Interpolymer association between hydrophobically modified poly(sodium acrylate) and poly(N-isopropylacrylamide) in water: The role of hydrophobic interactions and polymer structure

The association between hydrophobically modified poly(sodium acrylate) (HMPA) and poly(N-isopropylacrylamide) (PNIPAM) in aqueous solution was studied using turbidimetry, viscometry and fluorescence measurements. Both the polymeric and the amphiphilic nature of the HMPA influence the association process. The tendency for association, as reflected by the increase in the cloud point and the reduced viscosity of PNIPAM, increases with the length of the alkyl group and the degree of substitution of HMPA. The fluorescence study, using pyrene as a probe, ascertains that the association is of hydrophobic nature and the association process is gradual and less cooperative than the association of PNIPAM with ionic surfactants. When high molar mass HMPA is used, the hydrophobic association between HMPA and PNIPAM leads to the formation of a reversible network with significantly enhanced thickening properties as compared to the thickening ability of the corresponding pure HMPA in aqueous solution.     

Interactions of hydrophobically modified poly(sodium acrylate) with globular proteins

The association of a series of hydrophobically modified poly(sodium acrylate) (HMPA) with lysozyme, a cationic globular protein, or with bovine serum albumin (BSA), an anionic globular protein, was investigated at pH=9 by rheology and to a lesser extent by steady-state fluorescence spectroscopy. Under suitable concentration conditions, this association leads to a drastic viscosity enhancement which is improved when the polymer hydrophobicity is increased. A mechanism is proposed: the hydrophobic regions of the globular proteins interact strongly with the alkyl groups of one or more polymer chains. In the later case, the macromolecules are crosslinked via the proteins, which leads to viscosity enhancement and even gelation. Analogies and differences between these systems and surfactant/HMPA systems previously studied in our laboratory are emphasized and discussed.     

Application of hydrophobically modified water‐soluble polyacrylamide conjugated with poly(oxyethylene)‐co‐poly(oxypropylene) surfactant as emulsifier

Hydrophobically modified polyacrylamide (PAAm) was prepared by grafting PAAm with block copolymer of poly(ethylene oxide) and poly(propylene oxide), PEO‐PPO‐PEO, by melt method in the presence of benzoyl peroxide as initiator. The chemical structure of the graft copolymer was determined by FTIR and ¹HNMR analyses. The surface tension, critical micelle concentration, and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γ_max), the area per molecule at interface (A_min), and the effectiveness of surface tension reduction (Π_CMC) were determined at different temperatures from the adsorption isotherms of the prepared surfactants. The prepared surfactant was tested as emulsifier for water with xylene, cyclohexane, or petroleum crude oil synthetic emulsions. Copyright © 2010 John Wiley & Sons, Ltd.     

Association and phase behavior of hydrophobically modified photoresponsive poly(acrylamide)s in the presence of ionic surfactant

 The extent of association between the cationic surfactant TTAB and a series of hydrophobically modified polyacrylamides (HPAMs) containing an N-n-alkyl and substituted azobenzene hydrophobic sidegroup has been studied utilizing a cationic surfactant-selective membrane electrode. Binding of TTAB to the polymer hydrophobes is found to increase with increasing hydrophobicity of the hydrophobe. In the presence of electrolyte, aqueous solutions of HPAMs and ionic surfactant exhibit an associative phase separation. The temperature or clearing point (CP) at which the system goes from a one phase to two-phase system are reported. The area of the two-phase region is found to increase with increasing electrolyte concentration, hydrophobicity of the hydrophobe for the high molecular weight HPAMs, and decreasing hydrophobicity for low molecular weight HPAMs. Exposure of HPAMs containing an azobenzene hydrophobe to UV light results in a decrease in interaction between the hydrophobe and surfactant and a corresponding decrease in the CP due to conversion of azobenzene from the more hydrophobic trans form to the less hydrophobic cis isomer. Received: 23 September 1996 Accepted: 11 March 1997     

Swelling of hydrophobically modified poly(acrylamide) and poly(acrylamide)-co-(acrylic acid) gels in surfactant solutions

