Compatibilization of Poly(styrene-acrylonitrile) (SAN)/Poly(ethylene) Blends via Amine Functionalization of SAN Chain Ends

Styrene/acrylonitrile (SAN) copolymers with low polydispersity (M) over barw/(M) over barn (1.10-1.30) are synthesized by nitroxide mediated polymerization (NMP) in dimethylformamide (DMF) solution with a succinimidyl ester (NHS) terminal group from the N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl) nitroxide] (SG1) residue. These copolymers are thermally stabilized by removing the SG1, and then modified to form primary amine end-functional SAN (SAN-NH2). Proton nuclear magnetic resonance spectroscopy (H-1 NMR) and Fourier-transform infrared spectroscopy (FT-IR) indicated that the amine group is effectively placed at the chain end at a level of 90%. SAN-NH2 is reactively blended with maleic anhydride grafted poly(ethylene) (PE) at 20wt.% loading at 180 degrees C and the resulting morphology is compared against the non-reactive blend. Scanning electron microscopy (SEM) indicates finer SAN domains similar to 1 mu m which are thermally stable upon annealing in the reactive case. The dispersed SAN domains are reoriented using a channel die to impart elongated domains with aspect ratios similar to 14, which would be desirable for barrier materials.