For sweat's sake.

Soldiers may someday find comfort as well as safety in chemical-protection gear, now that researchers have created a breathable, chemical-blocking composite material.

Manufacturers commonly make protective garments out of butyl rubber, which blocks vapors and liquids. But in warm conditions, a person "might sweat to death in it," says chemist Douglas L. Gin of the University of Colorado at Boulder.

To create a breathable barrier, Gin and his colleagues turned to a lyotropic liquid crystal, which has two different ends: one water loving, the other water repelling. The researchers placed the liquid crystals in water, which caused the water-loving ends to pack together and form nanometer-scale pores. Next, the scientists blended the mixture into liquid butyl rubber. Once cured, the material consisted of a three-dimensional network of rubber and pores that contain water.

Chemical warfare agents can't pass through the pores because such chemicals are generally water repelling, says Gin. In tests, a patch of the composite material stopped a mustard gas--like chemical even better than plain butyl rubber did. Yet the composite would allow enough water vapor to move through to meet military standards for comfort, the team reports in the Dec. 15, 2006 Advanced Materials.--A.C.