A series of hydrophobically modified polyacrylamide and polyacrylamide-co-poly(acrylic acid) gels with systematically varying hydrophobicity were prepared by free-radical polymerization of acrylamide, n-alkylacrylamides (n = 10, 12, and 14), and acrylic acid. The swelling of these gels was examined in water and in both anionic and cationic surfactant solutions. It was found that the gels which incorporated acrylic acid showed extremely high swelling in water. Maximum swelling was observed in gels which incorporated 10 mol% acrylic acid. The swelling of these gels was much less in solutions of both anionic and cationic surfactants than in water. The gels which did not incorporate acrylic acid demonstrated little swelling in water, but showed increased swelling in both anionic and cationic surfactant solutions with increased hydrophobicity of the gel. Received: 1 February 1999 Accepted in revised form: 5 March 1999     

Aqueous solution behavior of alkali-soluble polyethylene periodic polyelectrolyte, poly(ethylene- per-ethylene-per-acrylic acid)

A sequence-ordered, periodic copolymer of ethylene, ethylene, and acrylic acid, poly (ethylene-per-ethylene-per-acrylic acid) (PEEA), with M _w=1.44×10⁵ has been synthesized by alternating copolymerization of 1,3-butadiene and methyl acrylate, followed by hydrogenation and hydrolysis. Aqueous solution and dissociation properties of the alkali-soluble PEEA were explored by potentiometric titration and intrinsic viscosity at 25 °C. The pH values of PEEA were almost constant (pH = 6.48 ∼ 6.55) with an increasing degree of dissociation (α) from 0.3 to 0.8 at C _s=50 mN NaCl. Correspondingly, the plots of negative logarithm of apparent dissociation constant (pK _a) against α showed a reversed S-shape curve over the whole α, indicating an extensive precipitation and subsequent tran-sition from compact to coiled conformation. The intrinsic viscosity steeply increased with α above 0.4 up to 9.97 dl/g at α = 1.0. Good agreement between the observed electrostatic potential and that calculated from the rod model with a smeared charge density was observed in the region of α higher than 0.9. The dissociation and dissolution processes of PEEA with neutralization in water were described. Received: 14 April 1998 Accepted: 3 June 1998     

Monolayers of hydrogen-bonded polymer blends at the air–water interface: poly(vinylacetate)+poly (4-hydroxystyrene)

 The surface pressure (Π) vs surface concentration (Γ_s) curves of the hydrogen-bonded polymer blend poly(vinylacetate)+ poly(4-hydro-xystyrene) (PVAc+P4HS) have been measured at 25 °C onto a water subphase at pH=2.0. While PVAc forms extended monolayers, and the free surface of water is found to be a good solvent for it, P4HS forms compressed monolayers, and the surface is a near Θ-type solvent for it. PVAc and P4HS form miscible non-ideal monolayers until near the collapse pressure through the whole concentration range. The composition dependence of the Π–Γ_s curves is rather complex. Contrary to what might be expected, the addition of PVAc to the blend does not reduce the rigidity of the monolayer until its weight fraction is larger than 0.5. The compressibility data of the P4HS-rich monolayers suggest the existence of a second maximum at high surface coverages, a result already observed in some polysiloxanes. Received: 11 March 1998 Accepted: 7 May 1998     

Small-angle neutron scattering study of poly(methyl methacrylate-block-sodium acrylate-block-methyl methacrylate) and poly(sodium acrylate-block-methyl methacrylate-block-sodium acrylate) triblock copolymers in aqueous solutions

 Small-angle neutron scattering experiments were made on poly(methyl methacrylate-block-sodium acrylate-block-methyl methacrylate) [p(MMA-b-NaA-b-MMA)] and p(NaA-b-MMA-b-NaA) solutions by varying the composition and the concentration of the polymer with and without 1 M NaCl added. Scattering curves could be evaluated by assuming that the polymers aggregate into polydisperse micelles. The experiments support the expectation that in the case of the p(MMA-b-NaA-b-MMA) block sequence the hydrophilic blocks form closed loops connected by both ends to the micellar cores; in the case of the p(NaA-b-MMA-b-NaA) block sequence they float freely in the solvent. The micellar cores exert considerable stability against dilution and added electrolyte. The interaction of charged micelles could be formally described in terms of volume exclusion and the Derjaguin–Landau–Verwey–Overbeek potential. Received: 20 December 2000 Accepted: 18 August 2001     

