Photo-enforced stratification of polymeric materials

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.