Avantor Performance Materials (Center Valley, PA) and NuSil Technology LLC (Carpinteria, CA), both of which are portfolio companies of New Mountain Capital LLC, have signed a definitive agreement to merge. This merger will create the global leader in ultra-high-purity materials for the life sciences and advanced technology markets, according to a press release issued today. Demand for these materials is on a growth trajectory driven by technological advances, market expansion and the increasingly strict regulatory and performance specifications of the life sciences and other industries, said the companies.