Soluble polymeric dual sensor for temperature and pH value

pH-Responsive Chiral Nanostructures

There is great current interest in the design of robust synthetic polymers for the preparation of novel functional, well-defined, biocompatible and tailorable materials for a range of possible applications. In this work we have used reversible addition fragmentation chain transfer (RAFT) polymerization to prepare chiral and responsive amphiphilic block copolymers (based on polyphenylalanine acrylamide), which can be assembled at different pHs to form well-defined nanostructures. The morphology and size of the derived block polymers were explored using TEM, DLS and SLS measurements, while stability was examined by fluorescence and NMR spectroscopy. The application of these chiral and responsive nanostructures in the resolution of hydrophilic racemic amino acids has also been explored.

A fluorescent thermometer based on a pyrene-labeled thermoresponsive polymer

Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate), which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

Multiple fluorescent chemical sensing and imaging

Optical sensors, unlike most others, enable multiple sensing of (bio)chemical species by making use of probes whose signals can be differentiated by spectral and/or temporal resolution. Multiple sensors are of substantial interest for continuous monitoring of chemical parameters in complex samples such as blood, bioreactor fluids, in the chemical industry, aerodynamic research, and when monitoring food quality control, to mention typical examples. Moreover, such sensors enable non-invasive, non-toxic and online detection. We discuss in this critical review the state of the art in terms of spectroscopic principles, materials (mainly indicator probes and polymers), and give selected examples for dual and triple sensors along with a look into the future (109 references).

Responsive micellar films of amphiphilic block copolymer micelles: control on micelle opening and closing

We reported the deliberate control on the micelle opening and closing of amphiphilic polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) micellar films by exposing them to selective solvents. We first treated the micellar films with polar solvents including ethanol and water (pH = 4, 8, and 12) that have different affinities to P2VP. We observed opening of the micelles in all the cases. Both the size of opened pores and the opening rate are dependent on the solvency of different solvents for P2VP. We then explored the closing behavior of the opened micelles using solvents having different affinities to PS. We found that the opened micelles were recovered to their initial closed micelle forms. The recovery was accompanied by a slow micelle disassociation process which gradually reduced the micelle size. The rates of the micelle closing and disassociation are also dependent on the solvency of different solvents for PS.

The Effect of Hofmeister Salts on the LCST Transition of Poly(2-oxazoline)s with Varying Hydrophilicity

The influence of Hofmeister salts was investigated on the cloud point of three poly(2-oxazoline)s, namely poly(2-ethyl-2-oxazoline) [PEtOx], poly(2-n-propyl-2-oxazoline) [PnPropOx], and poly(2-isopropyl-2-oxazoline) [PiPropOx]. In addition, a comb polymer based on oligo-2-ethyl-2-oxazoline side chains and a methacrylate backbone (POEtOxMA) was included in this investigation. It was found that the ionic response of the poly(2-oxazoline)s strongly depends on their hydrophilicity. The comb polymer POEtOxMA revealed a strikingly similar response to the salts as linear PEtOx even though the cloud points of the polymers in water differ. This indicates that the architecture does not significantly influence the effect of the Hofmeister ions, even though there is a difference in the absolute cloud point.

PEGylated Chromatography: Efficient Bioseparation on Silica Monoliths Grafted with Smart Biocompatible Polymers

Novel oligo(ethylene glycol)-based thermoresponsive stationary phases have been studied for the separation of bioanalytes. Well-defined copolymers of (2-methoxyethoxy)ethyl methacrylate and oligo(ethylene glycol) methacrylate were synthesized by atom-transfer radical polymerization in the presence of an N-succinimidyl-functionalized initiator. The reactive chain ends of these copolymers were then reacted with amino-functionalized silica monoliths. The formed composites were studied as chromatography materials. For instance, it was demonstrated that thermoresponsive oligo(ethylene glycol)-based stationary phases allow rapid, efficient separation of steroid and protein mixtures in pure water under isocratic high-performance liquid chromatographic elution.