Preparation and Application of a Dual Light-Responsive Triblock Terpolymer

Reported are the preparation and application of a triblock terpolymer poly(ethylene oxide)-ONB-poly[2(perfluorooctyl)ethyl methacrylate]-block-poly(2-cinnamoyloxyethyl methacrylate) (PEO-ONB-PFOEMA-b-PCEMA). Here PEO is water-soluble, PCEMA is photo-cross-linkable, PFOEMA is of low surface tension, and ONB denotes a photocleavable o-nitrobenzyl unit at the junction of the PEO and PFOEMA blocks. To prepare the copolymer, a macroinitiator bearing an ONB unit between PEO and the initiating site was first synthesized. FOEMA and 2-trimethylsilyloxyethyl methacrylate (HEMA-TMS) were then sequentially polymerized by atom transfer radical polymerization (ATRP) to yield the triblock copolymer PEO-ONB-PFOEMA-b-P(HEMA-TMS). Removal of the trimethylsilyl groups from the P(HEMA-TMS) block and cinnamation of the resultant poly(2-hydroxyethyl methacrylate) block with cinnamoyl chloride resulted in the targeted triblock copolymer. PEO-ONB-PFOEMA-b-PCEMA formed micelles in tetrahydrofuran/water at the water volume fraction of 80%, in which only the PEO block was soluble. Upon photolysis, the micellar PCEMA cores were cross-linked and the micellar coronal PEO chains were cleft, resulting in the precipitation of cross-linked PFOEMA-b-PCEMA nanoparticles. Films of the nanoparticles were water- and oil-repellent due to the exposure of the initially hidden PFOEMA block.