Intermolecular interactions in polyamides involving water

Abstract

The article specifies the classification of adsorption bands in the IR spectra of polyamides. The study revealed the presence of wagging, scissoring, rocking, and twisting which are characteristic of the structures in amide I, amide II, amide III, amide IV, amide V, and amide VI.
The IR spectroscopy demonstrated the presence of cyclic structures in the polyamide-6 and the su-pramolecular sorbent “Solid water”. The cyclic structures were formed by carbocylic groups: COOHCOOHin neighbouring parallel chains as a result of tautomeric transformations (involving amide groups) of lactam fragments: CH₃CH(CH₂)₂CONH₂CH₃CHCH₂CH₂COOOH
The study also demonstrated that polyamides can absorb phenol and its derivatives from aqueous so-lutions. This sorption is quite active since phenol forms stronger hydrogen bonds with С=О groups of amide groups than with -NHCO…Н₂О and OHOH₂.
The article suggests a modification principle of the triad of interacting components “water - micellar microreactor with surface-active material (SAM) - stationary phase”. The characteristic feature of the super-sorbent “solid water” is that when it is sown in dry soil and watered once, the stationary phase is the micelle modified with SAM. The surface-active material acts as a crystallite and as a liquid phase with laminar struc-ture.
The study demonstrated that in a three-component model, the key role belongs to the coefficient (КMW) of distribution between the micelle and water, as well as the coefficient of distribution (КSM) in the stationary phase (SP). Of much less importance in the three-component model is the coefficient of distribu-tion (КSW) between the stationary phase and water, since КSW is two and more times smaller than КMW.
The study also provided the information about the interaction of the micelles of SAM, which are protolytes that exist in the cation form RCHCOOHNH3+ (рН<рI) in acidic media; in the form of bipolar ions RCHCOONH3+- (рН=рI) in neutral media (with рН=рI, where I is an isoelectric point); and in the form of aniones RCHCOONH2- (рН>рI) in the media with high pH values. In protolytic reactions, they appear with indicators and initiate the transitions of benzol structures into quinoid ones and result in the appearance of conjugation chains with alternating single and multiple bonds.
The article also provides data demonstrating the influence of the distribution coefficients КL in the mobile (MP) and stationary phases (SP) of TLC on the protolysis constants Ка of the separated components and on the рН in micellar reactors.
We believe that polyamides, along with other polymers, will play a significant role as stationary phases in planar chromatography and high-performance liquid chromatography.