End-Group Functionalized Poly(α-olefinates) as Modular Building Blocks

Abstract

The development of living coordination chain transfer polymerization (LCCTP) has provided a viable path to practical and scalable bulk quantities of structurally well-defined polyolefins that are further characterized by having tunable molecular weight, narrow polydispersity and end-group moieties through the functionalization of the Zn(polymeryl)2 intermediate. These low molecular weight, atactic poly(α-olefinates) are attractive non-polar building blocks for new types of self-assembling polyolefin materials with tunable occupied volumes and lengths. In the present work, the investigation of self-assembled morphology manipulation through tunable occupied volume required a model α-olefin. Living coordinative group-transfer polymerization techniques were employed to determine the viability of low molecular weight, atactic poly(α-olefinates) (X-PAOs) as building blocks with bulky pendent groups.

Application of these X-PAOs for the synthesis and self-assembly of high χ, low N amphiphilic diblock copolymers demonstrated the ability to manipulate the morphology of the thin film nanostructures through variation in occupied volume of the X-PAO domain. The resulting materials proved the combination of X-PAOs and polyester blocks provided a high enough χ in order to demonstrate self-assembly with an N as low as 50 monomer units while maintaining sub-20 nm domain spacings.

It was of significant interest to develop a higher χ, lower N system to achieve sub-10 nm domain spacings. As a result a novel system using sugar-hybrid-PAO conjugates was developed. This system also demonstrated that variation in occupied volume of the X-PAO domain could influence thin-film morphology. The sugar-hybrid-PAO conjugates also demonstrated the ability to self-assemble in solution and encapsulate hydrophobic molecules. The sugar-hybrid-PAO conjugates proved to be a highly versatile system that has simplified the polysaccharide/synthetic block copolymer designs that have been previously used in the literature to obtain sub-10 nm domain spacings.

The ability to generate hydrophobic building blocks using LCCTP has opened up the possibility of further investigations of new, advanced self-assembling materials and applications thanks to these readily-available X-PAOs modular building blocks.