M10-CD02 Functional Fibers via Biomimetics and Inorganic-Organic ...

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NTC Project: M10-CD01
National Textile Center Annual Report: November 2010

Functional Fibers via Biomimetics and Inorganic-Organic Hybrids

Leader: You-Lo Hsieh/University of California, Davis; ylhsieh@ucdavis.edu; (530) 752-0843
Members: Michael S. Ellison/Clemson University; ellisom@clemson.edu

Gibson, Schreuder-Heidi/US Army Natick/ heidi.schreudergibson@us.army.mil


This project expands the biologically inspired concepts from the organic biopolymer arena to the
inorganics and organic-inorganic hybrids. As nature has shown in many organic-inorganic hybrid
systems, the goal of this project is to integrate the concepts of biomimetics with organic-
inorganic hybridized organization to discover ways to generate new fibers with novel structures
and properties. In the first stage of this project, imbedding carbon nanotubes in ultra-fine
cellulose fibers has been studied. Multi-walled carbon nanotubes (MWCNTs) were successfully
incorporated in ultrafine cellulose fibers by electrospinning MWCNT-loaded cellulose acetate
(CA) solutions, followed by deacetylation of CA to cellulose (Cell). Even at extremely low
loadings of 0.11 and 0.55 wt%, the added MWCNTs significantly improved fiber uniformity and
reduced mean fiber diameter from 321 nm to 257 and 228 nm, respectively, which were further
lowered by another 8 to 16% upon hydrolysis. The MWCNTs were observed to be well aligned
along the fiber axes. The MWCNT/Cell composite fibers had increased specific surface, from
4.27 m
/g to 5.07 and 7.69 m
/g at 0.11 and 0.55 wt% MWCNTs, respectively, and much
improved hydrophilicity. The mechanical properties of the fibers were also greatly enhanced
with increased MWCNT loading levels. The fact that MWCNTs were observed in only about a
third of the fibers at a very low 0.55wt% loading suggests significantly higher tensile strength
may be achieved by a further increase in MWCNT loadings. Current effort continues to explore
surface bound biomolecules for potential binding with inorganics.

This project builds on the successful achievement of a previous project M05-CD01 that focused
on incorporating and converting proteinenous compounds into fibrous structures. Specifically,
several enzymes that break down fatty acids and sugars of varying structural properties have
been effectively bound to nanofibrous templates via encapsulation, immobolization, covalent and
ionic interaction mechanisms and in varying physical manners, i.e., internally, surface gels and
bi- or multiple-nanolayers. Structurally and functionally distinct classes of proteins and enzymes
have been combined in various designed nanofiber structures [1-7]. Several mechanisms,
including amphiphilic linkers [1,2], surface bristles [2,3] and hydrogel fibers [5,6], on
nanofibrous structures have been developed to fabricate effectively bound systems for
hydrolyzing enzymes in robust biocatalysis. The main focus has been to protect the protein under
extreme fabrication and use environments while creating advantageous properties. Protein-
polymer hybrid structures have been devised to successfully entrap the very large and bulky b-
galactosidase in non-ionic polyacrylamide (PAAm) hydrogel nanofibers [6] as well as to
efficiently bond enzymes via affinity dye ligands [7,8] and engineer new fiber scaffolds with
Spidroin 1-collagen proteins. A layer-by-layer (LBL) physical sorption process has been
established to bind lipase enzyme on cellulose nanofiber surfaces [9]. This simple approach uses
strong secondary forces, such as electrostatic and ionic interactions, and is proven to be highly

NTC Project: M10-CD01
National Textile Center Annual Report: November 2010
Most recently, the lead PI’s lab has developed different strategies to fabricate ceramic fibers
from polymer precursors [10,11]. These include the use of fiber forming polymers as carrier and
dispersants to disperse nanoparticles (alumina) and carbon nanotubes (CNTs). The electrospun
fibers were then calcinated into CNT/alumina nanofibers [Figure 1]. Another silicone polymer
precursor was fabricated into fiber and calcinated into silicon oxycarbide SiOC ceramic
nanoporous fibers with unique luffa-like shell structures and a nanoparticle-filled core [Figure 2].
This process is highly desirable, as it does not require a pre-patterned template. The high-
surface-area nanostructure with silicon-containing groups accounts for its super hydrophobicity.
Meanwhile, oil-uptake capacity of the corresponding fibrous mat is superior due to its oil-
preservable inner porous structure. Such a refractory inorganic nanoporous fiber is also capable
of supporting catalysts, such as ruthenium nanoparticles to convert ammonia to hydrogen for the
green energy applications that operate more efficiently at elevated temperatures.

Figure 1. As-electrospun (first row) and
corresponding as-calcined fibers (500°C/2 hr in
Ar, second row) of CNT/alumina dispersed in
polymer carrier at: (a,e) 0/4, (b,f) 0.2/4, (c,g)
2.4/4, (d,h) 4/4 and (k) 4/4 calcined in air. TEMs
of (i) and (j) of calcined CA composite fibers
showing the axial alignment of CNTs [10].
Figure 2. Ultra-high specific surface (392 m
/g) silicon
oxycarbide fibers (SiCO) with luffa-like shells and nano-
particle filled core (left most) have been fabricated by
calcinations of ceramic and polymer precursors. The fibers
are super-hydrophobic with a water contact angle of 156∞
(middle) and are capable of absorbing nearly 40 times their
weight in oils (right) [11].


