Compatibilization of iPP/PS Blends with Diblock and Triblock Copolymers
ORAL
Abstract
Mechanical recycling of plastics benefits from block copolymer compatibilizers, yet limited understanding of optimal molecular design restricts their broader applications. In this study, we synthesized poly(styrene)-block-poly(ethylene-ran-ethylethylene) (SX) diblock and SXS triblock copolymers via sequential anionic polymerization followed by catalytic hydrogenation and investigated their effectiveness in compatibilizing semicrystalline isotactic polypropylene (iPP) blended with glassy polystyrene (PS). By varying the S block molecular weight (10−80 kDa) and block architecture (diblock vs. triblock), we explored the underlying compatibilization mechanisms. Our findings corroborate the recently proposed “threading-the-needle” mechanism describing engagement between X block loops and iPP homopolymer chains near domain interfaces. Additionally, a new mechanism for creating ductility in the semicrystalline iPP matrix without stress transfer across the phase separated interface with PS was revealed in SX diblock-compatibilized blends. Remarkably, incorporating only 0.1 wt% SX diblock enhances ductility in blends containing 20 wt% PS (strain at break, εb > 400%) by dissipating strain energy and suppressing void formation during deformation. This study provides insights into the design of block copolymer compatibilizers for recycled polymer blends.
*This work was supported by the National Science Foundation under grant DMR-2304179. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award Number DMR-2011401) and the NNCI (Award Number ECCS-2025124) programs. Parts of this work were carried out in the Polymer Characterization and Processing Facility, University of Minnesota, which has received capital equipment funding from the National Science Foundation through the UMN MRSEC under Award Number DMR-2011401.1H NMR spectra were collected on a Bruker Avance II HD 400 MHz spectrometer purchased by the Office of the Vice President of Research, the Department of Chemistry at the University of Minnesota.
