Carboxylic Acid Side Groups Research Articles

Kinetics of pH Response for Copolymer Films with Dilute Carboxylate Functionality

We have investigated the effects of film composition and thickness on the rate of pH-induced response of a copolymer film containing predominately polymethylene with randomly distributed carboxylic acid side groups (denoted as PM-CO2H). These responsive films are prepared directly onto a gold electrode surface by surface-catalyzed polymerization and subsequent hydrolysis. We measured electrochemical impedance at fixed frequency (100 Hz) to monitor the barrier properties of the polymer film during a step change in pH. At a 1-3% molar acid content, the copolymer films exhibit a 2 order of magnitude change in impedance at 100 Hz when the contacting solution pH changes from 11 to 4 (or 4 to 11). For all films, the rate of protonation is slower than that of ionization, consistent with a more gradual transfer of protons through an increasingly hydrophobic film at the outermost nanometers during the protonation step. Increased acid content within the film accelerates both the rate of protonation and ionization. Thinner films (50 nm) with the same acid content show faster response rate in both directions, since water and ions have a shorter transfer path. A large and reversible pH response was obtained for all films studied, but selection of appropriate film composition and thickness can greatly influence the rate of response.

Novel polymers with a high carboxylic acid loading

AbstractClick chemistry has been used to prepare a range of novel polymers with pendant carboxylic acid side groups. Four azido carboxylic acids, either mono‐ or difunctional and aliphatic or aromatic, have been prepared and thoroughly characterized. Extensive model reactions with 1‐ethyl‐4‐hydroxybenzene, the simplest model for poly(4‐hydroxystyrene), and the four azido carboxylic acids have been conducted to establish the proper reaction conditions and provide an analytical frame for the corresponding polymers. Poly(4‐hydroxystyrene) moieties in three different polymers—poly(4‐hydroxystyrene), poly(4‐hydroxystyrene‐co‐methyl methacrylate), and poly(4‐hydroxystyrene‐b‐styrene)—have been quantitatively transformed into oxypropynes by the use of either Williamson or Mitsunobu strategies and subsequently reacted with the azido carboxylic acids. Detailed differential scanning calorimetry investigations of all the polymers in general exhibit [when poly(4‐hydroxystyrene) is a substantial part] significant changes in the glass‐transition temperature from the polar poly(4‐hydroxystyrene) (120–130 °C) to the much less polar alkyne polymers (46–60 °C). A direct correlation between the nature of the pendant groups in the derivatized polymers and the glass‐transition temperature has emerged: the aromatic carboxylic acids give high glass‐transition temperatures (90–120 °C), and the aliphatic carboxylic acids give lower glass‐transition temperatures (50–65 °C). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:6360–6377, 2006

Dependence of Band Offset and Open-Circuit Voltage on the Interfacial Interaction between TiO2 and Carboxylated Polythiophenes

The interface of planar TiO(2)/polymer photovoltaic cells was modified with two carboxylated polythiophenes having different densities of carboxylic acid groups. Both of the interface modifiers increase the photocurrent of the cells but lower the open-circuit voltage. The work function of the TiO(2), measured using a Kelvin probe, increases with increasing density of carboxylic acid groups due to the formation of interfacial dipoles pointing toward the TiO(2) surface. The formation of interfacial dipoles results in a shift in the band offset at the TiO(2)/polymer interface, which explains the decrease in the open-circuit voltage. This work demonstrates that care must be taken when using carboxylic acid side groups to attach polymers to titania surfaces in photovoltaic cells. If the density of attachment groups is just enough to attach the polymer, then the benefits of the interface modifier can be realized without substantially decreasing the open-circuit voltage.

A redox responsive polymeric gel based on ionic crosslinking

We report here an electrochemically responsive polymer hydrogel based on ionic crosslinking. The crosslinking by metal cations and anionic carboxylic acid side groups can be controlled by redox reactions. The crosslinks dissociate when the cation crosslinker is reduced to a lower oxidation state and reform following oxidation, which leads to a reversible and localized swelling-contraction. By choosing biocompatible components and miniaturization designs, the system has potential in microrobotic and biomedical applications.

Poly( p-phenylene vinylene) derivatives with ester- and carboxy-functionalized substituents: a versatile platform towards polar functionalized conjugated polymers

A polar functionalized poly( p-phenylene vinylene) (PPV) derivative, ester containing poly(1,4-(2-(pentyloxy-5-carboxy methylester)-5-methoxyphenylene)vinylene), has been prepared via the sulfinyl precursor route. Subsequently, the carboxylic acid containing poly(1,4-(2-(5-carboxypentyloxy)-5-methoxyphenylene)vinylene) is readily obtained by the basic hydrolysis of the ester side groups. This carboxylic acid substituted polymer exhibits significantly improved optical properties as compared to previously reported similar polymers. To obtain polar functionalized PPV derivatives with more complex tailored substituents a versatile novel approach is presented based on the Mitsunobu reaction conditions via a post-polymerization functionalization of the carboxylic acid side groups. Using these reaction conditions substituents containing various ester groups, i.e. 4-nitrobenzyl, 2-nitrobenzyl, 5-(methyl)furfural and 3- N, N-dimethylamino-1-propane, have been covalently attached to the phenylene ring. Analytical data of the functionalized polymers are consistent with a quantitative functional group substitution. The results demonstrate that the employed functionalization method allows for the introduction of a large variety of polar substituents in a straightforward manner.