Multi-wall carbon nanotube (MWCNT) were incorporated in cellulose acetate (CA) in 2:1 w:w
acetone/DMAc at 0.01/15 and 0.05/15 mass ratios, electrospun into fibers, then alkaline
hydrolysis to cellulose. Based on the 39.8 wt% acetyl content in the CA used, the MWCNT
loadings in the final MWCNT/Cell composites regenerated from 0.01/15 and 0.55 wt%
MWCNT/CA were calculated to be 0.11 wt% and 0.55 wt%, respectively. The XRD patterns
(Figure 3) of the deacetylated samples showed cellulose characteristic peaks centered at 2θ =
12.3, 20.2, and 22.0° (curve b, d, and f), while those of as-spun samples had two broad
amorphous halos in the ranges of 8.5-11.0º and 14.1-20.2º (curve a, c, and e). The 20.2° peak is
close to the typical 101 reflection of cellulose II (2θ = 19.8°) whereas the one at 22.0° is close to
the 002 reflection of cellulose I (2θ=22.5°), but both are far weaker than those of cellulose I in
cotton (41) and cellulose II in regenerated cellulose, suggesting presence of low cellulose I and II
crystalline allomorphs and slightly enhanced crystallinity with MWCNTs.

NTC Project: M10-CD01
National Textile Center Annual Report: November 2010

Figure 3. XRD patterns of (a) as-spun CA,
(b) Cell, (c) as-spun 0.11 wt%
MWCNT/CA, (d) 0.11 wt% MWCNT/Cell,
(e) as-spun 0.55 wt% MWCNT/CA, and (f)
0.55 wt% MWCNT/Cell from e.

Figure 4. TEM images showing the embedded MWCNTs
oriented along the axes of 0.55 wt% MWCNT/Cell fibers.


1. Wang, Y., Y.-L. Hsieh, Enzyme immobilization to ultra-fine cellulose Fibers via amphiphilic
polyethylene glycol (PEG) spacers, Journal of Polymer Science, Polymer Chemistry, 42:16,
4289-4299 (2004).
2. Hsieh, Y. Wang, H. Chen, Enzyme immobilization onto ultra-high specific surface cellulose
fibers via amphiphilic (PEG) spacers and electrolyte (PAA) grafts, Polymer Biocatalysis and
Biomaterials, Eds. H.N. Cheng and R.A. Gross, ACS Symposium Series 900, 63-79 (2005).
3. Chen, H., Y.-L. Hsieh, Enzyme immobilization on ultra-fine cellulose fibers via poly(acrylic
acid) electrolyte grafts, Biotechnology and Bioengineering 90(4): 405-413 (2005).
4. Wang, Y., Y.-L. Hsieh, Immobilization of lipase enzyme in polyvinyl alcohol (PVA)
nanofibrous membranes, Journal of Membrane Science, 209: 73-81 (2008).
5. Li, L., Y.-L. Hsieh, Lipase immobilization on ultra-fine poly(acrylic acid)/poly(vinyl
alcohol) hydrogel fibers, Polymer Biocatalysis and Biomaterials II, 129-143 (2008).
6. Lu, P. and Y.-L. Hsieh, Organic compatible polyacrylamide hydrogel fibers, Polymer, 50:
3690-3679 (2009).
7. Lu, P., Y.-L. Hsieh, Layer-by-layer self assembly of Cibacron Blue F3GA and lipase on
ultra-fine cellulose fibrous membrane, Journal of Membrane Science, 348, 1-2, 21-27 (2009).
8. Lu, P.,Y.-L. Lipase bound cellulose nanofibrous membrane via Cibacron Blue F3GA affinity
ligand, Journal of Membrane Science, 330: 288-296 (2009).
9. Lu, P. and Y.-L. Hsieh, Layer-by-layer self assembly of Cibacron Blue F3GA and lipase on
ultra-fine cellulose fibrous membrane, Journal of Membrane Science, 348 (1-2):21-27
10. Lu, P., Q. Huang, D. Jiang, Bin Ding, Y.-L. Hsieh

, I. A. Ovid’ko, A. Mukherjee, Highly
Dispersive carbon nanotube/alumina composites and their electrospun nanofibers, Journal of
American Ceramic Society, 92(11): 2583-2589 (2009).
11. Lu, P., Q.Huang, B. Liu, Y, Bando, Y.-L. Hsieh, A,K. Mukherjee,
Nanaoporous silicon
oxycarbide fibers with luffa-like shells and superhydrophobility, Journal of American
Chemical Society 131(30): 10346-10347 (2009).

Project Website: http://www.ntcresearch.org/projectapp/?project=M05-CD01