.03 Cm^-2) for counterion condensation was tentatively calculated. In the present study, a differential conductivity method was applied.     

The effect of poly(N,N-dimethylacrylamide) on the lamellar phase of Aerosol OT/water

The effect of a water-soluble uncharged polymer on the stability of the lamellar phase of the Aerosol OT (AOT)/water system is studied. The lamellar phase still exists when water is replaced by an aqueous solution of poly(N,N- dimethylacrylamide) (R_gƼ᎒² Å). Since the coil dimensions are (much) larger than the thickness of the water layers (d_wᅣ Å), the polymer molecules do not enter the lamellar phase. Instead segregation in small domains occurs, and in equilibrium with the AOT-rich phase another separate phase containing the polymer is formed. The polymer-rich phase exerts an osmotic pressure that reduces the water content in the AOT-rich phase, and by compression the repeat distance is reduced.     

Preparation of a novel polymeric fluorescent nanoparticle

A new type of narrowly dispersed fluorescent crosslinked polystyrene (PS) nanoparticles (20-50 nm) was synthesized via a modified microemulsion copolymerization of styrene, crosslinker divinyl benzene (DVB) and a hydrophilic comonomer amino ethyl methacrylate hydrochloride (AEMH), in the presence of pyrene. Characterized by steady-state fluorescence spectra, these nanoparticles show high luminescent intensity and the embedded pyrene has a negligible desorption from the nanoparticles. The emission intensity I₁ of the pyrene in the crosslinked nanoparticles is 40 times higher than that of pyrene in toluene or styrene solution with the same concentration. The fluorescence emission intensity can be varied by the amount of the monomer, crosslinker and pyrene, but is influenced little by the amount of AEMH in the range of investigation. The surface of the nanoparticles is modified by amino and amidino functional groups introduced by the comonomer and the initiator 2, 2'-azobis(2-amidinopropane) dihydrochloride (V₅₀), which controls the zeta potential on the particle surface.     

A crystallographic study of polymers exhibiting side-chain crystallization

Fibers were drawn from polymers of octadecyl acrylate, octadecyl methacrylate, N-octadecylacrylamide, and a series of N-substituted acrylamides with a second amide group in the side chain as well as from copolymers of octadecyl and methyl esters of acrylic and methacrylic acid. Wide-angle and small-angle x-ray diffraction patterns were recorded for these materials. The interpretation of the characteristic difference between the behavior of the polycrylates and polymethacrylates, as proposed by Platé and his collaborators, is found to be inconsistent with a number of features of the experimental evidence. In the case of poly(octadecyl methacrylate) the data allow the estimation of two parameters of the electron density distribution in the side-chain crystallites. With polyacrylamide derivatives, a second amide group in the side chain is found to destabilize the side chain crystallites. The bahavior of the copolymers is very complex and exhibits, in one case, evidence for a long periodicity parallel to the fiber axis.     

Synthesis of amphiphilic diblock copolymers poly[2-(<Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>-dimethylamino)ethyl methacrylate]-<Emphasis Type="Italic">b</Emphasis>-poly(stearyl methacrylate) and their self-assembly in mixed solvent

Amphiphilic diblock copolymers consisting of 2-(N, N-dimethylamino)ethyl methacrylate (DMAEMA, abbreviated as DMA) and stearyl methacrylate (SMA) with different degrees of polymerization and compositions were prepared by reversible addition–fragmentation chain transfer (RAFT) copolymerization. The composition and chemical structures of (co)polymers were confirmed by the measurements of ¹H NMR spectroscopy and gel permeation chromatography (GPC). The self-aggregating structures of amphiphilic diblock copolymers with the concentration of 0.1~0.3 wt.% in THF/water mixed solvent was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). It was found that both the morphologies and aggregating particle size resulted from the amphiphilic diblock copolymers depended on the variation of pH values, the lengths of the hydrophobic PSMA chains, and the weight ratio of THF/water mixed solvent.     

The counterion releasing effect and the partition coefficient of branched alkanols in ionic micellar solution

In the micellar solution of SDS, the partition coefficient (K_x) of following branched alkanols at infinite dilution was determined by applying a differential conductivity method: the alkanols used were i-C_mH_2m+1OH (m=4-9, i=1-5) in which the position of OH group (i) shifts from an end to the center of a hydrocarbon chain. The method provides two significant quantities, d!/dX_am and dC_sf/dC_af in addition to K_x. The following results have been obtained. (1) The dependence of K_x on i indicates that the hydrophobicity of alkanol is weakened with increasing i, whereas the increase in m strengthens the hydrophobicity. (2) The degree of counterion disossiation of micelles (!) is accelerated by the solubilized alkanols in micelles (mole fraction: X_am) and the acceleration rate, d!/dX_am (=0.17), depends on neither m nor i. (3) In the bulk water, the monomerically dissolved alkanols (concentration: C_af) depresses the concentration of free monomer surfactant (C_sf), and the depressing rate, dC_sf/dC_af, in micellar solution is identical with the corresponding quantity, ((CMC/(C_a)_o at CMC.     

Aggregational behavior of N-butyloxycarbonyl-L-glutamic acid oligomeric benzyl esters (exact residue numbers 4, 6 and 8) in benzene. SAXS studies

N-Butyloxycarbonyl(BOC)-L-glutamic acid oligomeric benzyl esters with exact residue numbers (BOCN_pZ, N_p=4, 6 and 8) have been synthesized by a stepwise procedure in a liquid phase. The SAXS intensity spectra of the BOCN_pZ-benzene systems have been analyzed on the basis of the rod-like aggregate model, in which the #-sheet monomers are one-dimensionally stacked antiparallel to each other. The extracted parameters (the number-averaged aggregation number, the monomer-monomer bond energies corresponding to hydrogen bonding energies, and the number-averaged molecular weights) for these aggregates have been compared with those for the aggregates formed by N-acetyl-L-glutamic acid oligomeric benzyl esters (AN_pZ, N_p=4, 6 and 8) in benzene (PCCP, 2001, 3, 3140-3149). The results indicate that it is more difficult to form aggregates in the BOCN_pZ systems than in the AN_pZ systems. This difference is due to the bulky BOC group, which hinders the formation of aggregates.     

Fluorescence Probe Study of the Interaction Between Acrylic Acid-co-Ethyl Methacrylate Copolymers and Sodium Dodecylsulfate

The interaction between sodium dodecylsulfate (SDS) and acrylic acid (AA)–ethyl methacrylate (EMA) copolymers has been investigated using steady state fluorescence and conductimetric measurements to assess the effect of the polymer composition on the aggregation process. Micropolarity studies using the ratio between the emission intensities of the vibronic bands of pyrene (I₁/I₃) and the shift of the fluorescence emission of pyrene-3-carboxaldehyde show that the interaction of SDS with AA-EMA copolymers occurs at surfactant concentrations smaller than that observed for the pure surfactant in water and depends on the copolymer composition. The increase of ethyl methacrylate in the copolymers lowers the critical aggregation concentration (CAC) due to the larger hydrophobic character of the polymer backbone. The formation of aggregates on the macromolecule is induced mainly by hydrophobic interactions, but the process is also influenced by the ionic strength due to the counter-ions of the polyelectrolyte.