Self-Organization in Solutions of Stiff-Chain Amphiphilic Macromolecules

Complexation of oligochitosan with sodium caseinate in alkalescent and weakly acidic media

Сomplexation of oligochitosan (OCHI) having the degree of acetylation (DA 26 %) with sodium caseinate (SC) at pH 5.8 and 7.2 is described and compared with the complexation of OCHI (DA 2 %) at pH 5.8. In the alkalescent medium, the complexation of OCHI (DA 26 %) is weaker and dualistic depending on SC concentration in the system. In the diluted alkalescent system, the formation of only soluble complexes is observed at OCHI/SC ratio ≤0.9. In the semi diluted one, the complexation results in the formation of insoluble complexes those composition changes symbatically with the OCHI/SC ratio in the system. At pH 5.8, OCHI/SC ratio in insoluble complexes remains the same regardless of OCHI/SC ratio in the solution. At pH 5.8, the electrostatic complexation weakens with an increase in DA and is completely suppressed at a high ionic strength. These results can be promising for construction of biodegradable protein/chitosan drug delivery systems.

Molecular features of the interaction and antimicrobial activity of chitosan in a solution containing sodium dodecyl sulfate

Molecular interaction of chitosan with sodium dodecyl sulfate (SDS) is a more complicated process than it has been imagined so far. For the first time it has been shown that the shorter chitosan chains are, the more preferably they interact with the SDS and the larger-in-size microparticles they form. The influence of ionic strength, urea and temperature on microparticles formation allows interpreting the mechanism of microparticles formation as a cooperative electrostatic interaction between SDS and chitosan with simultaneous decrease in the surface charge of the complexes initiating the aggregation of microparticles. It is shown that hydrogen bonding is mainly responsible for the aggregation while hydrophobic interaction has a lesser effect. Chitosan demonstrates a high bacteriostatic activity in the presence of SDS in solution and can be promising for preparation of microbiologically stable pharmaceutical hydrocolloids, cosmetic products and chitosan-based Pickering emulsions containing strong anionic surfactants.

Detection and evaluation of polymer–polymer interactions in dilute solutions of associating polymers

An experimental tool for the evaluation of intramolecular associative/hydrophobic interactions in polymer/solvent systems was proposed and tested.

New strategy to create ultra-thin surface layer of grafted amphiphilic macromolecules

It was found first that macromolecules made of amphiphilic monomer units could form spontaneously an ultra-thin layer on the surface which the macromolecules are grafted to. The width of such layer is about double size of monomer unit consisting of hydrophilic A (repulsive) and hydrophobic (attractive) B beads. The hydrophilic A beads are connected in a polymer chain while hydrophobic B beads are attached to A beads of the backbone as side groups. Three characteristic regimes are distinguished. At low grafting density, the macromolecules form ultra-thin micelles of the shape changing with decrease of distance d between grafting points as following: circular micelles-prolonged micelles-inverse micelles-homogeneous bilayer. Those micelles have approximately constant height and specific top-down A-BB-A structure. At higher grafting density, the micelles start to appear above the single bilayer of amphiphilic macromolecules. The thickness of grafted layer in these cases is different in different regions of grafting surface. Only at rather high density of grafting, the height of macromolecular layer becomes uniform over the whole grafting surface. The study was performed by computer modeling experiments and confirmed in framework of analytical theory.

Polymeric Surfactants: Novel Agents with Exceptional Properties

This article presents recent progress in the field of polymeric surfactants made of permanently amphiphilic block copolymers or of stimulus-sensitive ones. We highlight key points in the design of amphiphilic macromolecules, to yield polymer surfactants with tailor-made properties, as well as recently developed and still challenging application fields for this new class of surfactants. The efficiency boosting of amphiphilic block copolymers as co-surfactants in microemulsions is discussed, as are surface modification by polymer surfactants, and stabilization of dispersions. Moreover, the use of block copolymers in nanosciences is presented, for instance as a tool for nanomaterial fabrication, or for biomedical and cosmetic applications in bio-nanotechnology. Finally, self-assembly and applications of some newly developed “exotic” amphiphilic block copolymer structures as new surface-active materials will be highlighted.