Poly(solketal methacrylate)-block-poly(2-cinnamoyloxyethyl methacrylate)-block-poly(allyl methacrylate): Synthesis and Micelle Formation

Abstract

A triblock copolymer, poly(solketal methacrylate)-block-poly(2-trimethylsiloxylethyl methacrylate)-block-poly(allyl methacrylate) or PSMA-b-P(HEMA-TMS)-b-PAMA, was synthesized by anionic polymerization. The TMS groups were removed from the P(HEMA-TMS) block by hydrolysis in methanol to yield poly(2-hydroxylethyl methacrylate) or PHEMA. Reacting PSMA-b-PHEMA-b-PAMA with cinnamoyl chloride yielded PSMA-b-PCEMA-b-PAMA, where PCEMA denotes poly(2-cinnamoyloxyethyl methacrylate). The PSMA-b-PCEMA-b-PAMA triblock was characterized by gel permeation chromatography, NMR, and light scattering and possessed the weight-average repeat units of 300 for SMA, 190 for CEMA, and 180 for AMA. The triblock was further derivatized by hydrolyzing the acetonide groups of the PSMA block to yield PGMA-b-PCEMA-b-PAMA, where PGMA denotes poly(glyceryl methacrylate). PGMA-b-PCEMA-b-PAMA formed spherical micelles in methanol with 5%, by volume, of THF and branched cylindrical micelles in pure methanol. The micelles formed had the soluble PGMA block as the coronas and the insoluble PCEMA and PAMA blocks as the shells and cores, respectively. In toluene containing 2% methanol, only the PGMA block was insoluble. PGMA-b-PCEMA-b-PAMA formed spherical micelles, consisting of PAMA coronas, PCEMA shells, and PGMA cores. Electron microscopy and NMR studies were performed to elucidate the structure of the micelles.