Tunable Dual‐Thermoresponsive Phase Behavior of Zwitterionic Polysulfobetaine Copolymers Containing Poly(N,N‐dimethylaminoethyl methacrylate)‐Grafted Silica Nanoparticles in Aqueous Solution

Abstract

Novel thermoresponsive copolymers of zwitterionic sulfobetaine methacrylate (SBMA)‐ and N,N‐dimethylaminoethyl methacrylate (DMAEMA)‐grafted silica nanoparticles are prepared via surface‐initiated atom transfer radical polymerization. The phase behavior of these nanoparticles is investigated. The hybrid nanoparticles exhibit tunable phase transition temperature between the upper critical solution temperature (UCST) and the lower critical solution temperature (LCST) in aqueous solution. A high PSBMA content in P(SBMA‐co‐DMAEMA) copolymer in the hybrid nanoparticles leads to aggregation at low temperatures because of dominant electrostatic interactions of ionic pairs, whereas a relatively low PSBMA content in the hybrid nanoparticles results in a phase transition at high temperatures as a result of predominant hydrophobic interactions of the PDMAEMA. Interestingly, hybrid nanoparticles with a suitable molar ratio of SBMA/DMAEMA exhibit both UCST and LCST in aqueous solution, where the water‐insoluble microdomains of hybrid nanoparticles are generated by the PSBMA or PDMAEMA region depending on the temperature. The above dual‐thermoresponsive phase transition is also controllable in salt solution. A facile change in the molar content of copolymer grafted on silica nanoparticles will tune the UCST and LCST readily.

Tunable Dual‐Thermoresponsive Core–Shell Nanogels Exhibiting UCST and LCST Behavior

“…A previous study by Yin et al demonstrated the formation of schizophrenic core−shell microgels via seeded emulsion polymerization which showed both LCST and UCST transitions . Several more studies have been carried out successfully using dual thermoresponsive systems for different biomedical applications; however, this behavior has been investigated mostly with polymeric systems such as noncrosslinked linear block copolymers. In a recent study, Yoshimitsu et al prepared a shape switching dual responsive di‐block copolymer using polymerized ionic liquid and 2‐methoxyethyl vinyl ether .…”

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

“…Analysis of samples is restricted by the requirement that the mobile phase must be compatible with both the analyte and the stationary phase. Common mobile phases in SEC are tetrahydrofuran (THF) [2] , [3] , [4] , [5] , [6] , dimethyl formamide (DMF) [5] , [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , Chloroform [4] and water [9] and common calibration standards used include polystyrene [2] , [3] , [4] , [5] , [7] , polyethylene oxide [8] or polymethyl methacrylate [5] , [6] , [10] , although many variations and alternatives have been reported [15] . However SEC measurements in eluent blends including alcohols have only been reported rarely [16] , [17] and there appears to be only one recent report on the use of methanol or ethanol as the sole component of the eluent, in an ultra high pressure SEC system [1] .…”

“…In our experience, the analysis of polyacrylamides often requires changing the eluent if pendant or chain-end functionalities are modified. Some polymers, such as poly( N -isopropyl acrylamide) (PNIPAM) are susceptible to adsorption to the stationary phase and often salts, such as tetrabutylammonium bromide (TBAB), must be added to the mobile phase to prevent interaction [12] , [23] . The use of salts requires careful control of eluent composition and in some cases salts precipitate and block components of the instrument.…”

Influence of cyclodextrin on the UCST- and LCST-behavior of poly(2-methacrylamido-caprolactam)-co-(N,N-dimethylacrylamide)

“…Below the critical temperature ( T C ) these polymers are soluble and they become insoluble by heating their solutions above the T C . In contrast, some polymers forming hydrogen bonds, like poly(acrylic acid) or polymers containing zwitter-ionic groups are soluble in water above a critical temperature (UCST) [6–7]. Only a few reports deal with polymers which have both, LCST- and UCST-behavior in water [8].…”