Role of the intermolecular interaction in polymer fibre chemistry and technology

Abstract

The existence of a specific intermolecular interaction of a hydrogen bond affects many polymerization processes and the occurrence of reactions in the chains of macromolecules. The features of the hydrogen bond in monomeric and oligomeric compounds are revealed. In production of aromatic polyamides, polyamido acids, polyimides, and the fibres based on them, the role of the hydrogen bond is reduced to the possibility of deliberate regulation of the chain rigidity.The intermolecular interaction (IMI) between molecular groups of monomeric and polymeric compounds active in its formation are very important in polymerization processes and also determines the features of fibre formation, properties of the fibres, and performance parameters of the articles made from them.The dipole-dipole interaction, H-bond, and π-π-electron interaction determine the kinetic and thermodynamic characteristics of polymer formation to a significant degree, including polycondensation, decyclization, and cyclodehydration of polymer systems. In addition, the orientation-crystallization processes that accompany fibre formation are also intentionally regulated by different types of IMI.The specific effect of the H bond occupies a special position among associative systems. It exists in many monomeric compounds, entering into polymerization, and in their reaction with polymer systems.Hydrogen bonding changes the electron-oscillation characteristics of groups active in formation of H bonds. In all cases, the frequency shifts can consist of 100-200 to 300-400 cm -1 , identified by vibrational, IR, and Raman spectroscopy [1]. A similar picture is observed for chemical shifts in nuclear magnetic resonance. The more important the frequency shifts and the greater the half-width of the corresponding bands, the higher the energy of the H-bonds.Let us consider some cases of the effect of the H-bond in the chemistry and technology of fibre-forming polymers. In decyclization of acid amides (lactams) in production of aliphatic polyamides, dissociation of lactam dimers is the first stage of the reaction [2, 3]. As the spectral studies showed, the cis-form of the amide group causes the formation of a double associate of chelate form:If n ≥ 7, the amide group is in the trans-form, the double H-bond passes into the n-dimensional form with a smaller frequency shift of (NH) stretching vibrations perturbed by the H-bond, from 210 to 120 cm -1 , respectively. The half-width of the NH bond absorption bands decreases from 50-60 to 20-25 cm -1 . Polymerization with rupture of the CN-bond ring in lactams takes place with formation of the trans-form of the amide group with reduced H-bond energy. The mechanism of hydrolytic polymerization is based on the reaction of lactam dimers with water. The energy of formation of an H-bond between water and the cis-form of the amide group decreases, which breaks the CN bond in the ring and causes polymerization.Moscow State Textile University.