11WWW.CEN-ONLINE.ORG MARCH 3, 2008

ANEW STRATEGY for establishing distinct chemical functionalities on the inside and outside of mesoporous silicon could ad-

vance design of sensors and drug delivery systems (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200704784). Such a route would be useful, for example, for making a material with a drug stored inside its pores and an external coating of antibody that targets the site where the drug is to be delivered.

Mesoporous materials have pores that range in size from 2 to 50 nm, which is advantageous for applications that in-volve biomolecules. For the materials to perform some of their intended tasks, the internal and external surfaces of the pores must be modified with different groups. But current methods cannot reliably and distinctively functionalize internal and external surfaces.

Chemistry professor J. Justin Gooding at the University of New South Wales in Australia, and colleagues harnessed hydrophobicity to overcome these limitations. “We can couple completely differ-ent things to the inside and outside of a mesoporous material by using self-assembled monolayers on the surfaces,” Gooding says. As a demonstration, the researchers immobilized ligands to promote cell adhe-sion on the exterior of a porous silicon crystal and then

introduced different chemical groups on the internal pore walls.

The strategy required modifying both the internal and external surfaces of the pores to create a hydro-phobic, succinimide ester-terminated monolayer via thermal hydrosilylation. Next, the researchers showed that the monolayer, aided by surface tension, prevents water from entering the pores. As a result, they could selectively derivatize the external surface with an aque-ous solution of peptides. Finally, the researchers used an organic solvent to functionalize the inside of the pores with groups that resist proteins.

Gooding says their approach is not necessarily lim-ited to silicon or mesoporous materials, but it would

also apply to materials with pore sizes that are smaller (<2 nm) or larger (>50 nm).

Christopher C. Landry, a professor of chemistry at the University of Vermont, highlights the strategy’s versatility for materials with various pore sizes but notes a limitation: At this point, the external surface must be modified by an aqueous solution, so groups that are water-insoluble cannot be added to the exter-nal surface. —RACHEL PETKEWICH

Functionalization

External: R = peptide or –(CH2)2OH

Internal: R = –(CH2)

7CH

3 or –(CH

2CH

2O)

6H

O10

( )

O

O

O

N RNH10

( )

O

FUNCTIONALIZED Researchers created a hydrophobic monolayer on the mate-

rial’s internal and external pore surfaces (black bars). Then both external (red) and

internal (green) surfaces were selectively functionalized with two different moieties.

Polyester fiber and resin maker Wellman

Inc., long troubled by high raw material

costs and a crushing debt burden, has

filed for Chapter 11 bankruptcy.

According to CEO Thomas Duff,

the company has tried reducing debt,

selling noncore businesses, laying off

workers, and cutting costs, but these

efforts were “not sufficient to offset

the deterioration in business conditions

and the cost of our substantial debt

obligations.”

According to its bankruptcy petition,

filed in New York City on Feb. 22, Well-

man has $600 million in debt but only

about $500 million in assets. The com-

pany has reported losses from continu-

ing operations every year since 2003.

Its 2006 sales were $1.3 billion.

The petition is only the latest setback

for Wellman. In December, the New York

Stock Exchange delisted the company’s

shares because they traded for less

than $1.00 for 30 days straight. Last

October, Wellman engaged investment

bank Lazard Frères to explore “strate-

gic alternatives” such as a sale of the

company.

Edgar Acosta, a polyester consultant

with Houston-based DeWitt & Co., says

the bankruptcy petition is a sign that

Wellman hasn’t received takeover offers

in excess of its debt obligation. Consid-

ering Wellman’s 1.5 billion lb in annual

polyethylene terephthalate (PET) ca-

pacity and its technology, market chan-

nels, and raw material contracts, Acosta

estimates that the company is worth

$250 million at most.

But a bigger PET plant could be built

in the U.S. with that much money. “If you

had $250 million, you could likely build

a bigger plant than what they are selling,

but you would not get the customer rela-

tionships,” he says. —ALEX TULLO

PLASTICS BUSINESS Polyester maker Wellman declares bankruptcy

NEWS OF THE WEEK

DIFFERENT INSIDE AND OUT

SURFACE CHEMISTRY: New route yields selectively functionalized

porous materials

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