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  • Templating multiple length scales by combining phase separation, self-assembly and photopatterning in porous films.

Templating multiple length scales by combining phase separation, self-assembly and photopatterning in porous films.

Journal of colloid and interface science (2008-10-17)
Lingyan Song, Quanyan Wu, Bryan D Vogt
ABSTRACT

Patternable nanoporous silica thin films with pore sizes on multiple length scales are fabricated using preformed block copolymer/homopolymer blend films as templates. Previous work by Tirumala et al. [V.R. Tirumala, R.A. Pai, S. Agarwal, J.J. Testa, G. Bhatnagar, A.H. Romang, C. Chandler, B.P. Gorman, R.L. Jones, E.K. Lin, J.J. Watkins, Adv. Mater. 18 (8) (2008) 1603] has demonstrated that hydrogen bonding between an amphiphilic copolymer and a homopolymer leads to significant enhancements in the long range order of the template self assembly. However if the copolymer template is simply changed from Pluronic F127 to Brij78, a well ordered template is no longer always obtained; the blend phase separates with apparent selective partitioning of the photoacid generator (PAG) at the interface of the polymer phases. UV exposure selectively generates a photoacid, which is utilized to catalyze tetraethylorthosilicate (TEOS) condensation. The large disparity in diffusivity of the photoacid between the glassy poly(hydroxystyrene) (PHOSt) and rubbery Brij78 phases results in selective templating of the Brij mesostructure and limited reaction into the PHOSt. Calcination yields relatively monodisperse mesopores from the Brij phase and macropores from the PHOSt phase. Simple variations in processing parameters allow the macropore morphology to be tuned to create high surface area materials with structures on the order of 1 nm, 100 nm and microms from self assembly, phase separation and lithographic patterning respectively.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Brij® S 100, average Mn ~4,670
Sigma-Aldrich
ECO Brij® S10, average Mn ~711
Sigma-Aldrich
ECO Brij® S100, average Mn ~4,670
Sigma-Aldrich
ECO Brij® S20
Sigma-Aldrich
SP Brij® S2 MBAL, main component: diethylene glycol octadecyl ether
Sigma-Aldrich
Brij® S20
Sigma-Aldrich
Brij® S10, average Mn ~711