Abstract
Summary: A series of telechelic OH polysulfones (PSU) were converted to atom transfer radical polymerization (ATRP) macroinitiators by reaction with 2βbromoisobutyryl bromide. Three macroinitiators with different chain lengths were extended with poly(butyl acrylate) (PBA) to form ABA triblock copolymers. The structure and dynamics of the ABA triblock copolymers with PSU central segments and various molecular weight PBA side chains were investigated by smallβangle Xβray scattering and rheology. The block copolymers form micelles with a PSU core and PBA corona. The length of each block has an important effect on the structure and resulting dynamics of the copolymers. Dynamic mechanical measurements indicate three relaxation modes: (i) PBA segmental relaxation at high frequency; (ii) PBA relaxation of the corona block at intermediate frequency; (iii) an additional relaxation process related to structural rearrangement of the micelles at low frequency. The shear modulus plateau corresponding to a soft rubbery state extends over a very broad time or temperature range because of this slow additional relaxation.
Schematic illustration of the structural elements and the bulk supramolecular structure for a symmetric triblock copolymer with a stiff central segment strongly incompatible with the other constituent.
magnified imageSchematic illustration of the structural elements and the bulk supramolecular structure for a symmetric triblock copolymer with a stiff central segment strongly incompatible with the other constituent.