Master's lecture in Chemistry - Daníel Arnar Tómasson
Master's student: Daníel Arnar Tómasson
Title: Exploring the role of urea and hydrazone moieties in supramolecular gel-network formation
Faculty: Faculty of Physical Sciences
Advisor: Krishna Kumar Damodaran, Professor at the Faculty of Physical Sciences
Also in the masters committee: Benjamín Ragnar Sveinbjörnsson, Assistant Professor at the Faculty of Physical Sciences
Examiner: Stefán Jónsson,Team Leader at Alvotech Iceland
Supramolecular gels based on low weight molecular gelators (LMWGs) are excellent class of soft materials due to their tunable properties, which depends on the geometric arrangement and the nature of intermolecular non-covalent interactions of the building blocks (hydrogen bonding). In this thesis, we explore the effect of hydrogen bonding motifs such as urea, hydrazone and semicarbazone on supramolecular gelation. This thesis is divided into two chapters and in Chapter I, we have studied the gelation properties of chiral compounds based on phenylalanine methyl ester tagged bis(urea) compounds. Multi-component gel was prepared by mixing equimolar amounts of the enantiomers (R and S), which showed enhanced thermal and mechanical strength compared to enantiomer and racemate gels. Analysis of the morphology of the gel fibers using SEM and AFM images revealed that a twisted-tape morphology was observed in mixed gel due to the presence of the enantiomeric and racemate fibers, which indicate that both self-sorting and co-assembly process occurred in mixed gel. In Chapter II, the effect of hydrazone and semicarbazone moieties in tuning gelation properties were studied. This was done altering the intermolecular non-covalent interaction of the gelators by modifying the hydrazone moiety to semicarbazone by adding an N-H moiety resulting in urea-like motif. The modification resulted versatile gelation and transformation gel fibers from crystalline to fibrous morphology. The enhanced mechanical and thermal stability of the modified gelator clearly indicate that gelation properties can be tuned by altering intermolecular non-bonding interactions.