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Post-doctoral Training
Fiber and
Polymer Science Department, North Carolina State University,
Rayleigh, NC, 1993-1995
Research Interest
Research in our group is in the general area of polymer science,
crystallization of and spectroscopy of polymers. Our primary objective
is to study the effect of hydrogen bonding in extensibility of hydrogen
bonded polymers. The second aim is to develop nanoscale systems such as
inclusion compounds for drug and fragrance delivery. Our third objective
is to develop various biodegradable polymers and polymer nanocomposites
for medical device applications.
Lewis Acid-Base Complexation of Hydrogen Bonded Polymers to Control
Hydrogen Bonding During Extension
First we have been studying the effect of hydrogen
bonding in the drawing behavior of polymers. It is generally believed
that hydrogen bonding makes polyamides important engineering plastics,
because of the high strength it imparts. However, the interchain
hydrogen bonds between amide groups are seen as a barrier to
ultradrawing of high molecular weight polyamides and, therefore, to the
achievement of high strength and high modulus fibers. The purpose of the
proposed research is to develop a new method to spin and draw high
strength fibers and films by suppressing the interchain amide group
hydrogen bonding. We have shown recently that hydrogen bond suppression
can be achieved by Lewis Acid - Base complexation of polyamides, and this
may provide a way to temporarily eliminate hydrogen bonding during drawing,
allowing orientation to the desired degree, followed by reformation of the
hydrogen bonds in the oriented state. We will investigate the influence of
hydrogen bonding on fiber formation in low and high molecular weight
polyamides, and examine morphological characteristics such as molecular
orientation in the crystalline and noncrystalline regions, degree of
crystallinity and crystallite size. We will also explore the Lewis acid - base
complexation reactions of polyamides as a means of probing the nature of
intermolecular hydrogen bonding in semicrystalline polymers. Another
issue of commercial importance is that polyamide fibers, unlike polyester
fibers, are difficult to heat-set, which often causes considerable
processing problems in manufacturing polyamide textiles. It has been
hypothesized that hydrogen bonding in polyamides is primarily responsible,
and the proposed study will permit a systematic examination of this question.
The complexation of polypeptides and proteins (nylon-2s) would be
additional amide bond containing polymers worthy of study, because of the
higher concentration of amide groups in their backbone bonds and because
in their crystals the amide bonds may form either interchain
(beta-sheets) or intrachain (alpha-helices) hydrogen bonds.
Formation and Characterization of Inclusion Compounds
Several small molecule hosts form inclusion compounds with polymers.
In these inclusion compounds polymer chains are confined to occupy in
the narrow channels in the crystalline matrix formed by the host. The
walls of the inclusion compound channels are completely formed by small
molecules. Each polymer chain included in the narrow channel is highly
extended and separated from the neighboring chains. A program to study
various urea and thiourea inclusion compounds has been in progress in our
laboratory. We have investigated the inclusion compounds formed between
poly lactides and urea. There have been numerous experimental and
theoretical results were reported. It is also known that amylose and
cyclodextrins form inclusion compounds with polymer and small molecule
guests. We plan to form inclusion compounds between various polymers and
additives with thiourea and amylose. These additives can then be delivered
via inclusion compounds to various food products. The additives coalesce
from its inclusion compounds and slowly diffuse into the food products.
Delivery of these additives to food products may offer several advantages
over conventional blending methods.
Modification of Poly Lactide Based Polymers
Finally we will seek to investigate new approaches to significantly
improve the performance of polylactic acid (PLA) derived materials and
offer a renewable resource and biodegradable alternative for high
performance fiber applications. The broad application of current
commercial PLA products for semi-crystalline, thermoplastic fiber
markets is limited by their relatively low Tg (ca. 50-60°C), poor mel
strength, low modulus, and unfavorable rate of hydrolysis above the Tg.
Thus PLA-based materials have been targeted for predominantly biomedical
applications from surgical sutures to drug delivery systems. We plan to
address these limitations and expand the use of PLA by preparing two
classes of PLA derived materials featuring: (1) self-assembled
"stereocomplexes" (i.e., L and D stereoisomers) and (2) hybrid inorganic
nanocomposites of PLA with, for example, clays, sol-gels, and metal oxides.
The structure property relationship of these materials will be
investigated using vibrational and solid state NMR spectroscopy.
Selected Publications
28. FTIR Spectroscopic Characterization of Structural Changes in Polyamide 6 Fibers During Annealing and Drawing. . N.Vasanthan and D. R. Salem. J. Polym. Sci, Polym Phy, 2001, 39, 536.
29. Effects of Heat Setting and Drawing on Structure and Morphology of Polyamide 66 Fibers. N.Vasanthan and D. R. Salem. Material Innovations, 2001, 4, 155.
30. Spectroscopic Methods: Infrared, Raman and Nuclear Magnetic Resonance." D. R. Salem and N. Vasanthan. Structure Formation in Polymeric Fibers, D.R. Salem Ed., Hanser Publishers: Munich (2001).
31. FTIR Investigation of the Ambient Dependent Photo damage in Hair. K. R. Ramaprasad, N. Vasanthan, and Y. Kamath. Journal of Cosmetic Science, 2001, 52, 334.
32. Structure Development of Polyamide 66 fibers by X-ray Diffraction and FTIR spectroscopy. .N.Vasanthan and D. R. Salem. J. Polym. Sci, Polym Phy, 2002, 40, 1940.
33. Orientation and Structure Development in Polyamide 6 Fibers Upon Drawing .N.Vasanthan. J. Polym. Sci, Polym Phy, 2003, 41, 2870.
34. Effect of Polymer Microstructure on Dye Diffusion in Polyamide 66 Fibers N.Vasanthan and Huang, X. X. J. Appl Polym. Sci, , 2003, 89, 3803.
35. Orientation Induced Memory Effect in Polyamides and the Relationship to Hydrogen Bonding. N.Vasanthan. J. Appl. Polym. Sci, 2003, 90, 772.
36. Effect of Heat Setting Temperatures on Tensile Mechanical Properties of Polyamide Fibers N. Vasanthan. Textile Research Journal, 2004, 74, 545.
37. Lewis Acid-Base Complexation of Polyamide 66 to Control Hydrogen Bonding, Extensibility and Crystallinity. N.Vasanthan, R. Kotek, D. W. Jung, D. Shin, A. E. Tonelli and D. R. Salem. Polymer, 2004, 45, 4077.
You can see my full CV here.
Office: M601
Phone: (718) 246-6328
Fax: (718) 488-1465
Email:
Nadarajah.Vasanthan@liu.edu
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created on Sept. 13, 2004