Zwitterionic polymers

Note An ampholytic polymer in which ionic groups of opposite sign are incorporated into the same pendant groups is called, depending on the structure of the pendant groups, a zwitterionic polymer, polymeric inner salt, or poly betaine. 

Title Zwitterionic Polymers Comprising Betaine-Type Units and Use of Zwitterionic Polymers in Drilling Fluids... 

TABLE 1. Selected Zwitterionic Polymers Containing Betaine-Type Units Used as Drilling Fluid Component... 

Fig. 12 Representation of the antibiofouling and sugar-specific recognition of a zwitterionic polymer-brush-based surface containing concanavalin A. Reprinted, with permission, from [171]. Copyright (2010) American Chemical Society...

More recently, Chen et al. described a surface modification whereby the polymer poly(Ar,Ar-dimethyl-Af-(ethoxycarbonylmethyl)-Ar-[2/-(methacryloyloxy)ethyl]-ammonium bromide) was grafted from a surface via ATRP [136], The cationic polymer effectively kills E. coli and is subsequently converted into a zwitterionic polymer by hydrolysis of the head group (Fig. 9). It then repels all attached cells dead or alive. This is the first example of a surface that can kill microbes on contact and repels them after that. The only downside of this elegant system is that it will eventually exhaust and turn into a more or less effective repelling surface. 

Several surface-active foaming materials may be distinguished, including surfactants (ionic, nonionic and zwitterionic), polymers (polymeric surfactants), particles that accumulate at the air/solution interface, and specifically adsorbed cations or anions from inorganic salts. Many of these substances can cause foaming at extremely low concentrations (as low as 10 mol dm ). 

Schlaad et al. [34] produced a biohybrid polymeric amphiphile by free-radical addition of an L-cysteine derivative onto a 1,2-PB with 40 repeat units (Fig. 7a). The zwitterionic polymer could be dispersed into very acidic (pH < 2.3) or basic (pH > 9) aqueous solutions under the formation of vesicles. As shown by DLS and SAXS in solution, the vesicles were about 250 nm in diameter and had a multilamel-lar structure with a lamellar spacing of about 7 nm. 

The introduction of the potentially biocompatible pyrrolidone unit (polymer (3b)) unexpectedly leads to a slightly higher toxicity, as compared to the starting material (1d). Decrease of the polyanion character in the zwitterionic polymer (4b), however, substantially lowers toxicity. 

DLS was used to study the hydrodynamic properties of the end-functionalized copolymers. The zwitterionic polymers have a substancially defferent behavior than their precursors, due to the formation of aggregates in CCU. The values of the diffusion coeflScient at infinite dilution, D are lower, the Rh values higher and the aggregates are polydisperse. The ko values are negative in most cases, due to the aggregation process and is consistent with the low A2 values obtained by LALLS. 

Comparative examination of Rv and Rh values show that Rvcapillary tube, due to the shear forces app ed therein. It seems that the increased steric repulsions introduced by the unfimctionatized arms lead to the formation of not so strong associates as in the case of linear polymers. 

Recently, new classes of synthetic and natural polymers such as zwitterionic polymers [215-221], peptoids [222], carbohydrate and glycerol derivatives [223-225], and poly-L-lysine-graft-dextran [226] have anerged as candidate materials for the development of non-PEG protein-resistant surfaces. For example, Jiang and coworkers danonstrated that zwitterionic materials such as poly(sulfobetaine methacrylate) were not only highly resistant to nonspecific protein adsorption [227-230] but also able to significantly decrease bacterial adhesion and biofilm formation [231]. 

Fig 1. Viscosity ratio, with/without added salt as a function of added salt. 0 is a copolymer of acrylamide and sodium styrene sulfonate (5%), a polyelectrolyte control. H is a copolymer of acrylamide and SPE, a zwitterionic polymer. is a copolymer of acrylamide and. Cg-alkyl acryl unide, a hydrophobe containing polymer. Q is a terpolymer of acylamide, Cs-alkyl acylamide and SPE, a polymer containing both hydrophobic and zwitterionic groups. 

Few studies have investigated interactions between zwitterionic polymers and lipid bilayers. This is surprising given the widespread use of these polymers as so-called nonfouling materials... 

Low intrinsic viscosities and high ku values were determined by dilute solution viscosity measurements, indicative of large hydrodynamic interactions supporting the conclusions drawn from LS that intramolecular association does occur at low concentrations. Comparative examination of R and Rh values showed that Rvshear rate in the capillary. Because these forces are generally not very strong, it was concluded that the critical shear rate should be small. Compared to linear cB-fimctionalized polymers, the lower stability of the aggregates formed by the end-functionalized stars was attributed to the steric repulsion of the unfiinctionalized arms. 

As discussed previously, zwitterionic polymers such as poly (sulfobetaine)s have thermoresponsive UCST properties. The water solubility of poly(sulfobetaine) depends on salt concentration. The site-binding ability of the cation and the anion allows polymer chains to preferentially complex the... 

Our experiments with zwitterionic polymers are in a very prelimi-ntury sttige, and have concerned only a single polymer poly n-amino-acrylic acid). Suspensions of DPPC or DPPG are unaffected by this polymer at pH 7.4 or at pH 10. These experiments are continuing. 

FIGURE 5.5.2 Switchable antibacterial surfaces [52]. (a) Mechanism of reversible cycles between attack and protect against bacterial cells using zwitterionic polymer-grafted surfaces, (b) Number of Escherichia coli K12 cells on the surfaces before and after the releasing procedure. 

Quintana, R. Gosa, M. Janczewski, D. Kutnyanszky, E. Vancso, G. J., Enhanced Stability of Low Fouling Zwitterionic Polymer Brushes in Seawater with Diblock Architecture. Langmuir 2013, 29(34), 10859-10867. 

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