Tubes by fiber templates

TUFT tubes by fiber template process method... 

Another concept on how to produce core shell fibers or hollow fibers is based on the exploitation of electrospun nanofiber as a template (TUFT tubes by fiber templates) onto which a second material is deposited as shell either from solution or melt, via layer by layer techniques or from the vapor... 

Martin and coworkers have demonstrated the use of cylindrical-pored templates for the preparation of tubes and fibers composed of metal oxides, metals and polymers [35,36]. Track-etching of polycarbonate films gives membranes with cylindrical pores that are randomly distributed across the membrane. The pore diameters are monodisperse and, in the example described here, are 600 nm. Lak-shmi et al. have used these membranes for the preparation of vanadium oxide fibers [36]. The pores of the organic filter were filled with vanadium(V) triiso-propoxy oxide in an argon atmosphere. Exposure to air at 60°C induces hydrolysis of the precursor before an oxygen plasma is used to remove the polycarbonate. The crystalline alpha phase vanadium oxide (V2O5) fibers obtained by this... 

Dong and Jones Jr. reported on the preparation of submicron electrically conductive polypyrrole/poly(methyl methacrylate) coaxial fibers and conversion to polypyrrole tubes and carbon tubes [47]. In this study, PMMA fibers with an average diameter of 230 nm were initially fabricated by electrospinning as core materials. The PMMA fibers were subsequently coated as templates with a thin layer of PPy by in situ deposition of the conducting polymer from aqueous solution. Hollow PPy nanotubes were produced by dissolution of the PMMA core from PPy/PMMA coaxial fibers. Furthermore, high temperature (1000 °C) treatment under an inert atmosphere can be used to convert PPy/PMMA coaxial fibers into carbon tubes by complete decomposition of the PMMA fiber core and carbonization of the PPy wall (Figure 4.13). 

Organoclay materials with higher-order organization can also be prepared by template-directed methods involving self-assembled supramolecular structures. In this approach, preformed organic architectures in the form of tubes, fibers, hollow shells, gyroids, helicoids, and so on are transferred into hybrid materials exhibiting structural hierarchy, complex form and ordered mesoporosity [47-55]. For example,... 

A newer addition is in-tube SPME that makes use of an open capillary device and can be coupled online with GC, HPLC, or LC/MS. All these techniques and their utilization in pharmaceutical and biomedical analysis were recently reviewed by Kataoka.45 Available liquid stationary fiber coatings for SPME include polydimethylsiloxane (PDMS) and polyacrylate (PA) for extracting nonpolar and polar compounds, respectively. Also in use for semipolar compounds are the co-polymeric PDMS-DVB, Carboxen (CB)-PDMS, Carbowax (CW)-DVB, and Carbowax-templated resin (CW-TPR). A few examples of in-tube SPME extractions from biological matrices are shown in Table 1.19 and drawn from Li and coworkers.166... 

The advantage of template synthesis is that the length and diameter of the polymer fibers and tubes can be controlled by the selected porous membrane which results in more regular nanostructures. The template method has been used to synthesize nanofibers and tubes of PPy [19,20], PANI, poly(3,4-ethylenedioxythiophene) (PEDOT) [21], and some other polymers. The general feature of conventional template method is that the membrane should be soluble to be removed after the synthesis in order to obtain single fibers or tubes. It restricts practical application of this method and gives rise to a search... 

The ALD process is mainly applied to produce hollow inorganic tubes and coreshell inorganic fibers by using organic fibers as templates that are calcinated in a second step. However, some authors have used this approach to produce composite fibers. Oldham et al. [95] produced nylmi-b fibers coated with either ZnO or AI2O3 and demonstrated that ALD coating could cmitrol the fiber wetting properties and chemical resistance. 

---