Free H‐Bonding Interaction Sites in Rigid‐Chain Polymers and Their Filling Approach: A Molecular Dynamics Simulation Study

Abstract

Hydrogen bond (H‐bond) plays an important role in structure evolution and properties of various polymers. Due to directivity and saturation of H‐bond, its formation is influenced by macromolecular chain conformation but the relationship is still not well understood up to now. In this paper, amorphous models of polyamide 66 (PA66), polyamide 6T (PA6T), and poly(p‐phenylene‐terephthamide) (PPTA) are built to study influence of chain rigidity on H‐bonding formation by utilizing Molecular Dynamics simulation. Compared with PA66 and PA6T, it is found that chain rigidity of PPTA is more remarkable and corresponding conformation adjustment is hindered more significantly, which leads to considerable weak H‐bonds and free H‐bonding sites. After introducing benzimidazole moiety into PPTA, more H‐bonds form due to more potential H‐bonding sites in benzimidazole units. However, the newly added H‐bonding donor and acceptor are in the co‐ring, and there is a high rotational energy barrier for benzimidazole ring, both of which hinder the formation of strong H‐bonds. Therefore, a strategy is proposed to fill free H‐bonding sites in rigid‐chain polymers through adding oligomers with high movement ability. Thus, the H‐bonds in rigid‐chain polymers are effectively enhanced due to bridging effect of oligomers and tensile modulus of the aramid is improved significantly.

Preparation and structure–property relationship of flexible aramid films with enhanced strength by introducing asymmetric and symmetric aromatic ether bond structures

“…Some literature reports suggest that a greater rigidity of a chain can result in a weaker ability to form intermolecular H-bonds. 36…”

“…The mobility of molecular chains is also a key factor affecting the rigidity of polymers. 36 Therefore, the mean square displacement (MSD) of 0-PMIA, MAPB10%-PMIA and PAPB10%-PMIA was calculated through molecular simulation, which can be used to evaluate the motion ability of molecular chains in dynamic processes. As shown in Fig.…”

“…Some literature reports suggest that a greater rigidity of a chain can result in a weaker ability to form intermolecular H-bonds. 36 In order to gain a clearer understanding of the structural transformation of polymer amorphous cells under external forces, the "stress-strain" script was used to stretch them under a tension of 100 MPa, 38 and the changes in the number of various H-bonds after stretching were calculated. It can be seen that the molecular chains undergo further migration and acquire more stable configurations under slight external forces, resulting in an increase in the number of all H-bonds.…”

Effects of Plasticizing on Mechanical and Viscous Characteristics of Poly(vinyl alcohol): A Comparative Study between Glycerol and Diethanolamine

“…The distinctions in the physical properties of the plasticizer are determined by the intermolecular hydrogen bond network composed of hydroxyl groups on the plasticizer and PVA chains, as has been widely proven in former work. [45,[50][51][52][53] The insertion of GLY and DEA increased the distance between the polymer chains, enhanced the motion of the segments, and extended the relaxation time, thereby contributing to the differences in the thermodynamics properties. [35] To further investigate the distinctions in the intermolecular hydrogen bonds at the atomic level, DFT in DMol3 was utilized for binding energy calculations, as shown in Figure 6a.…”

Properties of Aramid Fibers And Their Composites Based on Atomic/Molecular Scale Simulation Technology: A Review

“…Yang C [10]established amorphous models of polyamide 66 (PA66), polyamide 6T (PA6T), and polyparaxylylenediamine (PPTA), and used molecular dynamics simulations to study the effect of chain rigidity on hydrogen bond formation. Compared with PA66 and PA6T, the chain rigidity of PPTA is more pronounced, and the corresponding conformations adjustment is more obstructed, resulting in a large number of weak hydrogen bonds and free hydrogen bond sites.…”