Browsing by Author "Cui, Shuquan"

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    Data for Threading-the-Needle: Compatibilization of HDPE/iPP blends with butadiene-derived polyolefin block copolymers
    (2023-07-31) Shen, Liyang; Diaz Gorbea, Gabriela; Danielson, Evan; Cui, Shuquan; Ellison, Christopher J; Bates, Frank S; bates001@umn.edu; Bates, Frank S; University of Minnesota Department Chemical Engineering and Material Science
    Management of the plastic industry is a momentous challenge, one that pits enormous societal benefits against an accumulating reservoir of nearly indestructible waste. A promising strategy for recycling polyethylene (PE) and isotactic polypropylene (iPP), constituting roughly half the plastic produced annually worldwide, is melt blending for reformulation into useful products. Unfortunately, such blends are generally brittle and useless due to phase separation and mechanically weak domain interfaces. Recent studies have shown that addition of small amounts of semicrystalline PE-iPP block copolymers (ca. 1 wt%) to mixtures of these polyolefns results in ductility comparable to the pure materials. However, current methods for producing such additives rely on expensive reagents, prohibitively impacting the cost of recycling these inexpensive commodity plastics. Here, we describe an alternative strategy that exploits anionic polymerization of butadiene into block copolymers, with subsequent catalytic hydrogenation, yielding E and X blocks that are individually melt miscible with PE and iPP, where E and X are poly(ethylene-ran-ethylethylene) random copolymers with 6% and 90% ethylethylene repeat units, respectively. Cooling melt blended mixtures of PE and iPP containing 1 wt% of the triblock copolymer EXE of appropriate molecular weight, results in mechanical properties competitive with the component plastics. Blend toughness is obtained through interfacial topological entanglements of the amorphous X polymer and semicrystalline iPP, along with anchoring of the E blocks through cocrystallization with the PE homopolymer. Significantly, EXE can be inexpensively produced using currently practiced industrial scale polymerization methods, offering a practical approach to recycling the world’s top two plastics.
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    Supporting data for Core−Shell Gyroid in ABC Bottlebrush Block Terpolymers
    (2023-05-25) Cui, Shuquan; Zhang, Bo; Shen, Liyang; Bates, Frank S; Lodge, Timothy P; lodge@umn.edu; Lodge, Timothy P; University of Minnesota Department of Chemistry
    These files contain primary data supporting all results reported in Cui et al. "Core−shell gyroid in ABC bottlebrush block terpolymers." A series of bottlebrush block polymers containing 24 PEP-PS diblock copolymers and 109 PEP-PS-PEO triblock terpolymers were synthesized by ring-opening metathesis polymerization (ROMP) of norbornene-functionalized poly(ethylene-alt-propylene) (PEP), poly(styrene) (PS), and poly(ethylene oxide) (PEO) macromonomers. The molecular weights of the three macromonomers were around 1 kg/mol. The relatively modest total backbone degrees of polymerization ranged from ca. 20 to 40. Morphologies of these bottlebrush block polymers were characterized by small-angle X-ray scattering (SAXS). The PEP-PS diblocks exhibited only cylindrical (HEX) and lamellar (LAM) morphologies; the desired network phases did not appear in these materials, consistent with previous experimental studies. However, adding variable-length bottlebrush PEO blocks to diblocks containing 30% to 50% PS led to a substantial core-shell double gyroid (GYR) phase window in the ternary phase portrait. Encouragingly, the GYR unit cell dimensions increased almost linearly with the backbone degree of polymerization, portending the ability to access larger network dimensions than previously obtained with linear block polymers. This finding demonstrates a periodic network phase in bottlebrush block polymers for the first time and highlights extraordinary opportunities associated with applying facile ROMP chemistry to multiblock bottlebrush polymers.