Strategy for Scalable Comb Block Polyolefin Synthesis. Efficient Graft of Isotactic Polypropylene to a Commercial Broad Molecular Weight Distribution, Hyperbranched, Ethylene Methylacrylate Copolymer Patrick Brant,* Jiemin Lu, Maksim Shivokhin,* Sergey Yakovlev, Shuhui Kang, Bethany Welke, Melissa Raney, Joseph Throckmorton, Jennifer Rapp, Hao Wang, and Dalia Yablon Cite This: Macromolecules 2020, 53, 6353-6368 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Judicious selection and use of a readily available, reactive polyolefin backbone can facilitate scalable comb block construction. This can be further assisted by appropriate grafting chemistry. In this work, alcohol-terminated isotactic polypropylene (iPP-OH) is grafted to commercially available hyperbranched, very broad molecular weight distribution ethylene methyl acrylate copolymer (EMA; 20.9 wt % methylacrylate; melting peak 80 °C). iPP-OH (melting peak 135 °C; number average molecular weight 16 kDa/mole) is synthesized from vinyl-terminated isotactic polypropylene (vt-iPP) macromonomer by oxidative hydroboration in 75% yield based on initial vt-iPP mass charged and >95% yield based on the consumption of vinyl termini. This product is in turn grafted efficiently onto the EMA via the transesterification of less than 2% of the MA groups to yield comb block copolymers (EMA- cb-iPP). Two graft products containing 24 and 38 wt % iPP were prepared, with grafting efficiency determined to be greater than 80 and 95%, respectively, based on alcohol consumption ( 1 H NMR and 13 C NMR). Efficient grafting of iPP-OH to EMA and the hyperbranched nature of EMA and comb block products were further affirmed by GPC equipped with multiple detectors, including an infrared detector capable of differentiating polyethylene from polypropylene. Scanning transmission electron microscopy and atomic force microscopy, along with small-angle X-ray scattering, of the EMA-cb-iPP products show that, in spite of the structural complexity of the EMA, these products readily self-assemble into uniformly finely textured morphology of phase-separated EMA and iPP of the order 50-100 nm. These blocks act to compatibilize blends of EMA and iPP and disperse well into iPP. It is believed that the synthetic strategy illustrated hereinespecially the use of a commercially available reactive polyolefin to, from, or through which to graftwill encourage pursuit of economically viable and scalable comb block synthetic strategies for new material applications. ■ INTRODUCTION Grafting strategies for syntheses of graft blocks comprising polyolefins, including model reactive polyolefins accessed, especially by ring opening metathesis polymerization (ROMP), have been reported for some time and include successes grafting from 1-11 and grafting through. 5,11,12 A third strategy involves vinyl-terminated macromonomer incorpora- tion during the homogeneous polymerization of olefin monomers (also used to add medium to long chain branches). 13-24 All of these synthetic approaches have provided useful scientific insights and raised an awareness of material design opportunities for comb blocks. At the same time, these also add complexity regarding the exploration of comb block space for application to material design because, regardless of the approach employed, all have relied on skillful total laboratory batch syntheses of the block products. One key goal of the current research is the demonstration of a broadly applicable simplification of the graft block synthesis by eliminating the lab-scale synthesis of at least one of the polyolefin blocks, while retaining a significant degree of structural variety and control and second choosing a scalable synthesis for the second block. The first goal is accomplished by Received: April 14, 2020 Revised: June 8, 2020 Published: July 21, 2020 Article pubs.acs.org/Macromolecules © 2020 American Chemical Society 6353 https://dx.doi.org/10.1021/acs.macromol.0c00828 Macromolecules 2020, 53, 6353-6368 Downloaded via UNIV OF HOUSTON MAIN on November 12, 2020 at 20:58:31 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.