Search for: All records

Biomass-based polymers show promise for the mitigation of environmental issues associated with petroleum-derived commodity polymers; however, due to poor entanglement, many of these polymers typically lack mechanical strength and toughness. Herein, we report a facile approach to utilizing metal–ligand coordination to create physical crosslinking, and thus chain entanglements for plant oil-derived polymers. A series of soybean oil-derived copolymers containing a pendant acid group can be easily synthesized using free radical polymerization. The resulting chain architecture can be controlled through supramolecular interactions to produce bioplastics with enhanced thermomechanical properties. The metal–ligand coordination in this work can be varied by changing the metal lability and the density of metal–ligand bonds, allowing for further control of properties. The final bioplastics remain reprocessable and feature good thermoplastic and stimuli-responsive properties. 

Chemical reduction of a benzo‐fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of1. The doubly‐reduced helicene1²⁻has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes,1³⁻and1⁴⁻, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb⁺ions each, leaving three remaining Rb⁺ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in1⁴⁻vs. 2.09 Å in1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in1to 20.7° in1⁴⁻. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data.

 

Chemical reduction of a benzo‐fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of1. The doubly‐reduced helicene1²⁻has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes,1³⁻and1⁴⁻, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb⁺ions each, leaving three remaining Rb⁺ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in1⁴⁻vs. 2.09 Å in1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in1to 20.7° in1⁴⁻. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data.

 

Acoustic waves are increasingly used to concentrate, separate, and pattern nanoparticles in liquids, but the extent to which nanoparticles of different size and composition can be focused is not well‐defined. This article describes a simple analytical model for predicting the distribution of nanoparticles around the node of a 1D bulk acoustic standing wave over time as a function of pressure amplitude, acoustic contrast factor (i.e., nanoparticle and fluid composition), and size of the nanoparticles. Predictions from this model are systematically compared to results from experiments on gold nanoparticles of different sizes to determine the model's accuracy in estimating both the rate and the degree of nanoparticle focusing across a range of pressure amplitudes. The model is further used to predict the minimum particle size that can be focused for different nanoparticle and fluid compositions, and those predictions are tested with gold, silica, and polystyrene nanoparticles in water. A procedure combining UV‐light and photoacid is used to induce the aggregation of nanoparticles to illustrate the effect of nanoparticle aggregation on the observed degree of acoustic focusing. Overall, these findings clarify the extent to which acoustic resonating devices can be used to manipulate, pattern, and enrich nanoparticles suspended in liquids.