Synthesis, Physico-Chemical Properties and Immunoadjuvant Activity of Water-Soluble Phosphazene Polyacids

Mixed-substituted polyphosphazenes containing carboxylic acid and alkyl ether side groups were synthesized and characterized. Physicochemical properties of phosphazene polyacids in aqueous solutions were investigated as a function of copolymer structure and composition. The immunoadjuvant activity of polyphosphazenes was evaluated by studying the effect of copolymers on the immunogenicity of the influenza virus in mice. Synthesized polyphosphazenes demonstrated the ability to enhance the immune response as compared to the levels elicited by the vaccine alone.

Ultrathin Aluminosilicate Films from Langmuir−Blodgett Multilayers

Multilayer films incorporating both silicon and aluminum have been prepared by Langmuir−Blodgett deposition and subsequently decomposed by exposure to ultraviolet ozone (UVO) to yield films with a composition consistent with the formation of an aluminosilicate. The morphology of the deposited films was studied by atomic force microscopy both before and after UVO treatment, and their chemical structures and compositions were investigated by FTIR and XPS. Two film systems were investigated, namely, cyclic polysiloxanes with carboxylic acid side groups and octadecyltrimethoxysilane (OTMS). Aluminum was introduced into the films from a 10-5 M aluminum nitrate subphase at pH ∼ 4 in the first case and at pH = 9.5 in the second. It is shown that uptake of aluminum and control of aluminosilicate formation is likely to be easier with the OTMS system. It is also shown that inclusion of an ether linkage in the hydrophobic tails of the polysiloxanes leads to a much more rapid removal of carbon from the films during U...

Introduction of amino, aliphatic, and aliphatic carboxylic acid side groups onto poly(arylene ether sulfone)s via transimidization reactions

A versatile approach for the functionalization of a bisphenolic monomer, 3,8-bis(4-hydroxyphenyl)-N-phenyl-1,2-naphthalimide (1) as well as its corresponding poly(N-phenyl imido aryl ether sulphone) via transimidization reactions with hydrazine monohydrate, aliphatic amines, and an amino acid (11-amino undecanoic acid) is reported. The reactions proceeded in high conversion and high isolated yield to the desired novel functionalized monomers or polymers with N-amino, N-aliphatic, and N-aliphatic acid pendant groups. The N-amino functionalized monomer, 2, was reacted cleanly with naphthalic anhydride to form a bisimide. Polymers with phthalimide (7), 3-carboxy phthalimide (9), and bisphenol-A-(monoimide monoanhydride) (8) pendant groups were also formed by imidization of 6. A polymer with a cyclopropyl amide functional group, 10, was formed by reacting 6 with cyclopropyl carbonyl chloride. A brief description of the transimidization reactions and the properties of the functionalized polymers is included. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1095–1108, 1997

Water‐soluble polyamides as potential drug carriers, V. Carboxy‐functionalized polyaspartamides and copolyaspartamides

AbstractPoly‐α,β‐D, L‐aspartamides featuring carboxy‐functionalized side groups are synthesized by three different preparative routes: (i) aminolytic ring opening in polysuccinimide, (ii) N‐carboxymethylation of amine‐functionalized polyaspartamides, and (iii) nucleophilic addition of iminodiacetic acid to acryloylamino‐substituted poly‐aspartamides. The polymeric products, possessing inherent viscosities in the wide range of 5–30 ml g−1, are characterized microanalytically and spectroscopically. By virtue of the carboxylic acid side groups lending themselves to the reversible covalent bonding of suitably structured drug models, the polymers are designed to function as macromolecular carriers of chemotherapeutically active agents. Being perfectly soluble in aqueous media over a wide pH range, they fulfill a crucial precondition for carrier components in (parenterally administered) polymer‐drug conjugates.

CH 4/NH 3/H 2O spark tholin: Chemical analysis and interaction with Jovian aqueous clouds

