#20 from R&D
Innovator Volume 2, Number 1
Meister is an associate professor of chemistry at the University
I didn't know
what to expect when I started trying to alter lignin, the polymer
that binds cellulose fibers together and gives trees their sturdy
certainly didn't believe the work would lead to a new and
important type of chemistry.
But from previous
work with lignin in the Phillips Petroleum Company research labs,
I knew it comprised the second largest mass of polymer made on
this planet. I also
knew that, while nature is very good at making lignin as a
stiffening agent for trees, humans are not so good at finding uses
for it. Most of the
lignin separated from trees during paper production is burned or
dumped; its complicated chemistry is wasted.
Since I had just completed a successful research effort to
convert starch into water-treatment chemicals, I felt I might be
able to find new applications for lignin.
optimistic blinders firmly affixed, I set out to build a side
chain made from a monomer called 2-propenamide, then bind it to
lignin with a reaction called grafting.
I hoped the resulting compound could be used as a
one knew how to graft effectively to lignin. From a long review of the literature, I decided to break a
bond on lignin with cerium ion and have that broken bond attack
one of the monomer molecules.
This would leave a broken bond at the end of the monomer
and cause the reaction to attack other monomers.
Ideally, a chain would then form on the lignin, one monomer
at a time.
To begin this
project, I gave two undergraduates a list of chemicals and recipes
to try out various reactions.
For one reaction, we borrowed a bottle of the solvent
dioxane is usually contaminated with peroxides, we didn't bother
to purify it since we figured peroxides might actually help our
reaction looked very promising as it thickened and formed a
water-soluble solid. (Unlike lignin itself, grafted lignin should
be water-soluble.) Furthermore,
the mass of solid recovered was close to the sum of the lignin
plus the monomer. I was excited by these results and put in extra hours in the
We spent the
summer running reactions and developing tests for the products.
Our data continued to indicate that we were making grafted
lignin. But when the
summer ended, I could no longer repeat the reaction.
I wish I'd
applied the fundamental rule of trouble-shooting: "Identify and investigate what changed between the
successful process and the unsuccessful process."
That would have explained the sudden failure much quicker.
Instead, I wasted
time checking the purity of the key reagents, the cleanliness of
our equipment, and the quality of the nitrogen gas we used to
blanket the reaction. When
I finally checked whether the dioxane solvent was causing the
failure, I realized we'd lost critical information.
The borrowed bottle of dioxane had been exhausted just as
summer ended, when the reaction failed and the undergraduates
returned to class.
wondered if peroxides in the original dioxane had promoted the
reaction, weeks of irradiation and oxygen saturation experiments,
all intended to produce peroxided dioxane, yielded no new grafted
lignin. When I finally talked to the people who'd supplied the
original dioxane, I learned it had been dried over calcium
contamination of the solvent with a chloride salt should not have
changed our reaction product, as chloride salts are very stable
and play virtually no role in initiating this type of
But chemistry is
an experimental science, so we went back to the lab and tried the
reaction again, this time with chloride ion added to the
irradiated, peroxided dioxane.
grafting reaction worked.
As we began a
frantic rush to answer the seemingly endless questions about this
new reaction, one question seemed paramount:
"Are we really grafting onto lignin?"
Normal lignin is
a complex tangle of chains, and I assumed that we had added chains
of polymerized propenamide to the lignin.
But it was incredibly difficult to analyze this new
find the one bond in 10 million that distinguishes lignin grafted
to a polymeric side chain from lignin molecules mixed with polymer
molecules is to find a needle in a haystack.
Yet we had to prove the identity of our product before we
could fairly claim to have produced it.
We spent the next
two years developing analytical methods that proved we'd made
grafted lignin. In
1984, we patented the material and method and published the
results. This led to
a government grant that allowed us to pick up our research pace.
The grant meant I would receive a summer salary, a welcome
change from the previous five years.
Material May be Useful
investigated the properties of grafted lignin, a series of
inventions began to flow from the lab.
Unlike lignin, the modified material was water-soluble and
had the properties of a water-thickening agent.
It has potential to purify water for industrial processes,
dewater sewage sludge, and serve as a drilling-mud additive for
I certainly have
enjoyed the interest among government agencies and corporations in
my findings, not to mention their research support. But I am enjoying even more the fact that other laboratories
are currently working to develop my work into useful products.
new materials were triumphs in their own right, each time I
described these grafted lignins, I had to explain that the
starting material was derived from wood.
That got me wondering if we could graft to lignin while
it's still in the wood. Although I read a great deal about the structure and
composition of wood while pondering that question, the direct
route to the answer led right through the lab!
We prepared a
series of reactions and, after a year of experiments to identify
trends and prove synthesis, showed that we could graft lignin
directly in pieces of wood. We
then used styrene instead of 2-propenamide as the monomer.
That discovery, in 1989, led to a group of recyclable
composites based on plastic and wood.
These can be heat-molded into any shape and are based on a
While there have
been other reports of altering wood to make it compatible with
plastic, our reaction seems to be the most efficient and allows
the wood to bind with many types of plastics.
My finding of a method to "plasticize" wood is
attracting even more attention than the original grafted lignin
material is lighter than normal plastics, and it could make
It will be fun to see how this discovery develops.
Rock in the Pond
An invention is
like a rock hitting a pond—its waves radiate in all directions.
In chemistry, an inventor can ride one of these waves.
A new reaction can carry us and a bunch of new molecules to
a host of applications.
But there's an
irony here. When I
look back, I realize that 12 years of breakthroughs all originated
with the borrowing of a contaminated bottle of solvent.
I shudder at the thought of trying to develop another
grafting reaction for lignin because they are hard to produce.
Yet I don't dwell on the fact that all of our developments
depended on one fortuitous "borrowing."
I can't—I have a wave to ride.