Advances in polymer chemistry over the first one hundred years of the discipline has resulted in the production of materials with a wide-range of properties - from super soft gels to high modulus glasses - through the control of chemical composition, molecular weight, and architecture. Photopolymerizations are a particularly useful class of synthetic chemistry due to the specificity afforded by control of light, where illumination time, pattern, and wavelength can be treated as ‘reactants’ to control a given reaction. While the advantages of spatiotemporal control when coupled with self-assembly to produce high-performance materials has been elegantly demonstrated in liquid crystalline networks, it remains an outstanding challenge to synthesize other such materials via photochemical methods. Of particular interest are semi-crystalline materials, where self-assembly of polymer chains within crystalline lamellae endow the resulting materials with high tensile strength, toughness, and chemical resistance. Recently, we developed a method for synthesizing high molecular weight semi-crystalline polymers using thiol-ene photochemistry of commercially-available dithiol and diene monomers with Young’s moduli and extensibilities of up to 280 MPa and 800%, respectively. These properties approach those of commercially-relevant thermoplastics, and are amenable to digital light processing (DLP)-based additive manufacturing. Additionally, we show that semi-crystallinity is preserved upon the addition of small amounts of cross-linker for networks. Excitingly, these present opportunities for a variety of applications requiring specified parts with excellent mechanical properties as well as shape-memory behavior. This work demonstrates a new avenue within the photopolymerization space towards functional, high performance polymers through simple chemistry.

Photopolymerization approaches to high-performance semi-crystalline polymers and networks

ACS Fall 2021

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