(417f) Morphology of Nanocrystalline Domain Reinforced Rubber
Recently, we succeeded in synthesizing TPEs with hard domains having all three dimensions well below 100 nm by entropically limiting the degree of association due to favorable hydrogen bonding. Polyisobutylene (PIB) chains were synthesized with graft side chains, each containing a few Î²-alanine units. Mechanical studies have shown that this nanocrystalline structure is extraordinarily effective in reinforcing elastic networks. The nanocrystalline domains must have PIB chains tethered to their surfaces and we imagine this leads to a structure around the nanocrystallite that is similar to that of commonly known âpolymer brushes.â In our samples, the surfaces to which the chains are grafted are the surfaces of the nanocrystallites. The brush âchainsâ are portions of PIB backbones that go into and come out of a spot on the surface of the nanodomain where the oligo-Î²-alanine graft has been crystallized into the domain. Due to the kind of tethering that occurs here, the âbrushâ may look like a âloopâ brush, which can have properties quite different from those of brushes of linear chains. Details of the brush character can be tailored by tailoring the synthesis of the grafts. Small angle neutron scattering measurements have been used to probe the structure of the âbrushâ around the nanodomains.