Synthesis, swelling behavior and surface microstructure of poly(sodium acrylate) gels cross-linked by aluminum ions

We report the synthesis and some unique properties of polymer gels cross-linked by metal ions. They are made of poly(sodium acrylate) and aluminum ions. Cylindrical and thin plate gels were synthesized in glass molds by mixing poly(sodium acrylate) with aluminum hydroxide of various concentrations. The swelling ratio of the gels was measured by changing the solvent pH and adding NaCl with different concentrations. Each gel was found to swell at the first stage and shrink thereafter by repeated solvent exchanges; the swelling ratio ultimately returned to the initial one just after gelation. These features could be explained using a qualitative model based on the ion exchange and the formation of hydrogen bonding. A characteristic surface microstructure was observed on the dehydrated gels using an atomic force microscope. The microstructures were analyzed in terms of the autocorrelation function and the root-mean-square roughness. The surface microstructure of this system was characterized by the microdomains, the shape of which was found to depend strongly on the amount of aluminum ions and the gel thickness at gelation. It could be controlled not only by the concentration of the cross-linker but also by the dehydration condition.     

Investigation of molecular order and phase transitions of smectic poly(ester imide)s by means of small-angle X-ray scattering

The molecular order and phase transitions of two smectic poly(ester imide)s based on aminobenzoic acid trimellitimide (PEI 1) or aminocinnamic acid trimellitimide (PEI 2) and α,ω-dihydroxydodecane were investigated by X-ray scattering. During cooling, the polymers pass through monotropic smectic liquid-crystalline (LC) phases (S_A, S_C), which transform into higher-ordered smectic-crystalline phases (S_E, S_H). The smectic layer structure of about 3 nm gives rise to a sharp reflection at 2θ ≅ 3°. Peak shape analysis and analysis of the interface distribution function revealed long-range longitudinal correlation among the mesogens in the LC phase but short-range lateral correlation. The development of a broad reflection in the small-angle X-ray scattering (SAXS, 2θ < 1°) indicates the formation of a lamellar two-phase system. The long-period changes reversibly between 10 and 30 nm with increasing temperature. The crystalline lamellae comprise a number of smectic-crystalline layers with packed mesogens, while the noncrystalline interlamellar regions keep their smectic-LC order. In the metastable S_B phase, formed during annealing of quenched PEI 1, the diffuse SAXS indicates a random distribution of small, probably fringed, crystals with hexagonal-packed mesogens. In the lamellar S_E and S_H phases, tie molecules play an important role, but chain folding cannot be excluded. Received: 16 July 1999/Accepted: 28 April 2000     

Electrostatic contribution to the interaction of α, β poly (N-hydroxyethyl)-DL-aspartamide with sodium dodecylsulfate micelles

The enthalpic effect due to the interaction between α, β poly(N-hydroxyethyl)-DL-aspartamide (PHEA) and sodium dodecylsulfate (SDS) in aqueous solutions as a function of the surfactant concentration was measured by the calorimetric technique at various NaCl concentrations. A marked influence of the added electrolyte on the PHEA-SDS interaction was observed. An analysis of the experimental enthalpies allows to estimate the electrostatic and the hydrophobic contributions to the enthalpy of interaction between PHEA and SDS micelles. The results were rationalized in terms of effects due to the screening of the charges residing on PHEA and SDS micelles.     

New poly(amide-imide)s syntheses. XVII. Preparation and properties of poly(amide-imide)s derived from 3,3-Bis[4-(4-aminophenoxy)phenyl]phthalimidine and various bis(trimellitimide)s

A series of novel bis(phenoxy)phthalimidine-containing poly(amide-imide)s III were synthesized by the direct polycondensation of 3,3-bis[4-(4-aminophenoxy)phenyl]phthalimidine (BAPP) with various aromatic bis(trimellitimide)s in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Poly(amide-imide)s III , having inherent viscosities up to 1.36 dL/g, were obtained in quantitative yields. All resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N-dimethylacetamide. All the soluble poly(amide-imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range of 267–322°C and the 10% weight loss temperatures were above 490°C in nitrogen. Some properties of poly(amide-imide)s III were compared with those of the corresponding isomeric poly(amide-imide)s III′ prepared from 3,3-[4-(4-trimellitimidophenoxy)phenyl]-phthalimidine and various aromatic diamines. © 1996 John Wiley & Sons, Inc.     

