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

Abstract

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

Reactive compatibilization of poly(methyl acrylate‐ran‐acrylonitrile)/poly(ethylene) blends through amine–anhydride coupling

“…The shear rates were approximated as 9 and 27 s −1 at 50 rpm in the region with the minimum and maximum diameter, respectively, by using the screw speed, gap distance and, screw diameter. Using the data obtained and data previously measured, it can be seen that the η r of the non‐reactive system copolymer: PE‐ g ‐MAn = 0.19–0.23 and that of the reactive terpolymer: PE‐ g ‐MAn was 0.3–0.6 at the low and high shear rates estimated in the extruder. η r approaching unity should theoretically result in the minimum domain sizes .…”

“…Seeing that for the functionalized blends decreased relative to the non‐functionalized blend, it shows that morphology was stabilized due to the coupling reaction as was suggested by previous studies . Conversely, the small increase in after annealing indicates that coalescence was very slow at the temperature used, and that slight variations in were more likely to be caused by particle analysis, rather than the coalescence process . To compare the particle sizes with theoretical or semi‐empirical predictions, estimates of the blend interfacial were necessary.…”

“…Indeed, styrene/acrylonitrile (SAN) and methyl acrylate/acrylonitrile (MA/AN) copolymers are commercially available as barrier materials synthesized by conventional radical polymerization, however little is mentioned how these are compatibilized . We previously made SAN copolymers where we placed a single reactive amine group at the chain end . The amine‐terminated SAN was effective in compatibilization with maleic anhydride grafted PE (PE‐ g ‐MAn) and we were able to form elongated SAN domains in the PE .…”

“…We previously made SAN copolymers where we placed a single reactive amine group at the chain end . The amine‐terminated SAN was effective in compatibilization with maleic anhydride grafted PE (PE‐ g ‐MAn) and we were able to form elongated SAN domains in the PE . However, the dispersed phase particle size was limited to about 2 μm and further modulation could potentially be accessed by making the acrylonitrile‐containing copolymer with many pendant functional groups and perhaps diluting it with cheaper non‐functional SAN.…”

Advances in Chemically Modified and Functionalized Polymers

“…A new approach to reactive compatibilization of blends, which has been an area of traditional interest in the chemical modification of polymers is described in the paper by Oxby and Maric. [9] Finally a novel specialty application in transforming the surface properties of a diverse range of polymers is presented by Bagwell et al [10] This Special Issue demonstrates the true diversity and multidisciplinarity of this area. In the future, to achieve further and more rapid advances in the field, it will be essential to pull together scientists from all fields of expertise, ranging from polymer chemists to polymer processing experts.…”