Solvents are fundamentally essential for the synthesis and processing of soft materials.S upramolecular polymers (SPs), an emerging class of soft materials,are usually stable in single and mixtures of poor solvents.I nc ontrast to these preconceived notions,h ere we report the depolymerization of SPs in the mixture of two poor solvents.T his surprising behavior was observed for well-known cationic perylene diimides (cPDIs)i nt he mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPAbut readily depolymerize into monomers in 50-70 vol% IPAcontaining water.This is due to the selective solvation of the p-surface of cPDIs by alkylchains of IPAand ionic side chains by water,asevidenced by molecular dynamic simulations.M oreover,b ys ystematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity.
Cooperative supramolecular polymerization is important for the synthesis of functional supramolecular homo and block-copolymers of π-systems. Current strategies indicate the need of strong hydrogen bonding (H-bonding) and/or dipolar interactions in the π-systems to achieve cooperativity. In sharp contrast, here we report the cooperative supramolecular polymerization in alkyl chain substituted perylene diimides (alkyl PDIs) driven by dispersive interactions with molecular level understanding. Moreover, alkyl PDIs follow cooperative mechanism with cooperativity similar to the strong H-bonded π-systems (σ ~10 À 5 ) despite the lack of strong H-bonding and dipolar interactions. Computer simulations show that this surprising phenomenon in alkyl PDIs is driven by the efficient dispersive interactions among the alkyl chains and π-cores due to their zigzag arrangement in the supramolecular polymer. Importantly, alkyl PDIs display cooperative supramolecular polymerization in both polar and non-polar solvents which is difficult for H-bonded/dipolar πsystems thus highlighting the advantages of dispersive interactions.
Understanding the fundamental forces such as hydrophobic interactions in a crowded intracellular environment is necessary to comprehensively decipher the mechanisms of protein folding and biomolecular self-assemblies. The widely accepted entropic depletion view of crowding effects primarily attributes biomolecular compaction to the solvent excluded volume effects exerted by the “inert” crowders, neglecting their soft interactions with the biomolecule. In this study, we examine the effects of chemical nature and soft attractive energy of crowders on the water-mediated hydrophobic interaction between two non-polar neopentane solutes using molecular dynamics simulations. The crowded environment is modeled using dipeptides composed of polar and non-polar amino acids of varying sizes. The results show that amongst the non-polar crowders, Leu2 strengthens the hydrophobic interactions significantly, whereas the polar and small-sized non-polar crowders do not show significant strengthening. Distinct underlying thermodynamic driving forces are illustrated where the small-sized crowders drive hydrophobic interaction via a classic entropic depletion effect and the bulky crowders strengthen it by preferential interaction with the solute. A crossover from energy-stabilized solvent-separated pair to entropy-stabilized contact pair state is observed in the case of bulky non-polar (Leu2) and polar (Lys2) crowders. The influence of solute–crowder energy in affecting the dehydration energy penalty is found to be crucial for determining the neopentane association. The findings demonstrate that along with the entropic (size) effects, the energetic effects also play a crucial role in determining hydrophobic association. The results can be extended and have implications in understanding the impact of protein crowding with varying chemistry in modulating the protein free energy landscapes.
A strategy to synthesize hyper-crosslinked polymers with strong visible-light absorption and abundant ionic sites is discussed. This is achieved in a one-pot reaction via the simultaneous Friedel–Crafts alkylation and quaternization reaction between α,α′-dibromo-p-xylene (DBX) and perylene diimide (PDI) substituted with N,N-dimethyl ethylene to result in hyper-crosslinked ionic polymers (HIPs). These HIPs display good surface areas with strong visible-light absorption (400–650 nm) and dispersibility in polar solvents like water and DMSO. Importantly, our experimental and theoretical studies indicate that PDI-HIPs possess a dynamic network with good uptake of water up to seven times their weight. Notably, PDI in PDI-HIPs is not only responsible for visible-light absorption but also acts as a probe to study their dynamic nature. Moreover, the presence of ultramicropores and CO2-philic functional groups in PDI-HIPs renders good CO2 uptake up to 2.11 mmol/g at 273 K despite their relatively low surface area.
Solvents are fundamentally essential for the synthesis and processing of soft materials.S upramolecular polymers (SPs), an emerging class of soft materials,are usually stable in single and mixtures of poor solvents.I nc ontrast to these preconceived notions,h ere we report the depolymerization of SPs in the mixture of two poor solvents.T his surprising behavior was observed for well-known cationic perylene diimides (cPDIs)i nt he mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPAbut readily depolymerize into monomers in 50-70 vol% IPAcontaining water.This is due to the selective solvation of the p-surface of cPDIs by alkylchains of IPAand ionic side chains by water,asevidenced by molecular dynamic simulations.M oreover,b ys ystematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity.
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