Synthesis and mechanical properties of supramolecular composites
Block copolymers are excellent candidates for a bioinspired “bottom-up” strategy to design and develop composite materials with superior multifunctional properties. This is due to the scale of the microdomains (nanometers) where improved physical and mechanical properties (hydrophilic, hydrophobic, stiffness ductility) are met within the same supramolecular structure. Moreover, block copolymers can be tuned to the size and shape of self-assembled morphologies for which there are no interfacial and/or phase separation problems.
One of our main research goals is the establishment of synthetic strategies for the development of polymeric nanocomposites consisting of a nanostructured block copolymer matrix (bearing at least two kinds of constituents) and nanometer-sized fillers which would ideally be crosslinked polymeric nano-objects arisen from self-organization of block copolymers of different nature than the matrix.
We studied and compared the dynamic and static (tension/compression) mechanical properties of new copolymers with 2 and 3 blocks having linear and star architecture , AB, ABC, AnBn and An(B-b-C)n. All block copolymers were prepared via “living” anionic polymerization, where the arms of star block copolymers were connected in one core. Phase A was PS, B phase was PHMA or PEMA proportionally the case and C phase was PMMA.
Our results show that all block copolymers have better mechanical behaviour than pure PS and better overall mechanical performance than linear derivatives. Higher of strengths/moduli and reasonable ductility were found for the “glassy” PSnPEMAn heteroarm star copolymer. The presence in star architecture of ductile (soft) PHMA gives reasonable strength / modulus and high ductility. In contrast, the presence of glassy PMMA has not significant influence on the mechanical properties of all samples. Finally, the number of arms, n, had a positive effect on mechanical behaviour of star block copolymers.
• Georgia Tsoukleri