Ion-Specific Self-Assembly of Hydrophobically Modified Polycation of Natural Origin

Solution and Film Self-Assembly Behavior of a Block Copolymer Composed of a Poly(ionic Liquid) and a Stimuli-Responsive Weak Polyelectrolyte

Cu(0)-mediated atom transfer radical polymerization was used to synthesize a poly(ionic liquid), poly[4-vinylbenzyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (PVBBImTf2N), a stimuli-responsive polyelectrolyte, poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA), and a novel block copolymer formed from these two polymers. The synthesis of the block copolymer, poly[2-(dimethylamino) ethyl methacrylate]-block-[poly(4-vinylbenzyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (PDMAEMA-b-PVBBImTf2N), was examined to evaluate the control of "livingness" polymerization, as indicated by molecular weight, characterizations of degree of polymerization, and 1HNMR spectroscopy. 2D DOSY NMR measurements revealed the successful formation of block copolymer and the connection between the two polymer blocks. PDMAEMA-b-PVBBImTf2N was further characterized for supramolecular interactions in both the bulk and solution states through FTIR and 1H NMR spectroscopies. While the block copolymer demonstrated similar intermolecular behavior to the PIL homopolymer in the bulk state as indicated by FTIR, hydrogen bonding and counterion interactions in solution were observed in polar organic solvent through 1H NMR measurements. The DLS characterization revealed that the PDMAEMA-b-PVBBImTf2N block copolymer forms a network-like aggregated structure due to a combination of hydrogen bonding between the PDMAEMA and PIL group and electrostatic repulsive interactions between PIL blocks. This structure was found to collapse upon the addition of KNO3 while still maintaining hydrogen bonding interactions. AFM-IR analysis demonstrated varied morphologies, with spherical PDMAEMA in PVBBImTf2N matrix morphology exhibited in the region approaching the film center. AFM-IR further revealed signals from silica nano-contaminates, which selectively interacted with the PDMAEMA spheres, demonstrating the potential for the PDMAEMA-b-PVBBImTf2N PIL block copolymer in polymer-inorganic nanoparticle composite applications.

Serendipity discovery of fire early warning function of chitosan film

Transparent chitosan (CS) film is prepared and its application in high temperature/fire warning is discussed. NaCl-doped chitosan (CS-NaCl) film shows excellent performance in real-time temperature monitoring and fire warning. The temperature warning of CS-NaCl film can be triggered under approximately 50 °C, and it has a good repeatable warning performance under high-temperature conditions. The CS composite film exhibits an ultra-sensitive (0.4 s) warning under fire attacking. A possible electrical conduction and fire-alarm mechanisms are proposed. The addition of NaCl increases the number of charge carriers, which improves the ionic conductivity of the composite film. This study provides a possibility for the application of CS in the field of fire warning.

Interfacial Properties of Chitosan in Interfacial Shear and Capsule Compression

The time-dependent behavior of surface-active adsorption layers at the oil/water interface can dictate emulsion behavior at both the micro- and macroscale. In addition, self-healing behavior of the adsorption layer may benefit emulsion stability subject to large deformation under processing or during final application. We explore the behavior of chitosan, a known hydrophilic emulsifier, which forms nanoparticle aggregates when the concentration of acetate buffer exceeds 0.3 M. We observe a Pickering adsorption layer building and strain-dependent behavior of the chitosan at the medium chain triglyceride oil/water interface. We compare this to the behavior of identical chitosan layers coated on oil droplets via atomic force microscopy colloidal probe compression in both linear and oscillatory compressions. In both interfacial shear rheometry and the capsule compression, a thick, elastic layer with strong time-dependent recovery behavior is observed, suggesting that the layer has some self-healing capabilities.

A new and efficient carboxymethyl-hexanoyl chitosan/dodecyl sulfate nanocarrier for a pyrazoline with antileukemic activity

We describe herein a chitosan nanocarrier for drug delivery applications obtained through the self-assembly of carboxymethyl-hexanoyl chitosan and dodecyl sulfate (CHC-SDS). Nanocapsules with spherical morphology were obtained in phosphate buffer at pH 7.4. These CHC-SDS nanocapsules showed no toxicity toward Jurkat cells (acute lymphoblastic leukemia) and were used to encapsulate a new pyrazoline (H3TM04) with antileukemia activity. The samples were characterized by dynamic light scattering (DLS) and Laser Doppler Micro-Electrophoresis. The encapsulation efficiency was higher than 96% (293.6 μg mL^-1) and the H3TM04-loaded nanocapsules (CHC-SDS-H) had a negative surface charge (-29.8 ± 0.7 mV) and hydrodynamic radius of around 84 nm. For the first time, CHC-SDS-H were formed and the antitumoral cancer activity was proved. The in vitro assays showed the controlled release of H3TM04 from the CHC-SDS-H nanocapsules in phosphate buffer pH 7.4. The H3TM04 release data were described by the power law model, indicating that H3TM04 delivery occurred via an erosion mechanism. The cytotoxicity assays with Jurkat and K-562 cells (acute myeloid leukemia) demonstrated that the CHC-SDS-H nanocapsule decreases the half maximal inhibitory concentration (IC₅₀). The study showed that CHC-SDS nanocapsules represent a promising nanocarrier for pyrazoline derivates that could be applied in leukemia therapy.

Self-Assembly of Lecithin and Bile Salt in the Presence of Inorganic Salt in Water: Mesoscale Computer Simulation

The influence of inorganic salt on the structure of lecithin/bile salt mixtures in aqueous solution is studied by means of dissipative particle dynamics simulations. We propose a coarse-grained model of phosphatidylcholine and two types of bile salts (sodium cholate and sodium deoxycholate) and also take into account the presence of low molecular weight salt. This model allows us to study the system on rather large time and length scales (up to about ∼20 μs and 50 nm) and to reveal mechanisms of experimentally observed increasing viscosity upon increasing the low molecular weight salt concentration in this system. We show that increasing the low molecular weight salt concentration induces the growth of cylinder-like micelles formed in lecithin/bile salt mixtures in water. These wormlike micelles can entangle into transient networks displaying perceptible viscoelastic properties. Computer simulation results are in good qualitative agreement with experimental observations.