Solution properties of well-defined 2-(dimethylamino)ethyl methacrylate-based (co)polymers: A viscometric approach

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.

Bioprocessing of shrimp wastes to obtain chitosan and its antimicrobial potential in the context of ethanolic fermentation against bacterial contamination

This study investigated the bioprocessing of shrimp wastes to obtain chitin and its deacetylated product chitosan by a fermentation process mediated by Lactobacillus plantarum. The concentrations of glucose, bacterial inoculum, and shrimp wastes in the Man, Rogosa and Sharpe medium were optimized for the fermentation process performed in shake flasks to achieve the maximum titratable acidity to obtain chitin. The experiments were scaled up in a 700-mL working volume bioreactor, and the resulting chitin was deacetylated by the autoclave method. The bioextracted chitosan was characterized (Fourier transform infrared spectroscopy [FTIR], deacetylation degree, and molecular weight) and evaluated for its antimicrobial effects by comparing it with a commercial chitosan sample in the context of the ethanolic fermentation process for fuel alcohol production. The effect of chitosan on such a fermentation process has not been determined yet. The bacterial contaminant Lactobacillus fermentum and the main agent of ethanolic fermentation Saccharomyces cerevisiae were cultured in semi-synthetic medium and co-cultured in sugarcane juice to verify the effect of chitosan on their growth. The bioextracted chitosan (molecular weight 4.0 × 10⁵ g mol^-1 and deacetylation degree 80%) was comparable to commercial chitosan, although higher concentrations of the former were required to achieve similar antimicrobial activities. Both commercial and bioextracted chitosan samples exhibited antimicrobial activity against S. cerevisiae and L. fermentum, but the concentration that caused the inhibition of yeast growth was almost tenfold higher than for the bacterium. Moreover, bioextracted chitosan showed no yeast inhibition or lethality in the range of 0.0075-0.96% while for the bacterium, growth inhibition occurred in concentrations varying from 0.24 to 0.48% and lethality of more than 99% at 0.96%. These results indicate the potential use of chitosan and especially of bioextracted chitosan in the bioethanol industry as a safer and more natural approach to combat unwanted bacterial contamination.

Opto-electrical properties of some quaternized polysulfones

A novel quaternized polysulfone with N-dimethylethylammonium chloride (DMEA) and N-dimethyloctylammonium chloride (DMOA) pendent groups was investigated, as to its optical and electronic properties. Optical properties were investigated by refractivity and transmission spectra. To obtain the optical parameters, the approach proposed by Tauc for amorphous semiconductors has been used, because of the similarity of the absorption edges. The values of pseudogap energy ranged between 3.60 and 3.69 eV, while those of Urbach energy were modified over the 157—172 meV range. The dielectric properties and ac-conductivity were also studied as a function of temperature, frequency and structure of pendant groups. It was observed that the dielectric constant decreased as the frequency increased and the temperature decreased. In addition, quaternized polysulfone films were characterized by two relaxation processes, i.e., γ and β relaxation, which appeared at different temperatures, depending on the pendant groups. The frequency—temperature-dependent conductivity showed that conductivity increased with frequency and also that the quaternized polysulfones possessed typical semiconducting properties. All parameters were found to be slightly influenced by the polymer chain structure.

pH-triggered block copolymer micelle-to-micelle phase transition

We present a first experimental observation and provide a theoretical interpretation of a pH-induced micelle-to-micelle phase transition in aqueous solutions of spherical block copolymer micelles with polybasic coronas. Dynamic light scattering, static light scattering, and atomic force microscopy confirm sharp changes in micellar hydrodynamic size and aggregation number occurring in a narrow pH range, DeltapH<0.1. In agreement with theory, zeta potential measurements indicated an abrupt change in ionization of polymer chains in the micellar corona at the transition pH.

Polyelectrolyte complexes based on (quaternized) poly[(2-dimethylamino)ethyl methacrylate]: behavior in contact with blood

Polyelectrolyte complexes (PECs) between (quaternized) poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and (crosslinked) N-carboxyethylchitosan (CECh) or poly(2-acrylamido-2-methylpropane sodium sulfonate) (PAMPSNa) were prepared and characterized in terms of their stability, equilibrium water content, and surface morphology. The evaluation of the behavior of the studied PECs in contact with blood revealed that the (crosslinked) CECh/(quaternized) PDMAEMA complexes had lost the inherent PDMAEMA cytotoxicity but still preserved haemostatic activity. In contrast, the complex formation between (quaternized) PDMAEMA and PAMPSNa allowed the preparation of materials with improved blood compatibility.