Stela Dragan

Hydrophobically modified cationic polyelectrolytes

Abstract Cationic polyelectrolytes with hydrophilic/hydrophobic properties were synthesized by condensation polymerization of epichlorohydrin with dimethylamine, N,N-dimethyl-1,3-diaminopropane, and primary amines with nonpolar chains, hexyloxypropylamine and decyloxypropylamine. Viscometric measurements of these polymers in dilute aqueous solutions with and without salt revealed a typical polyelectrolyte behaviour. Thermal analyses of cationic polyelectrolytes showed that the relative thermal stability decreases with decreasing hydrophobic chain lengths and increasing quaternary ammonium salt group contents. The flocculating efficiency of these polycations on a suspension of montmorillonite was also studied.

Interaction of the low‐molecular weight salts with cationic polyelectrolytes

The interaction of several mono-, di-, and trivalent anions with cationic polyelectrolytes having different contents in N,N-dimethyl-2-hydroxypropylen ammonium chloride units (polymer A) or tertiary amine N-atoms and PEG (polymer PEGA) in the main chain was studied by viscosimetric and conductometric measurements. Both methods have shown a stronger interaction for tri- and bi- than for univalent counterions.

Influence of low-molecular-weight salts on the formation of polyelectrolyte complexes based on polycations with quaternary ammonium salt groups in the main chain and poly(sodium acrylate)

Abstract The effects of NaCl, NaI and Na2SO4 on the formation of polyelectrolyte complex (PEC) between a polycation with N,N-dimethyl-2-hydroxypropyleneammonium chloride units in the main chain (PCA5) and poly(sodium acrylate) (NaPA) were studied. The NaCl concentration in the polyelectrolyte solutions ranged from 0 to 2 M. Viscometric and turbidimetric measurements were used to follow the effect of the salt concentration and of the counterion nature on the PEC formation. The influence of counterions was different depending on both the radius of the hydrated ion and its valence. At the same concentration of the low-molecular-weight salt, the following order of the PEC separation in dependence on the counterion was evidenced: Rsep(SO42−)

Polyelectrolyte complexes. II. Specific aspects of the formation of polycation/dye/polyanion complexes

We report on the formation of the polycation/dye/polyanion (PC/D/PA) complexes by the interaction between nonstoichiometric polycation/dye (PC/D) complexes with polyanions. Polycations differed in their content of the (N,N-dimethyl-2-hydroxypropylene ammonium chloride) units in the main chain. Poly(sodium acrylate) (NaPA), poly(sodium 2-acrylamido-2-methylpropane sulfonate) (NaPAMPS) and poly(sodium styrenesulfonate) (NaPSS) were used as polyanions. Crystal Ponceau 6R (CP6R) and Ponceau 4R (P4R) with two or three sulfonic groups were used as anionic dyes. The interaction between nonstoichiometric PC/D complexes and polyanions was followed by UV-VIS spectroscopy, viscometry, and conductometry measurements. Formation of PC/D/PA complexes takes place mainly by the electrostatic interaction between the polyanion and the free positive charges of the nonstoichiometric PC/D complex. The stoichiometry and the stability of the tricomponent complexes depended on the polycation structure, the structure and molecular weight of polyanion, the dye structure, and the P/D molar ratio. A high amount of the dye was excluded from the complex before the end point when a branched polycation was used. The higher the solubility of the dye the lower the stability of the PC/D/PA complexes.

Thermal effects of some polymerisation and polycondensation reactions, polymeric ammonium quaternary salts

Abstract Reaction heats of the polymerisation of N,N-diallyl N,N-dimethyl ammonium chloride were determined with an original differential adiabatic calorimeter, adopting the compensation method of the evolved heat in the studied reaction. The reaction was carried out at 95°C, in an inert gas atmosphere (nitrogen or argon), with an aqueous monomer solution. The second reaction studied in this work was the polycondensation of epichlorohydrin with a mixture of dimethylamine and triethylenetetramine. A calorimetric installation, under controlled temperature conditions with the reaction heat being transferred by a thermostated cooling agent, was used to measure the reaction heat within the 18–21°C temperature range. Polymeric quaternary ammonium salts were obtained in both polymerisation and polycondensation reactions.

Thermal behaviour of some cationic polyelectrolytes and polyelectrolyte complexes

Thermogravimetric and differential thermal analysis were developed on some cationic polymers, different both by the content of the quaternary ammonium salt groups in the main chain and by the content and type of polyfunctional amines, as well as on some polyelectrolyte complexes (PECs), when the cationic component was one of the above cationic polymers and the anionic component was poly(acrylic acid) sodium salt (PANa). The polycation with the lowest content in the quaternary ammonium salt groups had the highest thermal stability. The electrostatic interactions between the oppositely charged polyions in PECs induced a greater thermal stability of their structure compared with the starting polycations. The thermal behaviour of the PECs was compared with that of the physical mixtures of the corresponding complementary polymers taken in the same mass ratio as in PECs.

Functional polymers based on acrylamide crosslinked copolymers

Crosslinked copolymers of acrylamide were obtained by the aqueous suspension polymerization method. Divinylbenzene and N,N-methylene-bis-acrylamide were used as crosslinking agents. Ethylacrylate was used as a third comonomer. The real acrylamide content in the crosslinked copolymers was calculated taking into account the found nitrogen content after the removal of the soluble fractions. The water uptake in dependence on the copolymer structure gave information on the hydrophilicity of these copolymers. Hofmann degradation of the amide groups led to copolymers containing vinylamine functional groups, which were characterized by IR spectroscopy and by anion exchange capacity. Carboxylic groups were generated by the alkaline hydrolysis of the ester groups.

Surface modification by self-assembled polycation/azo dye multilayers

The formation and stability of some polycation/azo dye multilayers by the alternate adsorption of one polycation of integral type having 95 mol % of N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA 5 ) and four multicharged azo dyes: Crocein Scralet MOO (CSMOO), Ponceau SS (PSS), Direct Blue 1 (DB I) and Direct Red 80 (DR 80) are discussed in this paper. The dyes were different either by the number of sulfonic groups (PSS, DB 1 and DR 80) or by their position (CSMOO and PSS). The multilayer growth, when PCA 5 was adsorbed from 0.2 M Na 2 SO 4 aqueous solution, was followed by UV-Vis spectroscopy and by electrokinetic measurements. Solid state polycation/azo dye complexes were also prepared to get qualitative information on the charge compensation in the multilayers.