Materials ETFs bolted higher Tuesday, getting a boost from an 11% spike for chemical giant DuPont (DD). Investors cheered news that DuPont CEO Ellen Kullman would step down on Oct. 16, even as the company announced plans to curb expenses. Overall, stock ETFs following the S&P, Dow and Nasdaq indexes attempted to extend their recent rally as investors eyed weak trade data and the start of earnings season.