ESI,APCI, and MALDI tandem mass spectrometry of poly(methyl acrylate)s: A comparison study for the structural characterization of polymers synthesized via CRP techniques and the software application to analyze MS/MS data

Research in polymer science and engineering is moving from classical methodologies to advanced analytical strategies in which mass spectrometry (MS)‐based techniques play a crucial role. The molecular complexity of polymers requires new characterization tools and approaches to elucidate the detailed structural information. In this contribution, a comparison study of poly(methyl acrylate)s (PMA) using different tandem mass spectrometry techniques (ESI, APCI, and MALDI MS/MS) is reported to provide insights into the macromolecular structure with the aid of a special MS/MS data interpretation software. Collision‐induced dissociation (CID) was utilized to examine the fragmentation pathways of PMAs synthesized via various controlled radical polymerization techniques. All three mass spectrometry techniques are used to analyze structural details of PMAs and the labile end‐groups are determined based on the fragmentation behavior in CID. Fragmentation products were identified which are characteristics for the cleavage between the polymer chain and the end‐group. The application of a tailor‐made software is shown to analyze complex MS/MS data, and it is proven that this kind of software will be helpful for polymer scientists to identify fragmentation products obtained by tandem mass spectrometry similar to the fields of proteomics, metabolomics, genomics, and glycomics. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Thermotropic liquid‐crystalline poly(oxadiazole)s with poly(methylene) spacers: Preparation and extraordinary odd–even effect

A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO (CH₂)_n OH, n = 5–10 or 12] in diphenyl sulfone at temperature greater than 230 °C with K₂CO₃ as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14–0.51 dL/g, and the decomposition temperatures were greater than 350 °C and decreased from 436 to 379 °C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd–even effect: odd ones showed higher transition temperatures (melting and clearing temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 293–301, 2002     

POSS‐based poly(aryl ether sulfone)s random terpolymer linked POSS to the main chain: effect of chemical structure and POSS content on properties

In order to investigate the effect of polyhedral oligomeric silsesquioxane content and the structure‐function related on the dielectric property and hydrophobicity, three kinds of poly(aryl ether sulfone)s (PAESs) random terpolymer with different chemistry structure at variable polyhedral oligomeric silsesquioxane content in the main chain are prepared. The structures of PAESs are characterized by infrared (IR), nuclear magnetic resonance (NMR), and wide‐angle X‐ray diffraction (WXRD) spectra. The results show that the dielectric constant initially increases then decrease to 2.68 at 100%‐double‐decker silsesquioxane (DDSQ)‐PAES(molar content of DDSQ = 100%) at 1 MHz. The contact angle increased to 97.5° at 100%‐DDSQ‐PAES. While the chemical structure of organic chains also plays an important role on thermostability, dielectric, and hydrophobic properties. The results are discussed and interpreted in detail. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of new type soluble poly(amide–imide)s based on 6FDA imide modified polyterephthalamides

A series of new poly(amide–imide)s (PAIs, series III ) with good processability and characteristics was synthesized by utilizing organosoluble polyimide (PI, 6FDA–PI series) to improve poor‐solubility polyamide (PA, PTPA series), which used terephthalic acid (TPA) as a monomer. The III series PAIs were synthesized starting from the 2 : 1 molar ratio of aromatic diamines ( I ) and 6FDA to prepare imide ring‐preformed diamines ( II ) and then reacted with equimolar amount of TPA by direct polycondensation. Furthermore, by adjustment of the stoichiometry of the I , II, and TPA monomers, PAIs IV having various components were prepared. Most of the resulting PAIs having inherent viscosities between 0.70 and 1.74 dL/g were obtained in quantitative yields, and they were readily soluble in polar solvents such as N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, dimethylformamide, and dimethyl sulfoxide. All of the soluble PAIs afforded transparent, flexible, and tough films. The glass‐transition temperatures of PAIs III were in the range of 236–256 °C, and the 10% weight loss temperatures were recorded at 522–553 °C in nitrogen. The char yields of the III series polymers in nitrogen atmosphere were all higher than 56% even at 800 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 93–104, 2001     

