Subject cationic polymers

The cationic polymer 40, prepared from chloromethylated polystyrene and 1, was subjected to ion-exchange to give the hydroxide or fluoride derivatives, and used in the asymmetric addition of 6 to 7 giving (S)-8 in 27% ee (Fig. 6) [36]. 

More subjective analyses show that deposition of cationic polymers onto hair and skin elicits improvements in the structure and appearance of these surfaces (160,161,163-166). Such techniques, however, cannot distinguish, for example, the conditioning effect... 

The subject of this review is complexes of DNA with synthetic cationic polymers and their application in gene delivery [1 ]. Linear, graft, and comb polymers (flexible, i.e., non-conjugated polymers) are its focus. This review is not meant to be exhaustive but to give representative examples of the various types (chemical structure, architecture, etc.) of synthetic cationic polymers or polyampholytes that can be used to complex DNA. Other interesting synthetic architectures such dendrimers [5-7], dendritic structures/polymers [8, 9], and hyperbranched polymers [10-12] will not be addressed because there are numerous recent valuable reports about their complexes with DNA. Natural or partially synthetic polymers such as polysaccharides (chitosan [13], dextran [14,15], etc.) and peptides [16, 17] for DNA complexation or delivery will not be mentioned. 

The subject of interactions between oppositely charged polymers and surfactants can be divided into two categories. One category deals with anionic polymer and cationic surfactant and the other deals with cationic polymer and anionic surfactant. The interactions are similar in principle in both the categories. 

Cationic polymerization is one of the least understood subjects in polymer science, and the data available are not as extensive as for radical polymerization. Normal temperatures of operation vary from — 100°C to -l-20°C. The appropriate temperature for any reaction is found only through experimentation and is extremely sensitive to the monomer and the catalyst chosen. Lower temperatures are preferred because they suppress several unwanted side reactions. It is necessary to have highly purified monomers and initiators because transfer reactions can easily occur with impurities, giving a polymer of very low molecular weight. 

The majority of the literature reports deal with the reaction of calixarenes with Group I and II cations. Polymeric calixarenes have been the subject of a more recent innovation. Harris et al. [23] have prepared a calix[4]ar-ene methacrylate, its polymerization, and Na complex-ation (Scheme 3). They concluded that both monomers and polymers form stable complexes with sodium thiocyanate. 

Therefore, an ideal polymer electrolyte must be flexible (associated with a low Tg), completely amorphous, and must have a high number of cation-coordination sites to assist in the process of salt solvatation and ion pair separation (see Table 11). A review on this subject has been recently published by Inoue [594]. 

In the 1960s, after Kennedy and Thomas [25] had established the isomerisation polymerisation of 3-methylbutene-l, this became a popular subject. From Krentsel s group in the USSR and Aso s in Japan there came several claims to have obtained polymers of unconventional structure from various substituted styrenes by CP. They all had in common that an alleged hydride ion shift in the carbenium ion produced a propagating ion different from that which would result from the cationation of the C C of the monomer and therefore a polymer of unconventional structure the full references are in our papers. The monomers concerned are the 2-methyl-, 2-isopropyl-, 4-methyl-, 4-isopropyl-styrenes. The alleged evidence consisted of IR and proton magnetic resonance (PMR) spectra, and the hypothetical reaction scheme which the spectra were claimed to support can be exemplified thus ... 

The next chapter is a contribution to a collective volume containing detailed treatments of various themes in polymer science. The author took the opportunity to provide answers to some of the well-aimed questions about cationic polymerisations that had been put by two experienced polymer chemists (A) and from this the piece evolved into a conspectus of most parts of the subject. As such it is a useful snap-shot of this author s thinking at that time. However, because of his familiarity with the subject, his piece turned out to be a rather daunting assembly of worst case scenarios , but for this very reason the article is also useful in showing just how complicated the subject can become. 

This paper may be regarded as a sequel to my second book on Cationic Polymerisation [1]. I have aimed here at providing a fairly detailed discussion of some theoretical aspects of the subject which is still (or perhaps now more than ever before) in Dainton s words rudis indigestaque moles (a crude and ill-digested, i.e., confused, mass) [2], I also intend to discuss specifically some of the problems raised by Mayo and Morton in their article Ionic Polymerization in the book Unsolved Problems in Polymer Science [3]. 

Reaction with solvent - The solvent influences the course of cationic reactions not only through its dielectric constant, but also because many substances used as solvents are far from inert in these reactions [22, 23]. Although much more experimental material is required before a full treatment of the subject becomes possible, at least one example, the cationic polymerisation of styrene in toluene, is amenable to quantitative discussion. Experiment shows that polymerisation is rapid and complete, the molecular weight is low and the polymer contains para-substituted rings which are almost certainly tolyl endgroups [22]. Theoretically, a polystyryl carbonium ion can react with toluene in six different ways, only two of which (a.l and b. 1 below) can lead to tolyl endgroups in the first case the tolyl group is at the end of the terminated chain, in the second it is the start of a new chain. The alternative reactions can be represented as follows... 

Polymerisations of undiluted, bulk monomer are rare except for those initiated by ionising radiations and they require a special treatment which will be given later. The most common situation is to have the propagating ions in a mixture of monomer and solvent, and as the solvation by the solvent is ubiquitous and may dominate over that by other components of the reaction mixture, mainly because of the mass-action effect, it will not be noted by any special symbol, except in a few instances. This means that we adopt the convention that the symbol Pn+ denotes a growing cation solvated mainly by the solvent correspondingly kp+ denotes the propagation constant of this species, subject to the proviso at the end of Section 2.3. Its relative abundance depends upon the abundance of the various other species in which the role of the solvent as the primary solvator has been taken over by any or all of the anion or the monomer or the polymer. The extent to which this happens depends on the ionic strength (essentially the concentration of the ions), and the polarity of the solvent, the monomer and the polymer, and their concentrations. 

Mauritz et al., motivated by these experimental results, developed a statistical mechanical, water content and cation-dependent model for the counterion dissociation equilibrium as pictured in Figure 12. This model was then utilized in a molecular based theory of thermodynamic water activity, aw, for the hydrated clusters, which were treated as microsolutions. determines osmotic pressure, which, in turn, controls membrane swelling subject to the counteractive forces posed by the deformed polymer chains. The reader is directed to the original paper for the concepts and theoretical ingredients. 

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