Reaction kinetics of end-functionalized chains at a polystyrene/poly(methyl methacrylate) interface

Forward recoil spectrometry (FRES) has been used to monitor the extent of r eaction between model end-functional polymers at a PS/PMMA interface. Bilay er samples comprising a high molecular weight polystyrene layer containing similar to 8.5 wt % of amino-terminal deuterated polystyrene (dPS-NH2) on a n anhydride-terminal poly(methyl methacrylate) (PMMA-anh) layer were anneal ed at 174 degrees C for various periods. Significant reaction with the PMMA -anh, indicated by an interfacial excess, was observed with three molecular weights (M = 22 000, 37 000, and 92 000 g/mol) of dPS-NH2. The measured gr owth of the interfacial excess with time for all three molecular weights co uld not be well described with recent theor ies of diffusion-controlled int erfacial reactions. A model that incorporates polymer chain reactivity fit the data better, with reaction rate constants k = 0.20, 0.055, and 0.042 kg mol(-1) s(-1) for dPS-NH2-22, -37, and -92, respectively. Furthermore, a n ovel trilayer sample geometry showed that the reactive dPS chains can diffu se throughout the PS matrix and sample the PS/PMMA interface several times before a significant amount of reaction occurs. The results Of this study a re consistent with other experimental systems where the in situ copolymer f ormation is limited by reaction rate, rather than the diffusion of reactive chains through the bulk.