US Patent 8,921,447
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
The invention provides a process for manufacturing a polymeric material having a compositional gradient, comprising: forming a mixture comprising a first photopolymerizable polymer precursor and a second photopolymerizable precursor, and subjecting said mixture to an intensity gradient of electromagnetic radiation, wherein said first precursor has a greater reactivity ratio than said second precursor, and/or said first precursor is mono-functional and said second precursor is di-functional, and/or said first precursor is less inhibited by oxygen than said second precursor.
Cook, Clinton J. and Guymon, Allan C. Photo-enforced stratification of polymeric materials. US Patent 8,921,447 filed April 08, 2011 and issued December 30, 2014. https://ir.uiowa.edu/patents/630