Stimuli-responsive ampholytic terpolymers ofN-acryloyl-valine, acrylamide, and (3-acrylamidopropyl)trimethylammonium chloride: Synthesis, characterization, and solution properties

Charge-Selective Aggregation Behavior of Thermoresponsive Polyelectrolytes Having Low Charge Density in Aqueous Solutions of Organic Counterions

The aggregation behavior of thermoresponsive polyelectrolytes with low charge density in aqueous solutions of organic counterions was investigated. We synthesized two thermoresponsive polyelectrolytes: anionic poly(N-isopropylacrylamide-co-(3-sulfopropyl)acrylamide potassium) (P-NIP-SPAK) and cationic poly(N-isopropylacrylamide-co-(3-acrylamidepropyl)trimethylammonium chloride) (P-NIP-AAPTAC). The polyelectrolytes remained soluble in their aqueous solutions even above the lower critical soluble temperature of P-NIP owing to the strong hydration property of the ionic groups. The aggregation occurred when organic counterions were added to the solution. In these solution systems, the concentration of counterions exceeds those of ionic groups introduced into the polyelectrolytes. The aggregation behavior is attributed to the salting-out effect of counterions accommodated near the polyelectrolyte surface by electrostatic interaction. This aggregation behavior was utilized for the charge-selective recognition of amino acids. P-NIP-SPAK aggregated only when basic amino acids were added under acidic conditions, whereas P-NIP-AAPTAC aggregated only when acidic amino acids were added under basic conditions. The results herein demonstrate that P-NIP-SPAK and P-NIP-AAPTAC have the potential to be used as charge-selective polymer sensors for amino acids without having to strictly control the experimental conditions.

Analysis of the microscopic interactions between processed Polygonatum cyrtonema polysaccharides and water

The dissolution and microscopic interactions of processed Polygonatum cyrtonema polysaccharides in water are extremely important because they strongly influence the process to extract these polysaccharides from water. In this paper, molecular dynamics simulation methods were used to analyse the influence of extraction temperature, concentration and molecular weight on the radial distribution function (RDF), mean square displacement (MSD), diffusion coefficient (D), radius of gyration (R_g), and microstructure of processed Polygonatum cyrtonema polysaccharides in water as well as the intrinsic viscosity (η), hydrogen bond characteristics and microscopic interactions in the solutions. The research results showed that the extraction temperature, concentration and molecular weight of the polysaccharides had important effects on the RDF, MSD, D, R_g, η, hydrogen bond characteristics and the microstructure of the polysaccharide molecules, but there were some major differences. The order of the influence of the factors affecting the dissolution of polysaccharides in water was temperature > concentration > molecular weight. Extraction temperature, material fluid ratio and molecular weight had greater influence on the fluidity and dissolution state of the polysaccharides in water. As the solute concentration and molecular weight increased, hydrogen bonds between polysaccharides and water inhibited their dissolution and diffusion. Properly increasing the temperature, reducing the concentration and selecting low molecular weight polysaccharides enhanced the dissolution and diffusion of the polysaccharides in the solution system. Molecular weight was the main factor affecting the η of the polysaccharide solutions. These results can provide theoretical guidance for the extraction or tea brewing process of Polygonatum cyrtonema polysaccharides in future work.

Analysis using size exclusion chromatography of poly(N-isopropyl acrylamide) using methanol as an eluent

Size Exclusion Chromatography is traditionally carried out in either aqueous or non-polar solvents. A system to present molar mass distributions of polymers using methanol as a mobile phase is presented. This is shown to be a suitable system for determining the molar mass distributions poly(N-isopropylacrylamide)s (PNIPAM); a polymer class that is often difficult to analyze by size exclusion chromatography. DOSY NMR was used to provide intrinsic viscosity data that was used in conjunction with a viscometric detector to provide absolute calibration. Then the utility of the system was shown by providing the absolute molar mass distributions of dispersed highly branched PNIPAM with biologically functional end groups.

pH Responsiveness of hydrogels formed by telechelic polyampholytes

We investigate the influence of pH on the rheological and structural properties of hydrogels formed by hydrophobic association of the sticky ends of the triblock terpolymer poly(methyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate-co-methacrylic acid)-b-poly(methyl methacrylate) (PMMA-b-P(DEA-co-MAA)-b-PMMA). The middle block is a weak polyampholyte having a pH dependent charge density and sign, which enables tuning of the rheological and structural properties by pH variation. Small-angle neutron scattering (SANS) studies of solutions in D₂O at 0.05 wt% and pH 3.0 reveal clusters of interconnected spherical micelles having PMMA cores, stabilized by repulsive ionic interactions in the middle polyampholyte block. With increasing pH, the degree of ionization of the DEA units decreases, whereas the one of the MAA units increases, resulting in a complete loss of the correlation between these micelles. At a concentration of 3 wt% at low pH values, the system forms a gel with charged fuzzy spheres from PMMA interacting via a screened Coulomb potential. With increasing pH, the gel disintegrates due to the decrease in the effective charge on the micelles. At both concentrations, the hydrophobic aggregation of micelles is observed near the isoelectric point. At pH 3.0-7.4, the autocorrelation functions measured by rotational dynamic light scattering at 3 wt% exhibit a decay steeper than single exponential, which confirms that the gels are frozen, presumably due to the glassy PMMA cores and hydrophobic interpolyelectrolyte complexes. At pH 11, the diffusion of single micelles is observed in addition to the frozen dynamics.

A novel and controllable route for preparing high solid-content and low-viscosity poly(acrylamide-co-acrylic acid) aqueous latex dispersions

High solid-content and low-viscosity poly(acrylamide-co-acrylic acid) aqueous latex dispersions were obtained through a novel strategy, which involves swelling followed by diffusion and redox initialized polymerization inside the seed particle.

Fabrication of a SERS based aptasensor for detection of ricin B toxin

Poly(N-acryoyl-l-valine, AVAL) brushes were grafted onto a silicon substrateviaRAFT polymerization, and then ricin B aptamer was covalently conjugated to the poly(AVAL) brushes to recognize and detect ricin B toxinviaSERS-based sandwich assay.

Carving Out Niches for Nanostructures: Implementation and Interplay of Building Blocks, Methods, and Tools

The number and diversity of techniques to create well-defined polymeric architectures has set the foundation to reinvent macromolecular chemistry’s tenor. This development offers the chance to build refined structures with multifaceted, cross-disciplinary applications. We discuss a few advances in the design and development of selected nanoobjects with far-reaching potential. Herein, well-defined building blocks and introduced methods to establish three-dimensional architectures will be presented. Sequential attachment strategies and tools taken from biological chemistries achieve new levels of specificity.