Cover: Amine end‐functional poly(styrene‐co‐acrylonitrile) (SAN) copolymers are synthesized using nitroxide mediated polymerization for use in reactive extrusion with maleic anhydride grafted poly(ethylene) (PE). Such SAN copolymers are envisioned as alternative barrier polymers with controlled microstructure for PE matrices. Further details can be found in the article by K. J. Oxby and M. Marić http://doi.wiley.com/10.1002/mren.201200081.

Styrene/acrylonitrile (SAN) copolymers with excellent chain-end fidelity and low polydispersity M w /M n (1.10 -1.30) were synthesized by nitroxide mediated polymerization (NMP) in dimethylformamide (DMF) solution with a succinimidyl ester (NHS) terminal group from the so-called SG1 nitroxide residue. These copolymers were thermally stabilized by removing the N-tertbutyl-N-[1-diethylphosphono-(2,2-dimethylpropyl) nitroxide] (SG1), and then modified to form primary amine end-functional SAN (SAN-NH 2 ). Homogeneous coupling reactions and Fourier-transform infrared spectroscopy (FTIR) indicated that the amine group was effectively placed at the chain end. SAN-NH 2 was reactively blended with maleic anhydride grafted poly(ethylene) (PE) at 20 wt.% loading at 180 °C and the resulting morphology was compared against the nonreactive blend. Scanning electron microscopy (SEM) indicated finer SAN domains ~ 1 μm which were thermally stable upon annealing in the reactive case.The dispersed SAN domains were reoriented using a channel die to impart elongated domains with aspect ratios ~ 14, which would be desirable for barrier materials.ii iii