New Block and Gradient Copolymers by Controlled/Living Radical Polymerization

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

The goal of this project is to synthesize and characterize new block and gradient copolymers prepared by controlled radical polymerization methods. Block and gradient copolymers tend to microphase separate and may form various periodic and continuous nanostructures. Three groups of copolymers will be prepared and characterized. They include copolymers composed of a-butyl acrylate (BA) and methyl methacrylate (MMA) which may have good adhesive properties, amphiphilic blocks for study as surfactants and end-functional polymers for potential use as blend additives. Various block and gradient copolymers will be made by precisely controlling the dimension, composition and functionality in the copolymer chains. Preliminary results on the BA/MMA copolymers indicate that the mechanical properties of the blocks containing a gradient structure in the outer blocks are dramatically different from the pure triblocks. Various di- and triblock copolymers will be prepared in which the overall composition, molecular weight and sequence distribution along the chain will be varied. In addition, the effect of the polydispersity and the gradient distribution on the mechanical and thermal properties of the copolymers will be studied in order to draw a structure-property correlation for the obtained polymers. Preliminary results for the surfactants composed of polystyrene (PS) and poly(acrylic acid) (PA) demonstrated that by controlling and systematically varying the composition and topology of the polymer chains, it was possible to design surfactants and to correlate the copolymer structure (AS, ASA, SAS, trifunctional SA) with its surfactant properties. Extension of this study will include the preparation of new amphiphiles containing a random and/or gradient hydrophobic segment and non-ionic surfactants and probing the effects of the alterations on the stability of conventional emulsions and water-borne ATRP. The final project will involve preparing end-functional copolymers and evaluating their efficacy as blend additives. A comparative study of block, random and gradient copolymers will be performed. %%% It is anticipated that through precise control and systematic variation of the structure of block and gradient copolymers, it will be possible to understand and predict how structural variations affect the thermal, mechanical and other properties of the targeted materials. More efficient adhesives, elastomers, surfactants and blend additives may be developed based on this type of structure-property correlation. ***