Amphiphilic Copolymer Having Acid-Labile Acetal in the Side Chain as a Hydrophobe: Controlled Release of Aldehyde by Thermoresponsive Aggregation−Dissociation of Polymer Micelles

Statistical amphiphilic copolymers of polymethacrylate having a lilial-derived acetal moiety as a hydrophobic side chain and poly(ethylene glycol) (PEG) as a hydrophilic side chain were synthesized with different unit ratios ( 3a ( x: y = 100:0), 3b ( x: y = 73:27), and 3c ( x: y = 24:76)). In aqueous media the polymer 3c ( x: y = 24:76) formed its micelles, whose particle diameter was ranged mainly from 10 to 220 nm and averaged diameter was 35 nm. Polymer 3c in aqueous media exhibited aggregation−dissociation behavior which was dependent sharply and reversibly on temperature in the presence of NaCl. The aggregation of the polymer micelles inhibited hydrolysis of the acid-labile acetal side chain and release of the resulting lilial, while its dissociation removed the inhibition. This responsive behavior by simply heating and cooling could control hydrolysis of the acid-labile acetal side chain and release of the resulting lilial.