Structural Modifications to Polystyrene via Self‐Assembling Molecules

Abstract

We have previously reported that small quantities of self‐assembling molecules known as dendron rodcoils (DRCs) can be used as supramolecular additives to modify the properties of polystyrene (PS). These molecules spontaneously assemble into supramolecular nanoribbons that can be incorporated into bulk PS in such a way that the orientation of the polymer is significantly enhanced when mechanically drawn above the glass‐transition temperature. In the current study, we more closely evaluate the structural role of the DRC nanoribbons in PS by investigating the mechanical properties and deformation microstructures of polymers modified by self‐assembly. In comparision to PS homopolymer, PS containing small amounts (≤ 1.0 wt.‐%) of self‐assembling DRC molecules exhibit greater Charpy impact strengths in double‐notch four‐point bending and significantly greater elongations to failure in uniaxial tension at 250 % prestrain. Although the DRC‐modified polymer shows significantly smaller elongations to failure at 1000 % prestrain, both low‐ and high‐prestrain specimens maintain tensile strengths that are comparable to those of the homopolymer. The improved toughness and ductility of DRC‐modified PS appears to be related to the increased stress whitening and craze density that was observed near fracture surfaces. However, the mechanism by which the self‐assembling DRC molecules toughen PS is different from that of conventional additives. These molecules assemble into supramolecular nanoribbons that enhance polymer orientation, which in turn modifies crazing patterns and improves impact strength and ductility.

Remarkable Toughening of Plastic with Monodispersed Nano-CaCO3: From Theoretical Predictions to Experimental Validation

“…Based on the above results of structures and properties of the models, an appropriate surface modification of CaCO 3 nanoparticles and a suitable filling content in PVC are the two keys to achieve good filler dispersity, an effective filler–matrix interfacial bonding action, and poor polymer chain mobility, which contribute to the remarkable improvement in toughness of the plastic nanocomposite. − Additionally, the regulation of these two key factors can also induce a decreased chain curling degree and then strengthen the model stiffness.…”

Bioinspired Polymeric Nanocomposites

“…The observed increase in birefringence was attributed to increased alignment of the polymer chains induced by the DRC nanofibers . The authors also noted that the Charpy impact strength of the polystyrene/DRC nanocomposite with 0.5 wt % DRC was nearly double that of pure polystyrene . It was also revealed that the improved toughness and ductility of the nanocomposites were due to increased stress whitening and craze density in the DRC modified films (Figure ).…”

“…72 The authors also noted that the Charpy impact strength of the polystyrene/DRC nanocomposite with 0.5 wt % DRC was nearly double that of pure polystyrene. 73 It was also revealed that the improved toughness and ductility of the nanocomposites were due to increased stress whitening and craze density in the DRC modified films (Figure 6). The smaller and higher-density crazes in DRC composites resembled those formed in more highly oriented polymers when stressed in tension along their axis of orientation.…”

Functional π-Gelators and Their Applications

“…Stupp and co-workers have studied the self-assembly and organogelation of DRC molecules consisting of coil-like, rod-like, and dendritic segments. − The use of bulky dendrons prevented the formation of 2D assemblies whereas identical aromatic rod-dendron segments enabled 1D aggregation through π–π stacking and hydroxyl groups at the periphery of the dendrons facilitated hydrogen bonding. The self-assembly of DRC molecule leads to a network of long ribbons consisting of two hydrogen bonded DRC molecules, leading to gelation in organic solvents , as well as in styrene and acrylates. − Further studies have utilized the amphiphilic nature of the generated twisted DRC ribbons as templates for the fabrication of single and double helices of CdS. The DRC scaffold has also been used to disperse ZnO crystals at room temperature .…”