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TRANSCRIPT
Research Summary:
Mesoporous silica films with controlled architectures are of interest for many applications. I am working on a two-‐step method to fabricate mesoporous films containing well aligned nanochannels of prescribed diameter and the preparation of mesoporous films with bicontinuous morphologies. Long-‐range alignment of cylindrical pores enables the fabrication of massively parallel pore arrays that can be incorporated into device architectures for separations and sensing. The fabrication of films with bicontinuous morphologies has long been sought for membrane-‐based separations. The architecture of the silica films is controlled by the microphase separated morphology of the block copolymer used as their template. Here, we use polystyrene-‐b-‐poly(tert-‐butyl acrylate) (PS-‐b-‐PtBA) block copolymers as templates. Replication of the templates in supercritical caron dioxide (scCO2) yields mesoporous silica films containing different size and shape channels and bicontinuous channels with periods between 20-‐80 nm.
Figure 1:
1. Mesoporous silicate films with different size and shape channels
2. Bicontinuous mesoporous silicate films
a b c d e
Well ordered materials can be fabricated from a weakly ordered or disordered block copolymer system by selectively hydrogen bond to one block to dramatically increase the phase segregation. I am working on using chiral acids to induce the ordering of weakly segregated poly(ethylene oxide-‐block-‐tert-‐butyl acrylate), PEO-‐b-‐PtBA. A disordering transition was also achieved upon UV-‐exposure of well ordered films of PEO-‐b-‐PtBA/tartaric acid blends containing a photo acid generator. Grazing incidence small angle X-‐ray scattering (GISAXS) was used to study the kinetic behavior of the disordering transition upon deprotection of PtBA to PAA.
GISAXS for mesoporus silicate films
after calcination
Figure 2: