Zwitterionic monomers

Water soluble block copolymers consisting of N-isopropylacrylamidc, NIPA, and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate, SPP, were prepared via the RAFT process [82] (Scheme 31). NIPA was polymerized first using AIBN as the initiator and benzyl dithiobenzoate as the chain transfer agent. To avoid the problem of incomplete end group functionalization the polymerization yield was kept very low (less than 30%). The block copolymerization was then performed... 

Zhang, L. M., Hu, Z. H. (2002). Synthesis and thermal degradation of a novel starch graft copolymer incorporating a sulpfobetaine zwitterionic monomer. Starch, 54, 290-295. 

A greater degree of certainty exists with zwitterion monomers that the growing chains are also zwitterions. Hence, they seem to be the most suitable class of compounds with which to study ionic reactions of this type. The concentration of growing zwitterions is high and any peculiarities associated with their growth are likely to be readily apparent. A closer examination of the polymerization of these monomers is warranted. 

Charge cancellation polymerizations must be considered as special cases. Some degree of charge separation already exists in acetonitrile oxide but a base is required to initiate its polymerization. Although linked by a conjugated system ionisation is essentially complete in cyclic sulfonium zwitterion monomers. No initiator is required and monomeric units add at both ends of the p>olymer chain. The initial step in the general scheme above is best considered as part of monomer synthesis. 

As for any other functional polymer, polymeric betaines are accessible by two different synthetic routes (1) the polymerization of zwitterionic monomers or (2) the zwitterionic functionalization of reactive precursor polymers. Both routes have inherent advantages and disadvantages. The polymerization of the zwitterionic monomers leads to polymers with 100% betaine functionality, but their molecular characterization is difficult for several reasons. For instance, the conformation of the polymers in aqueous solution is very sensitive, not only to the ionic strength but also to the type of added salt, and in the case of polycarbobetaines also to the pH. Furthermore, polymeric zwitterions often exhibit strong interactions with other matter, e.g., chromatographic colmnns. Hence, reliable GPC or HPLC measurements are very difficult to perform, if at all. 

The free radical cyclopolymerization of diallylammonium compounds leads to linear water-soluble polymers containing predominantly pyrroli-dinium rings as the structural unit of the polymer chain [14,15]. This well-established principle of polymer synthesis was used for the synthesis of the polycarbobetaines from their zwitterionic monomers (route (1), see above), which are summarized in Scheme 1. 

CRP is a powerful tool for the synthesis of both polymers with narrow molecular weight distribution and of block copolymers. In aqueous systems, besides ATRP, the RAFT method in particular has been used successfully. A mrmber of uncharged, anionic, cationic, and zwitterionic monomers could be polymerized and several amphiphilic block copolymers were prepared from these monomers [150,153]. The success of a RAFT polymerization depends mainly on the chain transfer agent (CTA) involved. A key question is the hydrolytic stability of the terminal thiocarbonyl functionaHty of the growing polymers. Here, remarkable progress could be achieved by the synthesis of several new dithiobenzoates [150-152]. 

Furthermore, a polycarboxybetaine with a peptide main chain was synthesized from poly(methyl L-glutamate) [57]. Several zwitterionic monomers based on isobutylene with long alkyl spacers between the polymerizable group and the zwitterionic moiety exhibit surfactant properties. They do not undergo free radical homopolymerization, but are copolymerizable with other monomers [58]. 

This chapter describes the synthesis, kinetics, and solution properties for copolymers ofN-vinylpyrrolidone (NVP) with sulfonate ionic and zwitterionic monomers. Examples of the sulfonate ionic monomers are sodium styrenesulfonate (NaSS) and sodium acrylamido-2-meth-ylpropanesulfonate (NaAMPS) an example of the zwitterionic sulfonate monomer is 2-hydroxyethyt)dimethyl(3-sulfopropyt)-ammonium inner salt, methacrylate (SPE). The NVP-NaAMPS monomer pair was exceptional, showing evidence for donor-acceptor character and an alternating tendency in copolymerization. The NVP copolymers containing simple sulfonate ionic monomers e.g., NaAMPS) showed polyelectrolyte solution properties. On the other hand, the NVP copolymers with zwitterionic sulfonate monomers showed antipoly electrolyte solution behavior. 

Terpolymers of acrylamide, N-alkyl acrylamide, and zwitterionic monomers [e.g. (hydroxyethyl) dimethyl (3<-sulfopropyl) eunmonium methacrylate (SPE) ] were prepared... 

Huang J, Xu W. Zwitterionic monomer graft copolymeiization onto polyurethane surface through a PEG spacer. Appl Surf Sci 2010 256(12) 3921-7. 

Synthesis and Aqueous Solution Behavior of Novel Polyampholytes Containing Zwitterionic Monomers... 

Polyzwitterions (Type B) containing the sulfonate functionality have been thoroughly studied beginning with the pioneering work of Hart and Timerman (3J). In that work, zwitterionic monomers were prepared by the reaction of 2-and 4-vinylpyridine with 1,4-butanesultone. Polysulfobetaines are typically insoluble in deionized water and require a relatively high content of hydrophilic comonomer or the addition of a critical concentration of electrolyte to achieve solubility and viscosity enhancement. Polysulfobetaines have also been synthesized from acrylic (32-36), acrylamido (37), and vinyl imidazolium (38,39) monomers. 

Water-soluble polyampholytes have been synthesized by copolymerization of both anionic and cationic monomers ipto the polymer backbone (2-8) or by incorporating zwitterionic monomer units into the polymer (9-JO). In pure water most polyampholytes having randomly distributed (+) and (-) functional groups, in the 40/60 to 60/40 range of mol ratios are insoluble due to intrapolymer electrostatic attractions (6-8). The solubility and the solution viscosity increase upon adding salt due to brea p of the intrapolymer ion ag egates and expansion of the polymer coil. 

Zwitterionic Monomer Perm enantly. Anionic Pernnenantly Cationic... 

Bogachev, V. S., Kumarev, V. P., and Rybalkov, V. N. (1986) Phosphorothioate analogues of nucleic acids. V. synthesis of S -phosphorothioate analogues of oligodeoxynbonucleotides with the aid of zwitterionic monomers. Sov. J. Bioorg. Chem. 12,64-70. 

Zwitterionic (monomers having both cation and anion groups)... 

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