ANIONIC SYNTHESIS, MODIFICATION, AND CHARACTERIZATION OF ABC TRIBLOCKCOPOLYMERS

ABC triblock copolymers of poly(styrene)-b-poly(tert-butyl methacrylat e)-b-poly(methyl methacrylate) (PS-P(t)BMA-PMMA) were anionically synt hesized by sequential addition of styrene, tert-butyl methacrylate, an d methyl methacrylate, respectively. Characterization of these tribloc k copolymers was done using nuclear magnetic resonance spectroscopy (N MR), infrared spectroscopy (IR), differential scanning calorimetry (DS C), gel permeation chromatography (GPC), and transmission electron mic roscopy (TEM). The gel permeation chromatograms were found to be somew hat broad (M(w)/M(n) approximate to 1.2) due to partial quenching of p olystyryl anion upon switching to tert-butyl methacrylate. The actual polydispersity of these triblocks, not including PS homopolymer, was d etermined to be less than 1.1. TEM micrographs of these ABC triblocks indicated that the morphology is essentially lamellar. The long-range order of the microstructure, however, seems to decrease with decreasin g spacer block length. The tert-butyl methacrylate middle block of the se PS-P(t)BuMA-PMMA triblocks could be selectively modified to anhydri de and carboxylic acid functionalities in the presence of the PMMA blo ck. Thermal treatment of these ABC triblocks (230 degrees C for 30 min ) quantitatively transformed the P(t)BMA middle block into poly(methac rylic anhydride) (PMAN). The PMAN block could then be quantitatively h ydrolyzed to poly(methacrylic acid) (PMAA) under mild conditions (NaHC O3, 70 degrees C, 1 h).