Abstract
To probe the effects of pendant side-chain structures on the properties of porous thermoresponsive polymer gels, oligo(ethylene glycol) alkyl ether acrylates were polymerised in an aqueous medium under radical-mediated phase-separation conditions. The monomer structures varied according to the lengths and termini of their ethylene glycol side chains. The porous poly(oligo(ethylene glycol) alkyl ether acrylate) (POEGA) gels exhibited variable lower critical solution temperatures (LCSTs) but similar and rapid swelling–deswelling behaviours. Although the LCST of the poly(tri(ethylene glycol) monomethyl ether acrylate) (PTEGA) gel decreased with increasing aqueous NaCl or CaCl2 concentration, PTEGA showed excellent thermosensitivity in highly concentrated salt solutions, recommending its application in saline environments. Examination of PTEGA adsorption performance in an oil–water emulsion showed that n-tridecane adsorption increased with temperature. Although n-tridecane was effectively adsorbed at 70 °C, its release from the fully adsorbed PTEGA gel was difficult despite a temperature reduction from 70 to 20 °C.
Highlights
Thermosensitive polymers have attracted research attention in fields as widespread as pharmaceutical drug delivery to engineering since the 1950s [1]
In a previous communication [11], we reported the synthesis of porous POEGMA300 gels by the thermal phase-separation polymerisation of OEGMA300 (Mn = ~300 g mol−1 ); these gels exhibited rapid swelling–deswelling and high thermosensitivity in a highly concentrated aqueous NaCl solution, the lower critical solution temperatures (LCSTs) measured by the equilibrium swelling ratio were decreased with increasing NaCl concentration
Gel displays identical swelling behaviours in solutions of NaCl and those of the divalent metal salt CaCl2 (Figure 5b). These results suggest that the poly(tri(ethylene glycol) monomethyl ether acrylate) (PTEGA) gel has an added advantage over the other gels, because but RT /R0 dramatically decreases for temperatures of 30 ◦ C and higher
Summary
Thermosensitive polymers have attracted research attention in fields as widespread as pharmaceutical drug delivery to engineering since the 1950s [1]. In a previous communication [11], we reported the synthesis of porous POEGMA300 gels by the thermal phase-separation polymerisation of OEGMA300 (Mn = ~300 g mol−1 ); these gels exhibited rapid swelling–deswelling and high thermosensitivity in a highly concentrated aqueous NaCl solution, the LCSTs measured by the equilibrium swelling ratio were decreased with increasing NaCl concentration. Tested techniques have included gravity separation [27], coagulation [28], electrochemical treatment [29], in situ burning [30], air flotation [31], filtration, and adsorption [32] Most of these techniques have drawbacks such as low efficiency, high operational cost, generation of toxic by-products, and inability to reuse or recycle materials [29]. In addition to characterising the properties of POEGA gels, we have examined the oil adsorption performance of one gel specimen
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