Abstract
Thermo-responsive polymers and copolymers derivatives of oligo(ethylene glycol) methyl ether methacrylate (Mn = 300 g mol−1) (OEGMA) and di(ethylene glycol) methyl ether methacrylate (DEGMA) have been synthesized by reversible addition fragmentation chain transfer polymerization (RAFT) using 5-amino-4-methyl-4-(propylthiocarbonothioylthio)-5-oxopentanoic acid (APP) as chain transfer agent (CTA). The monomer conversion was evaluated by hydrogen nuclear magnetic resonance (1H-NMR); number average molecular weights (Mn), weight average molecular weight (Mw), and dispersity (Đ) were obtained by gel permeation chromatography (GPC); glass transition temperature (Tg) was evaluated by modulated differential scanning calorimetry (DSC), cloud point temperature (Tcp) was measured and compared by turbidimetry and dynamic light scattering (DLS). The effect of polymer composition and concentration on the Tcp, either in water or in phosphate buffer saline (PBS), was studied. The values of Tcp using PBS were between 3 and 4 °C lower than using water. Results showed an ideal copolymerization behavior; therefore, the Tcp could be tuned by an adequate monomers feed ratio obtaining polymers which may be used in drug delivery and other applications.
Highlights
Thermo-responsive polymers which show an abrupt and reversible change in some properties within a small change of temperature, have been gaining much attention due to the wide variety of potential applications such as in drug delivery systems, tissue engineering, controlled cell or bacteria adhesion, protein separation, and sensors [1,2,3,4,5,6]
oligo(ethylene glycol) methyl ether methacrylates (OEGMAs) based polymers have been synthesized by anionic polymerization [13,14] and reversible deactivation free-radical polymerization like reversible addition-fragmentation chain-transfer polymerization (RAFT) or atom transfer radical polymerization (ATRP) [15,16,17,18,19,20]
Trithiocarbonate type compounds have been used as chain transfer agent (CTA) in RAFT polymerization; these offer some advantages with respect to other CTAs, for example more stability toward hydrolysis [26]
Summary
Thermo-responsive polymers which show an abrupt and reversible change in some properties within a small change of temperature, have been gaining much attention due to the wide variety of potential applications such as in drug delivery systems, tissue engineering, controlled cell or bacteria adhesion, protein separation, and sensors [1,2,3,4,5,6]. OEGMAs based polymers have been synthesized by anionic polymerization [13,14] and reversible deactivation free-radical polymerization like reversible addition-fragmentation chain-transfer polymerization (RAFT) or atom transfer radical polymerization (ATRP) [15,16,17,18,19,20] Each of these options have advantages and disadvantages, ; owing to its scientific and practical relevance, RAFT polymerization has become one of the most applied techniques to obtain polymers with a narrow dispersity of molecular weights. This can be reached only by choosing the appropriate reaction conditions such as the temperature, concentration of monomers, and the monomer: chain transfer agent (CTA):initiator mole ratio
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