Triblock terpolymer helices self-assembled under special solvation conditions

Abstract

We recently reported an accidental discovery that a linear triblock terpolymer, poly(butyl methacrylate)-block-poly(2-cinnamoyloxyethyl methacrylate)-block-poly(tert-butyl acrylate) (B₃₅₀C₁₆₀T₁₆₀, with the subscripts denoting the numbers of repeat units for the different blocks), self-assembled into double, and sometimes triple, helices in three binary solvent mixtures that were marginal for the B₃₅₀ block, poor for the C₁₆₀ block, and good for the T₁₆₀ block. We show in this paper that double helices were formed as a self-assembly product from B₃₅₀C₁₆₀T₁₆₀ in another three solvent mixtures. Also, a triple-stranded superstructure bearing helical sections was prepared from a new B_nC_mT_l sample, which was B₂₄₀C₁₂₀T₁₂₀. In addition, we have replaced some of the cinnamoyl groups of the C₁₂₀ block with three types of chiral groups. Multi-stranded superstructures bearing helical sections were produced in every case when the solvents met the special solvation conditions. The partial or full hydrolysis of the T₁₆₀ and T₁₂₀ blocks of the two terpolymers yielded acrylic acid bearing blocks and represented the largest structural change from the original terpolymers. Interestingly, these polymers formed helices as well. These helices were double-stranded and had regular pitch lengths. These new results suggest that the use of the special solvation conditions may represent a general paradigm for the production of helices from different triblock terpolymers.