Sodium cation affinity and basicity

As in the case of the lithium cation, there are roughly two major sources of sodium cation affinities and basicities ... 

Table 6.5 Sodium cation affinity (NaCA) and basicity (NaCB) scales (kj mol j at 298 K from CIDT measurements (unless indicated otherwise). 

Greater success was achieved by DuPont who copolymerized, the sodium salt of 5-sulfoisophthalic acid into PET to render the polymer dyeable with cationic (basic) dyes. Basic dyeable PET was successfully launched as Dacron 64 in the form of a low-pill staple product [64]. The presence of the sulfonate groups in the polymer chain also acts as an ionic dipolar cross-link and increases the melt viscosity of the polymer quite markedly. Thus, it is possible to melt-spin polymer with IV 0.56 under normal conditions, giving a low-pill fiber variant. The fiber also has a greater affinity for disperse dyes due to the disruption of the PET structure. Continuing this theme, there are deep dye variant PET fibers, often used in PET carpet yarns, which are copolymers of PET with chain-disrupting copolymer units like polyethylene adipate. They have less crystallinity and a lower Tg. therefore, they may be dyed at the boil without the use of pressure equipment or carrier at the cost of some loss of fiber physical properties. 

Synthetic polymers [5, 51] as well as derivatives of natural macromolecules, such as hydroxypropylcellulose acetate succinate [52, 53] or chitosan [54, 55] have been used. Precipitation can be induced by pH shift, salinity modification or temperature. Certain polysaccharides, such as sodium alginate whose solubility is sensitive both to acidic conditions and to the presence of divalent cations (e.g. Ca ) or carrageenan which precipitates upon decreasing temperature, have not yet been exploited but are eligible candidates for a future use in affinity precipitation. Various works can be selected from the literature to illustrate the basic principles of this technique. 

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