Synthesis and properties of amphiphilic maleic acid copolymers

New amphiphilic polymers derived from maleic acid copolymers and containing stearyl or oleyl residues were prepared. Their physicochemical properties were studied, and the possibility of using them as carriers for antifungal agents was examined with Amphotericin B as example.     

Stoichiometric polyelectrolyte complexes as comb copolymers

The collapse behavior of a single comblike copolymer chain has been studied by Monte Carlo simulations. It has been supposed that the solvent is good for the side chains but the solvent quality for the backbone chain changes. It has been shown that depending on the structural parameters of the comb copolymer (the lengths of the backbone and side chains, grafting density of the side chains) various thermodynamically stable morphologies of the collapsed backbone chain can be realized. In addition to ordinary spherical globule we have observed elongated structures as well as necklace-like conformations. The proposed model can be used to describe conformational behavior of stoichiometric complexes between block copolymers with a polyelectrolyte short block and oppositely charged linear homopolymers.     

Needlelike and spherical polyelectrolyte complex nanoparticles of poly(l-lysine) and copolymers of maleic acid

We report on the bulk and surface properties of dispersions consisting of nonstoichiometric polyelectrolyte complex (PEC) nanoparticles. PEC nanoparticles were prepared by mixing poly(l-lysine) (PLL) or poly(diallyldimethylammonium chloride) (PDADMAC) with poly(maleic acid-co-alpha-methylstyrene) (PMA-MS) or poly(maleic acid-co-propylene) (PMA-P). The monomolar mixing ratio was n-/n+ = 0.6, and the concentration ranged from 1 to 6 mmol/L. Subsequent centrifugation enabled the separation of the excess polycation, resulting in a stable coacervate phase further used in the experiments. The bulk phase parameters turbidity and hydrodynamic radius (R(h)) of the PEC nanoparticles showed a linear dependence on the total polymer content independently of the mixed polyelectrolytes. This can be interpreted by the increased collision probability of the polyelectrolyte chains when the overlap concentration is approached or exceeded. Different morphologies of the cationic PEC nanoparticles, which were solution-cast onto Si supports, were obtained by atomic force microscopy (AFM). The combinations of PLL/PMA-MS and PDADMAC/PMA-MS revealed more or less hemispherical particle shapes, whereas that of PLL/PMA-P revealed an elongated needlelike particle shape. Circular dichroism and attenuated total reflection Fourier transform infrared (ATR-FTIR) measurements proved the alpha-helical conformation for the PEC PLL/PMA-P and the random coil conformation for the PEC PLL/PMA-MS. We conclude that stiff alpha-helical PLL induces anisotropic elongated PEC nanoparticles, whereas randomly coiled PLL forms isotropic spherical PEC nanoparticles.     

A spectroscopic investigation of complexes of divalent metal ions with maleic acid copolymers

The absorption spectra of complexes of copper(II), nickel(II), and barium(II) with three partially neutralized maleic acid copolymers in aqueous solution have been investigated in the range 195–720 nm. Copper ions are always very strongly bound, giving electron transfer complexes. Relevant spectral features are found to depend on the number of methyl groups in the polymer backbone, and in particular, for each given polymer, on the amount of available ligand negative charge per divalent counterion. The spectra of the complexes of nickel(II) and barium(II) suggest that they interact with the polycarboxylates much more weakly than copper(II).     

Complexation of chitosan with maleic acid copolymers

The complexation of chitosan with alternating copolymers of maleic acid with N-vinylpyrrolidone, ethylene, or styrene is studied. It is found that the process is of a cooperative character and that the binding constants and the Hill parameters are dependent on the nature of a nonionogenic comonomer maleic acid in the synthetic polyanion and on the conditions of complexation. The data of atomic force microscopy and turbidimetric titration confirm the effect of temperature on the conformation of interacting macromolecules and the size of macromolecular aggregates. It is shown that the composition and yield of insoluble interpolyelectrolyte complexes at constant pH are determined by the reactant ratio, the temperature, and the initial concentration of polyelectrolytes.     

Chitosan based polyelectrolyte complexes

Polyelectrolyte complexes (PECs) are formed through the electrostatic interactions between polymers carrying opposite charges. Here are presented results of basic studies on the PECs of chitosan with other polysaccharides such as sodium alginate, carboxymethyl cellulose, polygalacturonic acid and κ‐carrageenan. An extensive study on chitosan/carboxymethyl cellulose membranes, regarding its swelling characteristics and water vapour sorption is offered. Also the interaction of chitosan with polyacrylic acid has been examined from the thermodynamic point of view.     

