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Synthesis of a new family of polymers having a polydisulfide structure can be conducted from sulfobetaine-based derivative of natural (R)-lipoic acid. A polydisulfide backbone of polymer can be depolymerized by response to external stimuli and sulfobetaine pendant groups ensure the upper critical solution temperature (UCST) behaviour temperatures that can be modulated according to the nature of the solvent and concentration. Sulfobetaine-bearing polydisulfides were synthesized from dithiolane derivatives and then characterized. UCST behavior of the polymers in water and in mixtures containing different alcohols (methanol, ethanol, isopropanol) was investigated. The regeneration of monomers from the polymers in response to external stimuli was examined using UV–vis and circular dichroism (CD) spectroscopy. Tunable surface wettability were shown on the grafted polymers. Decreasing polarity and/or increasing alcohol percentage in the water mixtures induced an increase in the cloud points of the polymers in the solutions. Thermoresponsive behaviour were repeatable and fully reversible with negligible hysteresis from aggregate to unimer state. The regeneration of monomers by depolymerization was tunable by temperature and sunlight. A thickness dependence on surface wettability was observed on wafers covalently modified with polydisulfides. This is the first report of sulfobetaine-based polydisulfides showing tunable UCST behavior and surface wettability. [ABSTRACT FROM AUTHOR]

In this study, two quaternary ammonium salts derived from l -lipoic acid were applied for self-assembled monolayers formation on rough structured gold surface. The derivatives differ in functionality since one possesses simple quaternary ammonium group whereas the other one is carboxybetaine ester containing quaternary ammonium group with pH hydrolysable ester group as a pendant. The response of surface wettability to ion exchange between Cl − and perfluorooctanoate, kinetics and gradient wettability were examined by water contact angle measurement and confirmed by X-ray photoelectron spectroscopy. Furthermore, adhesion forces related to applied counterion on the entire surface and after hydrolysis were investigated by atomic force microscopy measurement at nanometer scales. A dramatic change in wettability upon counterion exchange from superhydrophilic for Cl − to very or superhydrophobic for perfluorooctanoate in a repeatable manner was observed for both derivatives. Kinetics of counterion exchanges revealed faster hydration of simple quaternary derivate. The wettability gradient could be designed from superhydrophobic to superhydrophilic either in a reversible manner by simple immersion of the modified surface in a counterion solution modulated by ionic strength or in an irreversible manner for carboxybetaine ester derivate by time-controlled hydrolysis to charge balanced carboxybetaine. [ABSTRACT FROM AUTHOR]

Simple and robust methods for modifying hydrophobic polymer surfaces with zwitterionic polymers using UV irradiation were developed. Two random zwitterionic copolymers consisting of either carboxybetaine or sulfobetaine methacrylamide monomers and monomers bearing a photolabile azidophenyl group were directly photoimmobilized on polymeric surfaces (polyester, polyethylene and polystyrene) via covalent interactions in a spatially controlled manner. These copolymers were also electrospun to form self-standing mats. The modified surfaces were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, infrared spectroscopy and contact angle measurements. The electrospinning method involved the use of a trifluoroethanol solution with a copolymer concentration in the range from 2 to 10 wt.%. BHK 21 cell adhesion to both modified surfaces and mats was dramatically reduced compared to unmodified surfaces. [ABSTRACT FROM AUTHOR]