Liquid chromatography at the critical conditions in pure eluent: an efficient tool for the characterization of functional polystyrenes.

Functional polymers are usually separated by liquid chromatography at critical conditions (LC-CC) using a desorli/adsorli mixture as eluent. In this paper, we describe LC-CC using dimethylformamide (DMF) as pure eluent at 72 degrees C and its application to the analysis of functional polystyrenes. The critical adsorption point is reached by tuning the temperature so that the lack of repeatability is no longer a problem. We analysed several batches of polystyrenes, exhibiting different molecular weights and functionalities. We were able to differentiate di-, mono- and non-functional polystyrenes, bearing carboxylic acid, hydroxyl or nitroxide moieties. The behaviour of these polystyrenes expressed by the experimental results was compared with their behaviour described by the LC-CC theory through the calculation of the effective interaction parameter of each end group. The technique also makes it possible to quantify the fractions of different functional polymers in a blend.

Hydrogel Microparticles as Sensors for Specific Adhesion: Case Studies on Antibody Detection and Soil Release Polymers.

Adhesive processes in aqueous media play a crucial role in nature and are important for many technological processes. However, direct quantification of adhesion still requires expensive instrumentation while their sample throughput is rather small. Here we present a fast, and easily applicable method on quantifying adhesion energy in water based on interferometric measurement of polymer microgel contact areas with functionalized glass slides and evaluation via the Johnson⁻Kendall⁻Roberts (JKR) model. The advantage of the method is that the microgel matrix can be easily adapted to reconstruct various biological or technological adhesion processes. Here we study the suitability of the new adhesion method with two relevant examples: (1) antibody detection and (2) soil release polymers. The measurement of adhesion energy provides direct insights on the presence of antibodies showing that the method can be generally used for biomolecule detection. As a relevant example of adhesion in technology, the antiadhesive properties of soil release polymers used in today's laundry products are investigated. Here the measurement of adhesion energy provides direct insights into the relation between polymer composition and soil release activity. Overall, the work shows that polymer hydrogel particles can be used as versatile adhesion sensors to investigate a broad range of adhesion processes in aqueous media.