Synthesis, Characterization, and Aqueous Solution Behavior of Electrolyte- and pH-Responsive Carboxybetaine-Containing Cyclocopolymers

Abstract

A novel pH-and salt-responsive carboxybetaine monomer, 4-(N,N-diallyl-N-methylammonio)butanoate (2), was prepared and cyclocopolymerized with the cationic monomer N,N-diallyl-N,Ndimethylammonium chloride (3) in 0.5 M NaCl aqueous solution (pH ) 7.0) using 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959) as the free-radical photoinitiator. The molar feed ratio of 2:3 was varied from 100:0 to 0:100 with the total monomer concentration held constant at 2.5 M. Cyclopolymerization to five-membered ring structures common to diallylammonium salts was confirmed by 13 C NMR spectroscopy. Reactivity ratio studies indicate that 2 and 3 copolymerize in a nearly ideal fashion (r1 ) 0.86, r2 ) 0.99). Weight-average molecular weights and second virial coefficients vary from (6.0 to 12.8) × 10 4 g mol -1 and (1.62 to 5.36) × 10 -4 mL mol g -2 , respectively. Dilute solution viscosity behavior depends on copolymer composition, ionic strength, and pH. Copolymers with a large excess charge exhibit typical polyelectrolyte behavior, while those with balanced charge exhibit "antipolyelectrolyte" behavior reported for zwitterionic (co)polymers. The polymers studied here are closely analogous cyclocopolymers we prevoiusly reported containing sulfobetaine mer units. 25 Unlike solutions of sulfobetaine-containing polymers, soltuions of poly(2-co-3) remain soluble at very low ionic strength even up to 100% incorporation of 2. Additionally, while the sulfobetaine systems are insensitive to pH, solutions of poly(2-co-3) exhibit a pH-dependent viscosity. All the copolymers have an apparent pKa of ∼3.6. Copolymers with 2 incorporations of 28 mol % and above have viscosity responsiveness between pH values of 2.5 and 4.5. The maximum pH response was achieved for solutions of poly(2-co-3) containing 37 and 56 mol % of the carboxybetaine monomer 2. † Paper No. 98 in a series entitled "Water-Soluble Polymers".

Structures and Synthesis of Zwitterionic Polymers

“…In fact, it seems that nearly the full spectrum of polymerizable groups suited for radical polymerization has been used to make polyzwitterions in the past, including not only styrenes, vinylpyridines, vinylimidazoles or vinylesters [124], but also rather uncommon polymerizable groups such as dienoic acids [123,124,[131][132][133][134][135][136][137][138][139], vinylcyclopropanes [124,134] or isocyanides [69], and cyclopolymerizing species such as diallylammonium [64,87,88,124,134,[140][141][142][143][144][145][146][147][148][149][150][151][152][153] and closely related divinyl monomers [93,94]. Moreover, a number of monomers confined exclusively to (often alternating) radical copolymerization, such as vinylethers [124,134], fumarates and maleates [124,134,[154][155][156], isobutylenes [157] and ...…”

“…This has resulted in a continuous interest in zwitterionic diallylammonium carboxy-, phosphono-and sulfobetaines (cf. Figure 16, P-68 and P-69) [64,87,88,124,134,[140][141][142][143][144][145][146][147][148][149][150][151][152][153]431,433].…”

Anti‐Biofouling Properties of Polymers with a Carboxybetaine Moiety

“…[21,22] The solution behavior of zwitterionic polymers is often opposite to that of typical polyelectrolytes, exhibiting ''anti-polyelectrolyte'' behavior. Using Raman and IR spectroscopies, we have found that the hydrogen-bonded network structure of water in the vicinity of zwitterionic polymers (phosphobetaine, sulfobetaine and carboxybetaine polymers) was not greatly disturbed, [23][24][25][26][27] suggesting that the small perturbation effect of zwitterionic polymers on the structure of water at polymer-water interfaces is crucial for the biocompatibility of the polymers.…”

New Regular, Amphiphilic Poly(ampholyte)s: Synthesis and Characterization

“…[5] Noteworthy, cyclocopolymerization of allylamine, diallylamine and Nmethyldiallylamine with maleic acid was occasionally reported to yield regular poly(ampholyte)s systems in the form of alternating copolymers. [6][7][8][9][10] This is an attractive approach to well-defined poly(ampholyte)s which generally must be prepared by the polymerization of specially designed monomers, [11][12][13][14] or by multistep synthesis via reactive precursor polymers. [15][16][17] Within other interesting potential uses, poly(ampholyte)s may serve as models or mimics of proteins, especially when bearing hydrophobic fragments that render them amphiphilic.…”