All foamed up: Synthesis of macroporous polystyrene through polymerization of foamed emulsions

Feb 07, 2012

(PhysOrg.com) -- Packaging, insulation, and impact protection are examples of commercial uses of polymer foams. Depending on the intended application, the properties required of these foams can differ greatly. In the journal Angewandte Chemie, a team of German, Irish, and French researchers led by Cosima Stubenrauch at the University of Stuttgart has now introduced a new method for the controlled production of structured foams. Their technique is based on the polymerization of foamed emulsions of oil in water.

Not all foams are equal: a kitchen sponge, for example, is not the same as a piece of packaging. Different applications make different demands on a foam, which has led to efforts to control the properties of foams in a targeted fashion. In addition to a foam’s chemical composition, its structure also plays an important role. The property profile of a foam depends on the number and size of the pores, whether the pores are closed off or connected, and the thickness of the polymer supports between the pores. “The high complexity of conventional production processes, which generate foams from polymer melts and blowing agents, makes control over the morphology and properties of the product a big challenge,” explains Stubenrauch.

An alternative approach involves the use of microscopically small templates to force the foam into the desired structure. For example, tiny droplets of water can be finely dispersed (emulsified) in a solution of monomer, then removed after the polymerization is complete. Another process uses particles to stabilize air bubbles in the reaction mixture.

Stubenrauch’s team has now introduced a new concept for the synthesis of macroporous polystyrene foams: the polymerization of foamed oil-in-water . Styrene (the "oil phase") is first emulsified in an aqueous phase. Afterward, the emulsion is stabilized with an anionic surfactant and foamed with nitrogen. This forms bubbles surrounded by tightly packed drops of emulsion. In the third step, the is initiated by irriadiation with UV light. The drops of emulsion dissolve away, while the structure of the foam—that of the template—is maintained.

The resulting polymer foams contain pores that are partially interconnected through “windows”. “While the high density of the polymer and the strong bonds provide good mechanical stability, the presence of the windows allows air, fluids, or other materials to flow through the foam,” says Stubenrauch. “Control over these properties is desirable for many applications, such as supports, filter agents, or biologically inspired scaffolding. This production technique is simple and versatile and represents a highly promising alternative to other template-based synthetic methods.”

Explore further: Deconstruction of avant-garde cuisine could lead to even more fanciful dishes

More information: Cosima Stubenrauch, Synthesis of Macroporous Polystyrene by the Polymerization of Foamed Emulsions, Angewandte Chemie International Edition, dx.doi.org/10.1002/anie.201107806

Related Stories

Foam bubbles finally brought to order

Dec 23, 2011

Scientists have succeeded for the first time to turn the Weaire-Phelan foam model – a celebrated geometrical concept which received additional notoriety when used in Beijing’s Olympic Games iconic ...

Icy exposure creates armored polymer high tech foams

Jul 28, 2009

(PhysOrg.com) -- Chemists and engineers at the University of Warwick have found that exposing particular mixtures of polymer particles and other materials to sudden freeze-drying can create a high-tech armored foam that could ...

Micro-onions and magnetic ink

Aug 08, 2011

(PhysOrg.com) -- Microfluidic systems for the easy production of multiphasic emulsion drops and multishelled polymer capsules. Under a microscope they look like miniature onions, in fact, they are new microcapsules introduced ...

Titanium foams replace injured bones

Sep 22, 2010

Flexible yet rigid like a human bone, and immediately capable of bearing loads: a new kind of implant, made of titanium foam, resembles the inside of a bone in terms of its structural configuration. Not only ...

Recommended for you

Characterizing an important reactive intermediate

Oct 01, 2014

An international group of researchers led by Dr. Warren E. Piers (University of Calgary) and Dr. Heikki M. Tuononen (University of Jyväskylä) has been able to isolate and characterize an important chemical ...

Surfaces that communicate in bio-chemical Braille

Oct 01, 2014

A Braille-like method that enables medical implants to communicate with a patient's cells could help reduce biomedical and prosthetic device failure rates, according to University of Sydney researchers.

New material steals oxygen from the air

Sep 30, 2014

Researchers from the University of Southern Denmark have synthesized crystalline materials that can bind and store oxygen in high concentrations. Just one spoon of the substance is enough to absorb all the ...

User comments : 0