title: Reduction and control of domain spacing by additive inclusion: morphology and orientation effects of glycols on microphase separated PS-b-PEO.
abstract: Cylindrical phase polystyrene-b-polyethylene oxide (PS-b-PEO) block copolymer (BCP) was combined with lower molecular weight poly/ethylene glycols at different concentrations and their effect on the microphase separation of BCP thin films were studied. Well-ordered microphase separated, periodic nanostructures were realized using a solvent annealing approach for solution cast thin films. By optimizing solvent exposure time, the nature and concentration of the additives etc. the morphology and orientation of the films can be controlled. The addition of the glycols to PS-b-PEO enables a simple method by which the microdomain spacing of the phase separated BCP can be controlled at dimensions below 50 nm. Most interestingly, the additives results in an expected increase in domain spacing (i.e. pitch size) but in some conditions an unexpected reduction in domain spacing. The pitch size achieved by modification is in the range of 16-31 nm compared to an unmodified BCP system which exhibits a pitch size of 25 nm. The pitch size modification achieved can be explained in terms of chemical structure, solubility parameters, crystallinity and glass transition temperature of the PEO because the additives act as PEO 'stress cracking agents' whereas the PS matrix remains chemically unaffected.
authors: Materials Research Group, Department of Chemistry and Tyndall National Institute, University College Cork, Cork, Ireland; AMBER (Advanced Materials and Biological Engineering Research Centre), Trinity College Dublin, Dublin, Ireland. Electronic address: g_tandra@yahoo.co.in.
authors: Tandra
authors: T
authors: Ghoshal
authors: Intel Ireland Ltd., Collinstown Industrial Estate, County Kildare, Ireland.
authors: Matthew T
authors: MT
authors: Shaw
authors: Materials Research Group, Department of Chemistry and Tyndall National Institute, University College Cork, Cork, Ireland; AMBER (Advanced Materials and Biological Engineering Research Centre), Trinity College Dublin, Dublin, Ireland.
authors: Justin D
authors: JD
authors: Holmes
authors: Materials Research Group, Department of Chemistry and Tyndall National Institute, University College Cork, Cork, Ireland; AMBER (Advanced Materials and Biological Engineering Research Centre), Trinity College Dublin, Dublin, Ireland. Electronic address: m.morris@ucc.ie.
authors: Michael A
authors: MA
authors: Morris
keywords: Additives and glycols; Block copolymer; Domain spacing reduction; Morphology and orientation; Self-assembly