Potentiometric Behavior of Polyampholytes Based on N,N′‐diallyl‐N,N′‐dimethylammonium Chloride and Maleamic Acid Derivatives

Abstract

Strongly alternating copolymers (PalH, PalPh, PalPhBisCarb) composed of N , N ´-diallyl-N , N ´-dimethyl-ammonium chloride (DADMAC) and maleamic acid derivatives (MAD) are synthesized by a water-based free radical copolymerization using 4,4-azobis(4-cyanovaleric acid) (V501) as the initiator. The structure of the copolymers is verifi ed by 1 H-NMR, elemental analysis, and thermogravimetric measurements, and the physicochemical properties are investigated by viscometric and potentiometric techniques. Potentiometric titration curves show that the acidity of the carboxylic groups strongly depends on the degree of dissociation and the ionic strength. Since all copolymers behave as polycations at low degree of dissociation, a transition from an extended chain to a coil conformation can be identifi ed by reaching the isoelectric point (IEP). screening effect) [ 1 , 5 , 6 ] accompanied by the formation of a globular structure at the isoelectric point (IEP). In this context the net charge and thus the conformation can be infl uenced via the sequence of the monomer units as well as the pH, the ionic strength and the temperature. [ 4 ] By changing one of these parameters different structural transitions [ 7 , 8 ] can be promoted that may be of interest for special dynamic systems. A charge imbalance can lead to necklace-like structures in water, whereas a low charge density (weak electrostatic forces) promotes a Gaussian conformation. A change of the pH to lower or higher values (that means away from the IEP) leads to a charge asymmetry and thus a behavior that can be described in terms of polyelectrolyte theories, [9][10][11][12][13][14][15] where chain expansion and network swelling occurs due to the repulsion of equal charges. However, salt addition to a polyampholyte solution at or near the IEP leads to a screening of electrostatic attractive forces between the complementary charges and, therefore, a chain expansion becomes possible. Since synthetic PA can be regarded as model systems for biopolymers, a deeper insight concerning the nature of electrostatic interactions is of growing interest.

Ostwald Ripening Growth Mechanism of Gold Nanotriangles in Vesicular Template Phases

“…The phospholipid PL90G (purity > 97.3%) was obtained from PHOSPHOLIPID GmbH. The strongly alternating copolymer poly­( N , N ′-diallyl- N , N ′-dimethylammonium- alt -3,5-bis-carboxyphenyl-maleamic carboxylate) (PalPhBisCarb) was synthesized by free radical polymerization according to the procedure described by Fechner and Koetz . The molecular weight (15 000 g/mol) was estimated viscometrically by using available constants of the homopolymer poly­(diallyldimethylammonium chloride) (PDADMAC) for the Kuhn–Mark–Houwink–Sakurada equation ( K = 1.12 × 10 –4 dL g –1 , α = 0.82 in 1 M NaCl at 25 °C).…”

Polyampholyte/Surfactant Complexes at the Water–Air Interface: A Surface Tension Study

“…The strongly alternating, weak poylampholytes PalH (poly( N,N ′-diallyl- N,N ′-dimethylammonium- alt -maleamic carboxylate)), PalPh (poly( N,N ′-diallyl- N,N ′-dimethylammonium- alt - N -phenylmaleamic carboxylate)), PalPhCarb (poly( N,N ′-diallyl- N,N ′-dimethylammonium- alt -p-carboxyphenylmaleamic carboxylate)), and PalPhBisCarb (poly( N,N ′-diallyl- N,N ′-dimethylammonium- alt -3,5-bis(carboxyphenyl)maleamic carboxylate)) were synthesized by free radical polymerization according to the procedure already described previously . The molecular weights ( M η calculated in analogy to the PDADMAC homopolymer) for the different polyampholytes differ between 9000 and 21 000 g/mol (PalH = 21 000 g/mol; PalPh = 10 600 g/mol; PalPhCarb = 9100 g/mol; PalPhBisCarb = 15 000 g/mol) . Sodium dodecyl sulfate (SDS) (>99%) was purchased from Fluka and used without further purification.…”

“…34,35 Recently, we have reported that strongly alternating polyampholytes, which means maleamic acid copolymers with diallyldimethylammonium chloride, can be synthesized by free radical polymerization. 36 The resulting amphiphilic copolymers PalH, PalPh, PalPhCarb, and PalPhBisCarb are well-defined model compounds with varying hydrophobicity and carboxyl functionality for studying the interactions with anionic surfactants, e.g., SDS. Recently, we have shown by means of potentiometry (with a SDS-selective electrode) and isothermal titration calorimetry (ITC) that in dependence on the type of polyampholyte used interactions with the surfactant can be controlled by varying the pH and the ionic strength.…”

“…36 The molecular weights (M η calculated in analogy to the PDADMAC homopolymer) for the different polyampholytes differ between 9000 and 21 000 g/mol (PalH = 21 000 g/mol; PalPh = 10 600 g/mol; PalPhCarb = 9100 g/mol; PalPhBisCarb = 15 000 g/ mol). 36 Sodium dodecyl sulfate (SDS) (>99%) was purchased from Fluka and used without further purification. Hydrochloric acid (37%, Merck) and sodium hydroxide pellets (>99%, VWR) were used as received.…”

“…Recently, we have reported that strongly alternating polyampholytes, which means maleamic acid copolymers with diallyldimethylammonium chloride, can be synthesized by free radical polymerization . The resulting amphiphilic copolymers PalH, PalPh, PalPhCarb, and PalPhBisCarb are well-defined model compounds with varying hydrophobicity and carboxyl functionality for studying the interactions with anionic surfactants, e.g., SDS.…”