Living anionic copolymerization of 1-(alkoxy)ethyl methacrylates with polar and/or nonpolar monomers and the preparation of amphiphilic block copolymers containing poly(methacrylic acid) hydrophilic segments at higher temperatures than usually employed

The anionic copolymerization of each of the following three novel methacrylate monomers-1-(ethoxy)ethyl methacrylate (EEMA), 1-(butoxy)ethyl methacrylate (BEMA), and 1-(tert-butoxy)ethyl methacrylate (tBEMA)-with methyl methacrylate (MMA) and/or styrene (St) was carried out. (1) The random copolymerization with MMA proceeded smoothly in tetrahydrofuran (THF), using 1,1-diphenylhexyllithium (DPHL) as the initiator, in the presence of LiCl ([LiCl]/[DPHL](0) = 1), at -40 degrees C. The copolymer thus obtained possessed controlled molecular weight and composition, and its molecular weight distribution (MWD) was narrow (M(w)/M(n) = 1.08-1.10). (2) The block Copolymer of each of the new monomers with MMA was prepared by the sequential anionic polymerization of the tyro monomers; the polymerization sequence MMA-new monomer controlled better the molecular weight and led to a narrower MWD than the inverse one. (3) A well-controlled block copolymerization of St with EEMA or with tBEMA was achieved at higher temperatures (greater than or equal to-35 degrees C) than usually employed (-78 degrees C), and it should be emphasized that, even at 0 degrees C, a well-defined diblock copolymer consisting of poly(St) and poly(tBEMA) could be obtained. (4) A block copolymer consisting of poly(St) and a random copolymer of MMA and EEMA, poly[St-b-(MMA-co-EEMA)], was prepared by the sequential monomer addition St-mixture of MMA and EEMA, for various weight ratios of MMA and EEMA. (5) In the preparation of the triblock copolymer with the sequence St, MMA, and EEMA, the molecular weight of the polymer increased step by step and the MWD remained narrow (M(w)/M(n) = 1.09). By changing the polymerization sequence, the hydrophilic segment could be located either in the middle or at the end of the copolymer chain. The protecting group, 1-(alkoxy)ethyl of each of the new monomers, could be easily eliminated after copolymerization, using a mild acidic environment. Thus a copolymer, containing poly(MAA) as hydrophilic segment, with different solubility than its precursor copolymer could be obtained.