The organic solid (tholin) produced by spark discharge in a CH 4 + NH 3 + H 2O atmosphere is investigated, along with the separable components of its water-soluble fraction. The chemistry of this material serves as a provisional model for the interaction of Jovian organic heteropolymers with the deep aqueous clouds of Jupiter. Intact (unhydrolyzed) tholin is resolved into four chemically distinct fractions by high-pressure liquid chromatography (HPLC). Gel filtration chromatography reveals abundant components at molecular weights ⋍600–700 and 200–300 Da . Gas chromatography/mass spectrometry of derivatized hydrolysis products of unfractionated tholin shows about 10% by mass protein and nonprotein amino acids, chiefly glycine, alanine, aspartic acid, β-alanine, and β-aminobutyric acid, and 12% by mass other organic acids and hydroxy acids. The stereospecificity of alanine is investigated and shown to be racemic. The four principal HPLC fractions yield distinctly different proportions of amino acids. Chemical tests show that small peptides or organic molecules containing multiple amino acid precursors are a possibility in the intact tholins, but substantial quantities of large peptides are not indicated. Candidate 700-Da molecules have a central unsaturated, hydrocarbon- and nitrile-rich core, linked by acid-labile (ester or amide) bonds to amino acid and carboxylic acid side groups. The core is probably not HCN “polymer.” The concentration of amino acids from tholin hydrolysis in the lower aqueous clouds of Jupiter, about 0.1 μ M, is enough to maintain small populations of terrestrial microorganisms even if the amino acids must serve as the sole carbon source.

Ionic conductivities for poly(ethylene oxide) complexes with lithium salts of monobasic and dibasic acids and blends of poly(ethylene oxide) with lithium salts of anionic polymers

Lithium salts of two polyanionic addition polymers containing alkyl sulphonic acid and perfluoroalkyl carboxylic acid side groups were prepared. Blends of these polymers were formed with poly(ethylene oxide) (PEO). The blend containing alkyl sulphonate units showed some phase separation but this was not observed for the blend containing perfluoroalkyl carboxylate groups. In the latter case a comparatively high conductivity of ∼10 −5 Ω −1 cm −1 at 374 K was obtained. The anionic units in these blends are expected to be virtually immobile. Complexes formed from PEO and the Li-salt of hexafluoroglutaric acid had similar high ionic conductivities and there are grounds for supposing that the anions in these complexes may also be substantially immobilized. In addition, conductivity values were obtained for some PEO complexes containing lithium salts of some monobasic acids and it was found that the complex formed from the Li-salt of the strongest acid gave the highest conductivity ( ∼4 × 10 −4 Ω −1 cm −1 at 373 K for a PEO-LiSO 3CF 3 complex).

Structural defects in polyvinylchloride—II Structure and properties of polyvinylchloride prepared in presence of oxygen and carbon monoxide

To investigate oxygen-containing structures in PVC, arising for example from the presence of air in technical polymerization vessels, vinyl chloride (VC) suspension polymerizations were performed with various amounts of added oxygen. Quantitative investigations demonstrated that the low molecular peroxides formed in the induction period decompose, resulting in hydrogen chloride, formaldehyde and carbon monoxide. Residual peroxides have been determined in the final copolymers and found to be mainly responsible for the considerable reduction in the thermal stability. Considerable evidence is provided that carbon monoxide, copolymerized with VC, is incorporated as a carboxylic acid sidegroup. It is considered to arise from a 1,2 chlorine shift to the carbonyl radical chain-end. The resulting acryloyl chlorides are capable of reacting with water, alcohols or amines to yield the corresponding acids, esters or amides. A new i.r. band at 1770 cm −1 after alkali treatment of VC-CO copolymers containing acrylic acid groups is suggested as caused by the formation of butyrolactone structures. Butyrolactone formation by methyl chloride evolution was also observed in thermal degradation of VC-CO copolymers containing methyl acrylate units. The rates of dehydrochlorination of the copolymers are not very different from those of pure suspension PVC.

Photoresponsive polymers IV. Photocontrol of viscosity and pH-value in aqueous systems using poly(methacrylic acid) having spirobenzopyran side groups

Poly(methacrylic acid) having spirobenzopyran side groups has been synthesised to attempt to construct photoresponsive aqueous systems. The viscosity of an aqueous solution of the poly(methacrylic acid) was reversibly reduced by as much as 30% upon irradiation with visible light ( λ>470 nm), the initial value being restored in the dark. Reversible photocontrol (up to 0·1) in the pH-value of an aqueous solution has also been achieved by the use of this polymer. Changes of the polymer conformation and the pH-value are caused by the photoisomerisation of the spirobenzopyran attached to the side groups. The difference in hydrophobic nature of the merocyanine and spiropyran form of the spirobenzopyran side groups is considered to alter the balance of the intrachain interaction, resulting in changes in the main chain conformation and pK a value of the carboxylic acid side groups.

The crystallization of branched polymers. II. Substitutional solution of side chains

AbstractThe crystalline structure of bulk polyethylene containing short chain branches was investigated with the aid of small‐angle and wide‐angle x‐ray scattering. The crystalline density obtained from measurements of the invariant, the crystallinity, and the overall density were compared with the crystalline density following from the lattice constants. Good agreement was found for linear and alkyl branched samples; however systematic differences were observed for copolymers containing ester and carboxylic acid side groups. These results are explained by assuming the side groups to enter into the crystalline lattice by substitutional solution rather than at interstitial positions. The chains around the side groups would have to show a kinked structure. This type of crystallization is in agreement with the principle of optimal space filling laid down by Kitaigorodskii [5].