Investigation of dendrimer-reinforced PLA composite system and fluorescent supramolecular gels

Abstract

Dendrimer is a unique class of macromolecule, featured by regularly branched 3D structures having abundant functional surface groups. In this study, a family of phosphorus dendrimers of a series of generations has been synthesized and employed in form of composite fillers to modify properties of bulk Polylactide (PLA). Physical, thermal, and mechanical properties of the blends have been intensively studied and compared with neat PLA, accompanied by examining their rupture surfaces using scanning electron microscopy. It is claimed that both the G0.5 and G3 dendrimers are effective strengtheners by offering plasticizing as well as toughening effects to PLA, respectively. Besides, through a series of studies, an all-rounded understanding on the system can be realized. Organogel, a kind of supramolecular soft material, has attracted considerable attention over recent years due to its smart response to the external stimuli, both chemically and physically. This work describes new low molecular weight (LMW) gels with tunable fluorescent properties. Three LMW gelators containing pyrene and 1,3,5-benzenetricarboxamide units were designed and synthesized with alkyl and gallic substituents; they were then utilized to study the features governing the self-assembly behavior of these chromophore-linked molecular systems. It is realized that these materials are able to form self-assembled three-dimensional fibrous network as well as sheetlike lamellar structures in the gel state. The assembly of pyrene moieties in the gelators is dominated by the aggregation of 1,3,5-benzenetricarboxamide and the length of the alkylidene spacers during the gelation process. The results revealed from XRD, FT-IR and fluorescent spectroscopy suggest that H-bonding, π-π stacking, and van der Waals interactions play an important role in the gelation process. Besides, it is found that stable gels can be formed under a wide range of organic solvents. Gathering information obtained from the present study will wrap up a pack of valuable information for creating new advanced nanoscale materials.