Novel polyelectrolyte complexes based on diazo-resins

Polyelectrolyte complexes containing diazonium groups (PEC-N₂) with a high ionic crosslinking rate were prepared as a precipitate by mixing the diazo-resin with polyanion solutions. The photochemical decomposition of the complexes from different polyanions was studied. It was shown that PEC-N₂ exhibit high photosensitive properties. Under irradiation of UV light, the complexes which can be dissolved in ternary mixtures such as H₂O-DMF-LiCl,H₂O-DMF-NaSCN or H₂O-DMF-ZnCl₂ (DMF: N,N-dimethylformamide) become indissoluble since the crosslinking structure of the complexes changes from ionic to covalent.     

Formation and properties of positively charged colloids based on polyelectrolyte complexes of biopolymers

Formation of colloids based on polyelectrolyte complexes (PECs) was mainly studied with synthetic polyelectrolytes. In this study, we describe the elaboration of positively charged PEC particles at a submicrometer level obtained by the complexation between two charged polysaccharides, chitosan as polycation and dextran sulfate (DS) as polyanion. The complexes were elaborated by dropwise addition of default amounts of DS to excess chitosan. Quasi-elastic light scattering was used to investigate in detail the influence of the characteristics of components (chain length, degree of acetylation) and parameters linked to the reaction of complexation (molar mixing ratio, ionic strength, concentration in polymer) on the sizes and polydispersity of colloids. Chain length of chitosan is the major parameter affecting the dimensions of the complexes, high molar mass chitosans leading to the largest particles. Variations of hydrodynamic diameters of PECs with the molar mass of chitosan are consistent with a mechanism of particle formation through the segregation of the neutral and then hydrophobic blocks of the polyelectrolyte complexed segments. Resulting particles display probably a structure constituted by a neutral core surrounded by a chitosan shell ensuring the colloidal stabilization. Such a structure was evidenced by measurements of electrophoretic mobilities revealing that the positive charge of particles was decreasing with pH, in relation with the neutralization of excess glucosamine hydrochloride moieties.     

Stabilization of silver nanoparticles with copolymers of maleic acid

Silver nanoparticles are obtained by reducing AgNO₃ with sodium borohydride in an aqueous solution in the presence of maleic acid copolymers with ethylene, N-vinylpyrrolidone, or styrene, as well as their octadecylamide group-containing hydrophobized derivatives, as dispersants. The influence of the structural features of the dicarboxylic acid copolymers on the silver nanoparticle formation process and the conditions for producing sols containing spherical nanoparticles with sizes of 1.5–3.5 nm (according to the data of transmission electron microscopy) are determined. It is shown that, at the equimolar copolymer/silver cation ratio, the morphology of resulting silver nanoparticles weakly depends on the nature of comonomers of maleic acid and the presence of hydrophobic fragments, which play an auxiliary role in the stabilization of dispersions of nanoparticles by increasing their stability with respect to ionic strength and oxidation. Evolution of the particle sizes in the system is monitored beginning with copolymer solutions to silver sols by the methods of light scattering, transmission electron microscopy, and atomic force microscopy. According to the light scattering data, copolymers and their complexes with silver ions in solutions are partly aggregated at concentrations corresponding to the conditions of nanosilver synthesis. Silver sols are shown to contain stabilized nanoparticles, which represent core-polyelectrolyte corona-type micelles and micellar clusters with polyelectrolyte coronas.     

Optically active alternating copolymers of maleic acid and alkylvinylethers

Alternating copolymers of maleic acid (MAc) with optically active alkylvinylethers (RVE)[R = (S)-1-methylpropyl, (R)-1-methylbutyl, (S)-2-methylbutyl, (S)-3-methylpentyl, (S)-4-methylhexyl, (S)-1-methylheptyl and (S)-3,7-dimethyloctyl] were obtained by hydrolysis in aqueous alkaline medium of the corresponding copolymers with maleic anhydride (MAn). i.r. Absorption spectra, viscosity and potentiometric titration curves are described as well as u.v., ORD and CD spectra recorded in ethanol and water. Conductometric titrations in non-aqueous medium confirm the alternance of dicarboxylic and ethereal structural units. It is shown that the nature of alkyl substituents strongly affects the ionization process of the first carboxylic group. The u.v. bands connected with the $\text{n → π}{}^1$ electronic transitions of carboxylic chromophores are optically active and the ellipticities of the dichroic bands around 215 nm depend on the position of the asymmetric carbon atoms present in the side chain. Moreover for copolymers with ethereal structural unit containing an asymmetric carbon atom α with respect to the oxygen atom, the rotatory strength of such bands is dependent on the length of the alkyl substituents for measurements carried out in water, whilst no significant dependence is evident in measurements performed in ethanol. No ordered secondary structure is considered to account for these features which are probably due to asymmetric induction phenomena involving optically active side chains.     

