High-throughput Method for Determining Young’s Modulus
of Polymer Blends
Introduction
Manufacturing industries have a long history
of using polymer blending as an inexpensive method to create
new materials with desirable properties. Blending can be used
to optimize modulus, strength, morphology and crystallinity
and for these reasons blending is also receiving attention from
the tissue engineering community. Since a one-sample-for-one-measurement
approach can be slow, we have developed a high-throughput method
for determining the modulus of polymer blends in order to accelerate
development of new materials.
Experimental Approach
A polymer blend gradient library of poly(L-lactic
acid) (PLLA) and poly(D,L-lactic acid) (PDLLA) was created using
a three-syringe pump system and a translation stage. The library
was a strip-shaped film approximately 3 mm wide, 50 mm long
and 4 micrometers thick which was formed on a glass substrate
and its composition was measured by Fourier transform infrared
(FTIR) microspectroscopy. A gradient in composition ran along
the long axis of the film being PLLA-rich on one end and PDLLA-rich
on the opposite end. Nanoindentation measurements were made
across the gradient to obtain quantitative modulus data over
a wide range of PLLA-PDLLA blend compositions using only a single
polymer specimen.
Results
Image of a polymer solution being deposited from the sampling
syringe onto a glass substrate to form a strip-shaped film.
FTIR microspectroscopy was used to determine composition of
six PLLA-PDLLA gradients. Orange corresponds to PLLA and blue
corresponds to PDLLA.
The compositions of the six PLLA-PDLLA gradients determined
with FTIR-RTM were averaged and plotted versus position along
the gradient.
Young’s modulus was measured on the gradients using nanoindentation
and average values (solid circles) were plotted against composition
(bottom y-axis) and position (top y-axis). Open triangles are
the modulus from control discrete blend specimens (0, 25, 50,
75 & 100% PLLA) plotted against composition [use the bottom
y-axis only; the top y-axis (“Position”) does not
apply to these data].
Future Activities
Examine cell adhesion, morphology, proliferation and differentiation
after culture on composition gradients.
Make gradients of other polymer blends (tyrosine polycarbonates)
to explore applicability of the method.
Publications
PAPER: Simon Jr CG, Deng Y, Eidelman N, Washburn NR (2005)
High-throughput method for determining Young’s modulus
of polymer blends. Nature Materials, in preparation.
PAPER: Eidelman N, Simon Jr CG (2004) Characterization of
combinatorial polymer blend composition gradients by FTIR
microspectroscopy. Journal of Research of the National Institute
of Standards and Technology, in press.
POSTER: Simon Jr CG, Kennedy SB, Amis EJ, Eidelman N, Washburn
NR. “Gradient Libraries for Combinatorial and High-Throughput
Investigations of Polymeric Biomaterials”, 7th World
Biomaterials Congress, Australia, 2004.
POSTER: Simon Jr CG, Kennedy SB, Amis EJ, Eidelman N, Washburn
NR. “High-throughput Methods for Biomaterials Development”,
NIST Combinatorial Methods Center 4th Annual Meeting, Gaithersburg,
MD, 2003.
POSTER: Simon Jr CG, Kennedy SB, Amis EJ, Eidelman N, Washburn
NR. “High-throughput Methods for Biomaterials Development”,
Symposium on Metrology and Standards for Cell Signaling, NIST,
Gaithersburg, MD, 2003.
POSTER: Simon Jr CG, Kennedy SB, Amis EJ, Eidelman N, “Washburn
NR. High-throughput Methods for Biomaterials Development”,
RESBIO Kickoff Even, Rutgers University, NJ 2003.
NIST Contributors:
Carl G. Simon, Jr
Newell R. Washburn
Gale A. Holmes
Yan Deng
Naomi Eidelman
Chetan A. Khatri
Amit Sehgal
Michael D. Weir
Collaborators:
Joachim Kohn
(Rutgers University)
Biomaterials Group
Polymers Division
Materials Science and Engineering Laboratory
![Young’s modulus was measured on the gradients using nanoindentation and average values (solid circles) were plotted against composition (bottom y-axis) and position (top y-axis). Open triangles are the modulus from control discrete blend specimens (0, 25, 50, 75 & 100% PLLA) plotted against composition [use the bottom y-axis only; the top y-axis (“Position”) does not apply to these data].](image/Youngs_modulus.gif)