Modulating the solubility of zwitterionic poly((3-methacrylamidopropyl)ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties

Complementary to the well-established zwitterionic monomer 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate (SPP), the closely related monomers 2-hydroxy-3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate (SHPP) and 4-((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate (SBP) were synthesised and polymerised by reversible additionfragmentation chain transfer (RAFT) polymerisation, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar masses were characterised with respect to their solubility in water and aqueous salt solutions. Both poly(sulfobetaine)s show thermoresponsive behaviour in water, exhibiting phase separation at low temperatures and upper critical solution temperatures (UCST). For both polySHPP and polySBP, cloud points depend notably on the molar mass, and are much higher in D2O than in H2O. Also, the cloud points are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed nature of the spacer group separating the anionic and the cationic charges of the betaine moiety, on the other hand. As anticipated, the cloud points of polySBP are much higher than the ones of the analogous polySPP of identical molar mass. Surprisingly, the cloud points of polySHPP are also somewhat higher than the ones of their polySPP analogues, despite the additional hydrophilic hydroxyl group present in the spacer separating the ammonium and the sulfonate moieties. These findings point to a complicated interplay of the various hydrophilic components in polyzwitterions with respect to their overall hydrophilicity. Thus, the spacer group in the betaine moiety proves to be an effective additional molecular design parameter, apparently small variations of which strongly influence the phase behaviour of the polyzwitterions in specific aqueous environments

Novel fibre optic temperature sensors based on thermoresponsive polymers

In this paper we present the development of a novel fibre optic temperature sensor based on thermoresponsive polymers. The principle of our invention that is already applied for a patent is based on the detection of the optical power that is transmitted through an optical fibre, whilst a temperature sensitive element is integrated in this fibre. This element comprises a water-based solution wherein a thermoresponsive polymer is dissolved. The solution is clear like pure water when the temperature is below a specific, material-dependent temperature threshold. When the temperature exceeds this threshold, the solution becomes opaque, whilst this change is completely reversible when the temperature is set back to a value below this threshold. As a consequence, the optical transmission is a function of the temperature. This effect can be exploited for a measurement of the temperature by measuring the transmitted optical power in the fibre

Water-soluble random and alternating copolymers of styrene monomers with adjustable lower critical solution temperature

Random copolymers of 4-vinylbenzyl tri(oxyethylene) and tetra(oxyethylene) ethers, as well as alternating copolymers of 4-vinylbenzyl methoxytetra(oxyethylene) ether and a series of N-substituted maleimides, were synthesised by conventional free radical polymerisation, reversible addition fragmentation chain transfer (RAFT) and atom transfer radical polymerisation (ATRP). Their thermosensitive behaviour in aqueous solution was studied by turbidimetry and dynamic light scattering. Depending on the copolymer composition, a LCST type phase transition was observed in water. The transition temperature of the obtained random as well as alternating copolymers could be varied within a broad temperature window. In the case of the random copolymers, transition temperatures could be easily fine-tuned, as they showed a linear dependence on the copolymer composition, and were additionally modified by the nature of the polymer end-groups. Alternating copolymers were extremely versatile for implementing a broad range of variations of the phase transition temperatures. Further, while alternating copolymers derived from 4-vinylbenzyl methoxytetra(oxyethylene) ether and maleimides with small hydrophobic side chains underwent macroscopic phase separation when dissolved in water and heated above their cloud point, the incorporation of maleimides bearing larger hydrophobic substituents resulted in the formation of mesoglobules above the phase transition temperature, with hydrodynamic diameters of less than 100 nm

Label-free biosensor based on an all-polymer DFB laser

A monolithic active optical resonator biosensor is fabricated for label-free sensing. The all-polymer sensor consists of a polymer distributed feedback (DFB) laser and a hydrogel recognition layer. Specific binding of analyte modulates the effective refractive index, shifting the laser emission wavelength. Real time detection of avidinbiotin interactions is demonstrated as a model for the new label-free biosensing principle