Synthesis and aggregation behavior of grafted maleic acid copolymers

Grafted SMA containing poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether) (SMA-PEG) and its hydrophobically modified products poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether & dodecyl) (SMA-PEG+C(12)) and poly(styrene-co-maleic anhydride)-g-(dodecyl) (SMA-C(12)) were prepared using a single batch method. Their adsorption and rheology behavior was investigated using equilibrium surface tension and rheological techniques. The adsorption parameters, saturation surface excess concentration (Γ(max)), and the minimum area (A(min)) of these copolymers were evaluated. The results show that Γ(max) increased and A(min) correspondingly decreased with increasing hydrophobicity. Aggregation standard free energy of SMA-PEG+C(12) and SMA-C(12) suggested that increased hydrophobicity enhanced the tendency for aggregation to occur. The distinctive differences in the macroscopic appearance were shown by aqueous samples of the copolymers. The samples of SMA-M behaved as Newtonian fluids at all concentrations (from 1.0 wt% to 20.0 wt%), indicating that there were no macromolecular chain entanglements or interactions between aggregates in solution. For SMA-PEG+C(12), at concentrations above 10.0 wt%, the presence of cross-links between aggregates is presumed to be the reason for the viscoelastic behavior. Solid-like elastic behavior could occur at low concentration (5.0 wt%) of SMA-C(12), suggesting the formation of networks by inter-chain aggregation of the hydrophobic dodecyl chains.     

Stoichiometric polyelectrolyte complexes of ionic block copolymers and oppositely charged polyions

Micellization in dilute solutions of diblock copolymers with a polyelectrolyte and a hydrophilic nonionic blocks and oppositely charged polyions is studied using mean-field theory. In aqueous solutions the micelle core consists of the polyelectrolyte complex (PEC) while the corona is formed by hydrophilic blocks of the block copolymers. Describing PEC as a globule in the framework of the Lifshitz [Zh. Eksp. Teor. Fiz. 55, 2408 (1968)] globule theory we calculate the surface tension of the micellar core/solvent interface as a function of the polyion degree of ionization, solvent quality, and concentration of low-molecular-mass salt. The equilibrium aggregation number of starlike micelles formed by block copolymers and homopolymers of opposite charge at stoichiometric mixture compositions is found as a function of the system parameters. It is shown that micelles disintegrate upon addition of salt.     

Preparation and properties of foamed materials based on acrylonitrile-methacrylic acid copolymers

The physicomechanical properties of foamed polymethacrylimides formed by heat treatment of acrylonitrile-methacrylic acid copolymers were studied in relation to the kind of the foaming agent and to the concentrations of the foaming agent and acrylamide.     

Mechanical properties of reversibly cross-linked ultrathin polyelectrolyte complexes

Tensile properties of microcoupons of polyelectrolyte complex, formed by the multilayering method, were determined using a micromechanical analysis system. The degree of internal ion-pair ("electrostatic") cross-linking was reversibly controlled by exposure to salt solution of varying concentration, which "doped" counterions into the films, breaking polymer/polymer ion pairs in the process. Linear stress-strain behavior was observed for a poly(styrene sulfonate)/poly(diallyldimethylammonium) multilayer up to 2% deformation. The dependence of modulus on cross-link density could be rationalized well by classical theories of rubber elasticity, including some insight on the topology of polyelectrolyte complexes.     

Heterocyclic compounds based on maleic acid monoureide

The products of the bromination in water of maleic acid monoureide and its methyl ester have the 2-imino-5-bromocarboxy(carbomethoxy)methyl-4-oxazolidone structure. 2-Imino-5-bromocarboxymethyl-4-oxazolidone undergoes dehydrobromination in aprotic polar solvents to give 2-imino-5-carboxymethylidene-4-oxazolidone. In the presence of dry hydrogen chloride in dimethylacetamide the oxazole ring undergoes dehydrobromination and isomerization to an imidazole ring with the formation of 5-carboxymethylidenehydantoin. Methyl -bromofumarate monoureide is formed when the oxazole ring of 2-imino-5-bromocarbomethoxymethyl-4-oxazolidone is opened with alkali.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 972–975, July, 1979.The authors thank S.I. Zav'yalov, I. Ya. Shternberg, and I. P. Sekatsis for their participation in the discussion of this research.     

Photosensitive materials based on copolymers of vinyl cyclopropyl ether with maleic anhydride

Copolymers prepared from vinyl cyclopropyl ether and maleic anhydride were modified with allyl alcohol, and the products obtained were thermally cross-linked with styrene. Photoresists were prepared from these copolymers, and their photolithographic parameters were determined.     