Synthesis and properties of poly(silylenevinylene(bi)phenylenevinylene)s by hydrosilylation polymerization

Poly(silylenevinylene(bi)phenylenevinylene)s were synthesized by chloroplatinic acid-catalyzed hydrosilylation polymerization between α,ω-diethynylarenes and methylphenylsilane or diphenylsilane. The polymer structure was dependent on the substituent size of silane reagent. Poly(silylenevinylenephenylenevinylene)s showed fluorescence emission in the blue region. Optical and thermal properties of the polymers were extensively investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2933–2940, 1999     

New cohort of optically active nanostructure poly(amideimide)s: Production and properties

Novel aromatic-aliphatic poly(amide-imide)s containing chiral units in the main chain and hydroxyl benzamide units in the side chain have been obtained from the step-growth polymerization of 3,5-diamino-N-(4-hydroxyphenyl) benzamide(2) with different chiral diacid chlorides(1a-1e).Theoretical calculations were done by means of computational chemistry methods to narrate the stable conformation and orientation of each diacid chloride monomers under reaction conditions.These polymers were characterized by conventional techniques.The resulting polymers show good thermal stability.Other physical properties of polymers including crystallinity,inherent viscosity and morphological characteristics were also studied.     

Modeling the growth and molecular structure of conductive polymers: Application to poly(dialkoxybenzene)s

A modeling strategy, based on (i) quantum semiempirical calculation of the electronic structure of the successive intermediate oligomers and (ii) evaluation of the activation energy of the successive coupling reactions by use of the frontier orbital model, has been used to study the growth of a wide set of conductive polymers and is illustrated with poly(1,2-dialkoxybenzene) and poly(1,4-dialkoxybenzene) generated by electrochemical oxidation of the corresponding monomer. These monomers have been chosen because they are known to yield polymers of completely different structures. The strategy, which is designed to be as little computer time-consuming as possible, allows us to predict a growth trend in agreement with the structure inferred from spectrochemical experiments. In the case of poly(1,2-dialkoxybenzene) it suggests the formation of a cyclic tetramer as a byproduct detected in small quantities by means of MALDI spectroscopy. This modeling strategy allows one to describe the electronic modifications induced by the growth of a highly conjugated structure. It suggests that oxidation of the successive oligomers at high doping level and quinonic deformation are key factors for the growth of long and regular polymer structures     

Association of hydrophobic counterions in aqueous solution of poly(allylammonium) chloride: Comparison between p-n-propylbenzenesulfonate and p-iso-propylbenzenesulfonate ions

The hydrophobic association behavior of p-propylbenzenesulfonate ions (n-PBS^? and iso-PBS^?) around poly(allylammonium) cation (PAAH⁺ was studied by absorption and ¹H nuclear magnetic resonance (NMR) spectroscopy. In the presence of PAAH⁺Cl^?, the broadening (hypochromism) of absorption band of PBS^? were observed. In addition, all ¹H NMR signals of PBS^? exhibited up-field shift which resulted from the intermolecular ring current shift. These results indicate the hydrophobic association of negative PBS^? around PAAH⁺. The hydrophobic association arises from the accumulation of counterions around the polyion, and is stabilized by the hydrophobic interaction between propyl groups and the stacking interaction between benzene rings. The association of iso-PBS^? ions is rather weaker than that of n-PBS^?, suggesting that the steric hindrance of isopropyl groups prevents an effective association of hydrophobic counterions. Furthermore, through viscosity and Cl^? activity measurements, it was found that the binding of associated PBS^?,s to PAAH⁺ causes the change of its surroundings to hydrophobic character and its conformation. © 1994 John Wiley & Sons, Inc.