It is well documented that in semi-crystalline polymers crystallization is strongly influenced by thermal and flow conditions that the polymer experiences during its shaping process. It is also becoming evident that the processing conditions are strongly influenced by the entangled state that are established in the non-crystalline region during polymerization of a semi-crystalline polymer. The strong influence of the entangled state in the processing is realized when an intractable polymer can be processed even below its melting point. Two such examples that are documented in the literature are of linear polyethylene and isotactic polypropylene, both having molar mass exceeding a million g/mol.

In this paper we will demonstrate that the controlled polymer synthesis can result into the formation of single-crystals that are identified by scanning / transmission electron microscopy, imaging and diffraction techniques. Within these single crystals, solid state NMR identifies constrained chain segments residing in the non-crystalline region. Such single crystals can be deformed uniaxially and biaxially in solid state and are linked with the polymerization conditions. The knowhow thus developed is extended beyond polyethylene and isotactic polypropylene that the paper will address.

References:

1. Unprecedented Mechanical Properties in Linear UHMWPE Using a Heterogeneous Catalytic System; Macromolecules 2023, 56, 1, 361-378
2. Synthesis and Characterization of Well-Defined High-Molecular-Weight PDLA-b-PLLA and PDLA-b-PLLA-b-PDLA Stereo-Block Copolymers; Macromolecules 2023, 56, 5, 1995–2008.
3. An unconventional route for synthesis and solid-state processing of low entangled Ultra-High Molecular Weight Isotactic Polypropylene; Macromol. Rapid Commun.2023, 44, 2300039.
4. Primary Thickening in Nascent Single Crystals of High-Molecular-Weight trans-1,4-Polybutadiene; Macromolecules 2023, https://pubs.acs.org/action/showCitFormats?doi=10.1021/acs.macromol.3c01520&ref=pdf

Acknowledgement: The author extends thanks to his group members at KAUST whose contribution lead to the present abstract and forum for the presentation. To name, Dr Dario Romano, Dr Sumesh Raman, Dr Yogesh Patil, Dr Jiayi Zhao, Dr Joris van der Eem, Dr Feijie Li, Mr Ravindra Gote, Mr Fuhai Zhou, Mr Abulaziz Alsubhi. We extend thanks to Dr Virendra Gupta of Reliance Industries Limited for a part of work to be reported on isotactic polypropylene. Financial support from KAUST and the expertise available at the KAUST core labs is gratefully acknowledged.