Layer-by-layer assembly of salt-containing polyelectrolyte complexes for the fabrication of dewetting-induced porous coatings

The layer-by-layer (LbL) assembly of salt-containing nonstoichiometric polyelectrolyte complexes (PECs) with oppositely charged uncomplexed polyelectrolyte for the fabrication of dewetting-induced porous polymeric films has been systematically investigated. Salt-containing poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) complexes (noted as PAH-PAA) with a molar excess of PAH were LbL assembled with polyanion poly(sodium 4-styrenesulfonate) (PSS) to produce PSS/PAH-PAA films. The structure of the PAH-PAA complexes is dependent on the concentration of NaCl added to their aqueous dispersions, which can be used to tailor the structure of the LbL-assembled PSS/PAH-PAA films. Porous PSS/PAH-PAA films are fabricated when salt-containing PAH-PAA complexes with a large amount of added NaCl are used for LbL assembly with PSS. In-situ and ex-situ atomic force microscopy measurements disclose that the dewetting process composed of pore nucleation and pore growth steps leads to the formation of pores in the LbL-assembled PSS/PAH-PAA films. The present study provides a facile way to fabricate porous polymeric films by dewetting LbL-assembled polymeric films comprising salt-containing PECs.     

Boronate-containing copolymers: polyelectrolyte properties and sugar-specific interaction with agarose gel

Copolymers of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with acryamide (AA), N,N-dimethylacrylamide (DMAA), and N-isopropylacrylamide (NIPAM) were found to adsorb on cross-linked agarose gel (Sepharose CL-6B) in the pH range from 7.5-9.2, due to specific boronate-sugar interactions. The molar percentages of phenylboronic acid (PBA) groups in the boronate-containing copolymers (BCCs), as estimated by 1H NMR spectroscopy, were 13, 10, and 16%, respectively, whereas the apparent ionization constants, the pKa values, of the copolymers were similar and equal to 9.0 +/- 0.2 at 20 degrees C. The copolymers adsorption capacities were in the range of 15-30 mg x ml(-1) gel (14-36 micromol pendant PBA ml(-1) gel) at pH 9.2 and decreased with decreasing pH value. The interaction of monomeric NAAPBA with Sepharose CL-6B was characterized by an equilibrium association constant of 53 +/- 17 M(-1), the chromatographic capacity factor k' = 1.8, and a total content of binding sites of 27 +/- 10 micromol x ml(-1) gel at pH 9.2. The weak reversible binding of monomeric NAAPBA and almost irreversible binding of NAAPBA copolymers to the gel at pH 9.2 suggested a multivalent character of the copolymer adsorption. At pH 7.5, the maximal adsorption capacity was displayed by the AA-NAAPBA copolymer (15 mg x ml(-1) gel). All the BCCs could be completely desorbed from the gel by 0.1 M fructose in aqueous buffered media with pH values from 7.5-9.2. The strong adsorption of AA-NAAPBA on agarose gel probably relates to the conformation of the copolymer in aqueous solution and provides opportunities for biomedical applications of the copolymer under physiological conditions. Multivalent, weak-affinity adsorption of BCCs to the agarose gel seems to be a tentative model for the copolymers' binding to oligo- and polysaccharides of cell membranes and mucosal surfaces.     

Chitosan based nonstoichiometric polyelectrolyte complexes as specialized flocculants

The aim of this work was to evaluate the flocculation of kaolin by using positively charged nonstoichiometric interpolyelectrolyte complex (N-PEC) nanoparticles formed by the interaction of chitosan with poly(sodium 2-acrylamido-2-methylpropanesulfonate) (NaPAMPS) and two random copolymers of AMPS with t-butyl acrylamide, comparative with chitosan. The flocculation efficiency was evaluated by optical density at 500 nm. The N-PEC nanoparticles were more effective than chitosan in the kaolin separation, especially at low molar ratios between charges, when the flocculation window was more then double at an optimum dose lower than that of chitosan. The main advantage of N-PECs is the increase of critical concentration for kaolin re-stabilization, the N-PEC particles adsorbed on the kaolin surface protecting them more efficient against re-dispersion. The influence of low molar mass electrolytes on the flocculation with N-PECs was also investigated.     

Surface reorientation of hydrogels based on methacrylate copolymers

Surface molecular structures of two statistical copolymers, poly(2-hydroxyethyl methacrylate-co-butyl methacrylate) (HEMA-co-BMA) and poly[2-(2-ethoxyethoxy)ethyl methacrylate-co-butyl methacrylate] (EOEOEMA-co-BMA), were studied by X-ray photoelectron spectroscopy (XPS). Besides the classical “dry” XPS technique, where the polymer samples were air-dried, also “deep-freezing” technique was used, where the samples were investigated in deep-frozen hydrated state. The differences in results obtained by the two techniques are discussed from the point of view of the polymer surface chain reorientation in response to various environment. The reverse polymer chain reorientation from the hydrated towards dry state was also followed.