ISSN 1560-0904, Polymer Science, Ser. B, 2010, Vol. 52, Nos. 9–10, pp. 571–574. © Pleiades Publishing, Ltd., 2010. 571 1 INTRODUCTION Generation of nano/microtubes has become a challenging subject and increasingly has attracted interest due to their wide variety of applications in sen- sors [1], electronic devices [2] and materials with opti- cal properties [3, 4]. The use of polyelectrolyte multi- layers (PEMs) can be considered as an alternative way for production of nano/microtubes with approachable functionalities. The specific physical and chemical properties of PEMs make this class of materials highly applicable in different fields of science and industry such as drug delivery [5, 6], biosensors [7] and photo- voltaics [8]. Recently, modifying surface properties of carbon nanotubes has drawn interest from various research groups due to new opportunities that are offered by this approach to improve and expand the potential applications in such materials. The layer-by- layer (LbL) self-assembly technique has been employed to prepare polyelectrolyte/carbon nanotube multilayers [9] and in other cases to functionalize the surface of carbon nanotubes [10, 11]. 1 The article is published in the original. Recently, we have demonstrated a one step fabrica- tion of core-shell particles by using electrohydrody- namic co-jetting [12]. This approach enables the pro- duction of core-shell particles with hydrophilic core and shell using side-by-side flow of miscible polymer solutions. The core-shell particles were pH-responsive and were indicating selective uptake of different dye molecules. Herein, we demonstrate the generation of tubes of several micrometers in diameter made of PEMs. In this work, a combination of electrified jetting and LbL coating technique were employed. Using this approach, the physical and chemical properties of the core-shell and hollow fibers and consequently their function can be modified for different applications and can be considered as an alternative method for production of polymer microtubes. EXPERIMENTAL SECTION Reagents and Materials Poly(ethyleneimine) (PEI, M w = 55000, 50% (w/w) in water), poly(styrene sulfonate sodium salt) Preparation of Core-Shell and Hollow Fibers Using Layer by Layer (LbL) Self-Assembly of Polyelectrolytes on Electrospun Submicrometer-Scale Silica Fibers 1 Abbass Kazemi a,b , Joerg Lahann a , Mohammad Madani c , Naser Sharifi-Sanjani c , and Ahmad Hasan-Kaviar c a Departments of Chemical Engineering and Materials Science and Engineering, Macromolecular Science and Engineering Center, The University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109 (USA) b Division of Polymer Science and Technology, Research Institute of Petroleum Industry P.O.Box: 14665-1998, Tehran, Iran c School of Chemistry, University College of Science, University of Tehran, Tehran, Iran e-mail: kazemiab@ripi.ir Received July 27, 2009; in final form, January 26, 2010 Abstract—Herein, fabrication of hollow fibers made of polyelectrolyte multilayers is reported. Silica submi- crometer-scale fibers were fabricated by electrospinning and layer by layer deposition of polyelectrolytes were performed to coat silica fibers with polyelectrolyte multilayers, which were prepared by consecutive deposi- tion of poly(ethyleneimine) and poly(styrene sulfonate sodium salt)/sodium dodecyl sulfate onto the surface of the silica fibers. In order to obtain hollow fibers, the core removal was carried out by introducing the core- shell fibers to a hydrofluoric acid solution. The hollow fibers were stable in hydrofluoric acid solution and dis- played pH-dependent structural changes. SEM microscopy indicated the formation of the glass fibers and the fibers coated with polyelectrolyte multilayers (Silica—polyelectrolyte multilayers (PEM) fibers). The diam- eter of the core-shell fibers was increased after layer–by-layer coating. ATR-FTIR was performed for char- acterization of the glass fibers before and after layer-by-layer coating as well as after selective core removal. IR spectrum of the Silica-PEM fibers indicates C–H stretching modes of saturated hydrocarbons, confirm- ing multilayers formation. Core removal was also confirmed by IR spectroscopy as Si–O–Si band disappears for the IR spectrum of the fibers after core-removal. DOI: 10.1134/S1560090410090083 COMPOSITES