Shares in Arrowhead Research Corp. rose nearly 15 percent after the Pasadena-based firm said its subsidiary, Unidym Inc., would merge with Houston-based Carbon Nanotechnologies Inc.

The two companies will operate under the Unidym name and both will continue to produce carbon nanotube products. The deal was a stock swap worth about $5.4 million.

CNI was founded in 2000 by the late Rice University professor Richard Smalley, who received the Nobel Prize for his work in developing carbon nanotubes. The hair-like structures are extremely light and strong and are thought to have the potential for wide applications in building electronics, aircraft, cars and buildings.

“We chose Unidym as our partner because Unidym has the most advanced carbon nanotube-based electronic products with billion-dollar market potential, as well as an impressive carbon nanotube patent portfolio of its own,” said Chief Executive Bob Gower of Carbon Nanotechnologies.

Shares in the Pasadena-based research and development firm Arrowhead were up 56 cents, or 14 percent, to $4.38 in afternoon trading Thursday on the Nasdaq.