Self-assembled Nanostructures in Copolymer Blends: Saxs, sans and Tem Study

Phenomena associated with the phase behaviour and self-assembled nanostructures of three block copolymer systems have been studied by small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) and transmision electron microscopy (TEM). 1) System A-b-B/A (dPS-b-PMMA/PS homopolymer) were studied as a function of molecular weight and concentration of the added homopolymer. The parameter rM = MH / MC (molecular weight of homopolymer MH to that of corresponding block copolymer chain MC) was selected to encompass all possible types of mutual homopolymer/block copolymer sizes. It has been shown that the parameters rM and χ 3/2 N stipulate the slope of relation D vs concentration of homopolymer in the weak and the intermediate segregation regimes. 2) System (A-b-B)1 / (A-b-B)2 ( where A is perdeuterated polystyrene (dPS) and B is deuterated or hydrogenated poly(methyl methacrylate) (dPMMA or PMMA). The domain spacing D of the blends can be scaled with Mn by D ~ Mn 2/3 as predicted by postulate introduced by Hashimoto at al. [1]. (originally suggested and proved for blends of lamellar PS-b-PI copolymers). 3) System A-b-B / A-b-C i.e. with one block in common (A = dPS, B = PMMA, C = PI). One copolymer is in disordered microdomain state, while the other displays lamellar morphology at ordinary temperatures. Phenomena associated with the order-disorder transition (ODT), microdomain morphology and phase behaviour were investigated as a function of concentration of the added microphase-separated copolymer and temperature.